Experimental Study on the Activities of Al and Ca in Ferrosilicon

Experiments were carried out to determine the activities of Al and Ca in liquid ferrosilicon (with about 50 wt pct Si) at 1823 K (1550 °C) in their dilution ranges. Liquid FeSi50 and SiO₂-Al₂O₃-CaO slag were stirred mechanically in a graphite crucible to enhance the transfer of Al and Ca between the two phases. The stirring time for the two phases to reach equilibrium was studied. It was found that a time of 45 minutes was long enough to reach the slag–metal equilibrium. The activities of Al and Ca in the ferrosilicon alloy were calculated based on the compositions of the two liquid phases. The activity coefficients obtained for Al and Ca in the liquid FeSi50 at 1823 K (1550 °C) were found to be nearly constant in the composition range studied.