Laser-flash method has been applied to determine thermal diffusivities of mold fluxes containing iron-, zirconium- and titanium-oxides for continuous casting of steel in temperature range between room temperature and 800K for glassy samples and between room temperature and 1000K for crystalline samples. Thermal diffusivity of glassy samples was found to be 4.6±0.5×10-7m2/s, slightly higher than 4.0±0.5×10-7m2/s of liquid samples, and insensitive to the variation of temperature and concentration within the range presently investigated. When crystallized, the thermal diffusivity was increased by about 40% over that of glassy samples. The diffusivity was decreased with increasing temperature, exhibiting only 20% increment of that of the glassy ones at temperatures beyond 800K. The apparent absorption coefficients of crystalline samples estimated from the measured spectral transmissibity were over 2400m-1, indicating their opacity. Mold flux film was collected from the bottom part of mold for casting of steel and about 50mass% of which was confirmed by X-ray diffraction to be in crystalline state. The present results suggest that the change in radiative component due to absorption by the crystalline part of mold flux is one of the responsible factors in controlling the heat transfer through a continuous casting flux film between the mold and solidified shell.
