Effect of ladle-lining materials on inclusion evolution in Al-killed steel during LF refining

Abstract

The effect of lining materials (Al₂O₃ and Al₂O₃–MgO·Al₂O₃) of ladle on evolution of non-metallic inclusions in aluminum-killed (Al-killed) steel during ladle furnace refining without Ca treatment was investigated through industrial experiments. The results showed that non-metallic inclusions experienced the changes from Al₂O₃ → MgO–Al₂O₃ → CaO–Al₂O₃. During the refining process using either of the two ladle lining materials, for all non-metallic inclusions, the vast majority are distributed in the high Al₂O₃ area of the CaO–Al₂O₃–MgO phase diagram, with very little or none in the low melting point zone. Non-metallic inclusions are mainly smaller than 3 μm, while those larger than 3 μm consisted primarily of MgO·Al₂O₃ and CaO–Al₂O₃ inclusions. The use of an Al₂O₃–MgO·Al₂O₃-lining ladle is more effective in reducing the number density of inclusions in the steel. However, during the refining process, the Al₂O₃-lining ladle does not have a significant impact on the presence of MgO–Al₂O₃ and CaO–Al₂O₃ inclusions in the molten steel. The Al₂O₃–MgO·Al₂O₃-lining ladle does not have a significant effect on MgO–Al₂O₃ inclusions, but it does promote the formation of CaO–Al₂O₃ and CaS inclusions in the molten steel.