RADIATIVE HEAT-TRANSFER THROUGH MOLD FLUX FILM DURING INITIAL SOLIDIFICATION IN CONTINUOUS-CASTING OF STEEL

Absorption coefficient and extinction coefficient for various commerci al mold fluxes have been determined to quantify the radiative and the total heat transfer through the flux film in continuous Casting mold. The absorption coefficient is found to be less than 1 000 m(-1) for gl assy specimens whereas the extinction coefficient is ca. 3 000-30 000 m(-1) for crystalline ones. Comparison of observed with calculated rad iative heat flux from the absorption coefficient has shown that gray g as approximation is valid for evaluating the radiative heat flux acros s the mold flux film. Numerical calculation for both radiative and con ductive heat transfer has been carried out for a given total thickness of the flux film. Despite little difference in optical properties amo ng various mold fluxes, the radiative heat flux through molten layer o f the flux films for low carbon and ultra low carbon steel is found la rger than that for medium carbon steel. This is due to increasing thic kness ratio of molten layer to crystalline layer of flux films. Solidi fying and crystallizing behavior of mold fluxes is a key factor to con trol the radiative heat transfer in continuous casting mold, according ly.