Abstract: The effect of different calcium contents on the transient evolution of inclusions in sulfur-containing steel was studied by adding silicon calcium alloys to the steel. Under low calcium content conditions, the composition of inclusions changed little, the size and quantity showed an increasing trend and resulting in a lower removal efficiency. Under high calcium content conditions, the decomposition of CaS inclusions was rapid and the removal efficiency of inclusions was high. After 30 min of holding, the number density and area fraction of inclusions in the steel with high and low calcium content were almost the same. Therefore, high calcium content could promote the modification of Al?O? inclusions, generating more liquid and semi-liquid inclusions, while improving the liquid phase fraction of inclusions. Therefore, adopting a higher calcium content process was more conducive to effectively modifying inclusions in sulfur-containing steel and optimizing the liquid window control.

Key words: calcium treatment; sulfur-containing steel; inclusions transformation