MASS ACTION CONCENTRATION MODEL OF CaO-MgO-FeO-Al_2O_3-SiO_2 SLAG SYSTEMS AND ITS APPLICATION TO THE FORMATION MECHANISM OF MgO·Al_2O_3 SPINEL TYPE INCLUSION IN CASING STEEL

摘要

Large size MgO?Al_2O_3 spinel type inclusions in casing steel are harmful to the surface quality and performance of casing. In order to effectively control it in production, its existence in casing steel was analysed by scanning electron microscope and energy dispersive spectrometer, and its formation mechanisms were studied using coexistence theory of slag structure. The mass action concentration model of CaO-MgO-FeO-Al_2O_3-SiO_2 slag systems was established. The effect of slag basicity, aluminium content in molten steel, degree of vacuum during vacuum treatment of molten steel, and furnace lining on the magnesium content in molten steel was discussed. The results show that magnesium content increases with increasing slag basicity and aluminium content, and decreases with increasing CO partial pressure.