64-paper-thermodynamics of mno-sio2-tio2-ti2o3 system with c

1、ThermodynamicsofMnOSiO2“TiO2““Ti2O3“SystemwithConsiderationofInclusionFmationinMnSiTiContainingSteelsKANGYounBae1)KIMHanSoo2)JUNGInHo3)LEEHaeGeonGraduateInstituteofFerrousTechnology(GIFT)PohangUniversityofScienceTechnolo

2、gy(POSTECH)Kea1)CenterfResearchinComputationalThermochemistry(CRCT)EcolePolytechniquedeMontrealCanada2)ResearchInstituteofScienceTechnology(RIST)Kea3)NationalInstitutefMaterialsScience(NIMS)Japan.Abstract:Phaseequilibria

3、oftheMnOSiO2“TiO2““Ti2O3“systemweredeterminedexperimentallyundervarioustemperaturesoxygenpartialpressures.Fmationofvariousoxidesincludingthefollowingoxideswasidentified:manganosite(MnO)rutile(TiO2)tridymitecristobalite(S

4、iO2)tephroite(Mn2SiO4)rhodonite(MnSiO3)spinel(Mn2TiO4MnTi2O4)pyrophanite(MnTiO3Ti2O3)pseudobrookite(“MnTi2O5“Ti3O5).Thermodynamicoptimizationfthesystemwasconductedfrom25Ctoabovetheliquidustemperaturesovertheentirerangeof

5、compositionintherangeofpO2from1020to107atm.Complexphaserelationshipsinthesystemhavebeenelucidated.Theresultsshowedagoodagreementwithexperimentaldatafromthepresentstudyalsofromliteraturereptedbyvariousinvestigats.Aserieso

6、fexperimentswerecarriedouttoidentifyfmationofinclusionsintheMnSiTicontainingsteelsundervariousthermalhistiesindertosimulateconditionsprevailinginsteelrefiningcastingreheatingfrolling.Fmationofoxideinclusionswassuccessful

7、lyexplainedbytheoptimizedresultsofthepresentstudy.ItwasfoundthattheoptimizedthermodynamicdataftheMnOSiO2“TiO2““Ti2O3“systemisofusefpredictingcontrollinginclusionsfmationduringsteelmakingprocessingatelevatedtemperatures.K

8、eywds:MnOSiO2TiO2Ti2O3InclusionThermodynamicsSteelRefining1.IntroductionIndertoenhancemechanicalpropertiesofsteelsadditionofalloyingelementinsteelhasbeenrecognizedasoneofthesimplestway.Howeverthisrequiresincreasingcostof

9、steelproduction.Recentlyaninnovativeattemptcalled“oxidemetallurgy“hasbeenevolvedtoimprovethesteelpropertieswithoutadditionofexpensivealloy[1].Thatisfinenonmetallicinclusionscanactasinoculantsfthetransfmationfromγaustenit

10、etoαferrite.Thisferriteissofineenoughtoenhancethestrengthofsteel.Hencethisferriteistermedasintragranularferrite(IGF).2.3.Coupledexperimentalthermodynamicstudyfinclusionsinsteels.Investigationstoclarifyinclusionsevolution

11、inMnSiTicontainingsteelswereperfmedthroughexperimentsthermodynamiccalculations.Detailsofexperimentwereshownelsewhere[11].Anumberofsteelsamplescontaining0.1C1.5Mn0.1Si0.007S(masspct.)variouscompositionsofTi(0to0.012masspc

12、t.)werepreparedinaninductionfurnacebymeltingat1600Cfollowedbyquenchingtoroomtemperature.Allthesesamplesweresubsequentlyundertakenisothermalholdingat1200Ctosimulatesoakingprocess.Mphologiesofinclusionsinthesampleswereobse

13、rvedusingascanningelectronmicroscope(SEM)theircompositionsweremeasuredbyanenergydispersivespectrometer(EDS).TheobservedinclusionswerecomparedwiththermodynamiccalculationalongwiththeoptimizeddatabaseftheMnOSiO2“TiO2““Ti2O

14、3“system.AlthoughsulfurwasnotconsideredinthephasediagramexperimentthethermodynamicoptimizationitwasalsoincpatedinthethermodynamicdatabaseusingSulfideCapacitymodel[12]whichisapriimodeldoesnotrequireanyadjustablemodelparam

15、eter.ThermodynamicoptimizationallcalculationsshownherewereperfmedbyFactSagethermochemicalsoftware[13].3.Results3.1.FundamentalResearchPhaseEquilibriaThermodynamicsoftheMnOSiO2“TiO2”“Ti2O3”systemIthasbeenobservedthattheMn

16、OSiO2“TiO2““Ti2O3“systemiscomposedofmoltenoxideseveralsolidphaseswhichmayhavesolidsolubilitydependingontemperatureoxygenpartialpressure[23].Thosearemoltenoxide(MnOSiO2TiO2TiO1.5)manganosite(MnOTiO2TiO1.5)spinel(Mn2TiO4Mn

17、Ti2O4)pyrophanite(MnTiO3Ti2O3)pseudobrookite(“MnTi2O5“Ti3O5)rutile(TiO2TiO1.5).ApartfromtheseanumberofstoichiometriccompoundswereobservedMn2SiO4MnSiO3TinO2n1(n4)whichareknownas“Magneliphases“.TheseareillustratedinFigure1