Kinetics of Transformation of Al2O3 to MgO·Al2O3 Spinel Inclusions in Mg-Containing Steel

Chunyang Liu, Motoki Yagi, Xu Gao, Sun joong Kim, Fuxiang Huang, Shigeru Ueda, Shin ya Kitamura

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)113-122
Number of pages10
JournalMetallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
Issue number1
Publication statusPublished - 2018 Feb 1


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