Abstract
The equilibrium concentrations of Cr in the molten CaO-MgO-Al2O3-SiO2 system with Cr3C2, C, and one atmosphere of CO were determined at 1500°C and 1650°C. Chromium in the slag was found to exist as CrO from a thermochemical consideration. The activity coefficients of CrO, γCrO were calculated from the determined concentrations. The Cr2+ ion in the melts was found to behave amphoterically with a critical (SiO2) concentration of 30 wt%. In the CaO-Al2O3-SiO2 melts, Al2O3 was observed to increase γCrO in the region where chromium oxide behave as base. Therefore the equilibrium concentration of chromium decreased with increasing (Al2O3) at constant CaO/SiO2. In the system of CaO-MgO-Al2O3-SiO2, the effect of (Al2O3) was complicated, because of the existance of MgO. The γCrO values were found to have close relationship with γTiO1.5 and γMnO.
