The Calculation of Fe–Al–O Interaction Coefficient

Aluminum is a very common deoxidizer in steel-making processes. The solubility of oxygen in molten iron decreases with increasing aluminum content. For the deoxidation process, the solubility of oxygen in Fe–Al melts decreases with increasing aluminum content. When %Al is increased to 0.34 wt.%, %O decreases to 6.4 ppm, which is the lowest point of the FeAl2O4 curve. Then the Al2O3 curve appears and replaces the FeAl2O4 curve, where the interconnection point of the two curves is the coexistence point of FeAl2O4 and Al2O3 phases. When %Al is increased to 0.4%, the %O decreases to 6.35 ppm, which is the lowest point of the Al2O3 curve. The solubility of oxygen in Fe–Al alloys is about 6.35 ppm with 0.4 wt.% aluminum at 1873 K. Liquid FeO–Al2O3, hercynite (FeAl2O4), and alumina (Al2O3) are three possible products during the deoxidation process. Based on thermodynamic calculation, the value of the interaction coefficient of eoAl was determined as −0.75 at 1873 K. This value is in good agreement with experimental curves in the literature.