Phosphorus equilibrium between liquid iron and CaS-SiO₂-MgO-Al₂O₃-FeO-P₂O₅ Slags: EAF slags, the effect of alumina and new correlation

The increased use of electric arc furnace (EAF) steelmaking using up to 100% direct reduced iron (DRI) has prompted an interest in better control of phosphorus since iron ore and, consequently, DRI have higher phosphorus and silica compared to scrap. There is limited work reported on slag chemistries corresponding to that in the EAF when DRI is used. In the current research, phosphorus equilibria between molten Fe–P alloys and CaO-SiO₂-Al₂O₃-P₂O₅-FeO-MgO_saturated slags were investigated. The results indicate that there is a significant decrease in the phosphorus partition coefficient (L_P) as alumina in the slag increases. The observed effect of alumina on the phosphorus partition is probably caused by the decrease in the activities of iron oxide and calcium oxide. Finally, an equilibrium correlation for phosphorus partition as a function of slag composition and temperature has been developed. It includes the effect of alumina and silica and is suitable for both oxygen and electric steelmaking-type slags.