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 (T_crit  = 1040±10 K) beyond which there was a sharp drop in λ_THW 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 T_crit and λ_Tcrit was found to be 1.6±0.05 W m⁻¹ K⁻¹. Thermal conductivity (λ_LP) values calculated from reported thermal diffusivity (α_LP) values were in very good agreement with the measured λ_THW values for temperatures between 295 K and T_crit but λ_LP values did not decrease with increasing temperature above T_crit (cf. λ_THW). Consequently, it was found that λ_LP≈7λ_THW for mould slags.

Keywords:

• Sodium metasilicate
• Continuous casting
• Continuous casting slag
• Casting powder
• Thermal conductivity
• Thermal diffusivity
• Transient hot wire method
• Laser pulse
• Laser flash
• Transient plane source
• Heat capacity