热处理-铁碳相图-Fe3C-奥氏体,马氏体,铁素体.ppt

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1、IRONIRON-CARBONDIAGRAMIRONIRON-CARBONDIAGRAMFerriteAusteniteSteelCastironPearlitePearliteandCementinePearliteandCarbideEutecticeutectoidOutlineIntroductionCoolingcurveforpureironDefinitionofstructuresIron-Carbonequilibriumphasediagram–SketchTheIron-Iro

2、nCarbideDiagram-ExplanationTheAustenitetoferrite/cementitetransformationNucleation&growthofpearliteEffectofC%ageonthemicrostructureofsteelRelationshipb/wC%age&mechanicalpropertiesofsteelCoolingcurveforpureironDefinitionofstructuresVariousphasesthatappe

3、arontheIron-Carbonequilibriumphasediagramareasunder:AusteniteFerritePearliteCementiteMartensite*LedeburiteUnitCellsofVariousMetalsFIGURE-Theunitcellfor(a)austentite,(b)ferrite,and(c)martensite.Theeffectofthepercentageofcarbon(byweight)onthelatticedimen

4、sionsformartensiteisshownin(d).Notetheinterstitialpositionofthecarbonatomsandtheincreaseindimensioncwithincreasingcarboncontent.Thus,theunitcellofmartensiteisintheshapeofarectangularprism.MicrostructureofdifferentphasesofsteelDefinitionofstructuresFerr

5、iteisknownasαsolidsolution.Itisaninterstitialsolidsolutionofasmallamountofcarbondissolvedinα(BCC)iron.stableformofironbelow912deg.CThemaximumsolubilityis0.025%Cat723Canditdissolvesonly0.008%Catroomtemperature.Itisthesofteststructurethatappearsonthedia

6、gram.DefinitionofstructuresFerriteAveragepropertiesare:Tensilestrength=40,000psi;Elongation=40%in2in;Hardness>RockwellC0or>RockwellB90DefinitionofstructuresPearliteistheeutectoidmixturecontaining0.80%Candisformedat723°Converyslowcooling.Itisaveryfinepl

7、atelikeorlamellarmixtureofferriteandcementite.Thewhiteferriticbackgroundormatrixcontainsthinplatesofcementite(dark).DefinitionofstructuresPearliteAveragepropertiesare:Tensilestrength=120,000psi;Elongation=20%in2in.;Hardness=RockwellC20,RockwellB95-100,

8、orBHN250-300.DefinitionofstructuresAusteniteisaninterstitialsolidsolutionofCarbondissolvedin(F.C.C.)iron.Maximumsolubilityis2.0%Cat1130°C.Highformability,mostofheattreatmentsbeginwiththissinglephase.Itisnormallynotstableatroomtemperatu