Effect of calcium treatment on evolution of inclusions in low-carbon aluminum-killed steel

Abstract

Based on the steel samples collected from low carbon aluminum-killed steel at ladle furnace start, end of ladle furnace heating, ladle furnace end and tundish pouring process for inclusions analysis, the influence of calcium treatment on the evolution of inclusions in steel from ladle furnace refining to continuous casting was investigated under the condition of using Al2O3-lining ladle. The results show that when calcium treatment is not used, the inclusions in steel are mainly Al2O3 and MgO-Al2O3 spinel, and the mass fraction of Al2O3 in the inclusions composition is ≥90% from ladle furnace refining to continuous casting. After calcium treatment is carried out, the types of inclusions in steel are mainly MgO-Al2O3-CaS (-CaO) inclusions, in which the content of Al2O3 and CaS is higher than the samples without calcium treatment, and low-melting point calcium-aluminate inclusions were not found in the samples. The average size of inclusions in the steel was similar for both processes during ladle furnace refining, but the number density of inclusions in the steel increased significantly after calcium treatment. At the end of LF, the number density of inclusions in the calcium-treated is about twice that of the non-calcium-treated.