Influence mechanism of silicon content in Al-killed steel on compositions of inclusions during LF refining

To obtain solid inclusions in LF refining process, the influence of silicon content in steel on compositions of inclusions during LF refining were investigated in Al-killed steel. Influence of silicon on compositions of inclusions was found to be great. The [Ca] content of steel was supplied from the reaction of [Al] and CaO. The [Si] content affected the [Ca] content by the reaction (SiO₂) + 2[Ca]→[Si]+2(CaO), and [Ca] was consumed more readily by SiO₂ in Si-free steel than in Si-containing steel, as a result, Al₂O₃ and MgO·Al₂O₃ inclusions could be obtained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. Moreover, the inclusions were mainly solid Al₂O₃ with low contents of CaO and MgO when using low-calcium ferrosilicon alloy and adding all low-calcium ferrosilicon alloys required for the steel at the end of LF refining, this ensures high removal efficiency of inclusions in RH degassing.