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1、外文资料HEATTREATMENTOFMETALSTheunderstandingofheattreatmentisembracebythebroaderstudyofmetallurgy.Metallurgyisthephysics,chemistry,andengineeringrelatedtometalsfromoreextractiontothefinalproduct.Heattreatmentistheoperationdoheatingandcoolingametalinitssol
2、idstatetochangeitsphysicalproperties.Accordingtotheprocedureused,steelcanbehardenedtoresistcuttingactionandabrasion,oritcanbesoftenedtopermitmachining.Withtheproperheattreatmentinternalductileinterior.Theanalysisofthesteelmustbeknownbecausesmallpercent
3、agesofcertainelements,notablycarbon,greatlyaffectthephysicalproperties.Alloysteelsowetheirpropertiestothepresenceofoneormoreelementsotherthancarbon,namelynickel,chromium,manganese,molybdenum,tungsten,silicon,vanadium,andcopper.Becauseoftheirimprovedphy
4、sicalpropertiestheyareusedcommerciallyinmanywaysnotpossiblewithcarbonsteels.Thefollowingdiscussionappliesprincipallytotheheattreatmentofordinarycommercialsteelknownasplain-carbonsteels.Withthisprovestherateofcoolingisthecontrollingfactor,producestheopp
5、ositeeffect.ASIMPLIFIEDIRON-CARBONDAGRAMIfwefocusonlyonthematerialsnormallyknownassteels,asimplifieddiagramisoftenused.Thoseportionsoftheiron-carbondiagramnearthedeltaregionandthoseabove2%carboncontentareoflittleimportancetotheengineerandaredeleted.Asi
6、mplifieddiagram,suchastheoneinFig.2.1focusesontheeutectoidregionandisquiteusefulinunderstandingthepropertiesandprocessingofsteel.Thekeytransitiondescribedinthisdiagramisthedecompositionofsingle-phaseaustenite()tothetwo-phaseferritepluscarbidestructurea
7、stemperaturedrop.Controlofthisreaction,whicharisesduetothedrasticallydifferentcarbonsolubilitiesofausteniteandferrite,enablesawiderangeofpropertiestobeachievedthroughheattreatment.Tobegintounderstandtheseprocesses,considerssteeloftheeutectoidcompositio
8、n,0.77%carbon,beingslowcooledalonglineinFig.2.1Attheuppertemperatures,onlyausteniteispresent,the0.77%carbonbeingdissolvedinsolidsolutionwiththeiron.Whenthesteelcoolsto727,severalchangesoccursimultaneously.Theironwantstochangefromthebcca
