Phosphorus distribution between slag and liquid iron has been studied at the temperature range from 1 573 to 1 953 K. The slag system of Fe_tO–P₂O₅–M_xO_y(M_xO_y=CaO, MgO, SiO₂) ternary, and of Fe_tO–P₂O₅–CaO–M_xO_y(M_xO_y=MgO, SiO₂) quaternary were studied to clarify the effect of oxides on the phosphorus distribution equilibrium at steelmaking process.
In view of ionic theory, the approximate validity of regular solution model was examined to formulate the equilibrium reaction of phosphorus distribution between slag and metal. As the results, it was confirmed that the regular solution model was satisfied for all the experimental results including the present work and the previous studies by other investigators, except for extreamly high iron oxide region. The phosphorus and oxygen contents in liquid iron in equilibrium with slag can be estimated within the accuracy of ±10% by the quadratic formalism derived from an assumption of the regular solution of slag.