The Solubility of MgO-Cr<SUB>2</SUB>O<SUB>3</SUB> in MgO-Al<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB>-CaO Slag at 1600°C under Reducing Conditions

Abstract

The Solubility of MgO-Cr2O3 in MgO-Al2O3-SiO2-CaO Slag and the activilies of chromium oxide in the slags were measiredat 1 600°C under Reducing conditions. For MgO-SiO2 melts which were saturated with 2MgO·SiO2, the solubility of MgO·Cr2O3 increased with decreasing oxygen partial pressure, because of decrease in γCrO1.5.When CaO is added to the melts mentioned above, soluble total chromium content decreased because γCrO1.5 and γCrO increased with increasing CaO content in the melts.Under a fixed oxygen partial pressure, activities of chromium oxides in the chromite MgO·(CrxAl1-x)2O3 were also measured by equilibrating them with Ni-Cr alloys for which the activity coefficient γ°Cr(at 1 600°C) was determined as 0.421 in this study. It was found that the free energy change of the reaction : MgO(s)+Cr2O3(s) = MgO·Cr2O3(s) is expressed by-126 800+47.3 T (J/mol) and that MgO·Cr2O3 and MgO·Al2O3 form a solid solution which exhibits negative deviation from ideal behavior at 1600°C.