Activities in CaO-MgO-Al2O3 slags and deoxidation equilibria of Al, Mg, and Ca

The equilibrium experiments between CaO-Al2O3-MgO-0.06 to 0.85%MnO-0.5 to 2.1%FetO-0.07 to 0.3%S (mass content in %) slag and liquid iron were carried out at 1823 and 1873 K in order to assess the activities of Al2O3 and MgO along the spinel (MgO . Al2O3) saturation line. The activities of CaO in an entire liquid region were first determined at 1 823 and 1 873 K from the reported values for sulfide capacity, coupled with the activity coefficients of CaS which were estimated from those in the CaO-Al2O3 slags. On the basis of these iso-activity lines for CaO, the activities of Al2O3 and MgO were calculated by using the method of Schuhmann, in which the assessed activities of Al2O3 and MgO on the spinel saturation line were taken as the starting points. The activity coefficients of FetO and MnO along the spinel saturation line were determined and the deoxidation equilibria of Al, Mg, and Ca were discussed.