Mechanism of Heat Transfer Reduction by Crystallization of Mold Flux for Continuous Casting

Abstract

The mechanism by which crystallization of mold flux reduces the heat transfer between the steel shell and the mold has been investigated from the viewpoint of physical properties and characteristics of mold flux and air gap on the basis of a heat transfer model involving conduction and radiation processes. It has been found that, in mold fluxes for medium carbon steel, the reflectivity of the crystalline slag layer formed in mold flux film is an efficient factor for further reducing the total heat flux in the film. The heat transfer reduction based on this finding would be possible according to the following mechanism: Crystallization of mold flux film increases the reflectivity of the crystalline slag layer in the film owing to enhanced scattering of light by introduction of crystal grain boundaries, and thereby more radiation energy returns from the crystalline slag layer to the steel, leading to reduction in the total heat flux across the film.