Thermodynamic Assessment of Hot Metal and Steel Dephosphorization with MnO-containing BOF Slags

Abstract

The phosphorus distribution ratios between MnO (8–16 mass%)-containing CaO-SiO2-FetO slags and liquid iron were measured at 1 873 K in a MgO crucible. The addition of MnO was found to reduce the phosphorus distribution ratio at a given total Fe content and (mass%CaO)/(mass%SiO2) ratio. The equilibrium quotient of dephosphorlzation reaction, (mass%P)/{[mass%P] · (mass%T.Fe)5/2}, the activity coefficient of P2O5, and that of FetO in logarithmic form were formulated as a linear function of slag compositions. Based on these empirical formulas, the dephosphorization in hot metal and steel was thermodynamically assessed and the characteristics of double slag treatments were discussed from the mass balance relation between slag and metal with respect to phosphorus. © 1995, The Iron and Steel Institute of Japan. All rights reserved.