Multicomponent Reaction Mechanism at Steel-Slag Interface During Continuous Casting of High Mn–Al Steels: Modeling and Experimental Validation
摘要
High-Mn high-Al steels are widely used for their excellent mechanical properties, but degradation of mold flux and casting defects caused by multicomponent steel-slag reactions remain critical issues. In this study, a quantitative kinetic model for multicomponent reactions at the steel-slag interface was established based on double-film theory and coupled with thermodynamic equilibrium calculations. High-temperature crucible experiments using high-Mn high-Al steels and CaO–Al2O3–SiO2 based mold fluxes were conducted to validate the model and clarify reaction mechanisms. The model dynamically describes the coupled mass transfer of Al, Mn, and Si between steel and slag, and accurately predicts the time-dependent evolution of compositions, with an average deviation below 7 pct from experimental data. The results reveal a dual “competitive oxidation-cooperative reduction” mechanism between Al and Mn: when [Al] ≥ 1.5 wt pct, preferential Al oxidation suppresses MnO formation and limits Mn oxidation loss to 2 pct, while Al reduces MnO, leading to apparent Mn enrichment in steel. SiO2 content in the slag is identified as a key factor governing interfacial oxygen potential and reaction pathways. By extending the model to continuous casting conditions, the effects of molten slag layer thickness, mold flux consumption, and mass transfer coefficients on interfacial reactions were quantified. A molten slag thickness of 12-16 mm and mold flux consumption ≥ 0.5 kg/t are suggested to balance interfacial kinetics, lubrication, and heat transfer. For mold flux design, limiting SiO2 to ≤ 15 wt pct and employing low-reactivity systems such as CaO–Al2O3–BaO are recommended for high-Mn high-Al steel casting. This work provides a mechanistic and quantitative basis for controlling multicomponent steel-slag reactions and optimizing flux design and casting parameters.