Effects of CaF₂ on light absorption and radiation heat transfer characteristic of mould flux containing iron oxides

Optical properties were measured for synthesised mould flux containing iron oxides, and radiative heat transfer from the steel shell to the mould was estimated to investigate the effect of CaF₂ additions to mould fluxes on heat transfer in continuous casting process from the perspective of absorption by iron oxides. The sample compositions were designed so that T.CaO/SiO₂=1 and Fe₂O₃ concentration was 1 mass%. All the glassy samples show optical properties and radiative heat transfer similar to each other, suggesting that there is no effect of CaF ₂ on the basicity of flux. In addition, there was no change in the absorption wavelength and the absorptivity by divalent Fe ion, suggesting that the coordination of Fe ions and the electric charge strength do not change with additions of fluoride. On the other hand, crystallised samples show reflectivity increase and transmissivity decrease with increasing CaF₂ concentration, resulting in the decrease of the radiative heat transfer. The fluoride facilitates the crystallization of the flux, and induces a decrease in radiative heat transfer. The Fe ions were mainly contained in the glassy portion rather than in crystals (cuspidine or CaF₂ ) in the crystallised samples. To optimize the refractive index in the glassy portion is a possible way to reduce further radiative heat transfer of mould flux containing iron oxides.