Dissolution rate of Al ₂ O ₃ into molten CaO–Al ₂ O ₃ –CaF ₂ flux

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Dissolution of Al2O3 into molten CaO–Al2O3–CaF2, a base system of mould flux for continuous casting of high Al steel, has been investigated by employing a rotating cylinder method. The dissolution rate of an alumina rod into molten CaO–Al2O3–CaF2 flux increased with increase in rotating speed and temperature. The apparent activation energy for mass transport of flux C was calculated to be 255·6 kJ mol−1. The rate controlling step during the dissolution process of the alumina rod into molten CaO–Al2O3–CaF2 flux was found to be the diffusion of the solute in the flux boundary layer. The dissolution rate of alumina into molten CaO–Al2O3–CaF2 flux increased with increasing CaO/Al2O3, and it may be caused by the increase in thermodynamic driving force and the decrease in the viscosity of the flux. When the Al2O3 rod was immersed into molten flux, an intermediate compound of CaO.2Al2O3 formed firstly and then dissolved into molten flux.