2011 Volume 51 Issue 9 Pages 1369-1374
The solubility of calcium and oxygen in molten iron equilibrated with CaO–Al2O3–ZrO2 molten slag in CaO, Al2O3 or 5.5 mass% CaO-stabilized ZrO2 crucible at 1873 K was measured by means of the slag-metal equilibrium partition method under Ar gas atmosphere. From the results by XRD and the phase diagram of CaO–Al2O3–ZrO2 system, the slag in a CaO crucible was in equilibrium with CaO·ZrO2 and CaO and the slag composition was 57.36 mass% CaO-34.86% Al2O3-7.78% ZrO2. The slag in a Al2O3 crucible was in equilibrium with CaO·2Al2O3 and ZrO2–CaO solid solution (Css) and the slag composition was 27.08 mass% CaO-53.42% Al2O3-19.50% ZrO2. The slag in a CaO-stabilized ZrO2 crucible was in equilibrium with ZrO2–CaO solid solution (Css) and CaO·ZrO2 and the slag composition was 30.38 mass% CaO- 51.56% Al2O3-18.06% ZrO2. The average concentrations of oxygen and calcium in molten iron in equilibrium with slag and compounds were 251 ppm and 3 ppm in a CaO crucible, 33 ppm and 4 ppm in an Al2O3 crucible and 21 ppm and 5 ppm in a CaO-stabilized ZrO2 crucible, respectively. The logarithm of equilibrium constant, logK, for the reaction of CaO(s) = Ca + O is –4.38 and the interaction parameter of eCaO is 31.8. The value is satisfied the thermodynamic phase stability.