Metal Casting

By N K MurthyBy N K Murthy

Casting since about 4000 BCCasting since about 4000 BChelliphellip

Ancient Greece bronzestatue casting circa 450BC

Iron works in early Europeeg cast iron cannons fromEngland circa 1543

Outline1048707 Introduction1048707 Process Constraints1048707 Green Sand Casting1048707 Other Processes

History of CastingHistory of Casting

Heat treatment of stone to make it more Heat treatment of stone to make it more workable the burning of lime to make workable the burning of lime to make plaster and the firing of clay to produce plaster and the firing of clay to produce ceramics ceramics

SIX FACTORS INVOLVED IN CASTING

1 mould cavity 2 molten metal 3 escape of air gas 4 shrinking 5 mould removal 6 finishing

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting since about 4000 BCCasting since about 4000 BChelliphellip

Ancient Greece bronzestatue casting circa 450BC

Iron works in early Europeeg cast iron cannons fromEngland circa 1543

Outline1048707 Introduction1048707 Process Constraints1048707 Green Sand Casting1048707 Other Processes

History of CastingHistory of Casting

Heat treatment of stone to make it more Heat treatment of stone to make it more workable the burning of lime to make workable the burning of lime to make plaster and the firing of clay to produce plaster and the firing of clay to produce ceramics ceramics

SIX FACTORS INVOLVED IN CASTING

1 mould cavity 2 molten metal 3 escape of air gas 4 shrinking 5 mould removal 6 finishing

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Outline1048707 Introduction1048707 Process Constraints1048707 Green Sand Casting1048707 Other Processes

History of CastingHistory of Casting

Heat treatment of stone to make it more Heat treatment of stone to make it more workable the burning of lime to make workable the burning of lime to make plaster and the firing of clay to produce plaster and the firing of clay to produce ceramics ceramics

SIX FACTORS INVOLVED IN CASTING

1 mould cavity 2 molten metal 3 escape of air gas 4 shrinking 5 mould removal 6 finishing

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

History of CastingHistory of Casting

Heat treatment of stone to make it more Heat treatment of stone to make it more workable the burning of lime to make workable the burning of lime to make plaster and the firing of clay to produce plaster and the firing of clay to produce ceramics ceramics

SIX FACTORS INVOLVED IN CASTING

1 mould cavity 2 molten metal 3 escape of air gas 4 shrinking 5 mould removal 6 finishing

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

SIX FACTORS INVOLVED IN CASTING

1 mould cavity 2 molten metal 3 escape of air gas 4 shrinking 5 mould removal 6 finishing

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Some Facts 1048707 First casting 5000-3000 BC 1048707 Bronze iron age light metal age 1048707 Versatility bull Many types of metals bull Rapid production bull Wide range of shapes and sizes bull Complex parts as an integral

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Date Development Location

9000 BC Earliest metal objects of wrought native copper Near East

6500 BC Earliest life-size statues of plaster Jordan

5000-3000 BC

Chalcolithic period melting of copper experimentation with smelting

Near East

3000-1500 BC

Bronze Age arsenical copper and tin bronze alloys

Near East

3000-2500 BC

Lost wax casting of small objects Near East

2500 BC Granulation of gold and silver and their alloys Near East

2400-2200 BC

Copper statue of Pharoah Pepi I Egypt

2000 BC Bronze Age Far East

1500 BC Iron Age (wrought iron) Near East

700-600 BC

Etruscan dust granulation Italy

600 BC Cast iron China

224 BC Colossus of Rhodes destroyed Greece

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

200-300 AD Use of mercury in gilding (amalgam gilding) Roman world

1200-1450 AD Introduction of cast iron (exact date and place unknown)

Europe

Circa 1122 AD Theophiluss On Divers Arts the first monograph on metalworking written by a craftsman

Germany

1252 AD Diabutsu (Great Buddha) cast at Kamakura Japan

Circa 1400 AD Great Bell of Beijing cast China

16th century Sand introduced as mold material France

1709 Cast iron produced with coke as fuel Coalbrookdale

England

1715 Boring mill or cannon developed Switzerland

1735 Great Bell of the Kremlin cast Russia

1740 Cast steel developed by Benjamin Huntsman England

1779 Cast iron used as architectural material Ironbridge Gorge

England

1826 Zinc statuary France

1838 Electrodeposition of copper Russia England

1884 Electrolytic refining of aluminum United States France

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting MethodsCasting Methods

bull Sand CastingHigh Temperature Alloy Complex Geometry Rough Surface Finish

bull Investment CastingHigh Temperature Alloy Complex Geometry Moderately Smooth Surface Finish

bull Die CastingHigh Temperature Alloy Moderate Geometry Smooth Surface

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand Sand CastingCasting

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Example ndash Sand Casting

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand CastingSand CastingDescription Tempered sand is packed into wood or metal pattern halves removed form the pattern and assembled with or without cores and metal is poured into resultant cavities Various core materials can be used Molds are broken to remove castings Specialized binders now in use can improve tolerances and surface finish

Metals Most castable metals

Size Range Limitation depends on foundry capabilities Ounces to many tonsTolerances

Non-Ferrous 132 to 6 Add 003 to 3 364 from 3 to 6Across parting line add 020 to 090 depending on size (Assumes metal patterns)

Surface FinishNon-Ferrous 150-350 RMSFerrous 300-700RMS

Minimum Draft Requirements1deg to 5degCores 1deg to 1 12deg

Normal Minimum Section ThicknessNon-Ferrous 18 - 14 Ferrous 14 - 38

Ordering Quantities All quantities

Normal Lead TimeSamples 2-10 weeksProduction 2-4 weeks ASA

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand Casting

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand Casting Steps

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand Casting

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Sand Casting Mold FeaturesSand Casting Mold Features

Vents which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the molds and core They also exhaust air from the mold cavity as the molten metal flows into the mold

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Production sand castingProduction sand casting

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Example ndash Die Casting

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Example ndash Investment Casting

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Investment CastingInvestment CastingDescription Metal mold makes wax or plastic replica There are sprued then surrounded with investment material baked out and metal is poured in the resultant cavity Molds are broken to remove the castings

Metals Most castable metals

Size Range fraction of an ounce to 150 lbs

Tolerances 003 to 14 004 to 12 005 per inch to 3 003 for each additional inch

Surface Finish63-125RMS

Minimum Draft Requirements None

Normal Minimum Section Thickness030 (Small Areas)060 (Large Areas)

Ordering Quantities Aluminum usually under 1000Other metals all quantities

Normal Lead TimeSamples 5-16 weeks (depending on complexity)Production 4-12 weeks ASA (depending on subsequent operations)

Talbot Associates Inc

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting Process Physics andConstraints

1048707 Phase Change bull Density bull Solubility bull Diffusion rates 1048707 High melting temperature bull Chemical activity bull High latent heat bull Handling

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Analysis of Casting Processes

Heat transfer for solidification 1048707 Thermodynamics mass transfer and heat transfer for nucleation and growth 1048707 Materials behavior for structure-property relationships

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Mold Filling

Bernoullirsquos equation1048707 Reynoldrsquos numberbull Turbulencebull Injection Molding Re ~ 10-

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Mold FillingMold Filling

Bernoulirsquos Equation

Reynoldrsquos Number

bullShort filling times

bullPotential Turbulence

(see p 273 hellip Kalpakjian

2

2

Constg

v

pg

ph

vDP

Re

h

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Mold Filling ExampleMold Filling Example (1 of 2)(1 of 2)

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Mold Filling ExampleMold Filling Example (2 of 2)(2 of 2)

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

PhasePhaseChange ampChange ampShrinkageShrinkage

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Solidification of a binary alloySolidification of a binary alloy

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Composition change during Composition change during solidificationsolidification

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

SolidificationSolidification

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Cast structuresCast structures

Schematic illustration of three cast structures solidified in a square mold (a) pure metals (b) solid solution alloys and copy structure obtained by using nucleating agents Source G W Form J F Wallace and A Cibula

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Microstructure - Dendrites

Finer structure atwallsbull Grains dendritesgrow to center

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Microstructure - Dendrites

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Draft in Pattern

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Pattern Design Considerations(DFM)

Shrinkage allowance 1048707 Machining allowance 1048707 Distortion allowance 1048707 Parting line 1048707 Draft angle

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Pattern DesignPattern Design

Table 121Table 121

Normal Shrinkage Allowance for Normal Shrinkage Allowance for Some Metals Cast in Sand MoldsSome Metals Cast in Sand Molds

MetalMetal PercentPercentGray cast ironGray cast iron 083 ndash 13083 ndash 13White cast ironWhite cast iron 2121Malleable cast ironMalleable cast iron 078 ndash 10078 ndash 10Aluminum alloysAluminum alloys 1313Magnesium alloysMagnesium alloys 1313Yellow brassYellow brass 13 ndash 1613 ndash 16Phosphor bronzePhosphor bronze 10 ndash 1610 ndash 16Aluminum bronzeAluminum bronze 2121High-manganese steelHigh-manganese steel 2626

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Pattern Design suggestionsPattern Design suggestions

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Typical Shrinkage Allowance Aluminum alloy helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 13 Aluminum bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Yellow brass (thick sections) helliphelliphelliphelliphelliphellip 13 Yellow brass (thin sections) helliphelliphelliphelliphelliphellip 13 Gray cast iron (a) helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 8 - 13 White cast iron helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Tin bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 Gun metal helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Lead helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Magnesium helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Magnesium alloys (25) helliphelliphelliphelliphelliphelliphelliphelliphellip 16 Manganese bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Copper-nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Nickel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Phosphor bronze helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 11 - 16 Carbon steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 - 21 Chromium steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Manganese steel helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26 Tin helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 21 Zinc helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 26

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Typical Pattern MachiningAllowance

Pattern size mm Bore Surface Cope side For cast irons Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 48 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 48 40 64 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 48 79 For cast steels Up to 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 64 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 48 64 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 64 64 79 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 71 64 96 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 79 64 127 For nonferrous alloys Up to 76helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 16 16 16 76 - 152helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 24 152 - 305helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 24 16 32 305 - 510helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 24 32 510 - 915helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 32 32 40 915 - 1524helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Gating SystemSprue Runner and Gate

Rapid mold filling 1048707 Minimizing turbulence 1048707 Avoiding erosion 1048707 Removing inclusions 1048707 Controlled flow and thermal conditions 1048707 Minimizing scrap and secondary operations

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Riser Location and Size

Casting shrinkage 1048707 Directional solidification 1048707 Scrap and secondary operation

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Types of Parts Made bull Engine blocks bull Pipes bull Jewelry bull Fire hydrants Complex 3-D shapes bull Near net shape bull Low scrap bull Relatively quick process bull Intricate shapes bull Large hollow shapes bull No limit to size bull Reasonable to good surface finish

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Breakdown of Castings

Ingots for bulk deformation processing -

85 Cast to near net shape - 15

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Capabilities

Dimensions ndash sand casting - as large as you like ndash small - 1 mm or so bull Tolerances ndash 0005 in to 01 in bull Surface finish ndash die casting 8-16 micro-inches (1-3 μm) ndash sand casting - 500 micro-inches (10-25 μm)

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Processes

Sand bull Shell bull Plaster bull Ceramic bull Investment bull Lost foam bull Pressure bull Vacuum

bullDiebull Centrifugalbull Squeezebull Semi-solidbull Single crystalbull Directionalsolidificationbull Slushbull Continuous

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Metals processed by casting

Sand casting ndash 60 bull Investment casting ndash 7 bull Die casting ndash 9 bull Permanent mold casting ndash 11 bull Centrifugal casting ndash 7 bull Shell mold casting ndash 6

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

bull Melt metals bull Pour force liquid into hollow cavity (mold) bull Cool Solidify bull Remove bull Finish

Casting Stepsquick route from raw material to finished product

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Melting

bull Raw material (charge) ndash scrap alloying materials bull Atmosphere ndash Air (oxygen) vacuum inert gas (argon) bull Heating ndash External - electric gas oil ndash Internal - induction mix fuel with charge bull steel making in blast furnace -mix coke with iron bull Furnace material ndash refractory ceramics

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

FurnacesBasic Oxygen Furnace

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Blast furnace

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Electric Arc Furnace

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Induction Furnace

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Electric Furnace

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting Advantages Casting Advantages Applications and Market SizeApplications and Market Size

Molding and casting processes available Molding and casting processes available that are capable of producing complex that are capable of producing complex components in any metal ranging in weight components in any metal ranging in weight from less than an ounce to single parts from less than an ounce to single parts weighing several hundred tons weighing several hundred tons

Foundry processes are available and in use Foundry processes are available and in use that are economically viable for producing a that are economically viable for producing a single prototype part single prototype part

Virtually any metal that can be melted can Virtually any metal that can be melted can and is being castand is being cast

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Hot-forming die of 61500 kg (135600 lb) for

producing nuclear reactor pressure heads

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Cast iron automobile engine blocks Cast iron automobile engine blocks

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting techniques are grouped into Casting techniques are grouped into five categoriesfive categories

Conventional molding processes (green sand Conventional molding processes (green sand shell flaskless molding) shell flaskless molding)

Precision molding and casting processes Precision molding and casting processes (investment casting permanent mold die casting) (investment casting permanent mold die casting)

Special molding and casting processes (vacuum Special molding and casting processes (vacuum molding evaporative pattern casting centrifugal molding evaporative pattern casting centrifugal casting) casting)

Chemically bonded self-setting sand molding (no-Chemically bonded self-setting sand molding (no-bake sodium silicate) bake sodium silicate)

Innovative molding and casting processes Innovative molding and casting processes (rheocasting squeeze casting electroslag casting) (rheocasting squeeze casting electroslag casting)

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Rapid Transition to Finished ProductRapid Transition to Finished Product The casting The casting process involves pouring molten metal into a cavity process involves pouring molten metal into a cavity that is close to the final dimensionsthat is close to the final dimensions

Suiting Shape and Size to FunctionSuiting Shape and Size to Function Metal castings Metal castings weighing from less than an ounce to hundreds of tons weighing from less than an ounce to hundreds of tons in almost any shape or degree of complexity can be in almost any shape or degree of complexity can be produced If a pattern can be made for the part it can produced If a pattern can be made for the part it can be castbe cast

Placement of Metal for Maximum EffectivenessPlacement of Metal for Maximum Effectiveness With the casting process the optimum amount of With the casting process the optimum amount of metal can be placed in the best location for maximum metal can be placed in the best location for maximum strength wear resistance or the enhancement of strength wear resistance or the enhancement of other properties of the finished part other properties of the finished part

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Optimal AppearanceOptimal Appearance Complex Parts as an Integral UnitComplex Parts as an Integral Unit The inherent The inherent

design freedom of metal casting allows the design freedom of metal casting allows the designer to combine what would otherwise be designer to combine what would otherwise be several parts of a fabrication into a single several parts of a fabrication into a single intricate castingintricate casting

Improved DependabilityImproved Dependability The use of good The use of good casting design principles together with periodic casting design principles together with periodic determination of mechanical properties of test bars determination of mechanical properties of test bars cast from the molten metal cast from the molten metal

Functional advantages of castings Functional advantages of castings and the metal casting process and the metal casting process

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Compressor case for a jet engine Compressor case for a jet engine

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Major markets for metal castingsMajor markets for metal castings Ferrous castingsFerrous castings

ndash Gray ironGray iron Ingot molds Ingot molds Construction castings Construction castings Motor vehiclesMotor vehicles Farm equipment Engines Farm equipment Engines Refrigeration and heating Construction Refrigeration and heating Construction

machinery Valves machinery Valves Soil pipe Pumps and compressors Pressure Soil pipe Pumps and compressors Pressure

pipe pipe Other major markets include machine toolsOther major markets include machine tools mechanical power transmission equipmentmechanical power transmission equipment hardware home appliances and mining hardware home appliances and mining

machinery oil and natural gas pumping and machinery oil and natural gas pumping and processing equipment processing equipment

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Major markets for metal castingsMajor markets for metal castingsndash Malleable ironMalleable iron

Motor vehicles Valves and fittingsMotor vehicles Valves and fittings Construction machinery Construction machinery Railroad equipmentRailroad equipment EnginesEngines Mining equipmentMining equipment Hardware Hardware Other major markets include heating Other major markets include heating

and refrigeration motors and and refrigeration motors and generators fasteners ordnance generators fasteners ordnance chains machine tools general chains machine tools general industrial machineryindustrial machinery

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Major markets for metal castingsMajor markets for metal castings

ndash Ductile ironDuctile iron Pressure pipe Pressure pipe Motor vehicles Motor vehicles Farm machinery Farm machinery Engines Engines Pumps and compressors Pumps and compressors Valves and fittingsValves and fittings Metalworking machinery Construction machineryMetalworking machinery Construction machinery Other major markets include textile machinery Other major markets include textile machinery

wood working and paper machinery mechanical wood working and paper machinery mechanical power and transmission equipment motors and power and transmission equipment motors and generators refrigeration and heating equipment generators refrigeration and heating equipment air conditioning air conditioning

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

ndash SteelSteel Railroad equipmentRailroad equipment Construction equipmentConstruction equipment Mining machineryMining machinery Valves and fittings Valves and fittings General and special industrial machineryGeneral and special industrial machinery Motor vehicles Motor vehicles Metalworking machinery Metalworking machinery Other major markets include steel Other major markets include steel

manufacturing spring goods heating and air manufacturing spring goods heating and air conditioning recreation equipment industrial conditioning recreation equipment industrial material handling equipment ships and boats material handling equipment ships and boats

aircraft and aerospaceaircraft and aerospace

Major markets for metal castingsMajor markets for metal castings

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Nonferrous castingsNonferrous castings AluminumAluminum

Auto and light truck Auto and light truck Aircraft and aerospaceAircraft and aerospace Other transportation Engines Other transportation Engines Household appliances Household appliances Office machinery Power toolsOffice machinery Power tools Refrigeration heating and air conditioningRefrigeration heating and air conditioning Other major markets include machine Other major markets include machine

tools construction equipment mining tools construction equipment mining equipment farm machinery electronic and equipment farm machinery electronic and communication equipment power systems communication equipment power systems motors and generators motors and generators

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Copper-baseCopper-base Valves and fittings Valves and fittings Plumbing brass goodsPlumbing brass goods Electrical equipment Pumps and Electrical equipment Pumps and

compressors compressors Power transmission equipment Power transmission equipment General machineryGeneral machinery Transportation equipment Transportation equipment Other major markets include chemical Other major markets include chemical

processing utilities desalination processing utilities desalination petroleum refining petroleum refining

Nonferrous castingsNonferrous castings

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Simplified flow diagram of the basic operations for producing a steel casting

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Metal Casting Processes

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Metal Casting ProcessMetal Casting Process

Investment CastingInvestment Casting Vacuum CastingVacuum Casting Permanent-Mold CastingPermanent-Mold Casting Slush CastingSlush Casting Pressure CastingPressure Casting Die CastingDie Casting Centrifugal CastingCentrifugal Casting

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Investment CastingInvestment Casting

Also called Also called lost-wax processlost-wax process

First used 4000 ndash 3000 BCFirst used 4000 ndash 3000 BC

The pattern is made of wax or of a plastic by molding or The pattern is made of wax or of a plastic by molding or rapid prototyping techniquesrapid prototyping techniques

Term Term investment investment derives from the fact that the pattern is derives from the fact that the pattern is invested with the refractory materialinvested with the refractory material

Need careful handling because they are not strong Need careful handling because they are not strong enough to withstand the forces involved in mold makingenough to withstand the forces involved in mold making

Wax can be recovered and reusedWax can be recovered and reused

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Investment Casting ProcessInvestment Casting Process

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Investment CastingInvestment Casting

One-piece moldOne-piece moldndash Dried in the airDried in the airndash Heated to 90 ndash 175 CHeated to 90 ndash 175 Cndash Held inverted for 12 hrs to melt out waxHeld inverted for 12 hrs to melt out waxndash The mold is then heated to 650 ndash 1150 C for about 4 The mold is then heated to 650 ndash 1150 C for about 4

hrs depending on the metal to be cast to drive off the hrs depending on the metal to be cast to drive off the water of crystallizationwater of crystallization

ndash After the metal has been poured the mold is broken After the metal has been poured the mold is broken up and the cast is removedup and the cast is removed

ndash A number of patterns can be joined to make one mold A number of patterns can be joined to make one mold called a called a treetree which increases production rate which increases production rate

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

One-piece moldOne-piece mold - - conrsquotconrsquotndash Small partsSmall parts

The tree can be inserted on to a flask and filled with slurry The tree can be inserted on to a flask and filled with slurry investmentinvestment

The investment is then placed into a chamber and evacuated to The investment is then placed into a chamber and evacuated to remove air bubblesremove air bubbles

Next it is placed in a vacuum drawing machine to produce fine detailNext it is placed in a vacuum drawing machine to produce fine detail

ndash Not a cheap processNot a cheap processndash Produces fine detailsProduces fine detailsndash Good surface finishGood surface finishndash Few or no finishing operationsFew or no finishing operationsndash Can produce intricate parts from parts weighing 1g ndash 35KgCan produce intricate parts from parts weighing 1g ndash 35Kg

Ex Investment die casting examplesEx Investment die casting examples

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Properties of WaxProperties of Wax

Ash content (005 max)Ash content (005 max) Resistance to primary coat binders carriersResistance to primary coat binders carriers Viscosity StrengthViscosity Strength Ductile to brittle transition rangeDuctile to brittle transition range Solidification temp rangeSolidification temp range Oxidation resistanceOxidation resistance ToxicityToxicity Coefficient of thermal expansion shrinkage Coefficient of thermal expansion shrinkage

wettabilitywettability Hardness Hardness

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Typical Formulation of Injection Wax Typical Formulation of Injection Wax for Patternsfor Patterns

Hard Wax - 40Hard Wax - 40 Microcrystalline Wax ndash 25Microcrystalline Wax ndash 25 Soft resinous plasticizers ndash 15Soft resinous plasticizers ndash 15 Hard resins ndash 20Hard resins ndash 20 Antioxidants ndash 005Antioxidants ndash 005

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Typical Requirements of Investment Typical Requirements of Investment CastingsCastings

Product Stainless Steel Valve BodyProduct Stainless Steel Valve Body Pattern Die Material SteelPattern Die Material Steel Pattern Material WaxPattern Material Wax Type of Investment Ceramic ShellType of Investment Ceramic Shell Melting Method InductionMelting Method Induction Pouring Temp- 1595 deg CelsiusPouring Temp- 1595 deg Celsius Mold Temp- 950 deg CelsiusMold Temp- 950 deg Celsius No of castings per mold- oneNo of castings per mold- one

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Weight of Liquid Metal poured 675 KgWeight of Liquid Metal poured 675 Kg Weight of Trimmed castings 27 KgWeight of Trimmed castings 27 Kg

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Composition of Zircon SlurryComposition of Zircon Slurry

Colloidal Silica (30) gal - 25Colloidal Silica (30) gal - 25 Water gal - 10Water gal - 10 Zircon powder lb - 100Zircon powder lb - 100 Density - 27 to 275Density - 27 to 275 Viscosity sec (d) - 8 to 10Viscosity sec (d) - 8 to 10

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Dewaxing of Ceramic Shell MoldsDewaxing of Ceramic Shell Molds

Solvent MethodSolvent Method Wax patterns can be Wax patterns can be removed by action of hot vapor of a solvent removed by action of hot vapor of a solvent such as trichloroethylenesuch as trichloroethylene

Flash De waxingFlash De waxing in Furnace High thermal in Furnace High thermal gradient is established across the ceramic gradient is established across the ceramic shell amp pattern sectionshell amp pattern section

Autoclave de waxingAutoclave de waxing Super heated steam Super heated steam condensed on shell thus generating high condensed on shell thus generating high temptemp

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Firing amp Preheating of MoldsFiring amp Preheating of Molds

Remove residue of wax amp plasticRemove residue of wax amp plastic Permit filling of mold sections too thin to be Permit filling of mold sections too thin to be

filled in a cold moldfilled in a cold mold Minimises the size of riserMinimises the size of riser Minimises hot tearingMinimises hot tearing Continuous Furnaces Batch type Furnaces Continuous Furnaces Batch type Furnaces

Temp 1000deg Celsius time ndash 15hrsTemp 1000deg Celsius time ndash 15hrs

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Melting amp Melting amp PouringPouringPracticePractice Air Induction Furnace Air Induction Furnace Vacuum Induction MeltingVacuum Induction Melting Gravity PouringGravity Pouring Pressure PouringPressure Pouring Vacuum Assist Pouring Vacuum Assist Pouring Vacuum Centrifugal PouringVacuum Centrifugal Pouring CentrifugingCentrifuging

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Schematic illustration of investment castingSchematic illustration of investment casting 1 WAX INJECTION 1 WAX INJECTION Wax replicas of the Wax replicas of the

desired castings are produced by desired castings are produced by injection molding These replicas are injection molding These replicas are called patternscalled patterns

2 ASSEMBLY 2 ASSEMBLY The patterns are attached The patterns are attached to a central wax stick called a sprue to a central wax stick called a sprue to form a casting cluster or assemblyto form a casting cluster or assembly

3 SHELL BUILDING 3 SHELL BUILDING The shell is built by immersing The shell is built by immersing the assembly in a liquid ceramic slurry and then the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand Up to eight into a bed of extremely fine sand Up to eight layers may be applied in this mannerlayers may be applied in this manner

4 DEWAX 4 DEWAX Once the ceramic is dry the wax is Once the ceramic is dry the wax is melted out creating a negative impression of the melted out creating a negative impression of the assembly within the shellassembly within the shell

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

5 CONVENTIONAL CASTING5 CONVENTIONAL CASTINGIn the conventional process the shell is filled with In the conventional process the shell is filled with molten metal by gravity pouring As the metal molten metal by gravity pouring As the metal cools the parts and gates sprue and pouring cools the parts and gates sprue and pouring cup become one solid casting cup become one solid casting

6 KNOCKOUT6 KNOCKOUTWhen the metal has cooled and solidified the When the metal has cooled and solidified the ceramic shell is broken off by vibration or water ceramic shell is broken off by vibration or water blastingblasting

7 CUT OFF7 CUT OFFThe parts are cut away from the central sprue The parts are cut away from the central sprue using a high speed friction sawusing a high speed friction saw

8 FINISHED CASTINGS8 FINISHED CASTINGSAfter minor finishing operations the metal After minor finishing operations the metal castings--identical to the original wax patterns--castings--identical to the original wax patterns--are ready for shipment to the customerare ready for shipment to the customer

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Advantages of Investment Casting

Intricate geometry 1048707 Close dimensional tolerance 1048707 Superior surface finish 1048707 High-melting point alloys

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting DefectsCasting Defects

MisrunMisrun Cold shutCold shut Hot tears amp crackHot tears amp crack PorosityPorosity ShrinkageShrinkage InclusionsInclusions

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy

(d) The cast rotor produced to net or near-net shape (d) The cast rotor produced to net or near-net shape

Ceramic-Shell CastingCeramic-Shell Casting

ndash Variation of the investment-casting processVariation of the investment-casting processndash Uses same type of wax or plastic pattern as investment castingUses same type of wax or plastic pattern as investment castingndash Patten is then dipped into fluidized bed of Patten is then dipped into fluidized bed of

Fine- grained fused silicaFine- grained fused silica Zircon flourZircon flour

ndash Pattern is then dipped into coarser grained silica to build up additional Pattern is then dipped into coarser grained silica to build up additional coatings and proper thickness to withstand the thermal shock of pouringcoatings and proper thickness to withstand the thermal shock of pouring

ndash The rest of the procedure follows the investment casting processThe rest of the procedure follows the investment casting process

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Vacuum CastingVacuum Casting

11 Mixture of fine sand and Mixture of fine sand and urethane is molded over urethane is molded over metal dies a cured with metal dies a cured with amine vaporamine vapor

22 The mold is partially The mold is partially immersed into molten immersed into molten metal held in an metal held in an induction furnaceinduction furnace

33 The metal is melted in air The metal is melted in air or in a vacuumor in a vacuum

44 The molten metal is The molten metal is usually 55 C above the usually 55 C above the liquidus temperature ndash liquidus temperature ndash begins to solidify within a begins to solidify within a fraction of a secondfraction of a second

5 Alternative to investment shell-5 Alternative to investment shell-mold and green-sand castingmold and green-sand casting

6 Relatively low cost6 Relatively low cost

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Permanent-Mold CastingPermanent-Mold Casting Called hard-mold castingCalled hard-mold casting Two halves of a mold are made from materials such as iron Two halves of a mold are made from materials such as iron

steel bronze or other alloyssteel bronze or other alloys The mold cavity and gating system are machined in to the moldThe mold cavity and gating system are machined in to the mold Sand aggregate are placed in to the mold prior to casting for Sand aggregate are placed in to the mold prior to casting for

producing cavitiesproducing cavities Typical core materials areTypical core materials are

ndash Oil-bonded or resin-boned sandOil-bonded or resin-boned sandndash PlasterPlasterndash GraphiteGraphitendash Gray ironGray ironndash Low-carbon steelLow-carbon steelndash Hot-worked die steelHot-worked die steel

Mold cavity surfaces are coated with refractory slurry to increase Mold cavity surfaces are coated with refractory slurry to increase the life of the mold every few castingsthe life of the mold every few castings

Mechanical ejectors are used to remove complex partsMechanical ejectors are used to remove complex parts Can produce high production ratesCan produce high production rates Good surface finishGood surface finish

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Slush CastingSlush Casting Molten metal is poured into the metal moldMolten metal is poured into the metal mold A desired thickness of the solidified skin is obtainedA desired thickness of the solidified skin is obtained The remaining metal is poured outThe remaining metal is poured out The mold halves are then opened and the casting is removedThe mold halves are then opened and the casting is removed

Used a graphite or metal moldUsed a graphite or metal mold Molten metal is forced into the mold by gas pressureMolten metal is forced into the mold by gas pressure The pressure is maintained until the metal solidifies in the moldThe pressure is maintained until the metal solidifies in the mold Used for high-quality castingsUsed for high-quality castings

Pressure CastingPressure Casting

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

(a) The bottom-pressure casting process utilizes graphite molds for the (a) The bottom-pressure casting process utilizes graphite molds for the productin of steel railroad wheels (b) Gravity pouring method of casting a productin of steel railroad wheels (b) Gravity pouring method of casting a railroad wheel Note that the pouring basin also serves as a riser railroad wheel Note that the pouring basin also serves as a riser

Pressure CastingPressure Casting

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Die Casting Part Example

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Die CastingDie Casting

Further example of permanent-mold castingFurther example of permanent-mold casting Molten metal is forced into the die cavity at pressures Molten metal is forced into the die cavity at pressures

ranging from 7MPa ndash 700MParanging from 7MPa ndash 700MPa Parts made from here range fromParts made from here range from

ndash Hand toolsHand toolsndash ToysToysndash Appliance componentsAppliance components

There are two basic types of die casting machinesThere are two basic types of die casting machinesndash Hot-chamber - involves the use of a piston to push Hot-chamber - involves the use of a piston to push

molten metal in to the die cavitymolten metal in to the die cavityndash Cold-chamber ndash molten metal is poured in to the Cold-chamber ndash molten metal is poured in to the

injection chamber amp the shot chamber is not heated injection chamber amp the shot chamber is not heated

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Hot chamber Die-casting processHot chamber Die-casting process

11 The die is closed and The die is closed and the piston rises opening the piston rises opening the port and allowing the port and allowing molten metal to fill the molten metal to fill the cylinder cylinder

22 The plunger moves The plunger moves down and seals the port down and seals the port pushing the molten metal pushing the molten metal through the gooseneck through the gooseneck and nozzle into the die and nozzle into the die cavity where it is held cavity where it is held under pressure until it under pressure until it solidifies solidifies

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

33 The die opens and the The die opens and the cores if any retract The cores if any retract The casting remains in only one casting remains in only one die the ejector side The die the ejector side The plunger returns allowing plunger returns allowing residual molten metal to residual molten metal to flow back through the flow back through the nozzle and gooseneck nozzle and gooseneck

44 Ejector pins push the Ejector pins push the casting out of the ejector casting out of the ejector die As the plunger die As the plunger uncovers the filling hole uncovers the filling hole molten metal flows through molten metal flows through the inlet to refill the the inlet to refill the gooseneck as in step (1) gooseneck as in step (1)

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Cold-Die casting processCold-Die casting process

11 The die is closed and the The die is closed and the molten metal is ladled into the molten metal is ladled into the cold-chamber shot sleevecold-chamber shot sleeve

22 The plunger pushes the The plunger pushes the molten metal into the die cavity molten metal into the die cavity where it is held under pressure where it is held under pressure until solidificationuntil solidification

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

33 The die opens and the The die opens and the plunger advances to ensure plunger advances to ensure that the casting remains in the that the casting remains in the ejector die Cores if any ejector die Cores if any retractretract

44 Ejector pins push the Ejector pins push the casting out of the ejector die casting out of the ejector die and the plunger returns to its and the plunger returns to its original positionoriginal position

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Process Capabilities and Machine SelectionProcess Capabilities and Machine Selectionndash Dies are rated according to their clamping force that is neededDies are rated according to their clamping force that is neededndash Factors involved in selection of die cast machines areFactors involved in selection of die cast machines are

Die sizeDie size Piston strokePiston stroke Shot pressureShot pressure CostCost

ndash Die-casting diesDie-casting dies Single cavitySingle cavity Multiple-cavityMultiple-cavity Combination-cavityCombination-cavity Unit diesUnit dies

ndash Ratio of Die weight to part weight is 1000 to 1Ratio of Die weight to part weight is 1000 to 1ndash Surface cracking is a problem with dies due to the hot metal that Surface cracking is a problem with dies due to the hot metal that

is poured in to themis poured in to themndash Has ability to produce strong high- quality parts with complex Has ability to produce strong high- quality parts with complex

shapesshapesndash Good dimensional accuracy and surface detailsGood dimensional accuracy and surface details

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Various types of cavities in a die casting dieVarious types of cavities in a die casting die

a)a) Single ndash cavity dieSingle ndash cavity die

b)b) Multiple ndash cavity dieMultiple ndash cavity die

c) Combination diec) Combination die

d) Unit died) Unit die

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

bull800 ton 800 ton hot chamber die casting machinehot chamber die casting machine DAM 8005 This is the largest hot DAM 8005 This is the largest hot chamber machine in the world and costs about $125 millionchamber machine in the world and costs about $125 million

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Advantages of Die Casting

bullHigh production ratesbullCloser dimensional tolerancesbullSuperior surface finishbull Improved mechanical properties

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Centrifugal Casting

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Pipe CastingProcess

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Centrifugal CastingCentrifugal Casting Utilizes the inertial forces caused by rotation to distribute the molten metal Utilizes the inertial forces caused by rotation to distribute the molten metal

in to the mold cavitiesin to the mold cavities First used in the 1800rsquosFirst used in the 1800rsquos Three types of centrifugal castingThree types of centrifugal casting

ndash True centrifugal castingTrue centrifugal castingndash Semi centrifugal castingSemi centrifugal castingndash CentrifugingCentrifuging

Schematic illustration of the centrifugal casting process Pipes cylinder liners Schematic illustration of the centrifugal casting process Pipes cylinder liners and similarly shaped parts can be cast with this processand similarly shaped parts can be cast with this process

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Semi centrifugal Casting ProcessSemi centrifugal Casting Process

(a) Schematic illustration of the semi centrifugal casting process Wheels with spokes (a) Schematic illustration of the semi centrifugal casting process Wheels with spokes can be cast by this process (b) Schematic illustration of casting by centrifuging The can be cast by this process (b) Schematic illustration of casting by centrifuging The molds are placed at the periphery of the machine and the molten metal is forced into molds are placed at the periphery of the machine and the molten metal is forced into the molds by centrifugal forcethe molds by centrifugal force

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Squeeze Casting

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Squeeze CastingSqueeze Casting

(a) Melt Metal(a) Melt Metal

(b) Pour molten metal into die

(c) Close die and apply pressure

(d) Eject squeeze casting and charge melt stock and repeat cycle

Sequence of operations in the squeeze-casting process This process combines the advantages of casting and forging

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Directional Solidification

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Single Crystal Casting of Turbines bladesSingle Crystal Casting of Turbines blades

Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-Fig Methods of casting turbine blades (a) directional solidification (b) method to produce a single-crystal blade and (c) a single-crystal blade with construction portion still attachedcrystal blade and (c) a single-crystal blade with construction portion still attached

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Single Crystal-CastingSingle Crystal-Casting

Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone Fig Two methods of crystal growing (a) crystal pulling and (b) the floating zone method Crystal growing is especially important in the semiconductor industrymethod Crystal growing is especially important in the semiconductor industry

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Melt SpinningMelt Spinning

Fig Schematic illustration Fig Schematic illustration of melt-spinning to of melt-spinning to produce thin strips of produce thin strips of amorphous metalamorphous metal

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Types of Melting FurnacesTypes of Melting Furnaces

Fig Two types of melting furnaces are used in foundries (a) crucible and (b) cupolaFig Two types of melting furnaces are used in foundries (a) crucible and (b) cupola

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Lost Foam Casting

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Lost Foam Casting

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Receive raw polystyrene beads

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

SAND MOLDING (CASTING) SAND MOLDING (CASTING) is one of the most SAND MOLDING (CASTING) is one of the most versatile of metal-forming processes providing versatile of metal-forming processes providing tremendous freedom of design in terms of size tremendous freedom of design in terms of size shape and product quality Sand molding shape and product quality Sand molding processes are classified according to the way in processes are classified according to the way in

which the sand is held (bondedwhich the sand is held (bonded))

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Resin Binder ProcessesResin Binder Processes These organically bonded These organically bonded systems include no-bake binders heat-cured binders (the systems include no-bake binders heat-cured binders (the Shell process and warm box hot box and oven-bake Shell process and warm box hot box and oven-bake processes) and cold box binders Each of these systems processes) and cold box binders Each of these systems is described in the articles is described in the articles Resin Binder ProcessesResin Binder Processes and and CoremakingCoremaking in this Volume in this Volume

Bonded sand moldsBonded sand molds are based on inorganic bonds and are based on inorganic bonds and include such processes as green sand molding dry sand include such processes as green sand molding dry sand molding skin dried molds and loam molding sodium molding skin dried molds and loam molding sodium silicate-carbon dioxide systems and phosphate bonded silicate-carbon dioxide systems and phosphate bonded molds molds

Unbonded Sand MoldsUnbonded Sand Molds With unbonded sand molding With unbonded sand molding processes dry unbonded free-flowing sand surrounds the processes dry unbonded free-flowing sand surrounds the pattern Lost foam processing which uses expandable pattern Lost foam processing which uses expandable polystyrene patterns and vacuum molding are examples polystyrene patterns and vacuum molding are examples of unbonded sand molds Lost foam molds for large of unbonded sand molds Lost foam molds for large castings are sometimes backed up with a no-bake binder castings are sometimes backed up with a no-bake binder system system

Casting Defects - Porosity

Casting Defects

Differential Coolingbull Transition between thicker and thinner sections can lead to porosity

Defects - Hot Tears

Chills

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

Casting Defects

Differential Coolingbull Transition between thicker and thinner sections can lead to porosity

Defects - Hot Tears

Chills

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

Differential Coolingbull Transition between thicker and thinner sections can lead to porosity

Defects - Hot Tears

Chills

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

Defects - Hot Tears

Chills

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

Chills

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

Design Rules Summary

bull Uniform wall thickness bull Flat parting lines bull Gradual thickness transitions bull Draft for removal ndash tapers 05 to 2 degrees bull Surface of mold gives surface of part

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164

• Metal Casting
• Casting since about 4000 BChellip
• Slide 3
• History of Casting
• SIX FACTORS INVOLVED IN CASTING
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Casting Methods
• Slide 11
• Sand Casting
• Example ndash Sand Casting
• Slide 14
• Slide 15
• Slide 16
• Sand Casting
• Slide 18
• Sand Casting
• Sand Casting Steps
• Slide 21
• Slide 22
• Sand Casting Mold Features
• Production sand casting
• Slide 25
• Slide 26
• Slide 27
• Example ndash Die Casting
• Example ndash Investment Casting
• Investment Casting
• Casting Process Physics and Constraints
• Analysis of Casting Processes
• Mold Filling
• Mold Filling
• Mold Filling Example (1 of 2)
• Mold Filling Example (2 of 2)
• Phase Change amp Shrinkage
• Solidification of a binary alloy
• Composition change during solidification
• Solidification
• Cast structures
• Microstructure - Dendrites
• Slide 43
• Slide 44
• Slide 45
• Draft in Pattern
• Pattern Design Considerations (DFM)
• Pattern Design
• Pattern Design suggestions
• Typical Shrinkage Allowance
• Typical Pattern Machining Allowance
• Gating System Sprue Runner and Gate
• Slide 53
• Riser Location and Size
• Types of Parts Made
• Breakdown of Castings
• Capabilities
• Processes
• Metals processed by casting
• Slide 60
• Melting
• Furnaces
• Slide 63
• Electric Arc Furnace
• Induction Furnace
• Electric Furnace
• Casting Advantages Applications and Market Size
• Hot-forming die of 61500 kg (135600 lb) for producing nuclear reactor pressure heads
• Cast iron automobile engine blocks
• Casting techniques are grouped into five categories
• Functional advantages of castings and the metal casting process
• Slide 72
• Compressor case for a jet engine
• Major markets for metal castings
• Major markets for metal castings
• Slide 76
• Slide 77
• Nonferrous castings
• Slide 79
• Slide 80
• Slide 81
• Metal Casting Process
• Slide 83
• Slide 84
• Investment Casting Process
• Slide 86
• Slide 87
• Slide 88
• Slide 89
• Slide 90
• Slide 91
• Properties of Wax
• Typical Formulation of Injection Wax for Patterns
• Typical Requirements of Investment Castings
• Slide 95
• Composition of Zircon Slurry
• Dewaxing of Ceramic Shell Molds
• Firing amp Preheating of Molds
• Melting amp PouringPractice
• Schematic illustration of investment casting
• Slide 101
• Advantages of Investment Casting
• Casting Defects
• Fig Investment casting of an integrally cast rotor for a gas turbine (a) Wax pattern assembly (b) Ceramic shell around wax pattern (c) Wax melted out and the mold is filled under a vacuum with molten super alloy (d) The cast rotor produced to net or near-net shape
• Vacuum Casting
• Permanent-Mold Casting
• Slush Casting
• Pressure Casting
• Slide 109
• Die Casting Part Example
• Slide 111
• Die Casting
• Hot chamber Die-casting process
• Slide 114
• Cold-Die casting process
• Slide 116
• Slide 117
• Various types of cavities in a die casting die
• 800 ton hot chamber die casting machine DAM 8005 This is the largest hot chamber machine in the world and costs about $125 million
• Slide 120
• Slide 121
• Slide 122
• Slide 123
• Slide 124
• Slide 125
• Slide 126
• Slide 127
• Slide 128
• Slide 129
• Slide 130
• Slide 131
• Slide 132
• Slide 133
• Slide 134
• Slide 135
• Slide 136
• Slide 137
• Centrifugal Casting
• Slide 139
• Centrifugal Casting
• Semi centrifugal Casting Process
• Slide 142
• Squeeze Casting
• Squeeze Casting
• Directional Solidification
• Single Crystal Casting of Turbines blades
• Single Crystal-Casting
• Melt Spinning
• Types of Melting Furnaces
• Lost Foam Casting
• Slide 151
• Slide 152
• Slide 153
• Slide 154
• Casting Defects - Porosity
• Casting Defects
• Slide 157
• Slide 158
• Slide 159
• Defects - Hot Tears
• Chills
• Design Rules Summary
• Slide 163
• Slide 164