Dissolution Behavior of Mg from Magnesia-Chromite Refractory into Al-killed Molten Steel
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DUCTION
IN steelmaking processes, the formation of MgOÆAl2O3 spinel inclusions has gained worldwide attention.[1–26] Usually, MgOÆAl2O3 spinel inclusions form even though Mg is not intentionally added to the steel melts during refining. Therefore, many studies have been conducted to determine the MgO source for the dissolved Mg in the steel melts. Both MgO-containing refining slag and MgO-based refractory materials have been considered as possible sources.[22–26]
CHUNYANG LIU is with the Department of Metallurgy, Graduate School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan. MOTOKI YAGI is with the Central Japan Railway, 1-1-4 Meieki, Nakamura-ku, Nagoya, Aichi 450-6101 Japan. XU GAO, SHIGERU UEDA, and SHIN-YA KITAMURA are with the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 Japan. Contact e-mail: [email protected] SUN-JOONG KIM is with the Department of Materials Science & Engineering, College of Engineering, Chosun Unversity, 309, Pilmun-daero, Dong-gu, Gwangju 61452, Korea. FUXIANG HUANG is with the Steelmaking plant of Beijing Shougang Co., Ltd. Qian-an City, Hebei Province, China. Manuscript submitted September 26, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
Okuyama et al.[22] studied the effect of MgO-containing slag on the formation of MgOÆAl2O3 spinel using a vacuum-induction furnace. They determined that MgO in the slag was reduced by Al in the steel melts, and subsequently Mg dissolved into the steel melts and MgOÆAl2O3 spinel inclusions were generated. Harada et al.[23] studied Mg dissolution from both dense MgO material and MgO-containing slag. During their experiments, the dense MgO material or MgO-containing slag interacted with the Al-killed steel melts. It was found that both of these MgO sources supplied Mg to the steel melts. However, in their study, MgOÆAl2O3 spinel inclusions were generated in the steel melts only in the case of experiments involving the MgO-containing slag. Brabie[24] investigated the mechanism of the reaction between MgO-C refractory materials and Al-killed molten steel, determining that Mg dissolved into the steel melts from the MgO-C refractory, and MgOÆAl2O3 spinel inclusions were generated. One of the authors of the current study[25,26] investigated the dissolution of Mg from MgO refractory, MgO-C refractory, and MgO-containing slag into Al-killed steel. It was determined that Mg gradually dissolved into the steel melts, and the initial Al2O3 inclusions transformed into MgOÆAl2O3 spinel in all the cases studied. From the above works, it can be concluded that both MgO-containing slag and MgO-based refractory materials are MgO sources for the generation of MgOÆAl2O3 spinel inclusions.
Table I.
Composition of the Magnesia-Chromite Refractory
Component
MgO
Cr2O3
Al2O3
FeO
CaO
Content (mass pct)
70.23
18.58
4.69
6.01
0.49
Fig. 2—Mineralogical structure of the magnesia-chromite refractory observed by EPMA. Fig. 1—Mineralogical observed b
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