c3 Metal Alloys

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CHAPTER 3:CHAPTER 3:METAL ALLOYSMETAL ALLOYS


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Objective

At the end of the chapter, the students should be able to: Name four different types of steels and for each; cite

compositional differences, distinctive properties and typical uses.

Name the four cast iron types and for each; describe itsmicrostructure and note its general mechanical characteristics.

Name six different types of nonferrous alloys and for each; cite itsdistinctive physical and mechanical characteristics. In addition,list at least three typical applications.

State the purposes of and describe procedures for the followingheat treatments; process annealing, stress relief annealing,normalizing, full annealing and spheroidizing.


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metal

ferrousferrous non-ferrousnon-ferrous

steel cast iron

carbon steel

alloy steel

stainless steel

tool steel

gray cast iron

white cast iron

malleable iron

copper (Cu)

aluminium (Al)

nickel (Ni)

titanium (Ti)

low-carbon steel

medium-carbonsteel

high-carbonsteel

ductile iron magnesium (Mg)

ferritic

martensitic

austenitic

Lead (Pb)

super alloyssuper alloys

HSLAHSLA


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WHAT IS METAL?WHAT IS METAL?

Metal is referring strictly to puremetal, which are also chemicalelement.Ex: Ferrum, Cuprum


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WHAT IS ALLOY?WHAT IS ALLOY?

An alloy is a metal consisting of amix of two or more elements.


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Ferrous alloyFerrous alloy

The term ferrous alloy is used for those alloys that containiron as the main constituent

Their widespread use is accounted for by three factors: Iron-containing compounds exist in abundant

quantities within earths crust Metallic iron and steel alloys may be produced using

relatively economical extraction, refining, alloying andfabrication techniques

Ferrous alloys are extremely versatile

Disadvantage of many ferrous alloys: easy to corrode.


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How is iron processed tomake steel? Iron OreTo make iron, you start with iron ore .

Iron ore is simply rock that happensto contain a high concentration of iron.


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All of the iron ores contain iron combined with oxygen. To make ironfrom iron ore, you need to eliminate the oxygen to create pure iron.

The most primitive facility used to refine iron from iron ore iscalled a bloomery . In a bloomery, you burn charcoal with ironore and a good supply of oxygen (provided by a bellows orblower). Charcoal is essentially pure carbon. The carbon

combines with oxygen to create carbon dioxide and carbonmonoxide (releasing lots of heat in the process). Carbon andcarbon monoxide combine with the oxygen in the iron ore andcarry it away, leaving iron metal.

In a bloomery, the fire does not get hot enough to melt the ironcompletely, so you are left with a spongy mass containing ironand silicates from the ore (the bloom). By heating andhammering the bloom, the glassy silicates mix into the ironmetal to create wrought iron. Wrought iron is tough and easy towork, making it perfect for creating tools in a blacksmith shop.

Steel has made!!!!
http://www.howstuffworks.com/question43.htmhttp://www.howstuffworks.com/framed.htm?parent=iron.htm&url=http://www.unc.edu/courses/rometech/public/content/mines_and_iron/Roger_Smith/roger/BLOOM4.htm


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The more advanced way to smelt iron is in a blast furnace . A blastfurnace is charged with iron ore, charcoal or coke (coke ischarcoal made from coal) and limestone (CaCO3). Huge quantitiesof air blast in at the bottom of the furnace. The calcium in thelimestone combines with the silicates to form slag. At the bottomof the blast furnace, liquid iron collects along with a layer of slagon top. Periodically, you let the liquid iron flow out and cool.

The liquid iron typically flows into a channel and indentations in a

bed of sand. Once it cools, this metal is known as pig iron. Pig iron contains 4 percent to 5 percent carbon and is so hard andbrittle that it is almost useless.

You melt it, mix it with slag and hammer it to eliminate most of the carbon (down to 0.3 percent) and create wrought iron.Wrought iron is the stuff a blacksmith works with to create tools,horseshoes and so on. When you heat wrought iron, it ismalleable, bendable, weldable and very easy to work with.

You create steel.
http://www.steel.org/AM/Template.cfm?Section=Articles3&TEMPLATE=/CM/ContentDisplay.cfm&CONTENTID=12305


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SteelSteel

Steel is a metal alloy whose major component isiron, with carbon being the primary alloyingmaterial.

Containing of carbon less than 2.0 wt%. Steel can be grouped into 4 categories:

carbon steelalloy steelstainless steeltool steel


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Carbon Steel

most popular commercial steels Carbon as the principal alloying element with only small

amount of other elements less than 3% alloying elements

Plain carbon steels may include small amounts of theseelements as impurities: Manganese (up to 1.65%) Silicon (up to 0.60%) Copper (up to 0.60%) Phosphorus Sulphur Silicon


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Carbon Steel

Classified into 3 groupslow-carbon steelmedium-carbon steelhigh-carbon steel

carbon; strength of the metal But, higher amount of carbon also

reduce the ductility and toughness of metal

AISI designation: 10 XX


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Carbon steel:Low carbon steel

contain less than 0.3 wt% C unresponsive to heat treatments Properties: soft and weak but have

outstanding ductility and toughness;machinable, weldable and the leastexpensive to produce.

Typical applications include automobilecomponents, structural shapes, nails, pipeand railroad rails.

also called mild steel AISI designation: 1005 to 1030


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Low-carbon steel:High Strength Low-Alloy

(HSLA) steels Another group of low-carbon steels contain other alloying elements such as copper,

vanadium, nickel and molybdenum as high as 10 wt%

higher strength than the plain low-carbon steels Properties: ductile, formable, machinable and more

resistant to corrosion than plain carbon steels at

normal atmosphere. Typical applications where structural strength iscritical bridges, support columns in high-risebuilding and pressure vessels.


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Carbon steel:Medium carbon steel

contain between 0.3 wt% and 0.5 wt% C. heat-treatable

Properties: surface hardness, strength,stronger than low-carbon steels, low ductilityand low toughness.

Applications include railway wheels andtracks, to make engine parts (gear,crankshafts) and machinery components.

AISI designation: 1030 1052


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Carbon Steel:High-carbon steel

contain more than 0.5 wt% C, Properties: the hardest strongest and yet

least ductile of the carbon steels.

Typical applications: cutting tools and diesfor forming and shaping materials, as wellas razors, springs, knives and other wear-resistant parts

AISI designation: 1055 - 1095


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Alloy steel Alloy steel is a combination of two or more

elements, in addition to carbon in order tomodify the properties of the steel

AISI designation:

AISI-SAE designation

13XX Mn alloys

20XX Ni31XX Ni-Cr40XX Mo41XX Cr-Mo50XX Cr


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Manganese (Mn): improves the strength and hardness of steel. It is used in gears, auto parts, and impact-resistingtools.

Chromium (Cr): improves hardenability, hardness and wearresistance. It is used in ball bearings and cutlery.

Molybdenum (Mo): improves toughness, creep strength,restrict grain growth and wear resistance. It is used in heavy-duty bolts, gears, and transmission shafts.

Nickel (Ni): improves strength, toughness, restrict graingrowth and impact resistance. It is used in axle shafts,propeller shafts, and measuring devices.

Vanadium (V): forms carbides that improve strength,toughness, restrict grain growth and wear resistance. It isused in heat-treated forgings and heavy-duty springs.

These elements can have aneffect on:


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contain more than 15% chromium resist corrosion because the chromium

reacts with oxygen in the air to develop athin film of chromium oxide

the thin film protects the metal from rust. combination of strength and ductility.

There are three major groups:ferritic stainless steelmartensitic stainless steel

austenitic stainless steel

Stainless steel:


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Types of Stainless Steels:Ferritic stainless steel

low cost stainless steel. Properties: magnetic and easy to weld,

poor ductility.

not heat treatable. commonly used in automotive exhaustcomponents, kitchen utensils andcombustion chambers


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Types of Stainless Steels:Martensitic stainless steel

more expensive Properties: magnetic, stronger than ferritic stainless steel

capable of being heat treated. primarily used in cutlery, surgical instruments and jet

engine parts


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Types of Stainless Steels:Austenitic stainless steel

the most corrosion resistant type of stainless steel because of the high chromium contents and also the nickel additions

produced in the largest quantities.

non-magnetic cannot been harden by heat treatment the surface of this metal can be polished to a mirror finish,

which makes the steel visually attractive. expensive

used to make food processing and chemical equipment.


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Tool Steel

contain high levels of carbon. alloying elements are added to emphasize

and enhance various properties of thesteel.

most tool steels receive heat treatment to bring about specific properties.

have been designed to combine highstrength, hardness, wear resistance andtoughness under impact.


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Tool steel:Types of Tool Steels

7 groups of tool steels arecategorized according to theirintended use and specificproperties.

Each tool steel grade has amatching letter designation


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High-speed tool steels contain significant percentages of either tungsten (type T) or molybdenum (type M). They providetoughness required for cutting tools,

Hot-work tool steels (type H) often contain additionalchromium, tungsten, or molybdenum. They are used to makedies for forging metal at high temperatures.

Cold-work tool steels include air-hardening , oil-hardening,and high-carbon high-chromium types. High-carbon high-chromium tool steels (type D) provide added wear-

resistance and toughness for forming tools. Oil-hardeningtool steels (type O) are often used in tools that requiredimensional accuracy such as structural parts, jigs, andbushings. The relatively inexpensive air-hardening toolsteels (type A) are used to make punches for metal andmoulds for plastic that require high hardness.



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Shock-resisting tool steels (type S) demonstrate hightoughness, but less wear resistance for use in pneumaticchisels and heavy-duty punches.

Mould steels (type P) contain low amounts of carbon andare generally used to create moulds for plastics.

Special-purpose tool steels (types L and F) exist toprovide low cost alternatives that exhibit certain limitedproperties for dies or structural parts.

Water-hardening tool steels (type W) offer varyinghardness and wear resistance for some cuttingapplications.



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NAMENAME PROPERTIESPROPERTIES USED FOR USED FOR

High-speed tool steels contain tungsten (type T) or molybdenum (type M)

Tough

cutting tools

Hot-work tool steels(type H)

contain chromium, tungsten, or molybdenum

dies for forging metal at hightemperatures

Air-hardening tool steels(type A)

cold-work tool steels high hardness

punches for metal and moulds for plastic that require high hardness.

Oil-hardening tool steels(type O)

cold-work tool steels structural parts, jigs and bushings.

High-carbon high-chromiumtool steels(type D)

cold-work tool steels wear-resistance and toughness

for forming tools.

Shock-resisting tool steels(type S)

high toughness less wear resistance

pneumatic chisels and heavy-dutypunches

Mould steels(type P)

contain low amounts of carbon moulds for plastics

Special-purpose tool steels(types L and F)

low cost alternatives exhibitcertain limited properties

dies or structural parts.

Water-hardening tool steels(type W)

varying hardness wear resistance

cutting tools

D ig ti f St l


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Designation of Steels:Classification of Plain CarbonSteels

11XX steels are freemachining steels thatcontain extra sulfur

12XX steels contain extrasulfur and phosphorus

15XX steels containmanganese


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Designation of Steels:Classification of Alloy Steels

the last two digits describecarbon content of a steel,the first two digits identifythe family of the steel.


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Classification of Alloy Steels

E is used to indicatesteels produced in anelectric arc furnace.

H indicates thathardenability is a specialproperty of the metal.

B indicates the presenceof boron,

L indicates the presenceof lead.


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Tool steel grades

combine this letter withone or two numbers.


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C a s t ir o n

C a

s t ir o n

Cast irons are ferrous metals that contain high amountsof carbon (more than 2 wt%) in the form of flakes.

contain more than 2 wt% carbon, 1 wt% to 3 wt% silicon Silicon encourages the formation of graphite flakes

which determine the properties of the cast iron directly cast into their desired shape Properties:

excellent compressive strength good wear resistance effectively dampens sound and vibration

Cast irons are divided into 4 major groups: Gray cast irons White cast irons Ductile cast irons Malleable cast irons


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Gray cast irons

the most common cast irons. Properties: excellent compression strength high resistance to wear,

very poor ductility, weak and brittle. contains from 2.11wt% to about 4 wt% C and

from 1 wt% to 3 wt% Si respectively. Silicon facilitates the casting of the metal and

encourages the formation of graphite flakes. Typical applications are small cylinder blocks,

cylinder heads, pistons, diesel engine castingsclutch plates.


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White cast irons contain less than 1 wt% Silicon and rapid cooling

rates and are produced in smaller quantities. Most of the carbon exists as cementite instead

of graphite. A fracture surface of this alloy has a white

appreance Properties:

excellent wear resistance good tensile strength,

extremely hard very brittle.

Typical applications: rollers in rolling mills andrailway brake shoes .


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Ductile cast irons

a similar composition to grey cast iron chemically treated to create tiny graphite

sphere-like particles instead of flakes byadding a small amount of magnesiumand/or cerium,

Mg & Ce have improved its strength andductility approaching those of steel.

Typical applications for this material includevalves, crankshafts and gears.


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Malleable cast irons similar composition to white cast iron produced in smaller quantities. formed by annealing of white cast iron in

order to change its internal structure

Properties: high strength ductility malleability.

Typical applications for this material includetransmission gears, pipe fitting, valve partsfor marine and other heavy-duty services.


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STEEL VS. CASTIRON

steel is an alloy of iron and maximum2.1% carbon.

steel may containsmall amounts of silicon, but it is not akey element of themetal

steel products arefurther formed andshaped through hotworking and coldworking methods

good strength (the

strength increaseswith the contents of

cast iron refers to agroup of iron-basedalloys containing morethan 2% carbon

all cast irons containanywhere from 1% to3% silicon

cast irons are directlycast into their desiredshape

good strengthproperties, goodresistance to wear,good capacity to


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No nf e rro u

s a llo y :

No nf e rr o u

s a ll o y :

The term non-ferrous alloy is used forthose alloys which do not have iron astheir base element


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Nonferrous alloy:Copper an excellent conductor, malleable and

easily cast and shaped. Copper and its alloys may be classified in

many different ways. One classification is:Copper (99% Copper,small amounts of phosphorus, lead, nickel)Brasses (copper, zinc, lead)

Bronze (copper, tin, silicon, aluminum)


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Nonferrous alloy:Aluminium

Aluminum and its alloys are characterized by a relativelylow densityhigh electricalthermal conductivities

a resistance to corrosion.high ductility.Mechanical strength of aluminum can be enhanced bycold work and by alloying. However, both processes tendto diminish the resistance to corrosion

Principal alloying elements are copper, magnesium,silicon, manganese and zinc

N f ll


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Nickel is a hard, malleable, silvery white metal Nickel is actually very similar to iron and steel, but it is much

more corrosive resistant.

Certain alloys made of approximately 67% nickel and 30%copper are some of the most corrosion resistant alloys.

Nickel is also used as a plating metal for plain-carbon steels Nickel + chromium : resistant to high temperature oxidation

and corrosion.

Nickel + manganese: resistant to oxidation and reduction atelevated temperatures.

Nickel + cobalt provides high heat resistance which makes ituseful in chemical industry.

Nonferrous alloy:Nickel

N f ll


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Pure titanium: strong + lightweight, lowdensity, a high melting point (3035F) and anelastic modulus of 15.5 x 10 6 psi.

Titanium alloys: extremely strong; excellentstrength-to-weight ratio, low coefficient of thermal expansion, highly ductile and easilymachines.

The corrosion resistance of titanium alloys at

room temperature is unusually high, virtuallyimmune to air, marine and a variety of industrial environments.

Used in airplane structures, space vehicles andchemical industries.

Nonferrous alloy:Titanium


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Nonferrous alloy:Magnesium

Magnesium is the lightest commerciallyavailable metal, and consequently it almostalways appears in the form of an alloy.

Magnesium has a hexagonal close-packed

(HCP) crystal structure This makes the metal very brittle and difficult

to form. Advantages of magnesium alloys: lightweight,

suffer from poor wear resistance and creepstrength, very easy to machine.

Race cars often use wheels made frommagnesium alloys.


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Nonferrous alloy: Lead and Tin

PbPb Lead is a bluish-white metal

that is very soft, ductileand a relatively poor

conductor of electricity. Lead also resists corrosion,but it tarnishes whenexposed to air.

Common uses of leadinclude ammunition, x-rayshielding, and sound-dampening applications .

SnSn Tin is a soft, ductile

metal with poorstrength.

It is also used as aplating metal and themost common exampleis the tin can.

one of the major

ingredients in themetal that is used tomake bells.

alloyed with copper tomake bronze.


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S u

p e r a llo y s

S u p e r a llo y s Super alloys straddle the fence betweenferrous and nonferrous metals .

They are categorized according to the metalsmain ingredient

Most super alloys are based on iron, nickel, orcobalt, often with three or more metals in themix.

exhibit superior strength, corrosion resistance,and creep resistance at elevated temperatures

around 2000F (1090C). used to make jet engines, steam turbines, and

parts for nuclear reactors


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c3 Metal Alloys

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