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1、OxidationofMetals,Vol.18,Nos.5/6,1982CarburizationKineticsofHeat-ResistantSteelsG.M.Smith,*D.J.Young,tandD.L.TrimmtReceivedSeptember27,1982;revisedDecember10,1982Aseriesof21commercialausteniticheat-resistantalloyswascarburizedinH2-C3H6atmosphereswhichwerereducin
2、gtoCr203andSi02andwhichprovidedacarbonactivityofone.Reactionswerecarriedoutat900~T~llO0~andtheresultingdepthofcarburizationwasmeasuredmetal-lographicaIly.Allalloysshowedparaboliccarburizationkineticsafteraninitialbriefperiod,atlowtemperatures,ofmorerapidreaction
3、.Theapparentactivationenergiesforcarburizationarediscussedintermsofcarbonsolubilitiesanddiffusioncoefficients.ItisconcludedthatWagner'stheoryofinternaloxidationisquantitativelyapplicabletosimplealloysbutnottoalloyswhichcontainadditionsofreactiveelements.Theeffec
4、tivenessofadditionsofniobium,aluminum,titanium,andsiliconisdemonstratedandisdiscussedinthecontextofWagner'stheory.KEYWORDS:Austeniticsteels;carburization;carbondiffusion.INTRODUCTIONAusteniticheat-resistantsteelsareusedtomaketubingemployedinhigh-temperaturesteam
5、crackingfurnaces.Inthesefurnacesthetubesconveyaprocessstreamofhydrocarbonandsteamandarefiredontheoutsidetosurfacetemperaturesofupto1100~Underindustrialconditionsacarbonactivityofunityisrealizedattheinnersurfaceofthetubewall.Atthesametimetheoxygenpartialpressurei
6、ssufficienttooxidizechromiumandtheotherlessnoblealloyconstituents,butnotironornickel.Theoxidescaleswhichformonthesesteelsunderisothermalconditionstendtoprotectthemetalagainstcarburization.Forsomesteelsithasbeen*I.C.I,AustraliaOperationsPty.Ltd,BotanyWorks,Matrav
7、ille,N.S.W.2036,Australia.tSchoolofChemicalEngineeringandIndustrialChemistry,TheUniversityofNewSouthWales,P.O.Box1,Kensington,N.S.W.2033,Australia.2290030-770X/82/1200-0229503.00/091982PlenumPublishingCorporation230Smith,Young,andTrimmshown1-3thatunderuniformte
8、stconditionstheoxidescaleeffectivelypreventscarbondissolutionintothemetal.Nevertheless,allcommercialsteelseventuallyfailinservicethroughcarburization.Carburizationres
