The molten slags that are used not only in the continuous caster but also in every metal industry play an important role and affect the quality of products. The authors initially developed the double hot thermocouple technique (DHTT) for in situ observation of mold slag crystallization.
In this study, the DHTT was further developed to allow the measurement of the overall thermal diffusivity of molten slag applying the principle of the laser flash method. The affecting factors (finite pulse time, shape of pulse and heat loss from sample surface) on the measurement of thermal diffusivity using the DHTT were discussed theoretically using both the analytical and the numerical methods. New relationship between the thermal diffusivity a and the time at half-maximum temperature t_0.5 was obtained as follows:

a(×10⁴m₂/s) = 0.000707(t_0.5/t_p)^-1.8946

The thermal diffusivity obtained from the experimental half-maximum time t_0.5/t_p (t_p is the time of peak on the heat pulse) was in good agreement with the one from literature.