Equilibrium Phosphorus Distribution between CaO-saturated FetO-CaO-P2O5-CaF2 Slags and Liquid Iron

Equilibrium phosphorus distribution between FetO-CaO-P2O5-CaF2 slags and liquid iron has been studied at 1600°C under a CaO-saturated condition. The results are summarized as follows, (1) Increase of P2O5 content in CaO-saturated FetO-CaO-P2O5 slags contributes to an increase of the activity coefficient of iron oxide, γFetO and also a slight increase of the ratio (Fe3+/Fe2+), but decreases the activity coefficient, γP2O5.(2) For slags containing approximately 10 mass% P2O5, an addition of CaF2 contributes to a decrease of the γP2O5 as follows, logγP2O5=2.52NFetO-1.32NCaF2-19.4The addition of CaF2 also increases the γFetO and the ratio (Fe3+/Fe2+). It suggests that CaF2 in molten slags behaves as a basic component.(3) For slags having 10 mass% P2O5, most suitable slags for the dephosphorization are those containing 40-50 mass% CaF2.