Kinetic Modeling for the Dissolution of MgO Lining Refractory in Al-Killed Steels
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INTRODUCTION
WITH increasing demands for the high cleanliness of steel products, the accurate controlling of inclusion compositions is one of the main tasks for steelmakers.[1,2] Recently, the MgO-based refractory is widely used in the steelmaking process due to its high melting points and good wear resistance. The dissolution of the MgO refractory in melts results in the formation of spinels. The previous studies mainly focused on the dissolution behavior of the MgO-based refractory into the slag. Chen et al.[3] proposed a semi-empirical model to calculate the dissolution of MgO refractory in slag and obtained the mass transfer coefficients of various components in slag. Zhang et al.[4] found that MgO dissolution rate goes up with the increase of the CaF2 content in CaO-FeO-CaF2-SiO2 slag at 1673 K (1400 °C). Shim et al.[5] proposed an empirical formula of the solubility limit of the magnesia in FetO-MgO slags. Nightingale et al.[6,7] found that the spinel could reduce the degradation rate of MgO in CaO-SiO2MgO-FexO slags due to the formation of the cohesive spinel layer. Yan et al.[8] found that the activity coefficient of MgO in calcium ferrite-based slags was independent of the oxygen potential from 108 to 104 atm at 1573 K (1300 °C). Bygden et al.[9] observed a dense layer of magnesiowustite generated at the interface between the MgO refractory and FUXIANG HUANG, LIFENG ZHANG, YING ZHANG, and YING REN are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing 100083, China. Contact e-mail: [email protected] Manuscript submitted January 20, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
CaO-FeO-SiO2 slags. Amini et al.[10] measured the dissolution rate of MgO in CaO-Al2O3 slags in the air under the forced convention over the temperature range of 1723 K to 1873 K (1450 °C to 1600 °C). Umakoshi et al.[11] studied the dissolution rate and the mass transfer coefficient of MgO into FetO-CaO-SiO2 slags and found that a dense (Fe,Mg)O solid solution layer was formed on the surface of the sintered MgO refractory. Reactions occurred during the ladle treatment were usually investigated under the assumption of equilibrium conditions, differing from the realistic statement since the chemical reactions in the ladle could hardly reach their equilibrium state. There are several available kinetic models to investigate reactions of the refractory, slag, and steel, as summarized in Table I.[3,6,11–20] Shin et al.[20] proposed a kinetic model to predict compositional changes and inclusion evolution in molten steel considering the dissolution of the MgO refractory into slag. Harada et al.[16,21] developed a kinetic model to calculate compositional changes of inclusions considering the interactions among the steel, slag, and refractory, indicating that reactions between steel and slag had the largest effect on the formation of spinels on the MgO refractory surface. Besides, it was found that the dissolution rate of the MgO refractory rose up with the increasing rota
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