Effects of MoO3 + C on Crystallization and Radiative Heat Transfer of CaO–SiO2–B2O3-Based Glassy Fluoride-Free Mold Fluxes

Abstract

The fluorine in traditional mold fluxes could be harmful in steel-plant environments. Accordingly, fluoride-free mold fluxes have received great attention in recent years. In this work, a method to adjust the crystallization and radiative heat transfer of fluoride-free mold fluxes is proposed. MoO3 and C mixtures (mass ratio: 4:1) were added into CaO–SiO2–B2O3-based mold fluxes and produced MoB, Mo2CB and Mo2C foreign particles. The influences of foreign particles on the radiation of glassy CaO–SiO2–B2O3-based mold fluxes were investigated by measuring the transmissivity of a glassy disk for light in the wavenumber range of 300 to 2500 nm. It was found that transmissivity in all wavenumber ranges were reduced and extinction coefficients were enhanced by the scattering of foreign particles. The effect of foreign particles on crystallization (devitrification) of bulk glassy CaO–SiO2–B2O3-based mold fluxes was also investigated. The crystallization mechanism of glassy mold fluxes disks is mainly surface crystallization. The introduction of foreign particles induced heterogeneous nucleation and the crystallization mechanism of the bulk sample with MoO3% = 2% changed into bulk crystallization.