TY - JOUR
T1 - Kinetics of Transformation of Al2O3 to MgO·Al2O3 Spinel Inclusions in Mg-Containing Steel
AU - Liu, Chunyang
AU - Yagi, Motoki
AU - Gao, Xu
AU - Kim, Sun joong
AU - Huang, Fuxiang
AU - Ueda, Shigeru
AU - Kitamura, Shin ya
N1 - Funding Information:
The authors thank Professor Xinhua Wang of Shou-gang Corporation (earlier at University of Science and Technology, Beijing) for his kind support with regard to the P-SEM analysis. The authors gratefully acknowledge the financial support provided by ISIJ research promotion grant from the Iron & Steel Institute of Japan (ISIJ).
Publisher Copyright:
© 2017, The Minerals, Metals & Materials Society and ASM International.
PY - 2018/2/1
Y1 - 2018/2/1
N2 - During ladle furnace refining, initial Al2O3 inclusions generally transform into MgO·Al2O3 spinel inclusions; these generated spinel inclusions consequently deteriorate the product quality. In this study, the transformation from Al2O3 to MgO·Al2O3 was investigated by immersing an Al2O3 rod into molten steel, which was in equilibrium with both MgO and MgO·Al2O3 spinel-saturated slag. A spinel layer, with a thickness of 4 μm, was generated on the Al2O3 rod surface just 10 s after its immersion at 1873 K (1600 °C). The thickness of the formed spinel layer increased with the immersion period and temperature. Moreover, the MgO content of the generated spinel layer also increased with the immersion period. In this study, the chemical reaction rate at 1873 K (1600 °C) was assumed to be sufficiently high, and only diffusion was considered as a rate-controlling step for this transformation. By evaluating the activation energy, MgO diffusion in the generated spinel layer was found to be the rate-controlling step. In addition, this estimation was confirmed by observing the Mg and Al concentration gradients in the generated spinel layer. The results of this study suggest that the MgO diffusion in the spinel inclusions plays a substantial role with regard to their formation kinetics.
AB - During ladle furnace refining, initial Al2O3 inclusions generally transform into MgO·Al2O3 spinel inclusions; these generated spinel inclusions consequently deteriorate the product quality. In this study, the transformation from Al2O3 to MgO·Al2O3 was investigated by immersing an Al2O3 rod into molten steel, which was in equilibrium with both MgO and MgO·Al2O3 spinel-saturated slag. A spinel layer, with a thickness of 4 μm, was generated on the Al2O3 rod surface just 10 s after its immersion at 1873 K (1600 °C). The thickness of the formed spinel layer increased with the immersion period and temperature. Moreover, the MgO content of the generated spinel layer also increased with the immersion period. In this study, the chemical reaction rate at 1873 K (1600 °C) was assumed to be sufficiently high, and only diffusion was considered as a rate-controlling step for this transformation. By evaluating the activation energy, MgO diffusion in the generated spinel layer was found to be the rate-controlling step. In addition, this estimation was confirmed by observing the Mg and Al concentration gradients in the generated spinel layer. The results of this study suggest that the MgO diffusion in the spinel inclusions plays a substantial role with regard to their formation kinetics.
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U2 - 10.1007/s11663-017-1122-6
DO - 10.1007/s11663-017-1122-6
M3 - Article
AN - SCOPUS:85033503611
SN - 1073-5615
VL - 49
SP - 113
EP - 122
JO - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
JF - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
IS - 1
ER -