Phase Equilibria and Thermodynamics of FeO · Cr₂O₃−MgO · Cr₂O₃−MgO · Al₂O₃ Spinel Structure Solid Solution Saturated with (Cr, Al)₂O₃

Thermodynamic properties of chromium ore are important to control the new process for crude stainless steel production in a converter, in particular, pre-reduction of the ore in the process. In the present work, phase equilibria and the activities of iron chromite in FeO · Cr₂O₃−MgO · Cr₂O₃−MgO · Al₂O₃ spinel structure solid solution saturated with (Cr, Al)₂O₃ have been determined at 1 573 K, by the equilibrium of iron dissolved in liquid silver held in the spinel structure solid solution crucible with CO-CO₂ gas mixture. No measurable solubility of FeO · Cr₂O₃−MgO · Cr₂O₃−MgO · Al₂O₃ solid solution in (Cr, Al)₂O₃ phase was detected, while small solubility of (Cr, Al)₂O₃ in the spinel structure solid solution phase was found. Tie-lines between (Cr, Al)₂O₃ and the spinel structure phases were determined. The activity of FeO · Cr₂O₃ in FeO · Cr₂O₃−MgO · Cr₂O₃−MgO · Al₂O₃ spinel structure solid solution saturated with (Cr, Al)₂O₃ showed negative deviation from ideality. It was observed that the spinel structure solid solution showed regular solution behavior, and α-functions between each constituent in the FeO · Cr₂O₃−MgO · Cr₂O₃−MgO · Al₂O₃ system were determined as follows; [formula omitted].