Thermal Conductivities of Slags for Ironmaking and Steelmaking

Thermal conductivities of synthetic slags and a slag sample taken from a blast furnace in normal operation have been measured by the hot wire method. The synthetic slags are composed of CaO-SiO2-Al2O3, CaO-SiO2-Fe2O3, Na2O-SiO2, CaF2, and CaF2-CaO-SiO2-Al2O3. The measuring temperature was widely changed from 100 to 1 500°C. In the temperature range lower than 1 000°C, the thermal conductivities of solid slags increased from 1.0 to 2.0 W/m·K with increasing temperature, and above 1 000 °C, they rapidly decreased to values of between 0.5 and 0.1 W/m·K in liquid state. The thermal conductivity of CaF2, which crystalizes in solid state, decreased monotonously with increasing temperature. The thermal conductivities of slags at high temperatures were empirically expressed as λ=(a/T)exp(-bT), where a and b are constants and T is absolute temperature. The thermal conductivities of liquid slags were about one tenth of those of the common refractories at high temperature.