Proposal of Low‐Reactivity CaO–SiO ₂ –MnO‐Based Mold Slag for Continuous Casting of High‐Mn Cryogenic Steel

During the continuous casting (CC) of high‐Mn cryogenic steel, the intense steel–slag reactions caused by its high‐alloy content ([Mn] = 22–25 wt%) present a critical technical barrier to large‐scale production. To address this issue, this study first investigated the composition and property evolution of in‐service mold slag during CC at a steel plant. Thermodynamic calculations and laboratory steel–slag contact experiments clarified the interfacial reaction of slag with high‐Mn cryogenic steel. A design strategy for a low‐reactivity CaO–SiO 2 –MnO‐based mold slag was proposed by controlling the MnO/SiO 2 mass ratio, and its effectiveness was validated through industrial trials. The results indicated that the decrease in (SiO 2 ) content and the increase in (MnO) content in the liquid slag primarily originated from the redox reaction between [Mn] and (SiO 2 ) at the steel–slag interface. The application of the low‐reactivity CaO–SiO 2 –MnO‐based mold slag reduced composition and property fluctuations compared to in‐service mold slags, effectively suppressing reactions at the steel–slag interface. Additionally, this new low‐reactivity slag exhibited a stronger synergistic effect in lubrication and heat transfer control, enabling multiheat CC.