Heat Conduction through Different Slag Layers in Mold. Thermal Conductivity Measurement of Commercial Mold Fluxes

Abstract

The thermal conductivity of two commercial mold fluxes has been investigated using the transient hot-wire method in the temperature range of 298 K to 1573 K. Experiments were conducted on granules, sintered granules, molten fluxes and glassy samples under ambient atmosphere. Characteristic temperatures of the mold fluxes were investigated using a hot stage microscope. Results are discussed in the context of the characteristic temperatures, the particle size of granules, the bulk density and the structure of the mold fluxes. The temperature dependence of the thermal conductivity for granules of mold fluxes is positive in the temperature range of 298 to 873 K (λ = 0.058 + 1.245 × 10−4 T). The further temperature increase causes the rapid increase of the thermal conductivity above the temperature, at which the granules start to sinter Tdeformation. The thermal conductivity of the glassy sample is around two times lower than the thermal conductivity of the devitrified sample. The effect of the glass transition temperature on the thermal conductivity was shown. The thermal conductivity rapidly increases above the glass transition temperature in the glass transition region as the temperature rises and decreases above the softening temperature Tsoftening. The further temperature increase caused the crystallization of the sample. The crystallization of the sample was observed at T ≈ Tg + 100 K. Moreover, results show the dependence of the thermal conductivity of molten mold fluxes on the basicity (CaO/SiO2) at 1573 K.