Solubility of calcium and oxygen in molten iron Equilibrated with slag in CaO, Al₂O₃ or CaO-stabilized ZrO₂ crucible at 1 873 K

The solubility of calcium and oxygen in molten iron equilibrated with CaO-Al₂O₃-ZrO₂ molten slag in CaO, Al ₂O₃ or 5.5 mass% CaO-stabilized ZrO₂ crucible at 1 873 K was measured by means of the slagmetal 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 eCa°O is -31.8. The value is satisfied the thermodynamic phase stability.