Equilibrium between Molten Iron Alloys and CaO-Al<SUB>2</SUB>O<SUB>3</SUB>-CaS Slags Saturated with CaS

Experimental study was conducted on the equilibrium between molten Fe-Al-S alloys and CaO-Al2O3-CaS slags in a CaS crucible at 1 873 K. The equilibrium relation could be represented by the following reaction :3CaO(s)+2Al+3S=3CaS(s)+Al2O3(s)By application of the Gibbs-Duhem equation, integration techniques were developed which allowed us to calculate the activities of CaO and Al2O3 from the slag composition and the activities of aluminum and sulfur in the alloy. The free energy of the above reaction was also determined as well as the free energies of formation of calcium aluminate compounds, CaO·Al2O3(CA), CaO·2Al2O3(CA2), and CaO·6Al2O3(CA6)from their constituent oxides.