Dephosphorization equilibria between pure molten iron and CaO-saturated FeO_<i>n</i>-CaO-CaF₂slags

Abstract

Metal-slag refining reactions have been investigated to determine dephosphorization equilibria in steelmaking using CaO-saturated FeOn–CaO–CaF2 slags low in P2O5 content. Slag compositions have been optimized to achieve maximum partition ratios wt.%(P2O5)/wt.%[P] and minimum phosphorus contents in pure molten iron at 1 550 and 1 600°C. FeOn–CaO–CaF2 slags prove to be most effective dephosphorizers. Optimal slag compositions are between 10 and 20 wt.% FeOn. Attempts were also made to present phosphate capacities fractions of free oxygen ions and theoretical optical basicities Λ as a function of the FeOn content of slags. Dephosphorization capacity of FeOn–CaO–CaF2 slags is compared with that of FeOn–CaO–SiO2 and FeOn–CaO–Al2O3 slags.