The Physical Chemistry of Steel Deoxidation and Nozzle Clogging in Continuous Casting

Nozzle clogging in continuous casting of steel originates from the adherence of alumina particles and other oxides, precipitated during the liquid steel deoxidation, on the refractory material’s surface. This study analyzes the nucleation and growth rates of these particles in supersaturated melts, focusing on the interfacial tensions between alumina, silica, and other oxides with liquid metal. It was found that weak deoxidizers, such as silicon, do not require high supersaturations for high nucleation rates, which results in narrow particle size distributions due to rapid diffusion and Ostwald-ripening coagulation. In contrast, strong deoxidizers like aluminum necessitate high supersaturation levels, leading to broader size distributions. Additionally, the morphology of the particles is influenced by the nucleation and growth mechanisms. The adhesion forces among deoxidation particles, which form clusters, depend on both the morphology and the oxide’s chemistry. The stability of the nozzle clog attached to the nozzle wall is influenced by interface tensions between the melt and the nozzle’s refractory surface, as well as between the melt and the inclusion. Overall, the findings provide foundational recommendations for steel refining and the material specifications of casting nozzles.