PowerPoint to accompany Welding Principles and Practices 4th edition Edward R. Bohnart © 2012 The...

PowerPoint to accompanyPowerPoint to accompany

WeldingWeldingPrinciples and PracticesPrinciples and Practices4th edition4th edition

Edward R. BohnartEdward R. Bohnart

© 2012 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 3Chapter 3

Steel andOtherMetals

Steel andOtherMetals

© 2012 The McGraw-Hill Companies, Inc. All rights reserved.W

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ObjectivesObjectives

1.1. Describe steelmaking process.Describe steelmaking process.

2.2. List metalworking processes used to List metalworking processes used to shape and improve steel.shape and improve steel.

3.3. State proper use of each heat-treating State proper use of each heat-treating process for steel.process for steel.

4.4. Describe internal structures of metals.Describe internal structures of metals.

5.5. Name various alloying elements and their Name various alloying elements and their effects.effects.


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ObjectivesObjectives

6.6. List various types of ferrous metals and List various types of ferrous metals and their applications.their applications.

7.7. List various types of nonferrous metals List various types of nonferrous metals and their applications.and their applications.

8.8. Describe various systems used to Describe various systems used to designate metals.designate metals.

9.9. Explain heating and cooling effects on Explain heating and cooling effects on weldment and how they can be weldment and how they can be controlled.controlled.


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Metal Major GroupingsMetal Major Groupings

• FerrousFerrous– High iron contentHigh iron content– Includes:Includes:

• Many types of steel and its alloysMany types of steel and its alloys• Cast ironCast iron• Wrought ironWrought iron

• NonferrousNonferrous– Almost free of ironAlmost free of iron


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Nonferrous MetalsNonferrous Metals

• CommonCommon– Copper, lead, zinc, titanium, aluminum, nickel, Copper, lead, zinc, titanium, aluminum, nickel,

tungsten, manganese, brass, bronzetungsten, manganese, brass, bronze

• PreciousPrecious– Gold, platinum, silverGold, platinum, silver

• RadioactiveRadioactive– Uranium, radiumUranium, radium


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SteelSteel

• Combination of iron and carbonCombination of iron and carbon– Percentage of carbon determines how strong Percentage of carbon determines how strong

and hard the steeland hard the steel

• WeldmentsWeldments– 80% fabricated from steel80% fabricated from steel

• 85% welded is in mild (low carbon) steel 85% welded is in mild (low carbon) steel classificationclassification


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History of SteelHistory of Steel

• Assyrians (3700 B.C.) first recorded use of Assyrians (3700 B.C.) first recorded use of ironiron– Low carbon iron first produced in low flat Low carbon iron first produced in low flat

hearth furnaceshearth furnaces

• 1350 B.C. to 1300 A.D. all iron tools and 1350 B.C. to 1300 A.D. all iron tools and weapons produced directly from iron oreweapons produced directly from iron ore– Furnaces increased in height and charge Furnaces increased in height and charge

introduced through top (shaft furnaces)introduced through top (shaft furnaces)• Modern blast furnaceModern blast furnace


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History of SteelHistory of Steel

• Little known of first process for making steelLittle known of first process for making steel– Tools found dating back to 1000 to 500 B.C.Tools found dating back to 1000 to 500 B.C.

• Prior to Bessemer process two methods usedPrior to Bessemer process two methods used– Cementation processCementation process

• Increased carbon content by heating iron in contact with Increased carbon content by heating iron in contact with hot carbon in absence of airhot carbon in absence of air

• Still used to limited extentStill used to limited extent

– Crucible processCrucible process• Melting wrought iron in crucibles in which carbon Melting wrought iron in crucibles in which carbon

already addedalready added• Replaced by various electric furnace processesReplaced by various electric furnace processes


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Steelmaking in the USSteelmaking in the US

• Extends back over 300 yearsExtends back over 300 years– Ironworks in Saugus, Massachusetts (1646–1670)Ironworks in Saugus, Massachusetts (1646–1670)

• First patent for steel issued in 1728First patent for steel issued in 1728• Succession of events spurred growthSuccession of events spurred growth

– New uses for ironNew uses for iron– Discovery of large iron ore depositsDiscovery of large iron ore deposits– Development of Bessemer and open hearth Development of Bessemer and open hearth

processesprocesses– Civil War and AmericaCivil War and America’’s industrial growths industrial growth– Expansion of railroadsExpansion of railroads– World Wars I and IIWorld Wars I and II


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Annual Steel ProductionAnnual Steel Production


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11Changes in U.S. Steel ProductionChanges in U.S. Steel Production

• Reduction in number of blast furnacesReduction in number of blast furnaces– 250 down to 36250 down to 36

• No open hearth furnacesNo open hearth furnaces

• Increased use of recycled steelIncreased use of recycled steel

• Perfection of welding process to join Perfection of welding process to join metals speeded up and expanded use of metals speeded up and expanded use of steelsteel


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Raw MaterialsRaw Materials

• United States well supplied with basic United States well supplied with basic resourcesresources– Iron ore, limestone and coalIron ore, limestone and coal

• Other countries provide other necessary Other countries provide other necessary materialsmaterials– Manganese, tin, nickel and chromium Manganese, tin, nickel and chromium


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Iron OreIron Ore

• 5% of Earth5% of Earth’’s crusts crust

• Large depositsLarge deposits– Northern Minnesota near Lake Superior in Northern Minnesota near Lake Superior in

U.S.U.S.• Principally taconitePrincipally taconite

– BrazilBrazil• Largest and best sourceLargest and best source

– SwedenSweden• Purest iron orePurest iron ore


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Iron OresIron Ores

• Magnetite (FeMagnetite (Fe33OO44))– Brownish, richest, leastBrownish, richest, least

common, 65–70% ironcommon, 65–70% iron

• Hematite (FeHematite (Fe22OO33))– Red, mined in US, Red, mined in US,

70% iron70% iron

• Limonite (2FeLimonite (2Fe22OO33 • H • H22O)O)– 52–66% iron52–66% iron

• Siderite (FeCOSiderite (FeCO33))– 48% iron48% iron

• TaconiteTaconite– Green, 22–40% ironGreen, 22–40% iron

• JasperJasper– Iron-bearing rockIron-bearing rock

– Predominately Predominately magnetite or magnetite or hematitehematite


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Iron Ore MiningIron Ore Mining

• UndergroundUnderground– Vertical shaft sunk in rock next to ore bodyVertical shaft sunk in rock next to ore body– Tunnels drilled from shaft and blasted Tunnels drilled from shaft and blasted

horizontally into ore body at number of levelshorizontally into ore body at number of levels

• Open pitOpen pit– Mineral lying relatively near surfaceMineral lying relatively near surface– Earth and rock first removedEarth and rock first removed– Blast holes drilled, explosives shatter ore and Blast holes drilled, explosives shatter ore and

hauled out of pit by truck, train or conveyor hauled out of pit by truck, train or conveyor beltbelt


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OxygenOxygen

• Most abundant element on earthMost abundant element on earth– One half weight of land, 21% by weight of air One half weight of land, 21% by weight of air

and 90% by weight of seaand 90% by weight of sea

• Steel industry major consumerSteel industry major consumer– Used to purify the materialUsed to purify the material

• Oxidizes the carbon, silicon, manganese and other Oxidizes the carbon, silicon, manganese and other elementselements

– Speeds up process by supporting combustion Speeds up process by supporting combustion of other fuelsof other fuels


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FuelsFuels

• Three major natural fuelsThree major natural fuels– CoalCoal

• Most importantMost important

– OilOil– Natural gasNatural gas

• Used to provide heat essential in making Used to provide heat essential in making steel mill productssteel mill products


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CoalCoal

• Supplies more than 80% of total heat and Supplies more than 80% of total heat and energy requirementsenergy requirements

• Large part used in making coke for blast Large part used in making coke for blast furnacefurnace– About 1,300 pounds of coke per each ton of About 1,300 pounds of coke per each ton of

pig ironpig iron– Coking quality coal mined in 24 statesCoking quality coal mined in 24 states

• 90% comes from West Virginia, Pennsylvania, 90% comes from West Virginia, Pennsylvania, Kentucky and AlabamaKentucky and Alabama


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OilOil

• Used as both fuel and lubricantUsed as both fuel and lubricant

• Heaviest grade of oil most commonly usedHeaviest grade of oil most commonly used

• Percentage of usePercentage of use– 70% consumed in melting iron70% consumed in melting iron

– 20% burned in heating and annealing furnaces 20% burned in heating and annealing furnaces for special heat treatmentsfor special heat treatments

– 10% used in all other applications10% used in all other applications


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Natural GasNatural Gas

• Burned in furnaces and places where Burned in furnaces and places where clean burn necessaryclean burn necessary

• More heating value than all other gases More heating value than all other gases employedemployed– 1,000 BTU per cubic foot1,000 BTU per cubic foot

– Steel industry consumes over 400 billion cubic Steel industry consumes over 400 billion cubic feet per yearfeet per year• 50% used in heat-treating and annealing furnaces50% used in heat-treating and annealing furnaces


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CokeCoke

• Supplies heat for smelting iron in blast Supplies heat for smelting iron in blast furnacesfurnaces

• Solid residue obtained when coal heated to Solid residue obtained when coal heated to high temperature in absence of airhigh temperature in absence of air– Causes gases and other impurities to be releasedCauses gases and other impurities to be released

• Hard, brittle substance consisting chiefly of Hard, brittle substance consisting chiefly of carboncarbon

• 1919 – coal chemical process of producing 1919 – coal chemical process of producing coke developedcoke developed


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CokeCoke

• Leading fuel of steel industryLeading fuel of steel industry• Volatile products which pass out of ovens piped Volatile products which pass out of ovens piped

to chemical plantto chemical plant– Yields gas, tar, ammonia liquor, ammonium sulfate, Yields gas, tar, ammonia liquor, ammonium sulfate,

and light oiland light oil– Further refinement of light oil produces benzene, Further refinement of light oil produces benzene,

toulene, and other chemicalstoulene, and other chemicals

• Production in United States exceeds 64 million Production in United States exceeds 64 million tons per year (92% consumed as blast furnace tons per year (92% consumed as blast furnace fuel)fuel)


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Coke OvenCoke Oven

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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Steel ScrapSteel Scrap

• Oxygen furnaces (BOFs) capable of using Oxygen furnaces (BOFs) capable of using scrapscrap– 66% of steel used is recycled66% of steel used is recycled

• Integrated producerIntegrated producer– 80% liquid metal (from blast furnace)80% liquid metal (from blast furnace)– 20% scrap20% scrap

• Best source is old automobilesBest source is old automobiles


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LimestoneLimestone

• Used as flux in blast furnace to separate Used as flux in blast furnace to separate impurities from iron oreimpurities from iron ore

• Sedimentary rockSedimentary rock– Consists largely of calcium carbonateConsists largely of calcium carbonate– Color changes with presence of impuritiesColor changes with presence of impurities

• Silica makes it harderSilica makes it harder• Clay makes it softerClay makes it softer


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Refractory MaterialsRefractory Materials

• Nonmetallic materials which can tolerate Nonmetallic materials which can tolerate severe or destructive service conditions at severe or destructive service conditions at high temperatureshigh temperatures– 2,600ºF for light duty fireclay2,600ºF for light duty fireclay– 5,000ºF for magnesia brick5,000ºF for magnesia brick

• ApplicationsApplications– Linings for blast furnaces, steelmaking Linings for blast furnaces, steelmaking

furnaces, soaking pits, reheating furnaces, furnaces, soaking pits, reheating furnaces, ladles, submarine carsladles, submarine cars


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27Producing Refractory MaterialsProducing Refractory Materials

• Produced from quartzite, fireclay, alumina, Produced from quartzite, fireclay, alumina, magnesia, iron oxide, graphites, coal, coke magnesia, iron oxide, graphites, coal, coke and tarand tar

• Materials crushed, combined with binder Materials crushed, combined with binder and fed to forming machinesand fed to forming machines

• Methods for forming refractory bricksMethods for forming refractory bricks– Power pressingPower pressing– ExtrusionExtrusion– Hand moldingHand molding


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Iron Blast Furnace SlagIron Blast Furnace Slag

• Residue produced from interaction of Residue produced from interaction of molten limestone and impurities of ironmolten limestone and impurities of iron

• Contains oxides of calcium, silicon, Contains oxides of calcium, silicon, aluminum and magnesium (also iron oxide aluminum and magnesium (also iron oxide and sulfur)and sulfur)

• Processed for use in cement, road Processed for use in cement, road materials, insulating roofing material and materials, insulating roofing material and soil conditionersoil conditioner


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CarbonCarbon

• Nonmetallic element that can form Nonmetallic element that can form compound with other elementscompound with other elements– Organic compoundsOrganic compounds

• Three pure carbon formsThree pure carbon forms– Diamond (hard crystalline form)Diamond (hard crystalline form)– Graphite (soft form)Graphite (soft form)– Carbon black (amorphous form)Carbon black (amorphous form)


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Blast FurnaceBlast Furnace

• First step in converting iron ore into steelFirst step in converting iron ore into steel

• Iron freed from most impuritiesIron freed from most impurities

• Furnace charged with iron ore, limestone Furnace charged with iron ore, limestone and cokeand coke– Heat melts iron, limestone form slag and two Heat melts iron, limestone form slag and two

liquids separate (remove and repeat: 5–8 hrs)liquids separate (remove and repeat: 5–8 hrs)– Liquid iron poured into molds (pigs of iron)Liquid iron poured into molds (pigs of iron)

• Hard and brittleHard and brittle


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Blast Furnace SchematicBlast Furnace SchematicC

opyright © T

he McG

raw-H

ill Com

panies, Inc. Perm

ission required for reproduction or display.

American Iron & Steel Inst.


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Steelmaking ProcessesSteelmaking Processes

• CementationCementation

• CrucibleCrucible

• Bessemer furnaceBessemer furnace– Invented in both Europe and United States in Invented in both Europe and United States in

18561856

• Open hearth furnaceOpen hearth furnace– Invented in 1868 in the United StatesInvented in 1868 in the United States


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Cementation ProcessCementation Process

• Oldest method of steelmakingOldest method of steelmaking• Consists of heating wrought iron with Consists of heating wrought iron with

carbon in a vacuumcarbon in a vacuum– Increases carbon content of surfaces and Increases carbon content of surfaces and

edgesedges• Edges hardened by heating and quenchingEdges hardened by heating and quenching

– Impurities not removedImpurities not removed– Only surface is affectedOnly surface is affected

• Later process layered soft and hard metal Later process layered soft and hard metal for strengthfor strength


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Crucible ProcessCrucible Process

• Revived in England during early 1740sRevived in England during early 1740s

• Process involved melting wrought iron in Process involved melting wrought iron in clay crucible to remove impuritiesclay crucible to remove impurities– When fluid, slag skimmed off topWhen fluid, slag skimmed off top– Metal then poured into mold to solidify into a Metal then poured into mold to solidify into a

workable massworkable mass

• United States used graphite crucibles United States used graphite crucibles (100 lb. capacity) in gas-fired furnace(100 lb. capacity) in gas-fired furnace


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35Electric Furnace Processes:Electric ArcElectric Furnace Processes:Electric Arc

• French metallurgist Paul Heroult in 1899French metallurgist Paul Heroult in 1899

• Introduced into U.S. in 1904Introduced into U.S. in 1904

• Produce more than 800 tons of steel in 24 Produce more than 800 tons of steel in 24 hrs.hrs.

• Electricity used solely for production of heatElectricity used solely for production of heat

• Uses three carbon electrodes (4–24 inches) Uses three carbon electrodes (4–24 inches) for direct arcfor direct arc

• Circular furnace shape which can be titled to Circular furnace shape which can be titled to pour molten steel into ladlepour molten steel into ladle


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Electric Arc FurnaceElectric Arc FurnaceC

opyright © T

he McG

raw-H

ill Com

panies, Inc. Perm



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37Electric Furnace Processes:Electric Induction FurnaceElectric Furnace Processes:Electric Induction Furnace

• Transformer with molten metal acting as coreTransformer with molten metal acting as core• Consists of magnesia crucibleConsists of magnesia crucible

– Surrounded by layer of tamped-in magnesia refractorySurrounded by layer of tamped-in magnesia refractory– Copper tubing coil around this connected to current Copper tubing coil around this connected to current

source; encased in heavy box with silica brick bottom source; encased in heavy box with silica brick bottom lininglining

• Charge melted down in 45 minutesCharge melted down in 45 minutes– Further heated for 15 minutes to tapping temperaturesFurther heated for 15 minutes to tapping temperatures– Alloys and deoxidizers addedAlloys and deoxidizers added

• Furnace tilted and liquid metal runs outFurnace tilted and liquid metal runs out


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Electric Induction FurnaceElectric Induction Furnace



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Oxygen ProcessOxygen Process

• Also known as Linz-Donawitz processAlso known as Linz-Donawitz process• First established in Linz, Austria (1952)First established in Linz, Austria (1952)• First used in United States in 1954First used in United States in 1954• Method of pig iron and scrap conversion Method of pig iron and scrap conversion

whereby oxygen is injected downward over whereby oxygen is injected downward over bath of metalbath of metal– Chemical reaction of oxygen and fluxes Chemical reaction of oxygen and fluxes

refines pig iron and scrap into steelrefines pig iron and scrap into steel– Temperature reaches 3,000ºFTemperature reaches 3,000ºF– Refining continues for 20 to 25 minutesRefining continues for 20 to 25 minutes


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40OxygenProcessOxygenProcess

After scrap and hotmetal are charged into

furnace, dust cap isput on, and oxygenblown through the

lance to the surface ofthe molten metal inorder to burn out

impurities.



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41Vacuum Furnaces and DegassingVacuum Furnaces and Degassing

• Melting of steel and other alloys in vacuum Melting of steel and other alloys in vacuum reduces gases in metal and produces reduces gases in metal and produces metal with minimum of impuritiesmetal with minimum of impurities– Gases formed in vacuum furnace pulled out by Gases formed in vacuum furnace pulled out by

vacuum pumpsvacuum pumps

• Two general types of furnacesTwo general types of furnaces– Vacuum induction meltingVacuum induction melting– Consumable electrode vacuum arc meltingConsumable electrode vacuum arc melting


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Vacuum Induction MeltingVacuum Induction Melting

• First used in 1940sFirst used in 1940s

• Charge melted in furnace within airtight, Charge melted in furnace within airtight, water-cooled steel chamberwater-cooled steel chamber

• Advantages include: Advantages include: – Freedom form air contaminationFreedom form air contamination– Close control of heatClose control of heat– Fewer air inclusionsFewer air inclusions


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Vacuum Induction MeltingVacuum Induction MeltingC

opyright © T

he McG

raw-H

ill Com

panies, Inc. Perm



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44Consumable Electrode Vacuum Arc MeltingConsumable Electrode Vacuum Arc Melting

• Refining process for steel prepared by Refining process for steel prepared by other methodsother methods

• Steel electrodes of predetermined Steel electrodes of predetermined composition are remelted by an electric arc composition are remelted by an electric arc in airtight, water-cooled cruciblein airtight, water-cooled crucible– Principle similar to arc weldingPrinciple similar to arc welding

• Furnace consists of water-cooled copper Furnace consists of water-cooled copper crucible, vacuum system for removing air crucible, vacuum system for removing air from crucible during melting, and a from crucible during melting, and a d.c. power source for producing arcd.c. power source for producing arc


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45Consumable Electrode Vacuum Arc MeltingConsumable Electrode Vacuum Arc Melting



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46Vacuum Furnaces and DegassingVacuum Furnaces and Degassing

• Produce high quality steel and steel alloysProduce high quality steel and steel alloys• Advantages:Advantages:

– Production of alloys too expensive to Production of alloys too expensive to manufacture by air-melt processesmanufacture by air-melt processes

– Use of reactive elementsUse of reactive elements– Decreased amounts of hydrogen, oxygen, and Decreased amounts of hydrogen, oxygen, and

nitrogen in finished productnitrogen in finished product– Improved mechanical propertiesImproved mechanical properties– Close heat controlClose heat control– Better hot and cold workabilityBetter hot and cold workability


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47

Vacuum DegassingVacuum Degassing

• Refining operationRefining operation• Purpose to reduce amounts of hydrogen, Purpose to reduce amounts of hydrogen,

oxygen and nitrogen in steeloxygen and nitrogen in steel• Process carried out after molten metal Process carried out after molten metal

removed from furnace and before poured removed from furnace and before poured into ingotsinto ingots

• Three processes todayThree processes today– Steam degassingSteam degassing– Ladle degassingLadle degassing– Vacuum lifter degassingVacuum lifter degassing


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48Steam DegassingSteam Degassing

Steel is pouredinto a tank fromwhich air has

been removed.Collected in

ingot mold orladle.

Cop

yrig

ht ©

The

McG

raw

-Hill

Com

pani

es,

Inc.

P

erm

issi

on r

equi

red

for

repr

oduc

tion

or d

ispl

ay.


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49

Ladle Degassing ProcessLadle Degassing Process

A ladle of moltensteel placed in

tank and then airremoved from tank,

exposing it to vacuum.

Can processsmaller amounts

of steel thansteam degassing.



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50

Vacuum Lifter DegassingVacuum Lifter Degassing

Metal forced upward into vacuum chamber through nozzles by means of atmospheric pressure.

Copyright ©

The M

cGraw

-Hill C

ompanies, Inc. P

ermission required for reproduction or display.

A vacuum is created in a

chamber suspended above a ladle

of steel.


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51

Benefits From DegassingBenefits From Degassing

• Reduction of hydrogen eliminates flaking of Reduction of hydrogen eliminates flaking of steelsteel

• Reduction of oxygen promotes internal Reduction of oxygen promotes internal cleanlinesscleanliness– Oxygen reduction not as low as achieved in Oxygen reduction not as low as achieved in

vacuum-melted steelsvacuum-melted steels

• Nitrogen content reduced slightlyNitrogen content reduced slightly• Transverse ductility of most degassed Transverse ductility of most degassed

forced products nearly double that of air-forced products nearly double that of air-cast steelcast steel


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52

Continuous Casting of SteelContinuous Casting of Steel

• Process by which molten steel solidified Process by which molten steel solidified into semifinished billet, bloom, or slab for into semifinished billet, bloom, or slab for subsequent finishingsubsequent finishing– Prior method was forming ingotsPrior method was forming ingots

• Improved yield, quality, productivity and Improved yield, quality, productivity and cost efficiencycost efficiency

• Various shapes castVarious shapes cast• Complete operation can be achieved in 2 Complete operation can be achieved in 2

hourshours


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53Example of Continuous CastersExample of Continuous Casters

American Iron & Steel Inst.

into tundish


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Casting Process SectionsCasting Process Sections

• Tundish to feed liquid steel to moldTundish to feed liquid steel to mold

• Primary cooling zone to generate solidified Primary cooling zone to generate solidified outer shellouter shell

• Secondary cooling zone to further solidified Secondary cooling zone to further solidified the strandthe strand

• Unbending and straightening sectionUnbending and straightening section

• Severing unit to cut solidified strandSevering unit to cut solidified strand


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55

Liquid Steel TransferLiquid Steel Transfer

• Two steps involved in transferring liquid Two steps involved in transferring liquid steel from ladle to moldssteel from ladle to molds– From ladle to tundishFrom ladle to tundish– From tundish to moldsFrom tundish to molds

• Regulated by orifice control devices of various Regulated by orifice control devices of various designsdesigns

• Designs: slide gates, stopper rods, or metering Designs: slide gates, stopper rods, or metering nozzlesnozzles


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Tundish overviewTundish overview

• Enhances oxide inclusion separationEnhances oxide inclusion separation

• Provides continuous flow of liquid steel to Provides continuous flow of liquid steel to mold during ladle exchangesmold during ladle exchanges

• Maintains steady metal height above Maintains steady metal height above nozzles to moldsnozzles to molds

• Provides more stable stream patterns to Provides more stable stream patterns to moldsmolds


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57

MoldMold

• Purpose to allow establishment of solid Purpose to allow establishment of solid shell sufficient in strength to contain liquid shell sufficient in strength to contain liquid corecore

• Open-ended box structure containing Open-ended box structure containing water-cooled inner copper liningwater-cooled inner copper lining

• Oscillation necessary to minimize friction Oscillation necessary to minimize friction and sticking of solidifying shelland sticking of solidifying shell– Achieved either hydraulically or via motor-Achieved either hydraulically or via motor-

driven cams or leversdriven cams or levers


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58

Secondary CoolingSecondary Cooling

• Series of zonesSeries of zones• Sprayed medium either water of air and Sprayed medium either water of air and

waterwater• Three basic forms of heat transferThree basic forms of heat transfer

– Radiation: to atmosphereRadiation: to atmosphere– Conduction: by direct contactConduction: by direct contact– Convection: by moving airflowConvection: by moving airflow

• Purpose of spray chamberPurpose of spray chamber– Enhance and control rate of solidificationEnhance and control rate of solidification– Regulate strand temperatureRegulate strand temperature– Control machine containment coolingControl machine containment cooling


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59

Casting and Soaking IngotsCasting and Soaking Ingots

• Molten steel cast into molds directly gives Molten steel cast into molds directly gives us cast steelus cast steel– Cast steel inferior to wrought steelCast steel inferior to wrought steel

• Molten steel poured into ingot molds or Molten steel poured into ingot molds or continuous casting gives inside chance to continuous casting gives inside chance to become solid while outside kept from become solid while outside kept from cooling off too muchcooling off too much– Lowered into soaking pitLowered into soaking pit– Heat steel for rollingHeat steel for rolling


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60

DeoxidationDeoxidation

• Type of steel determined by control of Type of steel determined by control of amount of gas evolved during solidificationamount of gas evolved during solidification

• Increasing degrees of gas evolutionIncreasing degrees of gas evolution– Killed steelsKilled steels– Semikilled steelsSemikilled steels– Capped steelsCapped steels– Rimmed steelsRimmed steels


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Killed SteelKilled Steel

• Strongly deoxidizedStrongly deoxidized

• Relatively high degree of uniformity in Relatively high degree of uniformity in composition and propertiescomposition and properties

• Suitable for applications involvingSuitable for applications involving– ForgingForging– PiercingPiercing– CarburizingCarburizing– Heat treatmentHeat treatment


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Semikilled SteelsSemikilled Steels

• Intermediate in deoxidation between killed Intermediate in deoxidation between killed and rimmed gradesand rimmed grades

• Composition more uniform than rimmed Composition more uniform than rimmed steelssteels

• Used where neither cold-forming and Used where neither cold-forming and surface characteristics of rimmed steel nor surface characteristics of rimmed steel nor uniformity of killed steels essential uniformity of killed steels essential requirementsrequirements


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Capped SteelsCapped Steels

• Have thin low-carbon rimHave thin low-carbon rim

• Remainder of cross section approaches Remainder of cross section approaches degree of semikilled steelsdegree of semikilled steels

• Great increase in use of capped steels Great increase in use of capped steels over rimmed steels in recent yearsover rimmed steels in recent years


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64

Rimmed SteelsRimmed Steels

• Surface and cold-forming characteristics of Surface and cold-forming characteristics of capped steelscapped steels

• Only slightly deoxidizedOnly slightly deoxidized

• Low-carbon surface layer very ductileLow-carbon surface layer very ductile

• Rolling produces sound surfaceRolling produces sound surface

• Used when surface is of prime importanceUsed when surface is of prime importance


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65Environmental Progress in the Steel IndustryEnvironmental Progress in the Steel Industry

• Each year, 15% of steel industryEach year, 15% of steel industry’’s capital s capital spent for environmental facilitiesspent for environmental facilities– $10 to $20 per ton of steel produced$10 to $20 per ton of steel produced

• Amount of energy to produce ton of steel Amount of energy to produce ton of steel decreased by 45% from 1975 to 1998decreased by 45% from 1975 to 1998– Accurate and efficient microprocessor controlsAccurate and efficient microprocessor controls– Two-thirds less labor producing more steelTwo-thirds less labor producing more steel

• From 12 labor hours to 45 labor minutesFrom 12 labor hours to 45 labor minutes


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66Environmental Progress in the Steel IndustryEnvironmental Progress in the Steel Industry

• Air quality greatly improved since 1970Air quality greatly improved since 1970– Discharge of air and water pollutants reduced Discharge of air and water pollutants reduced

by over 90%by over 90%

• Made great strides in terms of recyclingMade great strides in terms of recycling– Over 95% of waterOver 95% of water

• Has worked cooperatively with federal Has worked cooperatively with federal environmental agenciesenvironmental agencies


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67

Metalworking ProcessesMetalworking Processes

• Shape it and improve its characteristicsShape it and improve its characteristics– ForgingForging– RollingRolling

• Destroy the cast structureDestroy the cast structure– ““Orienting the grainOrienting the grain””

• Steel strongerSteel stronger• More ductileMore ductile• Greater shock resistanceGreater shock resistance


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68

ForgingForging

• Method of reducing metal to desired shapeMethod of reducing metal to desired shape• Usually done with steam hammerUsually done with steam hammer

– Today most done with hydraulic pressesToday most done with hydraulic presses• Can take cooler ingots and work to closer dimensionsCan take cooler ingots and work to closer dimensions

• Drop forgingDrop forging– Piece of roughly shaped metal placed Piece of roughly shaped metal placed

between die-shaped faces of exact form of between die-shaped faces of exact form of finished piecefinished piece• Metal forced to take form by drawing dies togetherMetal forced to take form by drawing dies together• Many automobile parts made this wayMany automobile parts made this way


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69

RollingRolling

• Steel rolled hot except for finishing passesSteel rolled hot except for finishing passes• After rolling, ingots known by size and After rolling, ingots known by size and

shapeshape– BloomBloom

• Square or oblong with minimum cross-sectional Square or oblong with minimum cross-sectional area of 36 inchesarea of 36 inches

– BilletBillet• Square or oblong, but smaller than bloomSquare or oblong, but smaller than bloom

– SlabSlab• Oblong and varies in thickness from 2 to 6 inches Oblong and varies in thickness from 2 to 6 inches

and in width from 5 to 6 feetand in width from 5 to 6 feet


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70Samples of Various Shapes Produced by Hot RollingSamples of Various Shapes Produced by Hot Rolling



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71

Processes for Rolling SteelProcesses for Rolling Steel

• One-half rolled steel products in U.S. are One-half rolled steel products in U.S. are flat rolledflat rolled– Includes plates, sheet and stripIncludes plates, sheet and strip

• Flat-rolled steel divided into two categoriesFlat-rolled steel divided into two categories– Hot rolledHot rolled

• Finished at temperatures between 900 and 2,400ºFFinished at temperatures between 900 and 2,400ºF• Black ironBlack iron

– Cold rolledCold rolled• Finished at room temperatureFinished at room temperature• Coated with zinc (galvanized), tin (tin plate), tin and Coated with zinc (galvanized), tin (tin plate), tin and

lead (Terne plate)lead (Terne plate)


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72

Tubular Steel ProductsTubular Steel Products

• Classified according to method of Classified according to method of manufacturemanufacture– Welded (flash welding steel strip)Welded (flash welding steel strip)

• Metal pieces heated until contacting surfaces plastic Metal pieces heated until contacting surfaces plastic state, then forced together quickly under pressurestate, then forced together quickly under pressure

– SeamlessSeamless• Piercing: Heated steel bar pierced by mandrel and Piercing: Heated steel bar pierced by mandrel and

rolled to desired diameter and wall thicknessrolled to desired diameter and wall thickness

• Cupping: Heated plate formed around cup-shaped Cupping: Heated plate formed around cup-shaped diesdies


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PiercingPiercingC

opyright © T

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panies, Inc. Perm



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Structural Steel ShapesStructural Steel Shapes

Steel may also be shaped into wire, bars, forging, extrusions, rails and structured shapes. These are just a few of the basic steel shapes with which welder fabricator works.

Copyright ©

The M

cGraw

-Hill C

ompanies, Inc. P



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75

Rolling DirectionsRolling Directions

X Direction: Best strength and ductilityY Direction: 30% reduction in strength 30% reduction in ductilityZ Direction: Lower strength; virtually no ductility

In rolling operations, grains are oriented in direction of rolling.


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DrawingDrawing

• Operation of reducing cross section and Operation of reducing cross section and increasing length of metal bar or wireincreasing length of metal bar or wire– Draw through series of conical, tapering holes Draw through series of conical, tapering holes

in die platein die plate• Each hole smaller than preceding oneEach hole smaller than preceding one

• Shapes varying in size from finest wire to Shapes varying in size from finest wire to very large are drawnvery large are drawn


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77

ExtrusionExtrusion

• Forming by pressing through an openingForming by pressing through an opening

• Can obtain perfectly round rodsCan obtain perfectly round rods

• Metal placed in closed chamber fitted with Metal placed in closed chamber fitted with opening at one end and piston at other endopening at one end and piston at other end– Forced out through opening by hydraulic Forced out through opening by hydraulic

pressurepressure

• Used to form brass rodUsed to form brass rod


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78

Cold WorkingCold Working

• Shaping of metals by working at ordinary Shaping of metals by working at ordinary temperaturestemperatures

• MethodsMethods– HammeredHammered– RolledRolled– DrawnDrawn


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Heat TreatmentHeat Treatment

• Process of heating and cooling metal for Process of heating and cooling metal for purpose of improving its structural or purpose of improving its structural or physical propertiesphysical properties

• Done to remove stresses caused by Done to remove stresses caused by welding, casting, or heavy machiningwelding, casting, or heavy machining

• Can make it easier to work with or increase Can make it easier to work with or increase hardness for wear resistancehardness for wear resistance


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80Important Variables in Any Heat Treatment ProcessImportant Variables in Any Heat Treatment Process

1.1. Carbon contentCarbon content

2.2. Temperature of Temperature of heatingheating

3.3. Time allowed for Time allowed for coolingcooling

4.4. Cooling mediumCooling medium– Water, oil, or airWater, oil, or air


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HardeningHardening

• Process in which steel heated above its Process in which steel heated above its critical point and cooled rapidlycritical point and cooled rapidly– Critical point is point at which carbon changes Critical point is point at which carbon changes

structure of steelstructure of steel

• Produces hardness superior to that of steel Produces hardness superior to that of steel before heating and coolingbefore heating and cooling

• Only medium, high, and very high carbon Only medium, high, and very high carbon steel can be treatedsteel can be treated


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Case HardeningCase Hardening

• Process that gives steel hard, wear-Process that gives steel hard, wear-resistant surface while leaving interior soft resistant surface while leaving interior soft and toughand tough

• ProcessesProcesses– CyanidingCyaniding– CarburizingCarburizing– NitridingNitriding– Flame hardeningFlame hardening– Hard surfacing by weldingHard surfacing by welding– Metal sprayingMetal spraying

Plain carbon steels andalloy steels are often

case hardened.


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CyanidingCyaniding

• Method of surface-hardening low-carbon Method of surface-hardening low-carbon steelssteels

• Carbon and nitrogen absorbed in outer Carbon and nitrogen absorbed in outer layer of steel to depth of 0.003 to 0.020 layer of steel to depth of 0.003 to 0.020 inchinch

• Done in liquid or gas formDone in liquid or gas form– For hard, but very thin, surface over steelFor hard, but very thin, surface over steel


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CarburizingCarburizing

• Process whereby low carbon steel made to Process whereby low carbon steel made to absorb carbon in its outer surfaceabsorb carbon in its outer surface

• Depth to which carbon will penetrate Depth to which carbon will penetrate – Time heat heldTime heat held– Temperature reachedTemperature reached– Carburizing compound usedCarburizing compound used

• Can use carbonaceous solids, cyanidizing Can use carbonaceous solids, cyanidizing liquids, or hydrocarbon gasesliquids, or hydrocarbon gases


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NitridingNitriding

• Process used only with group of low alloy Process used only with group of low alloy steelssteels– Contain elements such as vanadium, Contain elements such as vanadium,

chromium or aluminumchromium or aluminum• Will combine with nitrogen to form nitridesWill combine with nitrogen to form nitrides• Nitrides act as super hard skin on surface of steelNitrides act as super hard skin on surface of steel

• Parts heated in nitrogenous atmosphere to Parts heated in nitrogenous atmosphere to temperature of 900 to 1,000temperature of 900 to 1,000ºFºF

• Quenching unnecessary with little Quenching unnecessary with little distortion or warpagedistortion or warpage


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Flame HardeningFlame Hardening

• Most recent of hardening processesMost recent of hardening processes• Permits localized treatment with complete controlPermits localized treatment with complete control• Steel must contain enough carbon for hardening Steel must contain enough carbon for hardening

to take placeto take place– Article heat treated and drawnArticle heat treated and drawn– Surface exposed to oxyacetylene flame that heats to Surface exposed to oxyacetylene flame that heats to

high temperature quicklyhigh temperature quickly– Cooled quickly by water (depth of hardness controlled Cooled quickly by water (depth of hardness controlled

by temperature of water)by temperature of water)

• Can be used on parts too bulky to put into Can be used on parts too bulky to put into furnacefurnace


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87

AnnealingAnnealing

• Includes several different treatmentsIncludes several different treatments• Effects of annealingEffects of annealing

– To remove stressesTo remove stresses– To induce softness for better machining propertiesTo induce softness for better machining properties– To alter ductility, toughness, or electrical, To alter ductility, toughness, or electrical,

magnetic, or other physical propertiesmagnetic, or other physical properties– To refine crystalline structureTo refine crystalline structure– To produce definite microstructureTo produce definite microstructure

• Changes depend on annealing Changes depend on annealing temperature, rate of cooling and carbon temperature, rate of cooling and carbon contentcontent


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88Difference Between Hardening and Softening of SteelsDifference Between Hardening and Softening of Steels

• Due to rate of coolingDue to rate of cooling– Fast cooling hardensFast cooling hardens– Slow cooling softensSlow cooling softens

• Both tempering and annealing reduce Both tempering and annealing reduce hardness of materialhardness of material


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89

TemperingTempering

• Process wherein hardness of steel reduced Process wherein hardness of steel reduced after heat treatment and relieve stressafter heat treatment and relieve stress

– Heat hardened steel to predetermined Heat hardened steel to predetermined temperature between room temperature and temperature between room temperature and critical temperaturecritical temperature

– Hold temperature for length of timeHold temperature for length of time– Cooling in air or waterCooling in air or water

• Reduction of hardness depends on 3 factorsReduction of hardness depends on 3 factors– Tempering temperatureTempering temperature– Amount of time steel is held at temperatureAmount of time steel is held at temperature– Carbon content of steelCarbon content of steel


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90

NormalizingNormalizing

• Improves grain structure of metal and Improves grain structure of metal and returns it to normal by removing stressesreturns it to normal by removing stresses– Stresses caused by uneven cooling following Stresses caused by uneven cooling following

welding, casting, or forgingwelding, casting, or forging

• Requires faster rate of cooling than used Requires faster rate of cooling than used for annealingfor annealing– Results in harder, stronger metal than Results in harder, stronger metal than

annealingannealing


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91

Metal Internal StructuresMetal Internal Structures

• MetallurgyMetallurgy– Science that deals with internal structure of Science that deals with internal structure of

metalsmetals

• Four states of matterFour states of matter– Solids, liquids, gases, and plasmasSolids, liquids, gases, and plasmas

• Subatomic particlesSubatomic particles– Electrons – carry negative chargeElectrons – carry negative charge– Protons – carry positive chargeProtons – carry positive charge– Attraction and repelling forces effect properties Attraction and repelling forces effect properties

of metalsof metals


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92

Metal Internal StructuresMetal Internal Structures

• Atoms are in constant state of vibrationAtoms are in constant state of vibration• Heat energy increases atomic movementHeat energy increases atomic movement

– Temperature rises, atomic structure expandsTemperature rises, atomic structure expands– Rises high enough, atoms move freely and Rises high enough, atoms move freely and

solid becomes liquidsolid becomes liquid– Continues to rise, vaporization occurs Continues to rise, vaporization occurs

• Liquid to gasLiquid to gas

– Superheated, it ionizes and becomes plasmaSuperheated, it ionizes and becomes plasma• Gas that has become electrical conductorGas that has become electrical conductor


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93

Solid MetalsSolid Metals

• Take on three-dimensional crystalline Take on three-dimensional crystalline structurestructure– Atoms align themselves into orderly layers, Atoms align themselves into orderly layers,

lines and rowslines and rows

• Common phases of metalsCommon phases of metals– Body-centered cubic (BCC)Body-centered cubic (BCC)– Face-centered cubic (FCC)Face-centered cubic (FCC)– Body-centered tetragonal (BCT)Body-centered tetragonal (BCT)– Hexagonal close-paced (HCP)Hexagonal close-paced (HCP)


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94

Metals Crystalline StructuresMetals Crystalline Structures

IronCarbon steelsChromiumMolybdenumTungsten

Aluminum Copper Nickel SilverAustenitic Stainless Steels

Martensite

ZincCadmium

Magnesium

Copyright ©

The M

cGraw

-Hill C

ompanies, Inc. P



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107

Cooling rate critical above 1333Not so critical below 1333


Cannot go between Matensite, Bainite, or Pearlitewithout going through Austenite first.


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108

SolidificationSolidification


Starts at interface between molten weld metal and coolerunmelted heat-affected zone. Clusters of atoms form grainsand grain boundaries.


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109

Grain Size Effects on MetalsGrain Size Effects on Metals

• Fine-grained metalsFine-grained metals– Good tensile strengthGood tensile strength– Good ductilityGood ductility– Good low temperature propertiesGood low temperature properties

• Coarse-grained metalsCoarse-grained metals– Slightly lower strengthSlightly lower strength– Slightly less ductilitySlightly less ductility– Good high temperature propertiesGood high temperature properties


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110Welding Effect on Grain SizeWelding Effect on Grain Size

• Heat inputHeat input

• Cooling rate (preheat)Cooling rate (preheat)

• Long or short arcLong or short arc

• Slow or fast travel speedSlow or fast travel speed

• Welding on high or low end of parameter Welding on high or low end of parameter rangesranges

• Process selectedProcess selected


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111

AlloyingAlloying

• Another method of affecting mechanical Another method of affecting mechanical properties of metalsproperties of metals

• Changes the orderly rows, lines, and layers Changes the orderly rows, lines, and layers of the three-dimensional crystalline structureof the three-dimensional crystalline structure

• Interstitial alloyingInterstitial alloying– Small atoms such as carbon, nitrogen and Small atoms such as carbon, nitrogen and

hydrogen can occupy spaces between larger hydrogen can occupy spaces between larger atomsatoms

• Substitutional alloyingSubstitutional alloying– Additional elements create irregularities in crystalAdditional elements create irregularities in crystal


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112

Alloying SchematicAlloying Schematic



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113Physical Properties of MetalsPhysical Properties of Metals

• Common properties divided into three Common properties divided into three general classificationsgeneral classifications– Those related to the absorption and Those related to the absorption and

transmission of energytransmission of energy– Internal structure of the metalInternal structure of the metal– Resistance to stressResistance to stress


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114Properties Related to EnergyProperties Related to Energy

• Melting pointMelting point– Temperature at which substance passes from Temperature at which substance passes from

solid to liquid conditionsolid to liquid condition– Higher carbon content, lower melting pointHigher carbon content, lower melting point

• WeldabilityWeldability– Capacity of metal substance to form strong Capacity of metal substance to form strong

bond of adherence while under pressure or bond of adherence while under pressure or during solidification from liquid stateduring solidification from liquid state


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• FusibilityFusibility– Ease with which metal may be meltedEase with which metal may be melted

• VolatilityVolatility– Ease with which substance may be vaporizedEase with which substance may be vaporized– Measured by degree of temperature at which Measured by degree of temperature at which

metal boils under atmospheric pressuremetal boils under atmospheric pressure

• Electrical conductivityElectrical conductivity– Ability of substance to conduct electrical Ability of substance to conduct electrical

currentcurrent


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• Electrical resistanceElectrical resistance– Opposition to electric current as it flow through Opposition to electric current as it flow through

wire wire – Measured by unit called Measured by unit called ohmohm

• Thermal conductivityThermal conductivity– Ability of substance to carry heatAbility of substance to carry heat

• Hot shortnessHot shortness– Brittleness in metal when hotBrittleness in metal when hot


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• Coefficient of thermal expansionCoefficient of thermal expansion– Amount of expansion metal undergoes when it Amount of expansion metal undergoes when it

is heated and amount of contraction that is heated and amount of contraction that occurs when cooledoccurs when cooled

– Linear coefficient of thermal expansionLinear coefficient of thermal expansion• Increase in length of bar 1 inch long when its Increase in length of bar 1 inch long when its

temperature raised 1ºCtemperature raised 1ºC

• OverheatingOverheating– When temperature exceeds its critical rangeWhen temperature exceeds its critical range

• Heated to such a degree that properties impairedHeated to such a degree that properties impaired


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118Properties Related to Internal StructureProperties Related to Internal Structure

• Specific gravitySpecific gravity– Unit of measurement based on weight of volume Unit of measurement based on weight of volume

of material compared with equal volume of waterof material compared with equal volume of water

• DensityDensity– Expressed as quantity per unit volumeExpressed as quantity per unit volume– Dense metal is compact and does not contain Dense metal is compact and does not contain

discontinuitiesdiscontinuities

• PorosityPorosity– Internal structure that lacks compactness of Internal structure that lacks compactness of

have discontinuities that leave voids in metalhave discontinuities that leave voids in metal


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119

Typical Stresses of MetalsTypical Stresses of Metals

• Compression: squeezingCompression: squeezing• Shear: strain on lap joint pulled in opposite Shear: strain on lap joint pulled in opposite

directionsdirections• Bending: deflection as result of compressive Bending: deflection as result of compressive

forceforce• Tension: pulling in opposite directionsTension: pulling in opposite directions• Fatigue: result of repeated cycles of forces Fatigue: result of repeated cycles of forces

applied and released in all directionsapplied and released in all directions• Torsion: twisting force in opposite directionTorsion: twisting force in opposite direction


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120

Typical StressesTypical Stresses


Compression – The application of pressure

Tension – A pulling action


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Bending – Pressure applied to force away from a straight line

Shear – A pulling action causing two bodies to slide on each other, parallel to their plane of contact



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Torsion – A turningor twisting action

Fatigue – Condition caused by repeated stretching, twisting, compression, while in service



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123Properties Related to Stress ResistanceProperties Related to Stress Resistance

• PlasticityPlasticity– Ability of material to deform without breakingAbility of material to deform without breaking– Combined with strength is most important Combined with strength is most important

combination of properties metal can havecombination of properties metal can have

• StrengthStrength– Ability of material to resist deformationAbility of material to resist deformation– Express ultimate tensile strength in pounds Express ultimate tensile strength in pounds

per square inchper square inch• Ultimate tensile strength of material is its resistance Ultimate tensile strength of material is its resistance

to breakingto breaking


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• ToughnessToughness– Has high tensile strength and ability to deform Has high tensile strength and ability to deform

permanently without breakingpermanently without breaking– Opposite of brittlenessOpposite of brittleness– No direct method of measuring accuratelyNo direct method of measuring accurately

• Impact resistanceImpact resistance– Ability of material to withstand maximum load Ability of material to withstand maximum load

applied suddenlyapplied suddenly– Often taken as indication of its toughnessOften taken as indication of its toughness


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• BrittlenessBrittleness– Fail without any warning as deformation, Fail without any warning as deformation,

elongation, or change of shapeelongation, or change of shape– Lacks plasticity and toughnessLacks plasticity and toughness

• MalleabilityMalleability– Ability to deform permanently under Ability to deform permanently under

compression without breaking or fracturingcompression without breaking or fracturing– Must have to be forgedMust have to be forged


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• HardnessHardness– Ability of one material to penetrate another Ability of one material to penetrate another

material without fracturematerial without fracture– Greater the hardness, greater resistance to Greater the hardness, greater resistance to

markingmarking– Measured by pressing hardened steel ball into Measured by pressing hardened steel ball into

materialmaterial• Brinell hardness test – diameter of impression Brinell hardness test – diameter of impression

measuredmeasured

• Rockwell hardness test – depth of impression measuredRockwell hardness test – depth of impression measured


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• ElasticityElasticity– Ability of material to return to original shape Ability of material to return to original shape

after load been removedafter load been removed

• Elastic limitElastic limit– Greatest load that may be applied after which Greatest load that may be applied after which

material will return to its original conditionmaterial will return to its original condition– Once reached, no longer behaves elasticallyOnce reached, no longer behaves elastically

• Permanent deformationPermanent deformation


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• Modulus of elasticityModulus of elasticity– Ratio of stress to strainRatio of stress to strain

– Measure of relative stiffnessMeasure of relative stiffness

– High modulus, material resist movement or High modulus, material resist movement or distortion; low modulus, material stretches easilydistortion; low modulus, material stretches easily

• ResilienceResilience– Energy stored in material under strain within its Energy stored in material under strain within its

elastic limit that causes it to resume its original elastic limit that causes it to resume its original shape when load removedshape when load removed


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• Yield pointYield point– Point at which definite increase in length of Point at which definite increase in length of

specimen occurs with no increase in loadspecimen occurs with no increase in load– Expressed as pounds per square inchExpressed as pounds per square inch

• DuctilityDuctility– Ability of material to be permanently deformed Ability of material to be permanently deformed

by loading and yet resist fractureby loading and yet resist fracture– Amount of stretching expressed as Amount of stretching expressed as percent of percent of

elongationelongation


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• Fatigue failureFatigue failure– Failure under repeated or alternating stressFailure under repeated or alternating stress– Fatigue limit: load which may be applied for Fatigue limit: load which may be applied for

indefinite number of cycles without causing indefinite number of cycles without causing failurefailure• Expressed in pounds per square inchExpressed in pounds per square inch

– Level of loading called Level of loading called endurance limit of the endurance limit of the materialmaterial• Maximum load that can be applied at which no Maximum load that can be applied at which no

failure will occur, no matter how many cycles load failure will occur, no matter how many cycles load is appliedis applied


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• CorrosionCorrosion– Gradual wearing away or disintegration of Gradual wearing away or disintegration of

material by chemical processmaterial by chemical process– Measured byMeasured by

• Determining loss in strength of tensile samplesDetermining loss in strength of tensile samples• Determining loss in weight of materials that Determining loss in weight of materials that

dissolve in corroding mediumdissolve in corroding medium• Determining gain in weight when heavy coating of Determining gain in weight when heavy coating of

rust is formedrust is formed

• Resistance to corrosionResistance to corrosion– Ability of metals to resist atmospheric Ability of metals to resist atmospheric

corrosion and corrosion by liquids or gasescorrosion and corrosion by liquids or gases


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132Effect of Common Elementson Steel: NonmetalsEffect of Common Elementson Steel: Nonmetals

• CarbonCarbon– Native state both as diamond (very hard) and as Native state both as diamond (very hard) and as

graphite (very soft)graphite (very soft)– Part coal, petroleum, asphalt, and limestonePart coal, petroleum, asphalt, and limestone– Increased carbon content increases tensile strength of Increased carbon content increases tensile strength of

steel but decreases ductility and weldabilitysteel but decreases ductility and weldability

• PhosphorusPhosphorus– SmallSmall amounts improve machinability of low and high amounts improve machinability of low and high

carbon steelcarbon steel– Considered impurity in weldingConsidered impurity in welding


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• BoronBoron– Occurs in nature in combination with other Occurs in nature in combination with other

elementselements– Gray, extremely hard solid with melting point Gray, extremely hard solid with melting point

in excess of 400ºFin excess of 400ºF– Increases hardenability of steelIncreases hardenability of steel

• SiliconSilicon– Main substance in sand and sandstoneMain substance in sand and sandstone– Added mainly as deoxidizing agent to produce Added mainly as deoxidizing agent to produce

soundness during steelmakingsoundness during steelmaking


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• SulfurSulfur– Considered a harmful impurity in steelConsidered a harmful impurity in steel

• Makes steel brittle and causes cracking at high Makes steel brittle and causes cracking at high tempstemps

– Should be kept below 0.05%Should be kept below 0.05%– Improves machinability of steelImproves machinability of steel

• SeleniumSelenium– Used interchangeably with sulfur in some Used interchangeably with sulfur in some

stainless steels to promote machinabilitystainless steels to promote machinability


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135Effect of Common Elementson Steel: MetalsEffect of Common Elementson Steel: Metals

• ManganeseManganese– Very hard, grayish-white metal with reddish Very hard, grayish-white metal with reddish

lusterluster– Pure state can scratch glassPure state can scratch glass– Addition to steel increases both tensile Addition to steel increases both tensile

strength and hardnessstrength and hardness– High manganese steelsHigh manganese steels

• Very resistant to abrasionVery resistant to abrasion• Used in equipment such as rock crushers, grinding Used in equipment such as rock crushers, grinding

mills, and power shovel scoopsmills, and power shovel scoops


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• MolybdenumMolybdenum– Silvery white metal that increases toughness of Silvery white metal that increases toughness of

steelsteel– Increases corrosion resistance of stainless steelsIncreases corrosion resistance of stainless steels

• ChromiumChromium– Hard, brittle, grayish-white metalHard, brittle, grayish-white metal– Highly resistant to corrosionHighly resistant to corrosion– Addition to low alloy steels increases tensile Addition to low alloy steels increases tensile

strength, hardness, and resistance to corrosion strength, hardness, and resistance to corrosion and oxidationand oxidation

– Ductility is increasedDuctility is increased


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• NickelNickel– Hard, silvery white elementHard, silvery white element– Used extensively for plating purposes and as Used extensively for plating purposes and as

alloying element in steelalloying element in steel• Increases strength, toughness, and corrosion Increases strength, toughness, and corrosion

resistance of steelresistance of steel

• NiobiumNiobium– Combines with carbon and improves corrosion Combines with carbon and improves corrosion

resistance in stainless steelsresistance in stainless steels


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• CobaltCobalt– Tough, lustrous, silvery white metalTough, lustrous, silvery white metal

– Used as alloying metal in high speed steel and Used as alloying metal in high speed steel and special alloys when high strength and hardness special alloys when high strength and hardness must be maintained at high temperaturesmust be maintained at high temperatures

• Titanium and ZirconiumTitanium and Zirconium– Added in small amounts to certain high strength, Added in small amounts to certain high strength,

low alloy steels to deoxidize metal, control fine low alloy steels to deoxidize metal, control fine grain size, and improve physical propertiesgrain size, and improve physical properties


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• CopperCopper– Soft, ductile, malleable metal that melts at 1,984ºFSoft, ductile, malleable metal that melts at 1,984ºF– Has expansion rate 1-1/2 times greater than steelHas expansion rate 1-1/2 times greater than steel– Thermal conductivity 10 times greater than steelThermal conductivity 10 times greater than steel– Very good conductor of heat and electricityVery good conductor of heat and electricity– Highly corrosion resistantHighly corrosion resistant– Added to steel to improve its resistance to Added to steel to improve its resistance to

corrosioncorrosion– Brass most common class of copper alloy (zinc)Brass most common class of copper alloy (zinc)– Bronzes other alloys (zinc, tin, silicon, aluminum)Bronzes other alloys (zinc, tin, silicon, aluminum)


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• AluminumAluminum– Never found in nature in pure stateNever found in nature in pure state

• Derived from bauxiteDerived from bauxite

– One of the lightest metalsOne of the lightest metals– Good conductor of heat and electricityGood conductor of heat and electricity– Highly resistant to atmospheric corrosionHighly resistant to atmospheric corrosion– Ductile and malleableDuctile and malleable– Used in both carbon and alloy steelsUsed in both carbon and alloy steels

• Produces fine austenitic grain sizeProduces fine austenitic grain size


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• LeadLead– Soft malleable, heavy metalSoft malleable, heavy metal– Very low melting point: 620ºFVery low melting point: 620ºF– Highly resistant to corrosionHighly resistant to corrosion– Additions to carbon and alloy steels improve Additions to carbon and alloy steels improve

machinability machinability – Leaded carbon steels have been used mainly Leaded carbon steels have been used mainly

for stock which is to be free machinedfor stock which is to be free machined– Used extensively in plumbing industryUsed extensively in plumbing industry


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• TungstenTungsten– Steel-gray metal more than twice as heavy as Steel-gray metal more than twice as heavy as

ironiron– Melting point above 6,000ºFMelting point above 6,000ºF– Improves hardness, wear resistance, and tensile Improves hardness, wear resistance, and tensile

strength of steelstrength of steel

• VanadiumVanadium– Increases toughness of steel and gives it ability Increases toughness of steel and gives it ability

to take heavy shocks without breakingto take heavy shocks without breaking– High resistance to metal fatigue and high impact High resistance to metal fatigue and high impact

resistanceresistance


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143

Carbon SteelsCarbon Steels

• Carbon most important alloying ingredient Carbon most important alloying ingredient in steelin steel– Has direct effect on physical propertiesHas direct effect on physical properties

• Divided into four typesDivided into four types– Low carbonLow carbon– Medium carbonMedium carbon– High carbonHigh carbon– Tool Tool


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144

Low Carbon SteelsLow Carbon Steels

• Carbon content does not exceed 0.30% and Carbon content does not exceed 0.30% and may be as low as 0.03%may be as low as 0.03%

• Referred to as mild steels and plain steelsReferred to as mild steels and plain steels– General purpose steel: 0.08–0.25%General purpose steel: 0.08–0.25%– Machine steel and cold-rolled steel: 0.08–0.30%Machine steel and cold-rolled steel: 0.08–0.30%

• Excellent weldabilityExcellent weldability• May be quenched very rapidly in water or May be quenched very rapidly in water or

brine and do not harden to any great extentbrine and do not harden to any great extent• Most structures fabricated: bridges, ships, Most structures fabricated: bridges, ships,

tanks, pipestanks, pipes


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145

Medium Carbon SteelsMedium Carbon Steels

• Have carbon content ranging from 0.30 to Have carbon content ranging from 0.30 to 0.60%0.60%

• Stronger than low carbon steels and have Stronger than low carbon steels and have higher heat-treat qualitieshigher heat-treat qualities

• Should be welded with shielded metal arc Should be welded with shielded metal arc low hydrogen electrodes and other low low hydrogen electrodes and other low hydrogen processeshydrogen processes– Best results obtained if preheated before Best results obtained if preheated before

welding and normalized after weldingwelding and normalized after welding


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146

High Carbon SteelsHigh Carbon Steels

• Have carbon content ranges from 0.60 to Have carbon content ranges from 0.60 to 1.7% 1.7%

• More difficult to weld than low or medium More difficult to weld than low or medium carbon steelscarbon steels

• Can be heat treated for maximum Can be heat treated for maximum hardness and wear resistancehardness and wear resistance

• Used in springs, punches, dies, tools, Used in springs, punches, dies, tools, military tanks, and structural steelmilitary tanks, and structural steel


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147

Alloy SteelsAlloy Steels

• Content of alloying elements exceed Content of alloying elements exceed certain limitscertain limits

• Amounts of alloying elements lie within Amounts of alloying elements lie within specified range for commercial alloy steelsspecified range for commercial alloy steels

• Elements added to obtain desired effect in Elements added to obtain desired effect in finished productfinished product

• Readily welded by welding processes such Readily welded by welding processes such as MIG/MAG, and TIGas MIG/MAG, and TIG


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148High Strength, Low Alloy SteelsHigh Strength, Low Alloy Steels

• Group of steels with chemical compositions Group of steels with chemical compositions specially developedspecially developed

– To give higher physical property values To give higher physical property values

– For materially greater corrosion resistanceFor materially greater corrosion resistance

• Generally used when need savings in weightGenerally used when need savings in weight• Includes oil-hardening steel, air-hardening Includes oil-hardening steel, air-hardening

steel and high speed steelsteel and high speed steel• Readily adaptable to fabrication by shearing, Readily adaptable to fabrication by shearing,

plasma cutting, laser cutting, welding, rivetingplasma cutting, laser cutting, welding, riveting


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149Stainless and Heat-Resisting SteelsStainless and Heat-Resisting Steels

• Possess unusual resistance to corrosion at Possess unusual resistance to corrosion at both normal and elevated temperaturesboth normal and elevated temperatures– Accomplished by addition of chromium to ironAccomplished by addition of chromium to iron

• Corrosion resistance increases with increasing Corrosion resistance increases with increasing chromiumchromium

• Thin layer of chromium oxide bonded to surfaceThin layer of chromium oxide bonded to surface• 11.5% chromium dividing line between low alloy 11.5% chromium dividing line between low alloy

steel and stainless steelsteel and stainless steel

• Practically indefinite lifePractically indefinite life– Some difficulty with pittingSome difficulty with pitting


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150Advantages of Stainless SteelsAdvantages of Stainless Steels

• Resist corrosion and effects of high Resist corrosion and effects of high temperaturestemperatures

• Maintain purity of materials in contact with Maintain purity of materials in contact with themthem

• Permit greater cleanliness than other Permit greater cleanliness than other steelssteels

• Stainless-steel fabrications usually cost Stainless-steel fabrications usually cost little to maintainlittle to maintain


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151Advantages of Stainless SteelsAdvantages of Stainless Steels

• Low strength-to-weight ratios are possible Low strength-to-weight ratios are possible both at room and elevated temperaturesboth at room and elevated temperatures

• Tough at low temperaturesTough at low temperatures

• Have high weldabilityHave high weldability

• Highly pleasing in appearance and require Highly pleasing in appearance and require minimum of finishingminimum of finishing


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152

Five Classifications of SteelsFive Classifications of Steels

• 5% chromium, hardenable 500 series5% chromium, hardenable 500 series– MartensiticMartensitic

• 12% chromium, hardenable 400 series12% chromium, hardenable 400 series– MartensiticMartensitic

• 17% chromium, non-hardenable 400 series17% chromium, non-hardenable 400 series– FerriticFerritic

• Chromium-nickel 300 seriesChromium-nickel 300 series– AusteniticAustenitic

• Chromium-nickel-manganese 200 seriesChromium-nickel-manganese 200 series– AusteniticAustenitic


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153Series 400 and 500 (Martensitic)Series 400 and 500 (Martensitic)

• Primarily heat resisting and retain large part Primarily heat resisting and retain large part of their properties at temperatures up to of their properties at temperatures up to 1,1001,100ºFºF

• More resistant to corrosion than alloy steelsMore resistant to corrosion than alloy steels• Not considered true stainless steelsNot considered true stainless steels• Satisfactory for mildly corrosive conditionsSatisfactory for mildly corrosive conditions• Satisfactory for both hot and cold workingSatisfactory for both hot and cold working• Air hardening and must be cooled slowly or Air hardening and must be cooled slowly or

annealed after forging or welding to prevent annealed after forging or welding to prevent crackingcracking


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154

Series 400 (Ferritic)Series 400 (Ferritic)

• Chromium content ranges from 11.5 to 27%Chromium content ranges from 11.5 to 27%• Carbon content low (under 0.20%)Carbon content low (under 0.20%)• No nickelNo nickel• Cannot be hardened by heat treatmentCannot be hardened by heat treatment• Hardness may be increased by cold workingHardness may be increased by cold working• Low coefficient of thermal expansionLow coefficient of thermal expansion• Good resistance to corrosionGood resistance to corrosion• Ductility fairDuctility fair• Difficult to weldDifficult to weld


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155Series 200 and 300 (Austenitic)Series 200 and 300 (Austenitic)

• Chromium content ranges from 16 to 26%Chromium content ranges from 16 to 26%• Nickel from 3.5 to 22% Nickel from 3.5 to 22% • Carbon from 0.15 to 0.08%Carbon from 0.15 to 0.08%• More numerous, more often used than 400 More numerous, more often used than 400

seriesseries• Stable structure at low temperaturesStable structure at low temperatures• Low yield point with high ultimate tensile Low yield point with high ultimate tensile

strength at room temperaturesstrength at room temperatures


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156Series 200 and 300 (Austenitic)Series 200 and 300 (Austenitic)

• Provide maximum resistance to corrosionProvide maximum resistance to corrosion

• Well-suited to standard fabricationWell-suited to standard fabrication– ductility required for severe deep drawing and ductility required for severe deep drawing and

formingforming

• High rupture and creep-strength values at High rupture and creep-strength values at high temperatureshigh temperatures– Also good oxidation resistanceAlso good oxidation resistance


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157Duplex Stainless-Steel (DSS) AlloysDuplex Stainless-Steel (DSS) Alloys

• Chromium content ranges from 18.0 to 29.0%Chromium content ranges from 18.0 to 29.0%• Nickel from 2.5 to 8.5%Nickel from 2.5 to 8.5%• Carbon from 0.03 to 0.08%Carbon from 0.03 to 0.08%• Interest due to resistance to stress corrosion Interest due to resistance to stress corrosion

cracking, crevice corrosion, general corrosion cracking, crevice corrosion, general corrosion and pittingand pitting

• Have yield strengths twice that of 300 seriesHave yield strengths twice that of 300 series• Used where thinner sections and weight Used where thinner sections and weight

reduction desirablereduction desirable


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158

Tool SteelsTool Steels

• Carbon or alloy steels capable of being Carbon or alloy steels capable of being hardened and temperedhardened and tempered

• Produced primarily for machine tools which Produced primarily for machine tools which cut and shape articles used in cut and shape articles used in manufacturingmanufacturing

• Vary in chemical composition depending Vary in chemical composition depending upon end useupon end use

• Many different types: carbon range from Many different types: carbon range from 0.80 to 1.50%0.80 to 1.50%


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159

Tool SteelsTool Steels

• Usually melted in electric furnaces in small Usually melted in electric furnaces in small batchesbatches

• Used in other applications when wear Used in other applications when wear resistance is importantresistance is important

• Rarely welded and must be preheated to Rarely welded and must be preheated to do sodo so– After-treatment also necessaryAfter-treatment also necessary

• Special hard-surfacing electrodes required Special hard-surfacing electrodes required for this workfor this work


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160

Carbon EquivalencyCarbon Equivalency

• Variety of formulas for calculationVariety of formulas for calculation

• One example: One example: – Intended for use with carbon and alloy steels Intended for use with carbon and alloy steels

that contain more than 0.5% carbon, 1.5% that contain more than 0.5% carbon, 1.5% manganese, 3.5% nickel, 1% chromium, 1% manganese, 3.5% nickel, 1% chromium, 1% copper and 0.5% molybdenum copper and 0.5% molybdenum


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161SAE/AISI Steel Numbering SystemSAE/AISI Steel Numbering System

• Based on chemical analysis of steelBased on chemical analysis of steel

• Number designations indicating Number designations indicating percentage of predominant alloying percentage of predominant alloying elementelement

Table 3-7 showsclassification system


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162

Types of Cast IronTypes of Cast Iron

• Iron-based material containing 91 to 94% ironIron-based material containing 91 to 94% iron– Carbon: 2.0 to 4.0%Carbon: 2.0 to 4.0%

• Cannot be formed by forging, rolling, drawing, Cannot be formed by forging, rolling, drawing, bending or spinningbending or spinning– Low ductility and lack of malleabilityLow ductility and lack of malleability

• Castings have low ductility and low tensile Castings have low ductility and low tensile strengthstrength

• Has excellent compressive strengthHas excellent compressive strength• Four classes: gray, white, nodular, malleableFour classes: gray, white, nodular, malleable


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163

Gray IronGray Iron

• May be fusion welded or braze welded if May be fusion welded or braze welded if preheating before welding cooling after are preheating before welding cooling after are controlledcontrolled

• Low in ductility Low in ductility

• Moderate tensile strengthModerate tensile strength

• High compression strengthHigh compression strength

• High machinabilityHigh machinability


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164

White IronWhite Iron

• Produced through process of rapid cooling Produced through process of rapid cooling which causes carbon to combine with ironwhich causes carbon to combine with iron

• Hard, brittle, very difficult to machineHard, brittle, very difficult to machine

• Considered unweldableConsidered unweldable

• First step in making of malleable ironFirst step in making of malleable iron

• Has fine grain structure Has fine grain structure

• Silvery white appearance when fracturedSilvery white appearance when fractured


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165

Malleable IronMalleable Iron

• Forms when white cast iron has been heat Forms when white cast iron has been heat treated by long annealing processtreated by long annealing process

• Higher tensile strength, impact strength, Higher tensile strength, impact strength, ductility, and toughness than gray or white ironductility, and toughness than gray or white iron

• Fusion welding destroys properties in weld Fusion welding destroys properties in weld areaarea

• Braze welding recommendedBraze welding recommended

• If broken, fracture shows white rim with dark If broken, fracture shows white rim with dark centercenter


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166

Nodular IronNodular Iron

• Referred to as ductile ironReferred to as ductile iron• Amounts of magnesium and/or cerium Amounts of magnesium and/or cerium

added to iron when producedadded to iron when produced– Change shape of graphite particles from flakes Change shape of graphite particles from flakes

to spheroids to spheroids

• Silicon contents higher than other ironsSilicon contents higher than other irons• Excellent machinability, shock resistance, Excellent machinability, shock resistance,

thermal shock resistance, wear resistance, thermal shock resistance, wear resistance, and rigidityand rigidity


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167Aluminum-making in the U.S.Aluminum-making in the U.S.

• WorldWorld’’s largest producers of aluminums largest producers of aluminum– More than 22 million pounds of metal More than 22 million pounds of metal

processed annuallyprocessed annually

• Refining of bauxite oreRefining of bauxite ore– Fundamental production process of reducing Fundamental production process of reducing

alumina to aluminum by means of electricityalumina to aluminum by means of electricity

• Production done across four-fifths of Production done across four-fifths of countrycountry


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168Primary Products and Their Industrial ApplicationsPrimary Products and Their Industrial Applications

• Sheet: Cans, construction materials, and Sheet: Cans, construction materials, and automobile parts automobile parts

• Plate: Aircraft and space fuel tanksPlate: Aircraft and space fuel tanks• Foil: Household aluminum foil, building Foil: Household aluminum foil, building

insulation, automotive parts insulation, automotive parts • Rod, bar, and wire: Electrical transmission Rod, bar, and wire: Electrical transmission

lines and nonrust staples lines and nonrust staples• Extrusions: Storm windows, bridgeExtrusions: Storm windows, bridge

structures structures


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169Environmental Progress in Aluminum IndustryEnvironmental Progress in Aluminum Industry

• Focus on reducing air emissions, water Focus on reducing air emissions, water discharges, and solid wastedischarges, and solid waste

• Recycling very importantRecycling very important– Amount doubled in last decadeAmount doubled in last decade– Saves almost 95% of energy needed to Saves almost 95% of energy needed to

extract aluminum for original oreextract aluminum for original ore– Nearly two-thirds of aluminum beverage cans Nearly two-thirds of aluminum beverage cans

producedproduced


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170

Types of AluminumTypes of Aluminum

• Four-digit numbering systemFour-digit numbering system

(see Table 3-23)(see Table 3-23)

• First digit indicates major alloying groupFirst digit indicates major alloying group

• Three categories of aluminum find most Three categories of aluminum find most welding applicationswelding applications– Commercially pure aluminumCommercially pure aluminum– Wrought aluminum alloysWrought aluminum alloys– Aluminum casting alloysAluminum casting alloys


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171


• Commercially pure wrought aluminum (1100)Commercially pure wrought aluminum (1100)– 99% pure (little iron and silicon)99% pure (little iron and silicon)

– Easily welded (weld strength equal to base Easily welded (weld strength equal to base metal)metal)

• Wrought aluminum-manganese alloyWrought aluminum-manganese alloy– 1.2% manganese, 97% aluminum1.2% manganese, 97% aluminum

– Stronger than 1100 type and less ductileStronger than 1100 type and less ductile

– Welded without difficultyWelded without difficulty

– Welds strongWelds strong


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172


• Aluminum-silicon-magnesium-chromium Aluminum-silicon-magnesium-chromium alloyalloy– Classification number of 6151Classification number of 6151– Silicon and magnesium main alloysSilicon and magnesium main alloys– Welds not as strong as base metalWelds not as strong as base metal

• Can be improved by heat treatmentCan be improved by heat treatment

• Aluminum-magnesium-chromium alloy Aluminum-magnesium-chromium alloy (5052)(5052)– Strong, highly resistant to corrosionStrong, highly resistant to corrosion– Good ductilityGood ductility

• Aluminum-magnesium-silicon alloy (6053)Aluminum-magnesium-silicon alloy (6053)– Readily welded and can be heat treatedReadily welded and can be heat treated


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173

Titanium-making in the U.S.Titanium-making in the U.S.

• Versatile metalVersatile metal– Light weight, physical properties and Light weight, physical properties and

mechanical propertiesmechanical properties

• Produced from heavy-mineral sands Produced from heavy-mineral sands containing ilmenite and/or rutile containing ilmenite and/or rutile – Also titaniferous slags made by smelting of Also titaniferous slags made by smelting of

ilmenite with carbonilmenite with carbon

• Typically associated with ironTypically associated with iron• One-third of world supply found in U.S.One-third of world supply found in U.S.


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174

TitaniumTitanium

• Titanium sponge produced by Kroll Titanium sponge produced by Kroll processprocess– Produced in a retort by vapor phase reduction Produced in a retort by vapor phase reduction

of titanium tetrachloride with magnesiumof titanium tetrachloride with magnesium

• Ingot produced by melting sponge, scrap Ingot produced by melting sponge, scrap or combination of bothor combination of both– Russia and U.S. produce bulk of world supplyRussia and U.S. produce bulk of world supply

• Vacuum arc remelt (VAR) process used to Vacuum arc remelt (VAR) process used to refine materialrefine material– Titanium electrode would be usedTitanium electrode would be used


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TitaniumTitanium

• Mill products formed by rolling, forging, Mill products formed by rolling, forging, drawing, or extruding slabs and ingotsdrawing, or extruding slabs and ingots

• Can be cast into variety of productsCan be cast into variety of products

• Scrap and waste produced at each step of Scrap and waste produced at each step of production processproduction process– Large source of feedstock material with growth Large source of feedstock material with growth

in cold hearth melting capacity in cold hearth melting capacity


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176

Titanium PropertiesTitanium Properties

• Great impact propertiesGreat impact properties

• Durability with excellent mechanical strengthDurability with excellent mechanical strength

• Modulus of elasticity half that of stainless Modulus of elasticity half that of stainless steelsteel

• Very lightweightVery lightweight

• Coefficient of thermal expansion half that of Coefficient of thermal expansion half that of stainless steel and copper, one third of stainless steel and copper, one third of aluminumaluminum

• Very corrosion resistantVery corrosion resistant


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Relative Corrosion RatesRelative Corrosion Rates


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Titanium ImplantsTitanium Implants

• Inert to human body fluidsInert to human body fluids

• Natural material to use for Natural material to use for implantsimplants

• Allows bone growth to Allows bone growth to adhere to implantadhere to implant

• Commonly used for Commonly used for reconstructive surgery reconstructive surgery applicationsapplications


© Scott Camazine


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Titanium ApplicationsTitanium Applications

• Largest single demand is commercial Largest single demand is commercial aerospace industryaerospace industry

• Chemical processing, oil and gas exploration Chemical processing, oil and gas exploration and processingand processing

• Heat exchangersHeat exchangers

• Pollution control equipmentPollution control equipment

• Bicycles, wheelchairs, motorcycle Bicycles, wheelchairs, motorcycle componentscomponents

• Eyeglass frames, writing pens, jewelryEyeglass frames, writing pens, jewelry


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TitaniumTitanium

• NontoxicNontoxic• PyrophoricPyrophoric

– Produces its own heat when in presence of Produces its own heat when in presence of oxidizing elements such as oxygenoxidizing elements such as oxygen• Small pieces with lot of surface contact area to air Small pieces with lot of surface contact area to air

can ignite and burn at extremely high temperaturescan ignite and burn at extremely high temperatures• Form of machining or grinding chipsForm of machining or grinding chips

– Store in nonflammable containers submersed Store in nonflammable containers submersed in water with thin layer of oil on topin water with thin layer of oil on top• Extinguish with dry sand, powdered graphite, Extinguish with dry sand, powdered graphite,

Metal-XMetal-X**


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181

Expansion and ContractionExpansion and Contraction

• All materials when loaded or stressed will All materials when loaded or stressed will deform shrink or stretchdeform shrink or stretch

• Metal expands when heated during Metal expands when heated during weldingwelding– Not free to move due to other welds, tackings, etc.Not free to move due to other welds, tackings, etc.

• Metal contracts when coolsMetal contracts when cools

• Combination of heating and cooling with Combination of heating and cooling with restraint causes stresses to build up in restraint causes stresses to build up in weldmentweldment


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182Two Major Aspects of ContractionTwo Major Aspects of Contraction

• Distortion (shrinkage)Distortion (shrinkage)– Overall motion of parts being welded from position Overall motion of parts being welded from position

occupied before welding to that after weldingoccupied before welding to that after welding

• StressStress– Force that will cause distortion later unless Force that will cause distortion later unless

relievedrelieved

• Residual stressResidual stress– Temporary distortion and stress occur while Temporary distortion and stress occur while

weldingwelding

– Remains after welded members coolRemains after welded members cool


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183Physical Properties of Metal and DistortionPhysical Properties of Metal and Distortion

• DistortionDistortion– Result of heating and cooling and involves Result of heating and cooling and involves

stiffness and yieldingstiffness and yielding

• Heat changes physical properties of metalsHeat changes physical properties of metals– Yield point lowersYield point lowers– Modulus of elasticity decreasesModulus of elasticity decreases– Coefficient of thermal expansion increasesCoefficient of thermal expansion increases– Thermal conductivity decreasesThermal conductivity decreases– Specific heat increasesSpecific heat increases


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184

Yield PointYield Point

• Point at which it will stretch and elongate Point at which it will stretch and elongate under load even though load is not under load even though load is not increasedincreased

• Higher the yield point of weld and base Higher the yield point of weld and base metal, the greater amount of residual metal, the greater amount of residual stressstress

• Lower the yield point, less severe residual Lower the yield point, less severe residual stressstress


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185Coefficient of Thermal ExpansionCoefficient of Thermal Expansion

• Amount of expansion a metal undergoes Amount of expansion a metal undergoes when heated and the amount of when heated and the amount of contraction that occurs when it is cooledcontraction that occurs when it is cooled

• High coefficient tends to increase High coefficient tends to increase shrinkage of weld metal and base metal shrinkage of weld metal and base metal next to weldnext to weld– Increases possibility of distortion in weldmentIncreases possibility of distortion in weldment


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186

Other Physical PropertiesOther Physical Properties

• Thermal conductivityThermal conductivity– Measure of flow of heat through metalMeasure of flow of heat through metal– Low thermal conductivity retards flow of heat Low thermal conductivity retards flow of heat

from weldfrom weld• Increases shrinkage of weld and plate next to itIncreases shrinkage of weld and plate next to it

• Modulus of elasticityModulus of elasticity– Measure of relative stiffness of metalMeasure of relative stiffness of metal– Modulus high, the material more likely to resist Modulus high, the material more likely to resist

movement and distortionmovement and distortion


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187Types of Distortion:Lengthwise ShrinkageTypes of Distortion:Lengthwise Shrinkage

• Occurs when weld is lengthwise on unclamped strip Occurs when weld is lengthwise on unclamped strip of steelof steel

• Bow upwards at both ends when coolsBow upwards at both ends when cools– Due to contraction of weld above plate surfaceDue to contraction of weld above plate surface

• Minimize by small weld beads, flat deep penetrating Minimize by small weld beads, flat deep penetrating beads or even heat on both sides of platebeads or even heat on both sides of plate

Copyright ©

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188

Neutral Axis of JointNeutral Axis of Joint

• Center of gravity of jointCenter of gravity of joint

• Welds kept close to neutral axis or Welds kept close to neutral axis or balancing weld sequences about neutral balancing weld sequences about neutral axis minimizes lengthwise shrinkageaxis minimizes lengthwise shrinkage

Copyright ©

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189Types of Distortion:Crosswise ShrinkageTypes of Distortion:Crosswise Shrinkage

• Also called transverse Also called transverse contractioncontraction

• Butt joint with free Butt joint with free movement during movement during welding allows welding allows opposite end from opposite end from weld to be drawn weld to be drawn together by contraction together by contraction of weld metalof weld metal



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190Controlling Transverse ContractionControlling Transverse Contraction

• Tack-weld at opposite ends on short Tack-weld at opposite ends on short seamsseams

• Tack-weld at several equidistant positions Tack-weld at several equidistant positions on long seamson long seams– Thickness of plateThickness of plate– Type of materialType of material– type of edge preparationtype of edge preparation– Usually twice as long as thickness of plate and Usually twice as long as thickness of plate and

spaced 8–12 inchesspaced 8–12 inches• Clamping devices and wedgesClamping devices and wedges• PrespacingPrespacing


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191


Controlling Transverse ContractionControlling Transverse Contraction


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192Types of Distortion:WarpingTypes of Distortion:Warping

• Contraction of weld depositContraction of weld deposit– Uneven deposit in V-groove and U-groove butt Uneven deposit in V-groove and U-groove butt

jointsjoints• Places most of weld above neutral axisPlaces most of weld above neutral axis

• Greater warping on multiple passes on jointGreater warping on multiple passes on joint



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193

Counteracting WarpingCounteracting Warping

• Setting plates before welding so bow in Setting plates before welding so bow in opposite directionopposite direction

• Clamping platesClamping plates– High internal stressHigh internal stress

• Deforming occurs when residual stress exceed yield Deforming occurs when residual stress exceed yield strength of metalstrength of metal



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194Types of Distortion:Angular DistortionTypes of Distortion:Angular Distortion

• Fillet welds contain Fillet welds contain both longitudinal both longitudinal and transverse and transverse stressesstresses



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195Types of Distortion:Angular DistortionTypes of Distortion:Angular Distortion

• Fillet weld in T-joint will pull vertical Fillet weld in T-joint will pull vertical member toward side that is weldedmember toward side that is welded

Dotted lines indicateoriginal position. Position

after welding is indicated by solid lines.



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196Effect on Butt Joint-Groove WeldsFactors Affecting Perpendicular Shrinkage

Effect on Butt Joint-Groove WeldsFactors Affecting Perpendicular Shrinkage

• Cross-sectional area of weld for given Cross-sectional area of weld for given thickness of platethickness of plate– Larger cross section yields greater shrinkageLarger cross section yields greater shrinkage

• Free distance spacing between roots and Free distance spacing between roots and type of groovetype of groove

• Total heat input: greater heat yields greater Total heat input: greater heat yields greater distortiondistortion

• Rate of heating: greater rate of heat inputRate of heating: greater rate of heat input• Weld searching like backstep proceduresWeld searching like backstep procedures• PeeningPeening


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197Factors that Affect Angular DistortionFactors that Affect Angular Distortion

• Increases with number of layersIncreases with number of layers• Greatest in butt joints with V-grooves welds, next Greatest in butt joints with V-grooves welds, next

in U-grooves, less in double-V and double-U in U-grooves, less in double-V and double-U grooves, and least in square groovesgrooves, and least in square grooves

• May be controlled by peening every fill pass May be controlled by peening every fill pass layer to suitable extentlayer to suitable extent

• Practically eliminated by welding alternately on Practically eliminated by welding alternately on both side in multilayer welding about neutral axis both side in multilayer welding about neutral axis in double-V and double-U groove weldsin double-V and double-U groove welds

• Time of welding and size of electrodeTime of welding and size of electrode• Rate of heatingRate of heating


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198Distortion Affects on Fillet WeldsDistortion Affects on Fillet Welds

• Shrinkage increases with size of weld and Shrinkage increases with size of weld and decreases as rate of heat input increasesdecreases as rate of heat input increases

• Shrinkage proportional to length of weld, if Shrinkage proportional to length of weld, if weld intermittentweld intermittent

• Shrinkage may be decreased materially by Shrinkage may be decreased materially by choosing suitable sequences and choosing suitable sequences and procedures of welding and peeningprocedures of welding and peening

• Transverse shrinkage less for lap joint than Transverse shrinkage less for lap joint than for V groove-butt jointfor V groove-butt joint


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199Prevention of Distortion Before WeldingPrevention of Distortion Before Welding

• DesignDesign– Joints should require minimum amount of filler Joints should require minimum amount of filler

metalmetal– Joints arranged to balance each otherJoints arranged to balance each other

• Selection of process and equipmentSelection of process and equipment– Higher welding speeds through use of Higher welding speeds through use of

powdered iron manual electrodespowdered iron manual electrodes• Reduces amount of base metal affected by heat of Reduces amount of base metal affected by heat of

arcarc


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• PrebendingPrebending– Plates bent in direction opposite to side being Plates bent in direction opposite to side being

weldedwelded– Shrinkage restrained curing welding by clampsShrinkage restrained curing welding by clamps

• More effective when weldedMore effective when weldedmembers are allowed to coolmembers are allowed to coolin clampsin clamps

– When clamps removed, When clamps removed, plates spring back so pulledplates spring back so pulledinto alignmentinto alignment



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201

• Spacing of partsSpacing of parts– Space parts out of position Space parts out of position

before weldingbefore welding– Arms pulled back to properArms pulled back to proper

spacing by shrinkagespacing by shrinkageforces of weldingforces of welding


Prevention of Distortion Before WeldingPrevention of Distortion Before Welding


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• Jigs and fixturesJigs and fixtures– Prevent warping by holding weldment in fixed Prevent warping by holding weldment in fixed

position to reduce movementposition to reduce movement– Widely used in production weldingWidely used in production welding– Strong backsStrong backs

• Temporary stiffeners for purpose of increasing Temporary stiffeners for purpose of increasing resistance to distortionresistance to distortion

• Removed after welding completed and cooledRemoved after welding completed and cooled


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203Distortion Control During WeldingDistortion Control During Welding

• Reduced by using sequence Reduced by using sequence of welding known asof welding known aswanderingwandering– Making welds at different Making welds at different

points of weldmentpoints of weldment• Shrinkage set up by on weldShrinkage set up by on weld

counteracted by shrinkagecounteracted by shrinkageset up by anotherset up by another

– Two methodsTwo methods• Chain intermittent fillet weldsChain intermittent fillet welds• Staggered intermittent filletStaggered intermittent fillet

weldsweldsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chain Staggered


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• Backstep method of weldingBackstep method of welding– Breaking up welds in short sections and Breaking up welds in short sections and

depends upon welding in proper directiondepends upon welding in proper direction– General progression of welding is left to right, General progression of welding is left to right,

but each bead is deposited from right to leftbut each bead is deposited from right to left– Reduces locked-up stresses and warpingReduces locked-up stresses and warping

• Skip-stop, backstep methodSkip-stop, backstep method– Direction same as backstep except short Direction same as backstep except short

welds not made in continuous sequencewelds not made in continuous sequence


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205

Backstep Method ExampleBackstep Method ExampleC

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206

Skip-stop, Backstep MethodSkip-stop, Backstep MethodC

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• Balanced welding sequenceBalanced welding sequence– Equal number of welders weld on opposite Equal number of welders weld on opposite

sides of structure at same timesides of structure at same time• Balanced stressesBalanced stresses

• Both wandering techniques and balanced Both wandering techniques and balanced welding contribute to completion of welded welding contribute to completion of welded connections in large fabricationsconnections in large fabrications


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208Correction of Distortion After WeldingCorrection of Distortion After Welding

• ShrinkageShrinkage– Alternate heating and cooling, frequently accompanied Alternate heating and cooling, frequently accompanied

by hammering or mechanical workingby hammering or mechanical working

• Shrink weldingShrink welding– Variation of shrinkage in which heat applied by Variation of shrinkage in which heat applied by

running beads of weld metal on convex side of running beads of weld metal on convex side of buckled area (after correction, ground off)buckled area (after correction, ground off)

• Added stiffeningAdded stiffening– Pulling plate into line with strong backs and welding Pulling plate into line with strong backs and welding

additional stiffeners to plate to make it retain its planeadditional stiffeners to plate to make it retain its plane– Can by used only on plateCan by used only on plate


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209Summary of Distortion ControlSummary of Distortion Control

• Metal expansionMetal expansion– Metal with high coefficient of expansion Metal with high coefficient of expansion

distorts more than one with lower coefficientdistorts more than one with lower coefficient

• Distortion effectsDistortion effects– Kind of welding process has influence on Kind of welding process has influence on

distortiondistortion

• Use of welding positionersUse of welding positioners– Allows use of larger diameter electrodes or Allows use of larger diameter electrodes or

welding procedures with higher deposition welding procedures with higher deposition rates and faster welding speedsrates and faster welding speeds


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• Balanced forcesBalanced forces– By prebending and presetting in direction By prebending and presetting in direction

opposite to movement caused by weld opposite to movement caused by weld shrinkageshrinkage

– Shrinkage pull material back into alignmentShrinkage pull material back into alignment

• Forcible restraintsForcible restraints– Restraining parts forcibly through use of clamps, Restraining parts forcibly through use of clamps,

fixtures, and tack weldsfixtures, and tack welds

– Welder must be careful not to overrestrain partsWelder must be careful not to overrestrain parts


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• Clamping parts during fabricationClamping parts during fabrication– Clamped or welded to heavy fixture which can Clamped or welded to heavy fixture which can

be stress relieved with weldmentbe stress relieved with weldment

• Heat distributionHeat distribution– Distribute welding heat evenly though planned Distribute welding heat evenly though planned

welding sequence and planned weld positionswelding sequence and planned weld positions

• Increase speed with heatIncrease speed with heat• General rule about warpingGeneral rule about warping

– Decrease in speed and increase in number of Decrease in speed and increase in number of passes increases warpingpasses increases warping


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• Welding from both Welding from both sidessides– Distortion reduced byDistortion reduced by

welding from both welding from both sidessides

– Welding from both Welding from both sides at sides at same timesame time all all but eliminates but eliminates distortiondistortion Copyright © The McGraw-Hill Companies, Inc.

Permission required for reproduction or display.


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• Welding directionWelding direction– Away from point of restraintAway from point of restraint– Toward point of maximum freedomToward point of maximum freedom

• Wandering sequencesWandering sequences– Skip welding and backstep welding prevents Skip welding and backstep welding prevents

local buildup of heat thus reduces shrinkagelocal buildup of heat thus reduces shrinkage

• End fixingEnd fixing– Boxing: when fillet weld wrapped around Boxing: when fillet weld wrapped around

corner of member as continuation of principal corner of member as continuation of principal weldweld


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• Avoid overweldingAvoid overwelding– Too much weldingToo much welding

increases distortionincreases distortion– Too many weld passesToo many weld passes

cause additional heat inputcause additional heat input• Single pass better than Single pass better than

several passesseveral passes

– Stringer bead produces lessStringer bead produces lessdistortion than weave beaddistortion than weave bead

– Use smallest leg size Use smallest leg size permissible when fillet weldingpermissible when fillet welding


Use Minimum number of passes


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• Reduce weld metalReduce weld metal– Excessive widths of groove weld increase Excessive widths of groove weld increase

weld shrinkage and costweld shrinkage and cost• Add nothing to strengthAdd nothing to strength

– Root opening, including angle should be kept Root opening, including angle should be kept to a minimumto a minimum

– Select joints that require little weld metalSelect joints that require little weld metal– Weld joints that cause most contraction firstWeld joints that cause most contraction first


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216Correct Edge Preparation and Good FitupCorrect Edge Preparation and Good Fitup



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• Fix tack welds firstFix tack welds first– Weak welds or cracked tack welds should be Weak welds or cracked tack welds should be

chipped or melted out before proceeding with chipped or melted out before proceeding with weldweld

• PeeningPeening– EffectiveEffective– Too much, causes loss of ductility and impact Too much, causes loss of ductility and impact

propertiesproperties


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218Control of Residual Stress:PreheatingControl of Residual Stress:Preheating

• Necessary to control or reduce rate of Necessary to control or reduce rate of expansion and contraction during weldingexpansion and contraction during welding– Preheat entire structure before welding and Preheat entire structure before welding and

maintaining heat during weldingmaintaining heat during welding

• Care taken to make sure preheat uniform Care taken to make sure preheat uniform throughout structurethroughout structure

• After weld completed, structure must be After weld completed, structure must be allowed to cool slowlyallowed to cool slowly


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219Control of Residual Stress:PostheatingControl of Residual Stress:Postheating

• Most common method of stress relievingMost common method of stress relieving• Must be done in furnace capable of Must be done in furnace capable of

uniform heating under temperature controluniform heating under temperature control• Work must be supportedWork must be supported• When weldment reaches maximum When weldment reaches maximum

temperature, permitted to soaktemperature, permitted to soak– One hour per one inch of thicknessOne hour per one inch of thickness

• Reduction of temperature must be gradual Reduction of temperature must be gradual and uniformand uniform


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220Control of Residual Stress:PostheatingControl of Residual Stress:Postheating

Suggested Preheat TemperaturesCarbon Equivalent (%) Temperature (Fº) Up to 0.45 Optional 0.45–0.60 200–400ºF Above 0.60 400–700ºF


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221Control of Residual Stress:Full AnnealingControl of Residual Stress:Full Annealing

• Superior to all other methodsSuperior to all other methods

• Very difficult to handleVery difficult to handle

• Must be heated to 1,600 to 1,650Must be heated to 1,600 to 1,650ºFºF– Causes formation of very heavy scaleCauses formation of very heavy scale– Danger of collapse on some types of Danger of collapse on some types of

weldmentsweldments


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222Control of Residual Stress:Cold PeeningControl of Residual Stress:Cold Peening

• Bead hammered to stretch it and counteract Bead hammered to stretch it and counteract shrinkage due to coolingshrinkage due to cooling

• Causes plastic flowCauses plastic flow• Identical to cold working steelIdentical to cold working steel• OverpeeningOverpeening

– Cracks, loss of ductility, work hardened, new Cracks, loss of ductility, work hardened, new stressstress

• Root and face layers of well should not be Root and face layers of well should not be peenedpeened


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223Control of Residual Stress:Vibratory Stress RelievingControl of Residual Stress:Vibratory Stress Relieving

• Uses low frequency, high amplitude Uses low frequency, high amplitude vibration to reduce stress levels to point vibration to reduce stress levels to point where they cannot cause distortionwhere they cannot cause distortion

• Vibration generator clamped to workpieceVibration generator clamped to workpiece– Vibration level adjusted to create desired Vibration level adjusted to create desired

amplitudeamplitude– Sine waves pass through parts, relaxing Sine waves pass through parts, relaxing

microstructuremicrostructure– Takes between 15 and 30 minutes depending Takes between 15 and 30 minutes depending

on sizeon size


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224Control of Residual Stress:Cryogenic Stress RelievingControl of Residual Stress:Cryogenic Stress Relieving

• Takes various structures at very slow rate Takes various structures at very slow rate down from room temperature to 300down from room temperature to 300º º below 0ºF by exposing them to liquid below 0ºF by exposing them to liquid nitrogen vaporsnitrogen vapors– Done at 1ºF per minuteDone at 1ºF per minute

• Allowed to soak at holding temperature for Allowed to soak at holding temperature for 24 to 36 hours24 to 36 hours– Molecules in structure get closer togetherMolecules in structure get closer together

• At end of holding period structure slowly At end of holding period structure slowly warmed back up to room temperaturewarmed back up to room temperature– Rate of 1ºF per minuteRate of 1ºF per minute


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225Control of Residual Stress:Mechanical LoadingControl of Residual Stress:Mechanical Loading

• Base metal stressed just at point of yielding Base metal stressed just at point of yielding by application of internal pressure to by application of internal pressure to pressure vesselpressure vessel

• Works well with simple weldmentWorks well with simple weldment• Important only very small yielding takes Important only very small yielding takes

placeplace• Hydraulic pressure used rather than air Hydraulic pressure used rather than air

pressurepressure– Danger with air pressure of vessel rupturingDanger with air pressure of vessel rupturing


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226Control of Residual Stress:Welding TechniqueControl of Residual Stress:Welding Technique

• Product designed to incorporate types of joints Product designed to incorporate types of joints having lowest residual stresshaving lowest residual stress

• Degree of residual stress considered when choosing Degree of residual stress considered when choosing processprocess

• Plan assembly welding sequences that permit Plan assembly welding sequences that permit movement of component parts during weldingmovement of component parts during welding

• Avoid highly localized and intersecting weldsAvoid highly localized and intersecting welds• Use electrodes that have an elongation of at least Use electrodes that have an elongation of at least

20% in 2 inches20% in 2 inches• Peening effective method of reducing stressesPeening effective method of reducing stresses

– Root and face layer and layers more than 1/8 inch should Root and face layer and layers more than 1/8 inch should not be peenednot be peened

PowerPoint to accompany Welding Principles and Practices 4th edition Edward R. Bohnart © 2012 The...

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Transcript of PowerPoint to accompany Welding Principles and Practices 4th edition Edward R. Bohnart © 2012 The...