Dynamic Wetting of High-Al Steel by CaO-SiO₂- and CaO-Al₂O₃-Based Mold Fluxes

Wetting of steel by mold fluxes affects the surface quality of steel products. Reaction between [Al] and mold fluxes in the continuous casting of high-Al steel leads to a dynamic interfacial phenomenon. This work investigated the wetting of the high-Al steel substrate by CaO-SiO₂-based and CaO-Al₂O₃-based mold fluxes. The interfacial tensions were estimated and related to their high-temperature structures. The interface morphology revealed that CaO-SiO₂-based mold flux and CaO-Al₂O₃-based mold flux with CaO/Al₂O₃ = 1 exhibited deep reaction zones in the steel substrates and irregular flux/steel interfaces, while CaO-Al₂O₃-based mold fluxes with CaO/Al₂O₃ = 2 and 3 showed smooth interfaces and superficial reaction zones. The sedation of dynamic wetting behavior in Samples 3 and 4 was related to the high viscosity in the flux droplet after the initial composition change, which led to the stabilization of the interface.