Activities in CaO-SiO2-Al2O3 slags and deoxidation equilibria of Si and Al

By using the data in previous and present slag-metal equilibrium experiments, the activities of SiO2 along the liquidus lines in CaO-SiO2-Al2O3 slags were determined at 1823 and 1873 K from the reaction <(Si)under bar> + 2 (O) under bar = SiO2 (s), in which the oxygen activities were estimated from the measured oxygen contents or from the combination of nitrogen distribution ratios (L(N)) and nitride capacities (C-N). The activities of Al2O3 were also determined from the reaction 2<(Al)under bar> + 3 (O) under bar = Al2O3 (s), in which the oxygen activities were estimated from the values for L(N) and C-N or from the reaction 3SiO(2) (s) + 4<(Al)under bar> = 2Al(2)O(3) (s) + 3<(Si)under bar>, in which the activities of SiO2 and the contents of Al and Si along with the respective interaction coefficients were used. The activities of Al2O3 and CaO in the entire liquid region were estimated from the Rein and Chipman's activities of SiO2 by using the method of Schuhmann. On the basis of these activities, the deoxidation equilibria of Si and Al in steels were discussed.