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1、CHAPTER2BASICHEATTREATMENTAsSteelworkers,weareinterestedintheheattreat-watervapor,andothervarioushydrocarbons.Fuel-firedmentofmetals,becausewehavetoknowwhateffectsfurnacescanprovidethreedistinctatmosphereswhentheheatproducedbyweldingorcuttinghasonmetal
2、.youvarytheproportionsofairandfuel.TheyarecalledWealsoneedtoknowthemethodsusedtorestoremetaloxidizing,reducing,andneutral.toitsoriginalcondition.TheprocessofheattreatingisthemethodbywhichmetalsareheatedandcooledinaSTAGESOFHEATTREATMENTseriesofspecifico
3、perationsthatneverallowthemetaltoreachthemoltenstate.ThepurposeofheattreatingisHeattreatingisaccomplishedinthreemajorstages:tomakeametalmoreusefulbychangingorrestoringlStagel—Heatingthemetalslowlytoensureaitsmechanicalproperties.Throughheattreating,wec
4、anmakeametalharder,stronger,andmoreresistanttouniformtemperatureimpact.Also,heattreatingcanmakeametalsofterandlStage2—Soaking(holding)themetalatagivenmoreductile.Theonedisadvantageisthatnoheat-treat-temperatureforagiventimeandcoolingtheingprocedurecanp
5、roduceallofthesecharacteristicsinmetaltoroomtemperatureoneoperation.Somepropertiesareimprovedattheexpenseofothers;forexample,hardeningametalmaylStage3—Coolingthemetaltoroomtemperaturemakeitbrittle.HEATINGSTAGEHEAT-TREATINGTHEORYTheprimaryobjectiveinthe
6、heatingstageistomaintainuniformtemperatures.Ifunevenheatingoc-Thevarioustypesofheat-treatingprocessesarecurs,onesectionofapartcanexpandfasterthananothersimilarbecausetheyallinvolvetheheatingandcoolingandresultindistortionorcracking.Uniformtempera-ofmet
7、als;theydifferintheheatingtemperaturesandtheturesareattainedbyslowheating.coolingratesusedandthefinalresults.Theusualmeth-odsofheat-treatingferrousmetals(metalswithiron)areTheheatingrateofapartdependsonseveralfactors.annealing,normalizing,hardening,and
8、tempering.OneimportantfactoristheheatconductivityoftheMostnonferrousmetalscanbeannealed,butnevermetal.Ametalwithahigh-heatconductivityheatsatatempered,normalized,orcase-hardened.fasterratethanonewithalowconductivity.Also,theconditionoft
