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t is well known that sulfur is harmful to the mechanical properties of steel product such as strength, ductility, toughness. Also, sulfide or oxy-sulfide inclusions deteriorate the corrosion resistance and oxidation resistance of stainless steels, and thus it is desirable that these harmful inclusions should be effectively removed.[1,2] However, sulfur is contained as an impurity in various alloying materials such as ferroalloys. The formation of rare earth sulfide or oxy-sulfide inclusions in molten steel is unavoidable due to high affinity between rare earth elements and sulfur at steelmaking temperatures. Therefore, the sulfur absorption ability of the oxide system containing rare earth elements should be necessarily investigated at high temperatures. Recently, Kwon et al.[3,4] investigated the thermodynamic behavior of Ce in austenitic stainless steel melts in terms of Ce yield and inclusion evolution procedure as well as interfacial reaction between alumina refractory and molten steel. Looking at the behavior of the inclusions, the Mn(Cr)-silicate inclusions were initially formed, followed by a transformation to the MnO-SiO2-Al2O3 ternary

SE JI JEONG, formerly Graduate Student with the Department of Materials Engineering, Hanyang University, Ansan, 426-791, Korea, is now Researcher with Technical Research Center, SeAH Changwon Integrated Specialty Steel (SeAH CSS), Changwon, Korea. TAE SUNG KIM, Graduate Student, and JOO HYUN PARK, Professor, are with the Department of Materials Engineering, Hanyang University. Contact e-mail: [email protected] Manuscript submitted July 28, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B

system by an Al deoxidation. Finally, the MnO-SiO2Al2O3-CeOX complex oxides were partly formed after Ce was added, which was well agreed to the results observed by Jeon et al.[1,2] Therefore, the sulfide capacity of the MnO-SiO2-Al2O3-CeOX melt needs to be measured to figure out the sulfur absorption ability of this quaternary oxide system. The sulfide capacity of the MnO-SiO2-Al2O3 ternary system is well known from the previous articles.[5–7] Sharma and Richardson described the iso-sulfide capacity contours from the measured capacity results at the compositions of XSiO2 £ 0.5 and XMnO £ 0.8 using gas-slag equilibration method at 1923 K (1650 C).[5] Nzotta calculated the iso-sulfide capacity contours using the mathematical model at 1873 K (1600 C), and the model predictions were agreed well with the measured results in the composition ranges of 0.3 £ XSiO2 £ 0.6 and 0.3 £ XMnO £ 0.6.[6] Recently, Kang and Pelton calculated the iso-sulfide capacity contours in the MnO-SiO2-Al2O3 system using the modified quasichemical model based on the quadruplet approximation at 1923 K (1650 C) and compared the calculated results with the experimental data measured by Sharma and Richardson.[7] From these previous results, it is generally known that the sulfide capacity increases with increasing content of MnO in the MnO-SiO2-Al2O3 ternary system. On the other hand, the activity of each component in the MnO-SiO2-Al2