论文部分内容阅读
To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace (LF) refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing, the effects of ferrosilicon alloy, Si content of steel, and slag basicity on the compositions of inclusions during LF refining were investigated in Al-killed steel. Al2O3 inclusions could be transformed into CaO–Al2O3–MgO–CaS inclusions after adding ferrosilicon alloy in the LF refining process as this alloy contains some CaSi alloy impurities. The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions. Si in liquid steel had a significant influence on the compositions of inclusions during LF refining when CaO–Al2O3–SiO2–MgO slag with high basicity of 7.0 was used. This was because [Ca] produced by the reaction of CaO and [Al] could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel, which was confirmed by the difference of total calcium content between Si-free and Si-containing steels. As a result, Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. For CaO–Al2O3–SiO2–MgO slag with low basicity of 2.8, Al2O3 and MgO·Al2O3 inclusions were obtained after LF refin-ing in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process. This was because the reaction of CaO and [Al] was weak, and residual [Ca] in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2, leading to a low total calcium content of 0.0003％ in Si-containing steel.