Thermodynamic Database for the Al-Ca-Co-Cr-Fe-Mg-Mn-Ni-Si-O-P-S System and Applications in Ferrous Process Metallurgy

Computerized thermodynamic databases for solid and liquid metals, slag, and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2 system (with dissolved S and P) have been developed by critical evaluation/optimization of various available phase equilibrium and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel, and solid oxide solutions such as spinel, pyroxenes, olivine, monoxide (wustite, periclase, lime), corundum, etc. By means of the optimization process, model parameters are found which reproduce various thermodynamic and phase equilibrium data within experimental error limits. Furthermore, the models permit extrapolation into regions of temperature and composition where data are not available. The databases are automatically accessed by user-friendly software that calculates complex equilibria involving slag, metals, refractories, and gases simultaneously, for systems with many components, over wide ranges of temperature, oxygen potential, and pressure. A short review of the available databases is presented. The critical evaluation/optimization procedure is outlined using the Al2O3-CaO-FeO-Fe2O3-MgO-SiO2 and Al2O3-CaO-MnO-SiO2 systems as examples. Several applications of the databases to deoxidation, dehydrogenation, and dephosphorization of iron and to inclusion control in steel are discussed.