METALS AND ITS ALLOYSMETALS AND ITS ALLOYS

CLASSIFICATION OF METALSCLASSIFICATION OF METALS

FERROUS METALS / ALLOYSFERROUS METALS / ALLOYS

NONFERROUS METALS / ALLOYSNONFERROUS METALS / ALLOYS

CLASSIFICATION OF METALS CLASSIFICATION OF METALS AND METAL ALLOYSAND METAL ALLOYS

FerrousFerrous Nonferrous Nonferrous

Cu & its AlloysCu & its Alloys SteelsSteels Cast Iron Cast Iron Al & its AlloysAl & its Alloys

Mg & its AlloysMg & its AlloysTi & its AlloysTi & its Alloys

The Refractory MetalsThe Refractory Metals The SuperalloysThe Superalloys The Noble MetalsThe Noble Metals

Miscellaneous Nonferrous AlloysMiscellaneous Nonferrous Alloys

FERROUS ALLOYSFERROUS ALLOYS

Those of which IRON ( Fe ) is the prime Those of which IRON ( Fe ) is the prime constituent.constituent.

Are produced in larger quantities than Are produced in larger quantities than any other metal type.any other metal type.

Considered as an especially important Considered as an especially important engineering construction material.engineering construction material.

Ferrous metals are iron-base alloys Ferrous metals are iron-base alloys with small percentage of C and other with small percentage of C and other elements added to achieve desired elements added to achieve desired properties.properties.

Include all forms of iron and steel Include all forms of iron and steel alloys.alloys.

Few examples include wrought iron, Few examples include wrought iron, cast iron, carbon steels, alloy steels cast iron, carbon steels, alloy steels and tool steels.and tool steels.

Reasons for the widespread use Reasons for the widespread use of ferrous alloysof ferrous alloys

(1)(1) iron-containing compounds exist in iron-containing compounds exist in abundant quantities within the abundant quantities within the earth’s crust;earth’s crust;

(2)(2) Metallic iron and steel alloys maybe Metallic iron and steel alloys maybe produced using relatively produced using relatively economical process;economical process;

(3)(3) Ferrous alloys are extremely Ferrous alloys are extremely versatile in terms of mechanical versatile in terms of mechanical and physical properties.and physical properties.

Principal Disadvantage of Principal Disadvantage of Ferrous AlloysFerrous Alloys

… … its susceptibility to CORROSION.its susceptibility to CORROSION.

Ferrous Metals & AlloysFerrous Metals & Alloys

Steel Cast IronsSteel Cast Irons

Low alloy High AlloyLow alloy High Alloy Gray cast ironGray cast iron

Low-CLow-C Ductile Ductile ( nodular ) iron( nodular ) iron

PlainPlainHigh-strength, High-strength, White IronWhite Iron

Medium-CMedium-CPlainPlain MalleableMalleableHeat treatable Heat treatable

High-CHigh-CPlainPlainToolTool Tool StainlessTool Stainless

Ferrous Metal AlloysFerrous Metal Alloys

SteelSteelLow Alloy SteelLow Alloy Steel

Low Carbon SteelLow Carbon SteelMedium Carbon SteelMedium Carbon SteelHigh Carbon SteelHigh Carbon Steel

High Alloy SteelHigh Alloy SteelStainless SteelsStainless SteelsTool SteelsTool Steels

Cast IronCast IronGray Cast IronGray Cast IronDuctile (nodular)Ductile (nodular)White IronWhite IronMalleable IronMalleable Iron

Nonferrous AlloysNonferrous Alloys

Copper and its AlloysCopper and its AlloysAluminum and its AlloysAluminum and its AlloysMagnesium and its AlloysMagnesium and its AlloysTitanium and its AlloysTitanium and its AlloysThe Refractory MetalsThe Refractory MetalsThe Super AlloysThe Super AlloysThe Noble MetalsThe Noble MetalsMiscellaneous Nonferrous AlloysMiscellaneous Nonferrous Alloys

HEMATITEHEMATITE

COMMON IRON ORESCOMMON IRON ORES

HematiteHematite - Fe2O3 - 70 percent iron - Fe2O3 - 70 percent iron MagnetiteMagnetite - Fe3O4 - 72 percent iron - Fe3O4 - 72 percent iron LimoniteLimonite - Fe2O3 + H2O - 50 percent to 66 percent iron - Fe2O3 + H2O - 50 percent to 66 percent iron SideriteSiderite - FeCO3 - 48 percent iron - FeCO3 - 48 percent iron

Usually, you find these minerals mixed into rocks Usually, you find these minerals mixed into rocks containing silica. Iron Orecontaining silica. Iron Ore

To make iron, you start with To make iron, you start with iron oreiron ore. Iron ore is simply . Iron ore is simply rock that happens to contain a high concentration of iron.rock that happens to contain a high concentration of iron.

IRONIRON

Pure iron rarely exists outside of the Pure iron rarely exists outside of the laboratory.laboratory.

Iron is produced by reducing iron ore Iron is produced by reducing iron ore to pig iron through the use of a blast to pig iron through the use of a blast furnace. furnace.

From PIG IRON, many other types of From PIG IRON, many other types of iron and steel are produced by adding iron and steel are produced by adding or removing of carbon and alloying or removing of carbon and alloying metals.metals.

PIG IRONPIG IRON

pig iron is composed of about 93% iron, pig iron is composed of about 93% iron, from 3% - 5% carbon, and various from 3% - 5% carbon, and various amounts of other elements.amounts of other elements.

Pig iron is comparatively weak and brittle, Pig iron is comparatively weak and brittle, therefore it has a limited use.therefore it has a limited use.

About 90% produced pig iron is refined to About 90% produced pig iron is refined to produce steel.produce steel.

Cast iron pipe and some fittings and Cast iron pipe and some fittings and valves are manufactured from pig iron.valves are manufactured from pig iron.

STEELSTEEL

An An iron-carboniron-carbon ( Fe-C ) alloy that may ( Fe-C ) alloy that may contain appreciable concentrations contain appreciable concentrations of other alloying elements; of other alloying elements;

there are thousands of alloys that there are thousands of alloys that have different compositions and/or have different compositions and/or heat treatments.heat treatments.

Mechanical properties are sensitive Mechanical properties are sensitive to the content of carbon, which is to the content of carbon, which is normally less than 1.0%wt.normally less than 1.0%wt.

Types of SteelsTypes of Steels

(1) Carbon Steels(1) Carbon Steels

(2) Tool Steels(2) Tool Steels

CARBON STEELSCARBON STEELS

Contain only residual concentrations Contain only residual concentrations of impurities other than C and a little of impurities other than C and a little manganese.manganese.

Type of steel when no minimum Type of steel when no minimum content is specified or required for content is specified or required for Cr, Co, Nb, Mo, Ni, Ti, W, V, Zr or any Cr, Co, Nb, Mo, Ni, Ti, W, V, Zr or any other element to be added to obtain other element to be added to obtain a desired alloying effect ; when C a desired alloying effect ; when C content not exceed the minimum of content not exceed the minimum of 0.40%.0.40%.

ALLOY STEELSALLOY STEELS

Type of steel where more alloying Type of steel where more alloying elements are intentionally added in elements are intentionally added in specific concentrations specific concentrations

TYPES OF CARBON STEELSTYPES OF CARBON STEELS

1.1. Plain CarbonPlain Carbon

2.2. Low Carbon Steel ( up to 0.25% C )Low Carbon Steel ( up to 0.25% C )

3.3. Medium Carbon Steel (0.25%-Medium Carbon Steel (0.25%-0.45%C )0.45%C )

4.4. High Carbon Steel (0.45%-1.50%C )High Carbon Steel (0.45%-1.50%C )

INGOT IRONINGOT IRON

Is commercially pure iron ( 99.85% Is commercially pure iron ( 99.85% Fe )Fe )

Easily formed and possesses good Easily formed and possesses good ductility and corrosion resistance.ductility and corrosion resistance.

Comparable to low carbon steel in its Comparable to low carbon steel in its chemical analysis and properties.chemical analysis and properties.

Low Carbon steel has about 0.06% Low Carbon steel has about 0.06% more C than ingot iron.more C than ingot iron.

C in iron is considered as an impurity C in iron is considered as an impurity but in steel, C is an alloying element.but in steel, C is an alloying element.

CAST IRONCAST IRON

Any iron containing greater than 2% Any iron containing greater than 2% C.C.

Has high compressive strength and Has high compressive strength and good wear resistance, however it good wear resistance, however it lacks ductility, malleability and lacks ductility, malleability and impact strength. impact strength.

WROUGHT IRONWROUGHT IRON

Is made from pig iron with some slag Is made from pig iron with some slag mixed to it during manufacture.mixed to it during manufacture.

Is almost pure iron, and the presence of Is almost pure iron, and the presence of slag enables it to resist corrosion and slag enables it to resist corrosion and oxidation.oxidation.

Is comparable to medium carbon steel in Is comparable to medium carbon steel in chemical analysis.chemical analysis.

Can be gas & arc welded, machined, Can be gas & arc welded, machined, plated and easily formed, however it has plated and easily formed, however it has low hardness and low fatigue strength. low hardness and low fatigue strength.

PLAIN CARBON STEELPLAIN CARBON STEEL

Although called plane C, actually Although called plane C, actually the iron and carbon alloy contains the iron and carbon alloy contains manganese, phosphorus, sulfur and manganese, phosphorus, sulfur and silicon.silicon.

Strength is primarily a function of its Strength is primarily a function of its C content, increasing with C content, increasing with increasing C.increasing C.

However, ductility decreases as C However, ductility decreases as C content increases.content increases.

Disadvantages of Plain C SteelsDisadvantages of Plain C Steels

Low hardenabilityLow hardenability

Its physical properties are decreased Its physical properties are decreased by both high and low temperatures.by both high and low temperatures.

Subject to corrosion in most Subject to corrosion in most environments.environments.

LOW CARBON STEELLOW CARBON STEEL

Contains up to 0.3% carbonContains up to 0.3% carbonProduced in greatest quantities among all Produced in greatest quantities among all

the different types of steels.the different types of steels.The largest category of this class of steel The largest category of this class of steel

is flat-rolled products ( in sheet or strip ), is flat-rolled products ( in sheet or strip ), usually in the cold-rolled or annealed usually in the cold-rolled or annealed condition.condition.

Unresponsive to heat treatment, that is Unresponsive to heat treatment, that is why, strengthening is accomplished by why, strengthening is accomplished by cold work.cold work.

Microstructures : pearlite and ferriteMicrostructures : pearlite and ferrite

PROPERTIES OF LOW C STEELPROPERTIES OF LOW C STEEL

Not heat treatable; strengthening by Not heat treatable; strengthening by cold work process only.cold work process only.

Relatively soft and weak ( pearlitic & Relatively soft and weak ( pearlitic & ferritic microstructure ) but have ferritic microstructure ) but have outstanding ductility and toughness.outstanding ductility and toughness.

Machinable, weldableMachinable, weldableThe least expensive to produce The least expensive to produce

among all steels. among all steels.

Advantages of Low-C SteelsAdvantages of Low-C Steels

Possess good formabilityPossess good formability Possess good weldability, best of all Possess good weldability, best of all

metals. NOTE: as C % increases, there is a metals. NOTE: as C % increases, there is a tendency for the metal to harden & crack.tendency for the metal to harden & crack.

Lowest costLowest cost Rated 55-60% machinability ( American Rated 55-60% machinability ( American

Institute of Iron and Steel AISI rating Institute of Iron and Steel AISI rating compares ability to machine with 100% compares ability to machine with 100% basis).basis).

APPLICATIONSAPPLICATIONS

Automobile body panels, tin plate and wire Automobile body panels, tin plate and wire products.products.

For rolled steel structural plates and sections, For rolled steel structural plates and sections, the C content may be increased to approx. the C content may be increased to approx. 0.30%, w/ higher Mn content up to 1.5%. 0.30%, w/ higher Mn content up to 1.5%. These materials may be used for stampings, These materials may be used for stampings, forgings, seamless tubes and boiler plates.forgings, seamless tubes and boiler plates.

0.1-0.2% C : chain, rivets, nails, wire, pipe 0.1-0.2% C : chain, rivets, nails, wire, pipe where very soft, plastic steel where very soft, plastic steel

is is needed.needed. 0.2- 0.3% C : structural steels, machine parts,0.2- 0.3% C : structural steels, machine parts, soft and tough steels soft and tough steels

Medium Carbon SteelMedium Carbon Steel

Have carbon concentrations betweenHave carbon concentrations between

0.3% - 0.80%0.3% - 0.80%

Maybe treated by austenitizing, Maybe treated by austenitizing, quenching and then tempering to quenching and then tempering to improve their mechanical properties.improve their mechanical properties.

Advantages of Medium-C SteelsAdvantages of Medium-C Steels

Machinability is 60-70%Machinability is 60-70%Good toughness and ductility.Good toughness and ductility.Fair formability.Fair formability.Extremely popular and have Extremely popular and have

numerous applications.numerous applications.Responds to heat treatment but is Responds to heat treatment but is

often used in the natural condition.often used in the natural condition.

A good balance of properties can be A good balance of properties can be found.found.

That is optimum C level where That is optimum C level where high high toughness and ductility ( of toughness and ductility ( of the low C the low C steels) is compromised steels) is compromised with the with the strength and hardness strength and hardness of the increased of the increased C.C.

APPLICATIONSAPPLICATIONS

0.3 – 0.4%C : 0.3 – 0.4%C : lead screws, gears, spindles, shafts and lead screws, gears, spindles, shafts and machine parts.machine parts.

0.4 – 0.5%C : 0.4 – 0.5%C : crankshafts, gears, axles, mandrels, tool crankshafts, gears, axles, mandrels, tool shanks and heat-treated machine partsshanks and heat-treated machine parts

0.6 – 0.7% C: 0.6 – 0.7% C: called “ low carbon tool steel” and is used called “ low carbon tool steel” and is used where a keen edge is not necessary but where a keen edge is not necessary but

where where shock strength is wanted: drop shock strength is wanted: drop hammer dies, hammer dies, set screws, screw set screws, screw driversdrivers

0.7 – 0.8%C : 0.7 – 0.8%C : tough and hard steel. Band saws, Hammers, tough and hard steel. Band saws, Hammers, wrenches, cable wire Etc.wrenches, cable wire Etc.

High Carbon SteelsHigh Carbon Steels

Normally having C content between Normally having C content between 0.8% to 1.4%0.8% to 1.4%

Are the hardest, strongest and yet Are the hardest, strongest and yet least ductile of the carbon steels.least ductile of the carbon steels.

Advantages of High-C SteelsAdvantages of High-C Steels

Hardness is highHardness is high

Wear resistance is highWear resistance is high

Fair formabilityFair formability

Capable of holding a sharp cutting Capable of holding a sharp cutting edgeedge

Disadvantages of High-C SteelsDisadvantages of High-C Steels

Toughness and formability and Toughness and formability and hardenability are quite low.hardenability are quite low.

Not recommended for welding.Not recommended for welding.

Usually joined by brazing with low Usually joined by brazing with low temperature silver alloy making it possible temperature silver alloy making it possible to repair or fabricate tool-steel parts to repair or fabricate tool-steel parts without affecting their heat-treated without affecting their heat-treated condition.condition.

APPLICATIONSAPPLICATIONS

Drills, saw, planer tools, embossing Drills, saw, planer tools, embossing dies, cutlery, cutting tools, concrete dies, cutlery, cutting tools, concrete drills, blacksmith tools, woodworking drills, blacksmith tools, woodworking tools.tools.

Tool and die steels are high C steels, Tool and die steels are high C steels, usually containing Cr, V, W and Mo. usually containing Cr, V, W and Mo. These alloying elements combine with These alloying elements combine with C to form very hard and wear resistant C to form very hard and wear resistant carbide compounds ( Crcarbide compounds ( Cr2323CC66, V, V44CC33, WC ), WC )

ALLOY STEELSALLOY STEELS

Steels that exceed the element limits of C Steels that exceed the element limits of C steels.steels.

Also includes steels that contain elements Also includes steels that contain elements

not found in C steels such as Ni, Cr ( up to not found in C steels such as Ni, Cr ( up to 3.99%), Co etc.3.99%), Co etc.Common alloying elements : Common alloying elements :

Ni, Cr, V, Si, and W.Ni, Cr, V, Si, and W.

One or more elements maybe added to the steel One or more elements maybe added to the steel during manufacturing process to produce the during manufacturing process to produce the desired characteristics.desired characteristics.

May be produced in structural May be produced in structural sections, sheets, plates and bars for sections, sheets, plates and bars for use in the “ as rolled” condition.use in the “ as rolled” condition.

Are used in structures where the Are used in structures where the strength of material is especially strength of material is especially important.important.

APPLICATIONSAPPLICATIONS

Bridge members, railroad cars, dump Bridge members, railroad cars, dump bodies, dozer blades and crane bodies, dozer blades and crane booms.booms.

COMMON ALLOY STEELSCOMMON ALLOY STEELS

1). Chromium steels 1). Chromium steels

2). Nickel Steels2). Nickel Steels

3). Chrome-vanadium steel3). Chrome-vanadium steel

4). Tungsten steel4). Tungsten steel

5). Molybdenum steel5). Molybdenum steel

6). Manganese steel 6). Manganese steel

Chromium SteelsChromium Steels Steel + Cr to improve hardening ability, Steel + Cr to improve hardening ability,

wear resistance and strength.wear resistance and strength. Contain between 0.20-0.75% CrContain between 0.20-0.75% Cr Some are highly resistant to wear that Some are highly resistant to wear that

they are used for the races and balls in they are used for the races and balls in antifriction bearings.antifriction bearings.

Are highly resistant to corrosion and to Are highly resistant to corrosion and to scale. scale.

Nickel SteelsNickel Steels Contain from 3.5%-5% Ni.Contain from 3.5%-5% Ni. Ni increases the strength and toughness of Ni increases the strength and toughness of

steel.steel. More than 5% Ni increases resistance to More than 5% Ni increases resistance to

corrosion and to scale.corrosion and to scale. Used in the manufacture of aircraft parts Used in the manufacture of aircraft parts

such as propellers and airframe support such as propellers and airframe support members.members.

Chrome Vanadium SteelChrome Vanadium Steel Has the maximum amount of strength with Has the maximum amount of strength with

the least amount of weight.the least amount of weight. Contains from 0.15% to 0.25% V, 0.6% to Contains from 0.15% to 0.25% V, 0.6% to

1.5% Cr and 0.1 to 0.6% C.1.5% Cr and 0.1 to 0.6% C. Is used in the manufacture of crankshafts, Is used in the manufacture of crankshafts,

gears, axles and other items that requires gears, axles and other items that requires high strength.high strength.

Also used in the manufacture of high Also used in the manufacture of high quality hand tools, such as wenches and quality hand tools, such as wenches and sockets. sockets.

Tungsten SteelTungsten Steel A special alloy that has the property of red A special alloy that has the property of red

hardness, that is, the ability to continue to hardness, that is, the ability to continue to cut after it becomes red hot.cut after it becomes red hot.

A good grade contains 13%-19% W, 1%-A good grade contains 13%-19% W, 1%-2% V, 3%-5% Cr, and 0.6 to 0.80% C.2% V, 3%-5% Cr, and 0.6 to 0.80% C.

Because this alloy is expensive to produce, Because this alloy is expensive to produce, its use is largely restricted to the its use is largely restricted to the manufacture of drills, lathe tools, milling manufacture of drills, lathe tools, milling cutters and similar cutting tools.cutters and similar cutting tools.

Molybdenum SteelMolybdenum Steel Used as an alloying agent for steel in Used as an alloying agent for steel in

combination with Cr and Ni.combination with Cr and Ni. Mo adds toughness to the steel.Mo adds toughness to the steel. Can be used in place of tungsten to make Can be used in place of tungsten to make

the cheaper grades of high speed steel the cheaper grades of high speed steel and in carbon molybdenum high pressure and in carbon molybdenum high pressure tubing. tubing.

STAINLESS STEELSSTAINLESS STEELS

Highly resistant to corrosion in a wide Highly resistant to corrosion in a wide variety of environmentvariety of environment

Predominant alloying element is Cr, at Predominant alloying element is Cr, at least 11% wt of Cr.least 11% wt of Cr.

Corrosion resistance may be enhanced Corrosion resistance may be enhanced by the addition of Ni and Mo.by the addition of Ni and Mo.

Very versatile in their applicability Very versatile in their applicability because of their wide range of because of their wide range of mechanical properties combine with mechanical properties combine with excellent resistance to corrosion.excellent resistance to corrosion.

IRON ALLOY PHASESIRON ALLOY PHASES

AusteniteAustenite (γ-iron; hard) (γ-iron; hard)BainiteBainiteMartensiteMartensiteCementiteCementite (iron carbide; Fe (iron carbide; Fe33C)C)LedeburiteLedeburite (ferrite - cementite (ferrite - cementite

eutectic,eutectic,4.3% carbon) 4.3% carbon)

FerriteFerrite (α-iron; soft) (α-iron; soft)PearlitePearlite (88% ferrite, 12% cementite) (88% ferrite, 12% cementite)

AUSTENITEAUSTENITE Is a FCC form of iron in which some C is Is a FCC form of iron in which some C is

dissolved. It forms above the critical dissolved. It forms above the critical temperature.temperature.

MARTENSITEMARTENSITE A BCC form of iron in which some C is A BCC form of iron in which some C is

dissolved. It forms during quenching, when dissolved. It forms during quenching, when FCC austenite changes to the BCC structure FCC austenite changes to the BCC structure w/o precipitation of cementite. Instead, the w/o precipitation of cementite. Instead, the C is retained in the Fe crystal structure.C is retained in the Fe crystal structure.

Is also defined as a hardened microstructure Is also defined as a hardened microstructure of steel that is obtained by quick cooling, of steel that is obtained by quick cooling, avoiding the formation of pearlite.avoiding the formation of pearlite.

CEMENTITECEMENTITE Is Iron Carbide, Fe3CIs Iron Carbide, Fe3C

FERRITEFERRITE Is a BCC form of iron in which Is a BCC form of iron in which

some C some C is dissolved. is dissolved.

SteelSteel

cooled at a rate of about 400cooled at a rate of about 400ooC/ minC/ min

transform austenite to pearlite attransform austenite to pearlite at 727727ooC C

Faster cooling produces martensite.Faster cooling produces martensite.

3 CLASSES OF STAINLESS 3 CLASSES OF STAINLESS STEELSSTEELS

(1) Ferritic Steels(1) Ferritic Steels

(2) Austenitic Steels(2) Austenitic Steels

(3) Martensitic Steels(3) Martensitic Steels

MartensiteMartensite

most commonly refers to a form of most commonly refers to a form of ferriteferrite supersaturated with supersaturated with carboncarbon found in very hard found in very hard steelssteels, for use in such products as , for use in such products as springssprings and and piano wirepiano wire. .

The martensite is formed by rapid cooling (The martensite is formed by rapid cooling (quenchingquenching) of ) of austeniteaustenite which traps carbon atoms which traps carbon atoms that do not have time to diffuse out of the crystal that do not have time to diffuse out of the crystal structure.structure.

Martensite is usually considered to be a grain Martensite is usually considered to be a grain structure not a phase. For this reason, martensite is structure not a phase. For this reason, martensite is not shown in the equilibrium not shown in the equilibrium phase diagramphase diagram of the of the iron-carbon system. It consists of grains of iron-carbon system. It consists of grains of ferriteferrite supersaturated with carbonsupersaturated with carbon

FerriteFerrite

or or alpha ironalpha iron ( (α-Feα-Fe) ) is a is a materials sciencematerials science term for iron, term for iron,

or a solid solution with iron as the or a solid solution with iron as the main constituent, with a main constituent, with a body centred cubicbody centred cubic crystal structure. crystal structure.

It is the component which gives It is the component which gives steelsteel and and cast ironcast iron their magnetic their magnetic properties, and is the classic properties, and is the classic example of a example of a ferromagneticferromagnetic material. material.

In pure ironIn pure iron, ferrite is stable below 910°C., ferrite is stable below 910°C.

Above this temperature Above this temperature the the face-centered cubicface-centered cubic form of iron, form of iron, austeniteaustenite (gamma-iron) (gamma-iron) is stable. is stable.

Above 1390°C, up to the Above 1390°C, up to the melting pointmelting point at at 1534°C, the 1534°C, the body-centred cubic crystal body-centred cubic crystal structure is again the more stable form structure is again the more stable form (delta-iron).(delta-iron).

FERRITIC STEELFERRITIC STEEL

16-18% chromium; rustless iron with low carbon 16-18% chromium; rustless iron with low carbon contentcontent

Has high resistance to corrosion but low impact Has high resistance to corrosion but low impact and cannot be refined by heat-treatment alone. and cannot be refined by heat-treatment alone.

Prolonged service at 480°C can cause Prolonged service at 480°C can cause embrittlement.  embrittlement.  

Used for trim moldings and decorative applications. Used for trim moldings and decorative applications.

25-30% chromium iron for furnace parts; resistant 25-30% chromium iron for furnace parts; resistant to sulphur compounds. to sulphur compounds.

Has low amount of carbon to chromium ratio; Has low amount of carbon to chromium ratio; therefore hardening by heat-treating is not done.therefore hardening by heat-treating is not done.

ADVANTAGES:ADVANTAGES: Readily weldableReadily weldable Cheapest of the Cheapest of the

stainless steels.stainless steels. MagneticMagnetic Hardened and Hardened and

strengthened by strengthened by cold work; not heat cold work; not heat treatable.treatable.

Easiest of all to Easiest of all to machine.machine.

DISADVANTAGES:DISADVANTAGES: Poor ductility.Poor ductility. Poor formability Poor formability

because of the bcc because of the bcc crystal structure.crystal structure.

AUSTENITIC STEELSAUSTENITIC STEELS

Best corrosive resistance, but hardenable Best corrosive resistance, but hardenable only by cold working. only by cold working.

Not heat treatable, but cold workable.Not heat treatable, but cold workable. With both nickel and chromium, the fcc With both nickel and chromium, the fcc

austenite is stabilized at room austenite is stabilized at room temperature to produce a stainless steel.temperature to produce a stainless steel.

Most corrosion resistant because of the Most corrosion resistant because of the high Cr content and Ni addition high Cr content and Ni addition

ADVANTAGES:ADVANTAGES: Best corrosive resistance,Best corrosive resistance, Highest of all for strength Highest of all for strength

at high temperatures,at high temperatures, Best of all for ductility at Best of all for ductility at

low temperatures.low temperatures. NonmagneticNonmagnetic Highly resistant to Highly resistant to

chemical corrosion, mirror chemical corrosion, mirror polish,polish,

Attractive appearance.Attractive appearance. Formability is outstanding Formability is outstanding

characteristic of the fcc.characteristic of the fcc. Strengthen drastically Strengthen drastically

when cold workedwhen cold worked

DISADVANTAGES:DISADVANTAGES: Corrosive in Corrosive in

hydrochloric acid and hydrochloric acid and other halide acids and other halide acids and salts.salts.

Most expensiveMost expensive

MARTENSITIC STEELSMARTENSITIC STEELS

High amount of carbon to chromium ratio High amount of carbon to chromium ratio therefore can be heat treated. therefore can be heat treated.

More corrosive resistant than ferrite, but More corrosive resistant than ferrite, but still corrosive. still corrosive.

This material can be austenitic at high This material can be austenitic at high temperatures. At the high temperature, temperatures. At the high temperature, carbon can be dissolved in the fcc carbon can be dissolved in the fcc austenite, which in turn is quenched to austenite, which in turn is quenched to form a bcc martenitic structure. So the form a bcc martenitic structure. So the steel is austenitized, quenched, then steel is austenitized, quenched, then stress relief tempered.stress relief tempered.

ADVANTAGES:ADVANTAGES: Increase in Increase in

strengthstrength more corrosive more corrosive

resistant than resistant than FerriticFerritic

ability to hold an ability to hold an “edge”“edge”

good for impactgood for impact

DISADVANTAGESDISADVANTAGES May be susceptible May be susceptible

to red rust when to red rust when annealed for annealed for machining or machining or fabrication.fabrication.

Cost 1 ½ times Cost 1 ½ times more than the more than the Ferritic stainless Ferritic stainless steels.steels.

GENERAL PROPERTIES OF STEEL GENERAL PROPERTIES OF STEEL (@25(@25ooC)C)

PROPERTIESPROPERTIESCARBON CARBON STEELSSTEELS

ALLOY ALLOY STEELSSTEELS

STAINLESSTAINLESSS STEELS STEELS

TOOL TOOL STEELSSTEELS

Density ( 1000 Density ( 1000 kg/mkg/m33))

7.857.857.857.857.75-8.17.75-8.17.72-8.07.72-8.0

Elastic Modulus Elastic Modulus ( GPa)( GPa)

190-210190-210190-210190-210190-210190-210190-210190-210

Thermal Thermal Conductivity ( Conductivity ( W/m-K)W/m-K)

24.3-24.3-

65.265.2 26-48.626-48.6 11.2-11.2-

36.736.7 19.9-19.9-48.3 48.3

Electrical Resistivity Electrical Resistivity (10(10-9 -9 W-m)W-m)

130-130-

12501250 210-210-

12511251 75.7-75.7-1020 1020

Tensile Tensile Strength(MPa)Strength(MPa)

276-276-18821882

758-758-18821882

515-827515-827640-640-20002000

Yield Strength Yield Strength ( MPa)( MPa)

186-758186-758366-366-17931793

207-552207-552380-440380-440

Percent Percent Elongation(%)Elongation(%)

10-3210-324-314-3112-4012-405-255-25

Stainless Stainless steelssteels have higher have higher resistance to resistance to oxidationoxidation ( (rustrust) and ) and corrosioncorrosion in many natural and man in many natural and man made environments; however, it is made environments; however, it is important to select the correct type important to select the correct type and grade of stainless steel for the and grade of stainless steel for the particular application.particular application.

High oxidation resistance in air at ambient High oxidation resistance in air at ambient temperature is normally achieved with additions temperature is normally achieved with additions of a minimum of 13% (by weight) chromium, and of a minimum of 13% (by weight) chromium, and up to 26% is used for harsh environments.up to 26% is used for harsh environments.

The chromium forms a passivation layer of The chromium forms a passivation layer of chromium(III) oxide (Crchromium(III) oxide (Cr22OO33) when exposed to ) when exposed to oxygen. oxygen.

The layer is too thin to be visible, meaning the The layer is too thin to be visible, meaning the metal stays shiny. It is, however, impervious to metal stays shiny. It is, however, impervious to water and air, protecting the metal beneath. water and air, protecting the metal beneath.

Also, when the surface is scratched this layer Also, when the surface is scratched this layer quickly reforms. quickly reforms.

This phenomenon is called passivation and is This phenomenon is called passivation and is seen in other metals, such as aluminium and seen in other metals, such as aluminium and titanium. titanium.

When stainless steel parts such as nuts When stainless steel parts such as nuts and bolts are forced together, the oxide and bolts are forced together, the oxide layer can be scraped off causing the layer can be scraped off causing the parts to weld together. When parts to weld together. When disassembled, the welded material may disassembled, the welded material may be torn and pitted, an effect that is be torn and pitted, an effect that is known as galling.known as galling.

Nickel also contributes to passivation, as Nickel also contributes to passivation, as do other less commonly used do other less commonly used ingredients such as molybdenum and ingredients such as molybdenum and vanadium.vanadium.

EFFECTS OF ALLOYING ELEMENTSEFFECTS OF ALLOYING ELEMENTS

Usually only a small amount of alloying Usually only a small amount of alloying element are added to steels (usually less element are added to steels (usually less than 5%). than 5%).

Mostly the purpose is: Mostly the purpose is:

1. to improve the hardenability and1. to improve the hardenability and

2. strength corrosion resistance,2. strength corrosion resistance,

3. stability at high/low temperatures,3. stability at high/low temperatures,

4. control grain size4. control grain size

EFFECTS OF ALLOYING ELEMENTSEFFECTS OF ALLOYING ELEMENTSManganese Manganese - increases ductility, hardenability, - increases ductility, hardenability, high strainhigh strain

hardening capacity, slightly hardening capacity, slightly strengthens, strengthens,

excellent wear resistanceexcellent wear resistance

Sulfur Sulfur - if carefully proportioned can add- if carefully proportioned can add

machinability without imparting machinability without imparting embrittlementembrittlement

Nickel Nickel - increases toughness and impact - increases toughness and impact resistance, resistance,

good properties at low temperatures. good properties at low temperatures.

With other alloys imparts excellent With other alloys imparts excellent corrosioncorrosion

resistance. resistance.

Increase strength with little loss of Increase strength with little loss of ductilityductility

Chromium Chromium - if added in large enough amounts can - if added in large enough amounts can impartimpart

corrosion resistance and heat corrosion resistance and heat resistance andresistance and

wear resistance and hardenability.wear resistance and hardenability.

Molybdenum Molybdenum - improves hardenability and - improves hardenability and increasesincreases

strength primarily under dynamic strength primarily under dynamic and highand high

temperature conditions. temperature conditions.

Extremely stable at elevated Extremely stable at elevated temperatures. temperatures.

It helps to retains fine grain sizes It helps to retains fine grain sizes whichwhich

provides strength and creep provides strength and creep resistance atresistance at

elevated temperatures. elevated temperatures.

Molybdenum carbides are used in hot Molybdenum carbides are used in hot workwork

tool steels and forging dies to imparttool steels and forging dies to impart

hardness even at red heat.hardness even at red heat.

Vanadium Vanadium - like molybdenum, forms strong - like molybdenum, forms strong carbides atcarbides at

elevated temperatures. elevated temperatures.

Also limits grain size.Also limits grain size.

TungstenTungsten- used in tool steels to maintain their- used in tool steels to maintain their

hardness at elevated temperatures.hardness at elevated temperatures.

Copper Copper - increases the corrosion resistance. - increases the corrosion resistance.

Limits have to be controlled or it’llLimits have to be controlled or it’ll

sacrifice surface quality and hot-sacrifice surface quality and hot-workingworking

behavior.behavior.

Silicon Silicon - increases strength without limiting grain - increases strength without limiting grain size*size*

Used to promote large grain sizes used inUsed to promote large grain sizes used in

magnetic applications. Used in spring magnetic applications. Used in spring steels.steels.

Boron Boron - very important harden ability agent being - very important harden ability agent being severalseveral

hundred times better than nickel, hundred times better than nickel, molybdenummolybdenum

and chromium. and chromium.

Used more for low carbon steels. Used more for low carbon steels.

Also improve machinability and cold Also improve machinability and cold forming.forming.

*Limits on grain size can effectively *Limits on grain size can effectively increase strength properties like increase strength properties like elastic limit, yield point, and impact elastic limit, yield point, and impact strength (toughness) with little loss strength (toughness) with little loss of ductility.of ductility.

CARBON STEELCARBON STEELSummary of PropertiesSummary of Properties

Mild (low carbon) steelMild (low carbon) steel: : with up to 0.4% manganese contentwith up to 0.4% manganese contentLess strong but cheap and easy to shape; Less strong but cheap and easy to shape; surface hardness can be increased through surface hardness can be increased through carburizingcarburizing..

Medium carbon steelMedium carbon steel: : with 0.60 to 1.65% manganese content. with 0.60 to 1.65% manganese content. Balances ductility and strength and Balances ductility and strength and has good wear resistance; has good wear resistance; used for large parts, forging and automotive used for large parts, forging and automotive components components

High carbon steelHigh carbon steel: : with 0.30 to 0.90% manganese content.with 0.30 to 0.90% manganese content.Very strong, used for springs and high-strength wires. Very strong, used for springs and high-strength wires.

TOOL STEELSTOOL STEELS

refers to a variety of refers to a variety of carboncarbon and and alloyalloy steelssteels that are particularly well-suited to that are particularly well-suited to be made into be made into toolstools. .

Their suitability comes from their Their suitability comes from their distinctive toughness, resistance to distinctive toughness, resistance to abrasionabrasion, their ability to hold a cutting , their ability to hold a cutting edge, and/or their resistance to edge, and/or their resistance to deformation at elevated temperatures deformation at elevated temperatures (red-hardness). (red-hardness).

With a carbon content between 0.7% and With a carbon content between 0.7% and 1.4%, tool steels are manufactured under 1.4%, tool steels are manufactured under carefully controlled conditions to produce carefully controlled conditions to produce the required quality. the required quality.

HSLA ( High Strength Low Alloy ) HSLA ( High Strength Low Alloy ) SteelSteel

is a type of is a type of steelsteel alloy that provides many alloy that provides many benefits over regular steel benefits over regular steel alloysalloys. .

In general, HSLA alloys are much stronger In general, HSLA alloys are much stronger and tougher than ordinary and tougher than ordinary plain-carbon steelsplain-carbon steels. .

They are used in cars, trucks, cranes, They are used in cars, trucks, cranes, bridges, and other structures that are bridges, and other structures that are designed to handle large amounts of designed to handle large amounts of stressstress, often at very low temperatures., often at very low temperatures.

HSLA steels are so called because they only HSLA steels are so called because they only contain a very small percentage of contain a very small percentage of carboncarbon. .

A typical HSLA steel may contain 0.15% A typical HSLA steel may contain 0.15% carbon, 1.65% carbon, 1.65% manganesemanganese and low levels and low levels (under 0.035%) of (under 0.035%) of phosphorusphosphorus and and sulphursulphur. .

It may also contain small amounts of It may also contain small amounts of coppercopper, , nickelnickel, , niobiumniobium, , nitrogennitrogen, , vanadiumvanadium, , chromiumchromium, , molybdenummolybdenum, , siliconsilicon, or , or zirconiumzirconium..

are also referred to as "are also referred to as "microalloyedmicroalloyed", as ", as they are indeed alloyed in extremely small they are indeed alloyed in extremely small amounts by comparison to other main amounts by comparison to other main commercial alloy steelscommercial alloy steels. .

Ferrous Metals & AlloysFerrous Metals & Alloys

Steel Cast IronsSteel Cast Irons

Low alloy High AlloyLow alloy High Alloy Gray cast ironGray cast iron

Low-CLow-C Ductile Ductile ( nodular ) iron( nodular ) iron

PlainPlainHigh-strength, High-strength, White IronWhite Iron

Medium-CMedium-CPlainPlain MalleableMalleableHeat treatable Heat treatable

High-CHigh-CPlainPlainToolTool Tool StainlessTool Stainless

CAST IRONCAST IRON

Class of ferrous alloys with carbon content Class of ferrous alloys with carbon content above 2.14%wt.above 2.14%wt.

In practice, however, most cast irons In practice, however, most cast irons contain between 3.0% and 4.5% wt C + contain between 3.0% and 4.5% wt C + other alloying elements.other alloying elements.

Alloys within this composition range Alloys within this composition range becomes completely liquid at becomes completely liquid at temperatures between aprrox. 1150 – temperatures between aprrox. 1150 – 13001300ooC, considerably lower than steel.C, considerably lower than steel.

Are easily melted and amenable to castingAre easily melted and amenable to casting Some are very brittle that casting is the Some are very brittle that casting is the

most convenient fabrication technique. most convenient fabrication technique.

Iron accounts for more than 95%, Iron accounts for more than 95%, while the main alloying elements are while the main alloying elements are carboncarbon and and siliconsilicon. .

Cast irons contain appreciable Cast irons contain appreciable amounts of silicon, normally 1 - 3%, amounts of silicon, normally 1 - 3%, and consequently these alloys should and consequently these alloys should be considered be considered ternaryternary Fe-C-Si alloys. Fe-C-Si alloys.

Cast iron tends to be Cast iron tends to be brittlebrittle, unless , unless the name of the particular alloy the name of the particular alloy suggests otherwise. suggests otherwise.

With its With its low melting point, low melting point, good fluidity, good fluidity, castability, castability, excellent machinability and excellent machinability and wear resistance, wear resistance,

cast irons have become an cast irons have become an engineering material with a wide engineering material with a wide range of applications, including pipes, range of applications, including pipes, machine and car parts.machine and car parts.

(1) GRAY CAST IRON(1) GRAY CAST IRON

C and Si content vary from 2.5 – 4.0% and C and Si content vary from 2.5 – 4.0% and 1.0 – 3.0%, respectively.1.0 – 3.0%, respectively.

Graphite exists in the form of flakes, which Graphite exists in the form of flakes, which are surrounded by are surrounded by ferrite and pearliteferrite and pearlite..

because of this microstructure, gray iron because of this microstructure, gray iron

are comparatively weak and brittle in are comparatively weak and brittle in tension.tension.

Strength and ductility are much higher Strength and ductility are much higher under compressive loads.under compressive loads.

Silicon is essential to making of grey cast Silicon is essential to making of grey cast iron as opposed to white cast iron.iron as opposed to white cast iron.

Silicon causes the carbon to rapidly come Silicon causes the carbon to rapidly come out of solution as out of solution as graphitegraphite, leaving a , leaving a matrix of relatively pure, soft iron. Weak matrix of relatively pure, soft iron. Weak bonding between planes of graphite lead bonding between planes of graphite lead to a high to a high activation energyactivation energy for growth in for growth in that direction, that direction,

resulting in thin, round flakes. resulting in thin, round flakes.

This structure has several useful properties.This structure has several useful properties.

PROPERTIESPROPERTIES

The graphite content offers good The graphite content offers good corrosioncorrosion resistance.resistance.

Graphite acts as a lubricant, improving Graphite acts as a lubricant, improving wear resistance. wear resistance.

The exceptionally high The exceptionally high speed of soundspeed of sound in in graphite gives cast iron a much higher graphite gives cast iron a much higher thermal conductivitythermal conductivity. .

Since ferrite is so different in this respect Since ferrite is so different in this respect (having heavier atoms, bonded much less (having heavier atoms, bonded much less tightly) , grey cast iron tends to “damp” tightly) , grey cast iron tends to “damp” mechanical vibrations (including mechanical vibrations (including soundsound), ), which can help machinery to run more which can help machinery to run more smoothly.smoothly.

All of the properties mentioned above ease All of the properties mentioned above ease the the machiningmachining of grey cast iron. of grey cast iron.

Grey cast iron has less Grey cast iron has less tensile strengthtensile strength and and shock resistanceshock resistance than steel. than steel.

It is also difficult to weld.It is also difficult to weld.

(2) DUCTILE (Nodular) IRON(2) DUCTILE (Nodular) IRON

Gray iron + small amount of Mg and/or Gray iron + small amount of Mg and/or Cerium before casting.Cerium before casting.

A distinctly different microstructure is A distinctly different microstructure is produced --- and set of mechanical produced --- and set of mechanical properties.properties.

Graphite still forms but in nodules or Graphite still forms but in nodules or sphere like particles.sphere like particles.

Stronger and more ductile than gray iron.Stronger and more ductile than gray iron. Has mechanical properties approaching Has mechanical properties approaching

that of steel.that of steel.

APPLICATIONS:APPLICATIONS:Automotive and machine Automotive and machine

components, gears, valves etc. components, gears, valves etc.

(3) WHITE IRON(3) WHITE IRON

Low silicon cast iron ( less than 1.0%), and rapid Low silicon cast iron ( less than 1.0%), and rapid cooling rates, most of the C exists as cementite cooling rates, most of the C exists as cementite instead of graphite.instead of graphite.

A fracture surface of this alloy has a white A fracture surface of this alloy has a white appearance, thus termed as white iron.appearance, thus termed as white iron.

As a consequence of its large amount of As a consequence of its large amount of cementite phase, white iron is extremely hard, cementite phase, white iron is extremely hard, very brittle to the point of being unmachinable.very brittle to the point of being unmachinable.

Its use is very limited to applications that Its use is very limited to applications that necessitate a very hard and wear resistant necessitate a very hard and wear resistant surface without a high degree of ductility.surface without a high degree of ductility.

Example of its applicationExample of its applicationRollers in rolling millsRollers in rolling mills

(4) MALLEABLE IRON(4) MALLEABLE IRON

Heating white iron at temps between 800-Heating white iron at temps between 800-900900ooC for a prolonged time period and in a C for a prolonged time period and in a neutral atmosphere causes the neutral atmosphere causes the decomposition of cementite, forming decomposition of cementite, forming graphite, which exists in the form of graphite, which exists in the form of clusters or rosettes.clusters or rosettes.

Relatively high strength and appreciable Relatively high strength and appreciable ductility or malleability.ductility or malleability.

Applications:Applications:Pipe fittings, valve parts for Pipe fittings, valve parts for

railroad, railroad, marine and heavy duty marine and heavy duty applications, applications, transmissions, gears transmissions, gears etc. etc.