Effect of ladle slag of previous heat on number of non-metallic inclusions in ladle treatment of tool steel

Abstract

Nine series of industrial trials were carried out using the same ladle in each series to examine the effect of ladle slag on the number of non-metallic inclusions in the next heat. Steel and slag samples were taken after ladle vacuum treatment for chemical composition analysis. Samples of the final steel product were examined to determine the number of non-metallic inclusions. It was found that the number of inclusions increased with SiO₂ content of the ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions.Theoretical analysis based on the experimental results suggested that the formation of 2CaO.SiO₂ followed, but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.