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.