Examples of How Fundamental Knowledge can Improve Steelmaking: Desulphurisation Kinetics Calcium and Modification

Sulphur control is an essential part of steel production. This paper summarises two aspects of sulphur in secondary metallurgy. First, it is shown that silicon can contribute to ladle desulphurisation if the ladle slag is low in silica; the effect of silicon is primarily on the equilibrium sulphur level, rather than a specific kinetic effect. Second, sulphur is shown to capture calcium (as calcium sulphide) upon calcium injection to modify inclusions. In steels with less than approximately 100 ppm sulphur, the calcium sulphide subsequently back-reacts with alumina inclusions, to modify the oxide inclusions to calcium aluminates.