Iron and Steel Division - Activities of Oxides in SiO2-FeO-Fe2O3 Melts

The activities of SiO2, FeO, and Fe2O3 are calculated from previous experimental data on the activity of oxygen in Fe-Si-O melts at 1550°C. Using the oxide-activity data, the free energy of formation of fayalite from its oxides is evaluated for 1550°C. A number of investigators1-4 contributed to the study of the state of oxidation of iron in SiO,-FeO-Fe,O3 melts and the phase equilibria in the system Fe-Si-O. In a more detailed study, Schuhmann and Ensio5 and Michal and Schuhmann% easured the state of equilibrium in the SiO,-FeO-Fe,O3 melts saturated with y-iron or silica or both under low-oxygen potentials and within the temperature range 1250" to 1350°C. Similar measurements were also made by Turkdogan and Bills7,' over wide ranges of composition and oxygen potentials at 1550"C. Using the experimental data on the oxygen activities in the ternary system, Schuhmann' calculated the activities of silica and ferrous oxide in Si0,-FeO-Fe2O3 melts for 1350°C. Adequate knowledge on the activities of the constituent oxides of melts is essential in the study of reaction-equilibria and reaction-kinetics in oxide-melts. With this in view, the activities of oxides in SiO2-FeO-Fe2O3 melts at 1550°C are computed using the experimental data of Turkdogan and Bills7'8 on the oxygen activities in these melts.