Thermodynamic Aspects of Steel Reoxidation Behavior by the Ladle Slag System of CaO-MgO-SiOg-AlsOs-FetO-MnO-PgOs

The reoxidation behavior of steels by slag in the secondary steeinnaking process was addressed by investigating the thermodynamic equilibria between the liquid iron containing Mn and P and CaO-MgO-SiO2Al2OP2O5-MnO-Fe1O ladle slag at 1873 K. The activity coefficient ofFe,0 shows a maximum value in the vicinity of the basicity ((Xca3O+ XMgO + XMnO)(XsiO2 + XA? 12O5)) = 2.5 at the specific mole fraction range of Fe,0, while that of MnO seems to increase gradually with increasing the basicity. However, the values of (gamma)(FetO) and (gamms)(Mno) Mno showed minima with respect to P2O5 content of slag. In addition, the values of (gamma)(FetO) and (gamma)(MnO) increased as (pct CaO)/(pct Al2O3) ratio increased at given SiO2 MgO, an dAP2O5 contents. The conversion equations between the Fe,0 and MnO activities and their calculated activities via regular solution model were derived by the correlation between the measured and calculated activities over the limited ranges ofFe,0 and MnO contents. The regular solution model was used to estimate the oxygen potential in the slag. For MgO saturated slags, a(FetO(l)= = 0.864a(FeO(R.S),a(MnO(1)=p 6.38a(MnO(R.S). For Al2O3 saturated slags, aFetO(l) =2.086a(FeO(R.S)ʹa(MnO(l)=14.39a(MnO(R.S)