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1、外文资料HEATTREATMENTOFMETALSTheunderstandingofheattreatmentisembracebythebroaderstudyofmetallurgy.Metallurgyisthephysics,chemistry,andengineeringrelatedtometalsfromoreextractiontothefinalproduct.Heattreatmentistheoperationdoheatingandcoolingametalinitssolidstatetochangeitsphysicalproper
2、ties.Accordingtotheprocedureused,steelcanbehardenedtoresistcuttingactionandabrasion,oritcanbesoftenedtopermitmachining.Withtheproperheattreatmentinternalductileinterior.Theanalysisofthesteelmustbeknownbecausesmallpercentagesofcertainelements,notablycarbon,greatlyaffectthephysicalprop
3、erties.Alloysteelsowetheirpropertiestothepresenceofoneormoreelementsotherthancarbon,namelynickel,chromium,manganese,molybdenum,tungsten,silicon,vanadium,andcopper.Becauseoftheirimprovedphysicalpropertiestheyareusedcommerciallyinmanywaysnotpossiblewithcarbonsteels.Thefollowingdiscussi
4、onappliesprincipallytotheheattreatmentofordinarycommercialsteelknownasplain-carbonsteels.Withthisprovestherateofcoolingisthecontrollingfactor,producestheoppositeeffect.ASIMPLIFIEDIRON-CARBONDAGRAMIfwefocusonlyonthematerialsnormallyknownassteels,asimplifieddiagramisoftenused.Thoseport
5、ionsoftheiron-carbondiagramnearthedeltaregionandthoseabove2%carboncontentareoflittleimportancetotheengineerandaredeleted.Asimplifieddiagram,suchastheoneinFig.2.1focusesontheeutectoidregionandisquiteusefulinunderstandingthepropertiesandprocessingofsteel.Thekeytransitiondescribedinthis
6、diagramisthedecompositionofsingle-phaseaustenite()tothetwo-phaseferritepluscarbidestructureastemperaturedrop.Controlofthisreaction,whicharisesduetothedrasticallydifferentcarbonsolubilitiesofausteniteandferrite,enablesawiderangeofpropertiestobeachievedthroughheattreatment.Tobegintound
7、erstandtheseprocesses,considerssteeloftheeutectoidcomposition,0.77%carbon,beingslowcooledalonglineinFig.2.1Attheuppertemperatures,onlyausteniteispresent,the0.77%carbonbeingdissolvedinsolidsolutionwiththeiron.Whenthesteelcoolsto727,severalchangesoccursimultaneously.Theironwantstochang
8、efromthebcca
