Reaction Behaviors of Al-Killed Medium-Manganese Steel with Different Refractories
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NON-METALLIC inclusions have an important effect on the mechanical properties of steel, e.g., yield strength, tensile strength, and fatigue resistance.[1] With the increasing demand for higher steel quality, the control of inclusions must also become increasingly strict. In industrial practice, some reactions between molten steel and the refractory may occur; these reactions not only decrease the refractory service life, but also significantly influence the characteristics of the inclusions in the steel. For instance, the particles dropped from the refractory would generate some macro-inclusions in steel, which would seriously degrade the steel quality. Therefore, the reaction behaviors of steel with refractories still present their significance for inclusion control in the metallurgical industry. Many publications[2–24] have focused on the reaction between steel and different refractories. Khanna et al.[12] studied the reaction between an Al2O3-10 pct C refractory and Fe, and found that the Al2O3-10 pct C refractory caused degradation because of the carbon in the refractory, whereas no degradation was found for the carbon-free Al2O3 refractory. The present authors[15] also obtained a similar result. For MgO-based refractories, Brabie[2] and Cirilli et al.[5] proposed that MgO
LINGZHONG KONG, ZHIYIN DENG, and MIAOYONG ZHU are with the School of Metallurgy, Northeastern University, Shenyang 110819, P.R. China. Contact e-mail: [email protected] Manuscript submitted August 25, 2017.
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would be reduced by the C in MgO-C bricks to form magnesium vapor at molten steel temperature, and lead to the generation of MgOÆAl2O3 inclusions.[7,10,16–20] Meanwhile, a layer of MgOÆAl2O3 was also found at the interface between Al-killed steel and a MgO refractory.[11,15–18] Both of them were considered as the primary sources of MgOÆAl2O3 inclusions in liquid steel.[21,22] Furthermore, Tripathi et al.[23] and Mantovani et al.[24] also showed that the refractories of ladle and tundish have a significant influence on the behavior of non-metallic inclusions according to their industrial experiments. In fact, the above results were obtained mainly in Al-killed low-alloy steel; the case of high-alloy steel is rarely considered, especially in the case of high-Mn steel grades. Recently, medium- and high-manganese steels have been a focus because of their excellent mechanical properties.[25,26] In an earlier publication of the present authors,[27] (Mn, Mg)OÆAl2O3 inclusions were found in medium-manganese steel during the secondary refining process, and the inclusions were generated after the formation of MgOÆAl2O3 inclusions at the middle stage of LF refining. Further study indicated that (Mn, Mg)OÆAl2O3 inclusions could be formed from the reaction between the MgOÆAl2O3 spinel inclusions and dissolved Mn in the steel. Still, the effect of the refractory on the formation of (Mn, Mg)OÆAl2O3 inclusions needs further investigation. Refractories of Al2O3, MgO, and MgOÆAl2O3 are widely used in the steelmaki
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