Thermodynamic Consideration on the Oxide System Containing MnO and TiO₂ as Deoxidization Products in Steels

Abstract

Thermodynamics of the MnO-SiO₂-TiO₂ and the MnO-Al₂O₃-TiO₂ systems have been studied for optimizing the property of oxides in steel. Iso-activity curves of each component, which are necessary for the determination of the composition of steel equilibrated with such oxides, have been estimated in the wide range of liquid phases. Although in the study of the MnO-SiO₂-TiO₂ system, iso-activity curves of SiO₂ and TiO₂ were partially obtained due to the lack of integration limit on the saturated line of SiO₂ and TiO₂, integration limits of each component have been derived by ternary Gibbs-Duhem equation. This enabled the estimation of steel composition in equilibrium with a wide range of the oxide system. In addition, the behavior of sulfur in the MnO-SiO₂-TiO₂ and the MnO-Al₂O₃-TiO₂ oxides in steels were simulated using the sulfide capacities of these systems in order to optimize processing conditions.