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1、HeatTreatmentandWorkingEquipment“shaping”是什么意思？(单选)：Whatthemeaningof“Shaping”?(radio)提交Wecanalterthecharacteristicsofsteelinvariousways.Inthefirstplace,steelwhichcontainsverylittlecarbon,willbemilderthansteel,whichcontainsahigherpercentageofcarbon,uptothelimitofabout1.5％.
2、Secondly,wecanheatthesteelaboveacertaincriticaltemperature,andthenallowittocoolatdifferentrates.Atthiscriticaltemperature,changesbegintotakeplaceinthemolecularstructureofthemeta1.Intheprocessknownasannealingweheatthesteelabovethecriticaltemperatureandpermitittocoolveryslo
3、wly.Thiscausesthemetaltobecomesofterthanbefore,andmucheasiertomachine.Annealinghasasecondadvantage.Ithelpstorelieveanyinternalstresseswhichexistinthemetal.Thesestressesareliabletooccurthroughhammeringorworkingthemetal,orthroughrapidcooling.Metalwhichwecausetocoolrapidlyco
4、ntractsmorerapidlyontheoutsidethanontheinside.Thisproducesunequalcontraction,whichmaygiverisetodistortionorcracking.Metalwhichcoolsslowlyislessliabletohavetheseinternalstressesthanmetal,whichcoolsquickly.Ontheotherhand,wecanmakesteelharderbyrapidcooling.Weheatitupbeyondth
5、ecriticaltemperature,andthenquenchitinwaterorsomeotherliquid.Therapidtemperaturedropfixesthestructuralchangeinthesteel,whichoccurredatthecriticaltemperature,andmakesitveryhard.Butabarofthishardenedsteelismoreliabletofracturethannormalsteel.Wethereforeheatitagaintoatempera
6、turebelowthecriticaltemperature,andcoolitslowly.Thistreatmentiscalledtempering.Ithelpstorelievetheinternalstresses,andmakesthesteellessbrittlethanbefore.ThepropertiesoftemperedsteelenableUStouseitinthemanufactureoftools,whichneedafairlyhardsteel.Highcarbonsteelishardertha
7、ntemperedsteel,butitismuchmoredifficulttowork.Theseheattreatmentstakeplaceduringthevariousshapingoperations.Wecanobtainbarsandsheetsofsteelbyrollingthemetalthroughhugerollsinarollingmill.Therollpressuresmustbemuchgreaterforcoldrollingthanforhotrolling,butcoldrollingenable
8、stheoperatorstoproducerollsofgreataccuracyanduniformity,andwithabettersurfacefinish.Othershaping
