Thermodynamics of oxygen solutions in the complex reduction of Fe-Co melts

Abstract

Thermodynamic analysis of the complex reduction of metal melts is considered. The proposed analytical method identifies the influence of the weaker reducing agent in amplifying the effect of the stronger reagent. The curves of oxygen solubility pass through a minimum. Analysis of the extremal curves of oxygen concentration in the melt as a function of the content of reducing agents yields a formula for the content of the stronger reducing agent such that the oxygen concentration is minimal. Thermodynamic analysis of the combined influence of aluminum and silicon on the oxygen solubility in Fe-Co melts indicates that the reac tion products may contain both mullite (3Al 2 O 3 ⋅ 2SiO 2 ) and kyanite (Al 2 O 3 ⋅ SiO 2 ). The presence of silicon in the melt intensifies the reducing action of aluminum: slightly when mullite is formed and significantly when kyanite is formed. When kyanite is formed, the curves of oxygen solubility pass through a minimum, whose position depends on the aluminum content in the melt but not on the silicon content. The aluminum content at the minimum declines slightly from iron to cobalt, as for Fe-Co-Al systems. Further addition of aluminum elevates the oxygen concentration. The formation of the compounds Al 2 O 3 , 3Al 2 O 3 ⋅ 2SiO 2 , Al 2 O 3 ⋅ SiO 2 , and SiO 2 is investigated as a function of the Al and Si content in the melt.