Reoxidation of IF Steel Caused by Cr₂O₃-Based Stuffing Sand and Its Optimization

Stuffing sand, as a critical auxiliary material, plays an important role in ladle teeming during the continuous casting process and is closely related to steel cleanliness. Based on thermodynamic calculations, a melting test in a vacuum induction furnace, and industrial statistical data analysis, the reoxidation of IF steel caused by conventional Cr₂O₃-based stuffing sand was investigated. The results show that Cr₂O₃-based stuffing sand is one of the main factors resulting in the reoxidation of IF steel. [Al] and [Ti] in IF steel can be oxidized by FeO, Cr₂O₃, and SiO₂ from the Cr₂O₃-based stuffing sand, which leads to the mass burning loss of [Al] and [Ti], thus resulting in the deterioration of steel cleanliness. After reoxidation caused by Cr₂O₃-based stuffing sand, the [Cr] content in IF steel increases by 70 ppm on average. To avoid reoxidation pollution by conventional Cr₂O₃-based stuffing sand, a new kind of Al₂O₃-based stuffing sand with low reactivity was developed and applied in industrial production. After adopting this new kind of stuffing sand, the burning loss of [Al] and [Ti] decreases by 41.3% and 24.2%, respectively, and the total oxygen content (T.[O]) of the steel in the tundish decreases by 35.2% compared with the conventional Cr₂O₃-based stuffing sand.