Calcium Transfer to Oxide Inclusions in Al-Killed Steel Without Calcium Treatment

Alumina inclusions generated from aluminum deoxidation may undergo several transformations depending on steelmaking conditions. Under reducing conditions, in contact with MgO-saturated slag, alumina inclusions are known to transform to spinel. However, there are uncertainties related to CaO pick-up by alumina-based inclusions. This work aims to provide some clarification of CaO pick-up by alumina inclusions through a series of experiments. First, the role of silicon in calcium transfer from slag was examined by conducting two similar experiments: one without any silicon addition and a second with 1 wt pct electronic grade silicon addition. Second, the role of crucibles was tested by conducting experiments in ZrO₂ and CaO-3 pct ZrO₂ crucibles. It was found that the addition of silicon significantly enhances the rate of CaO pick-up when there was no silica in the slag at the start of reaction. The effect of the crucible on CaO pick-up was found to be weaker than that of the 1 wt pct silicon addition.