STUDYONTHENON-STOICHIOMETRICMETALLURGICALPRO CESS-AMODELFORTHEBATH-SMELTINGPROCESS¥XUShi zheng(NortheasternUniversity,Shenyang.China Manuseriptreceived26December,1994)Astract:A modelbasedonthebath-smeltingprocessforthepr oductionofqualitysteelshasbeendevelopedcons ideringnon-stoichiometricsystem.Thethermody namicfunctionofslaghasbeenusedtocalculatthe activitiesa(i)ofcomponentspresentintheslaga ndmetal.Todeterminethevalencyoftheelementsi nbathslagandmetalphase,anexperimentalmethod hasbeensuggested.Keywords:non-stoichiometry ,bath-smelting,thermodynamic,activitiyReduc tionprocessesinferrousprocessmetallurgyhasa lwaysbeeninthestudiedcenter.Manyideasandpro posalsaimingatbetterefficiencyandlowercosth avebeenpresented.Inbath-smeltingprocess,ane wlyemergingironmakingandsteelmakingprocesse shavethepotehtialityofextensiveapplications becauseoftheirattractivefeatures,suchasflex ibilityinrawmaterials,scaleandsimplicityoft heplant.Incurrentcentury,metallurglstshavet heuniquechanceofbeingabletoformulateasetofc riteria,whichshouldbefulfilledbyafuturesmel tingreductionprocess.1.ModelInviewoftheabov e,amodelbasedonthebath-smeltingprocesshasbe endevelopedfortheproductionofeconomicalandq ualitysteels.1.1StoichiometricmodelInthepre sentstudy,chemicalequilibriumexpressionswer eusedforanalysingtheprocessstepssuchasdepho sphorization,decarburizationandthereduction ofchromiumandmanganesefromtheslag.Forexampl e,theoxidationoftheimpuritiesinthesteelcanb eexpressedasfollows:x[Me]+y[o]=(Mexoy)Thest oichiometryshowsthecharacteristicsofthesyst ematcertaintemperatureandpressure,tberefore ,theequilibriumconstantfortheabovecanbeexpr essedasfollows:Thecalculatedresultsusingabo verelationshipandthedatagiveninthehandbooko fphysicalchemistrydeviatedobviouslyfromthem easuredresults.Duetothelackofreliabledataat hightemperatures,itisverydifficulttoconfirm theactivitiesandchemicalcompositionsofthein dividualconstituentsintheslag.Forillustrati on,theoxidationofCrinthemeltisgivenby:Whent heoxygenpotentialisconstant.i.e.a[o]=consta nt,theequilibriumconstantwillbe:Inthepresen tstudy,theactivityofchromiumintheslagwasfou ndtobealinearfunctionofthechromiuminthemelt ,whichdoesnotsatisfyaboverelationship.Accor dingtothepresentexperimental,theoxidationof chromiumcanbewrittenasfollows:Thepresenceof chromiumintheformofCrO1.5couldnotbeverified .1.2Non-stoichiometricmodelInviewoftheabove mentioned,wehaveusednon-stoichiometrytoobta inthemetallurgicalprocessparameters,forexam ple,activitiesofdifferentconstituentsinboth slagandmetalphases.Thisexerciserequiresonly toknowthethermodynamicparametersoftheelemen tsinonephasefromwhichthethermodynamicparame tersforotherphasecanbedeterminedeasily.This canbewrittenas:[i]=(i)={i}(7)Theaboveconcep tionhasbeenalsousedbyNerrnstforthedistribut ionofsulphurinslag-metalphase[1]:[s]=(s)(8) Ls=(s)/[s]In1911,Sieverthasdescribedthereac tionprocessofhydrogeninmetalgasphaseas:Ineq uilibriumstatethechemicalpotentialoftheelem entiineachphaseisWherea[i]istheactivityofic omponentsinthemetalphaseandisthepartialpres sureofielements.Wherea(i)istheactivityofele mentiintheslagcalculatedfromthethermodynami cfunctionofslagwhichisconsideredtobeacollec tiveelectronicconfigurationoftheoxidesinthe slag.WhereX(i)isthetotalconcentrationofelem entsiintheslagandistheatomicactivitycoeffic ientofelementiintheslag.WhereEijistheexchan geenergyofelementsiandjWhereKiandKjareatomi cparametersofelementsiandjwhichcanbetakenfr omMendeleev'speriodictable[2].Undertheshado wofGibbsequationthemassactionequationcanbew rittenasfollows:Becausethethermodynamicfunc tionisrelatedtothefirstandlaststateoftherea ctononlythevalueofKcanbecalculatedasfollows .2.ValencyofElementiinSlag(ValencyFactor)2. 1TheoreticalanalysesTheactivitiesofslagwasc alculatedusingthermodynamicfunctionsofslagw hichwasconsideredasaphaseofacollectiveelect ronicsystem.Thistheoryhasavoidedtheendlessd ebateabouttheformsofexistenceofslagcomponen ts,anditwasthefirsttimetopointoutthattheactivityofslagcomponentsisrelatedtothepressureofoxygenandthevalenceofelementsintheslag[3].Itwasreportedthatthetheorycanbeusedtodesig