Radiative heat transfer behavior of mold fluxes for casting low and medium carbon steels

An investigation was carried out to study the radiative heat transfer behavior of two typical mold fluxes for casting low (Flux1) and medium (Flux2) carbon steels. By using an infrared radiation emitter, a radiative heat flux was applied to a copper mold covered with solid mold flux disk to simulate the heat transfer phenomena in continuous casting. The effective thermal conductivities were determined by measuring the temperature gradient in the copper mold system. It was found that the solid crystalline mold Flux2 for casting medium carbon steel has a better capability to transfer heat than that of solid crystalline Flux1, while their glassy fluxes behave similar capability. The DHTT (Double Hot Thermocouple Technique) was employed in this paper to study the heat transfer capability of the crystalline mold fluxes. DHTT measurements suggested that the thermal diffusivity of crystalline sample of Flux2 is higher than that of Flux1. The XRD and SEM results were indicated that the precipitated crystalline phase for Flux1 is only granular cuspidine, Ca₄Si₂O ₇F₂, while those for Flux2 are consisted of dendritic cuspidine, Ca₄Si₂O₇F₂ and gehlenite, Ca₂Al₂SiO₇.