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1、沈阳理工大学学士学位论文-9-沈阳理工大学学士学位论文英文原文HEATTREATMENTOFMETALAnnealingThewordannealhasbeenusedbeforetodescribeheat-treatingprocessesforsofteningandregainingductilityinconnectionwithcoldworkingofmaterial.Ithasasimilarmeaningwhenusedinconnectionwiththeheattreatingofallotropicmate
2、rials.Thepurposeoffullannealingisodecreasehardness,increaseductility,andsometimesimprovemachinabilityofhighcarbonsteelsthatmightotherwisebedifficulttocut.Thetreatmentisalsousedtorelievestresses,refinegrainsize,andpromoteuniformityofstructurethroughoutthematerial.Machi
3、nabilityisnotalwaysimprovedbyannealing.Thewordmachinabilityisusedtodescribeseveralinterrelatedfactors,includingtheabilityofamaterialtobecutwithagoodsurfacefinish.Plainlowcarbonsteels,whenfullyannealed,aresoftandrelativelyweak,offeringlittleresistancetocutting,butudual
4、lyhavingsufficientductilityandtoughnessthatacutchiptendstopullandtearthesurfacefromwhichitisremoved,leavingacomparativelypoorqualitysurface,whichresultsinapoormachinabilityrating.1Forsuchsteelsannealingmaynotbethemostsuitabletreatment.Themachinabilityofmanyofthehigher
5、plaincarbonandmostofthealloysteelscanusuallybegreatlyimproyedbyannealing,astheyareoftentoohardandstrongtobeeasilycutatanybuttheirsoftestcondition.2Theprocedureforannealinghypoeutectoidsteelistoheatslowlytoapproximately60abovetheAc3line,3°°tosoakforalongenoughperiodtha
6、tthetemperatureequalizesthroughoutthematerialandhomogeneousausteniteisformed,andthentoallowthesteeltocoolveryslowlybycoolingitinthefumaceorburyingitinlimeotsomeotherinsulatingmaterial.Theslowcoolingiseasentialtotheprecipitationofthemaximumferriteandthecoarsestpearlite
7、toplacethesteelinitssoftest,mostductile,andleaststrainedcondition.NormalizingThepurposeofnormalizingissomewhatsimilartothatofannealingwiththeexceptionsthatthesteelisnotreducedtoitssoftestconditionandthepearliteisleftratherfineinsteadofcoarse.Refinementofgrainsize,reli
8、efofinternalstresses,andimprovementof-9-沈阳理工大学学士学位论文structuraluniformitytogetherwithrecoveryofsomeductilityprovidehightoughn
