Effects of high Al content on the steel–slag reaction and inclusion formation in molten steel

Three groups of refining experiments using the slags with different CaO/Al₂O₃ mass ratio (C/A = 0, 1.32 and 2.52 for No. 1 [without slag], No. 2 and No. 3) were carried out. The experiment results show that the increase of C/A led to the decrease of Al content. The steel–slag–inclusion multiphase reactions (SSIMR) model under high Al content conditions was constructed by the effective equilibrium reaction zone and FactSage 8.2 software. The modeling predictions of changes of [Al], [Ca] and [Mg] and SiO₂, MgO and CaO in the slag are consistent with the experimental results. The SSIMR modeling suggested that the reactivity of [Al] and SiO₂ in slag decreased with the increase of C/A, while the reactivity of [Al] and CaO in slag increased with the increase of C/A. The increase of C/A has little effect on the reaction between [Al] and MgO in slag. Inclusion observations in the No. 2 and No. 3 experiments show that inclusions change from Al₂O₃ and MgAl₂O₄ in early stages to CaO-MgO-Al₂O₃-SiO₂ inclusions in the late stages. This study may help predict steel–slag reaction and inclusion formation under high Al content conditions.