Silicates slags are widely used and produced in iron- and steel-making processes. In the continuous casting they play an important role as mold flux to enhance the surface quality by controlling heat transfer from molten iron to mold. Recently, the recycling of blast furnace slag also became to require its thermophysical data. The data of thermal conductivity, however, is not sufficient, especially in the temperature range of above liquidus temperature, because of the difficulty in measurement. In this research, the thermal conductivity of silicate melts is being measured by the hot wire method.The hot wire method is a transient measurement in short time before convection. Furthermore, since the radiation effect can be also ignored in this method because of small surface area of hot wire, heat is transferred mainly by the conduction through a sample. The thermal conductivity of the sample is obtained from the relationship between the heat generation and the temperature change of wire by the following equations.

where Q means heat generation rate per unit length of the wire. Consequently, the thermal conductivity of sample is calculated by Q(electrical power) and the slope of the plot of ΔT vs. ln t. In practice, electrical power is supplied to the hot wire (Pt-13%Rh, φ0.15mm) immersed in the sample as shown in Fig.1. The slope can be derived from the slope of the linear relationship between continuously recorded voltage change of the hot wire versus natural logarithm of time.　Figure 2 shows the data obtained in the measurements, compared with the data previously reported. Although the results of present study show positive deviation from those by literatures, as shown in Fig.2, the thermal conductivity of sample tends to decrease as increasing temperature. The tendency may indicate that the efficiency of heat transfer through the sample was appreciably reduced by the change of microstructure.

After establishing our method, the measurement of the conductivity of BF slag will be carried out at the temperature higher than 1400℃. Also the relationships between the thermophysical properties of silicate melts and the structure of silicate will be investigated.