Effect of Sulfur Content on Evolution of Nonmetallic Inclusions in Low Sulfur Al‐Killed Steels during Heat Treatment

Abstract

Herein, the effect of total sulfur (T.S) on the transformation of inclusions in Al‐killed steels is investigated through lab experiments and kinetic calculations. During the heating process, CaS content in inclusions obviously rises up, while the CaO content reduces. The CaO content in inclusions with 11 ppm S in steel is higher than 15%, while it is less 5% for the steel with 25 ppm S. The initial CaO–Al2O3 inclusions before heating change to CaS–MgO–Al2O3 at 1200 °C. The higher T.S promotes the transformation of inclusions in low sulfur Al‐killed steels, leading to the higher CaS content in inclusions after the heat treatment. A kinetic model is developed to predict the transformation of inclusions in low sulfur Al‐killed steels during the heat treatment. The transformation fraction of inclusions decreases with the larger size of inclusions and increases with the higher T.S content in steel at the heating temperature.