Thermal resistance between solidifying steel shell and continuous casting mold with intervening flux film

Conductive thermal resistance from solidifying steel shell through mold flux to continuous casting mold was investigated in bench tests. Thermal diffusivities of six mold fluxes used in continuous casting of steels were determined in glassy, crystalline and molten states with a laser flash method. Interfacial thermal resistance between the solidifying mold fluxes and copper mold was also investigated by pouring the molten fluxes onto copper mold and measuring transient heat transfer to the mold. The surface morphology of solidified fluxes in contact with the mold was observed with a stylus type profile meter and related to the interfacial thermal resistance. Thermal diffusivity of glassy state (ca. 4.5 × 10^-7 m² s^-1) and molten state (ca. 5 × 10^-7 m² s^-1) was insensitive to chemical composition and temperature, while that of crystalline state was higher (5.8-7.8 × 10^-7 m² s^-1 at room temperature) and decreased with increasing temperature, reaching similar value to that for glassy and molten state at high temperatures. The surface morphology consisted of large cells on which small cells were superimposed. Observed interfacial thermal resistance increased with increasing height of the large cells, contributing more than 50% of the total conductive heat transfer resistance and being a significant factor to control the heat transfer between the solidifying steel shell and the mold.