Diapositiva 1

Casting of Metals and Alloys in 2000 and BeyondPresented toDr. N.C. UpadhyayAssociate ProfessorDept. of Metallurgical and Materials Engg. MNIT Jaipur

Presented byBhavanish Kumar Singh2012umt1402 B.Tech 4th YearDept. of Metallurgical and Materials Engineering

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Introduction

Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify.Advantages of casting1.Lowest cost method for manufacturing complex parts2.Reduces part count, weight, machining3.Reduces manufacturing space and inventory

Vacancies in the market1.Shortage of Skilled Technicians and competition because of globalization2.Requirement of more capable computer programs.3.Much of development in metal casting driven by solidification simulation packages.

Benefits of Computer Simulation Packages Automotive and aircraft industriesHigh degree of accuracyPredict the cast structure depending on cast parametersStatic and dynamic properties of the component can be predicted and compared with designers requirement Identify Casting Defects and so Non Destructive 6.Evaluation is done.7.Reduce life cycle costs of casting8.Minimized machining

Metal Shaping RoutesFinal properties of a casting greatly influenced by casting and moulding process alone .Major contribution to casting industry new developments given by Automotive industry.For e.g.1.Aluminum Suspension parts used in steering as its first production application2.Dashboard in Plymouth Prowler is die cast Mg alloy

Car Steering Suspension parts

Plymouth Prowler

Squeeze casting, also known as liquid metal forging, is a combination of casting and forging process. Both ferrous and non-ferrous materials can be produced using this method. Slow Ingate velocities with minimal turbulence and slow application(50-100mm/min) of high pressures (35-105 MPa)

Low porosityHigh integrityHeat treatable Two typesDirect application of pressure to the piston, which contacts the molten metal. Indirect the melt is forced from a system of runners to the mould cavity gate.

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Lost-foam casting (LFC) or Evaporative-pattern casting process i.e. Similar to investment casting except foam is used for the pattern instead of wax. 1.Advantage of the low boiling point of foam by removing the need to melt the wax out of the mold.2.Applications: Making truck, pipe, and automotive high volumecomponentsCommonly cast metals include cast irons, aluminium alloys. steels, and nickel alloys;less frequently stainless steels and copper alloys are also cast.

Shell MouldingShell mold casting or shell molding is a metal casting process in manufacturing industry in which the mold is a thin hardened shell of sand and thermosetting resin binder, backed up by some other material. Shell mold casting is particularly suitable for steel castings The sand mixture is poured or blown over the hot casting pattern. Reaction of the thermosetting resin with the hot metal pattern, a thin shell forms on the surface of the pattern.

The excess "loose" sand is then removed, leaving the shell and pattern. The shell and pattern are then placed in an oven for a short period of time, (minutes),. the hardened shell is separated from the casting pattern by way of ejector pins Two of these hardened shells, each representing half the mold for the casting, are assembled together either by gluing or clamping.

Counter Gravity CastingProduction PartsCast Stainless Steel ExhaustCast Steel Contoured Camshaft, Brake Rotor, Primary Pump Body, Crank Case for Air compressors, Bearing case for Industrial machinery

Differential pressure sand casting: Alternative to conventional gravity casting.Create differential pressure by evacuating the mould cavity, in contrast to most processes, Relatively SimpleCan be used for small batch melting operations Ex. Light alloys aerospace foundries.

Flaskless vertically parted green sand moulding

In flaskless moulding, no flask is used for supporting the moulding sand; the mould itself is made sufficiently strong to bear the liquid metal pressure.Two types:1.Vertical Parting Flaskless Moulding (DISAMATIC) 2.Horizontal Parting Flaskless Moulding

(Website: www.ijrdet.com (ISSN 2347 - 6435 (Online) Volume 2, Issue 4, April 2014) )Fig: Vertical Parting Flaskless Moulding (DISAMATIC)

Advantages of Flaskless Moulding It does not use flasks, which avoids a need of their transporting, storing and maintaining. No repair expenditure on flasks By adopting aeration sand filling technology, energy saving and noise reduction have been achieved Stable pattern draw is secured by automatic pattern spray Minimize turbulence and porosity in casting

Freeze Cast Process(FCP): By subjecting an aqueous slurry to a directional temperature gradient crystals will nucleate on one side of the slurry Steps:Making a solid master pattern by traditional machining and materials, or by any one of the state of the art pattern generating methods such as stereo lithography, laminated object manufacturing(LOM), selective laser sintering(SLS)2. Making rubber moulds using silicon rubber or urethane polysulfide, which are available in liquid form, from the master pattern.3. Pouring water containing additives into rubber mould and freeze the water4. Stripping the ice pattern5. Repeated stripping of the ice pattern into refrigerated ethyl (alcohol) silicate slurry

6. Exposing the shell containing ice pattern to slow heating pouring out water and then firing of shell.7. Pouring of molten metal into the shell solidify to get final casting.

Metals and alloys like gray iron, ductile iron, steel, aluminium and copper.

Significance:Near net shape castings, fast pattern making, pattern is not burned out

Not Suitable for large casting, flat parts with thin walls.

Semisolid ProcessingThixomolding is one step process for making near net shape castingsE.g. Mostly Magnesium and Zinc alloy parts. Electronics and communication, Automotive shift cams, throttle bodies, etc.

Notebook computer casesDigital camera bodies

Hand held power tools

Hot Isostatic Pressing (HIP)Components are subjected to the simultaneous application of heat and high pressure in an inert gas medium.Pressure by gas makes it Isostatic and uniform and leading to plastic state collapses any left voids.Use as precision castings.Complex shapes can be formed without expensive tooling.

Plasma Cupola

Plasma Cupola Pilot Plant at General MotorsFirst used for the production of Cast iron engine blocks.Cost effective melting in difficult to melt raw materials such as Loose cast iron borings and production of world class automotive castingsMelting and Melt Treatments

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Mg HeatingHumid conditions must be avoided and mixing gases must contain less than 0.1 %moisture.SF6 base gases and SO2 air mixtures are used as oxide barrier for melting Mg and its alloys but are very harmful for environment even in ppm

Ultrasonic degassing of Al melt

Water vapour and Al2O3 reacts and H2 evolves causing microstructure degradation and embrittlementSo Ultrasonic (cavitational) degassing more effective than fluxes/argon/vacuum degassing in lowering the hydrogen content of Al melt.10% increase in tensile strength(UTS) and 80% more % elongationattained with combined vacuum and ultrasonic treatment.Produce non dendritic microstructure& very low H2content

Ultrasonic vibrationAl Melt

Running, Gating and RiseringDesigned to introduce clean, dross- free, tranquil metal into the mould cavity and continue to feed liquid metal to casting as it solidifies.Gating system should ensure non-turbulent pouring at lowest velocityDistance between sprue and ingates should be maximized to allow time for dross to float out and trapped at top surface of the runner bar.American Foundrymens Society, USA found a software simulation package called AFS 3D solid model system that provides data related to casting quality without manufacturing the casting.Finite Difference Method (FDM) used to find energy during pouring, including mixing and turbulence during mixing.

ToolingComputer Tomography (CT) for reverse engineering and Rapid proto typing (RP) techniques are used for producing patterns for tools.Rapid pattern making gives the foundry new possibilities for the fast production of metal prototypes and series parts.Rapid tooling for sand casting can be made using Computer numerically Controlled (CNC) machining of non-ferrous pattern materials By using patterns created directly in rapid prototyping machines.

Development and usage of New Alloys and materialsTodays NeedCost effective in global economyIntegrated approach incorporating materials scienceProcess technology Design and Performance of the product is must. For e.g.. Use of New high grade H13 tool steel for shot sleeves and other die components of aluminium pressure die casting machine has yielded a 10-20 % enhanced die life and huge savings.Protein based ,water soluble binder for sand casting has been developed as also environment friendly.Used or unused cores can be placed in a water bath and the resin can be reclaimed.Lower cost Aluminium metal matrix composites (AMMC) expanded its market potential e.g. in automobiles parts like brake rotors, drums, calipers and pads back plated, Cylinder liners, Steering links, Clutch Plates, Structural Oil Pans, Brackets, Suspension arms, etc.

Reuse, Recycling And Eco friendliness Increasing pressure to improve its environmental performance to meet sustainable development Reuse of foundry by-products Cryogenic sand reclamation could be a potential route of the future (liquid N2 is used to reduce sand temperature to as low as -80 C which separates sand from other valuable constituents)Recycled aluminium for making automotive Al castings in US was around 63% in 1999.Process control, major tool for waste reduction generally a little or no capital cost and quality improvement.Foundries are most polluting industry

ConclusionFoundries of tomorrow have to exploreNear net shape processConcept of cast-to-fill and HIP-to-density for critical componentsConsortium/ co-operative approach towards R&DBeneficial reuse optionsUse newer tools such as computer simulation, expert system, neural net work, etc.Reduction of production cost by better controlConverting into an ecofriendly industry.

References

Casting of Metals and Alloys in 2000 and BeyondR.M Pillai, B.C. Pai and K.G. SatyanarayanaRegional Research Laboratory, Council of Scientific and Industrial Research, Thiruvananthapuram-695019