Mass Action concentration model of CaO-MgO-FeO-Al₂O₃-SiO₂ slag systems and its application to the formation mechanism of MgO·Al₂O₃ spinel-type inclusion in casing steel

¹ State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, P.R. China
e-mail: tanghaiyan@metall.ustb.edu.cn
² School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China

Received: 11 September 2014
Accepted: 5 August 2015

Abstract

Large-size MgOfflAl₂O₃ spinel-type inclusions in casing steel are harmful to the surface quality and performance of casing. In order to effectively control them in production, their existence in casing steel was analysed by scanning electron microscope and energy dispersive spectrometer, and the formation mechanisms were studied using the coexistence theory of slag structure. The mass action concentration model of CaO-MgO-FeO-Al₂O₃-SiO₂ slag systems was established. The effect of the 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 is discussed. The results show that magnesium content increases with increasing slag basicity and aluminium content, and decreases with increasing CO partial pressure.