2015 Volume 56 Issue 8 Pages 1192-1198
Equilibrium between molten iron and the 2CaO·SiO2-3CaO·P2O5 solid solution saturated with CaO was measured by the chemical equilibrium method with the oxygen partial pressure of 5.22 × 10−12 atm at 1823 K and 1.41 × 10−11 atm at 1873 K. The activity of P2O5 relative to hypothetical pure liquid P2O5 was determined from the analyzed content of P in molten iron and reported thermodynamic data. For the compositions in which the CaO phase was detected by XRD after reaction, the activity of 3CaO·P2O5 was determined by the estimated activity of P2O5 and the activity of CaO which was unity due to its saturation. The activity coefficients of P2O5 and 3CaO·P2O5 in solid solution and the phosphorus partition ratio between molten iron and the mixture of 2CaO·SiO2-3CaO·P2O5 solid solution and CaO were also estimated. Besides, the activity of 2CaO·SiO2 and SiO2 in the solid solution were also estimated by applying the Gibbs-Duhem equation.