Thermal conductivity of powders used in continuous casting of steel

Abstract

Measurements of the thermal conductivity (λ) and thermal diffusivity (α) have been carried out on samples of Na2O·SiO2 and four mould slags for temperatures between 295 and 1300 K. These measurements were carried out using the transient plane source (TPS) method (295–373 K) and the transient hot wire (THW) technique (295–1300 K) and the laser pulse (LP) or laser flash method in the case of Na2O·SiO2 Values of λ295 were very similar (1.07±0.03 W m−1 K−1) and all samples exhibited a maximum at the critical temperature (Tcrit = 1040±10 K) beyond which there was a sharp drop in λTHW with increasing temperature. Measurements were also carried out on semi-crystalline samples with increasing λ and fraction of crystalline phase. These samples also exhibited a sharp drop in the thermal conductivity for temperatures above Tcrit and λTcrit was found to be 1.6±0.05 W m−1 K−1. Thermal conductivity (λLP) values calculated from reported thermal diffusivity (αLP) values were in very good agreement with the measured λTHW values for temperatures between 295 K and Tcrit but λLP values did not decrease with increasing temperature above Tcrit (cf. λTHW). Consequently, it was found that λLP≈7λTHW for mould slags.