Effect of Ce2O3 on the fluoride vaporization of CaF2–CaO–Al2O3-(Ce2O3) slag used for vacuum electroslag remelting

In order to explore the slag with less fluoride vaporization for vacuum electroslag remelting of Ce-bearing steel, the fluoride vaporization behavior of CaF2–CaO–Al2O3-(Ce2O3) slag was investigated by thermo gravimetry analysis at 1673 K. For the purpose of figuring out the mechanism of the Ce2O3 effect on fluoride vaporization in slags, the viscosity of slags was measured, and the activity of components in molten slag was calculated based on the ion and molecule coexistence theory. The fluoride vaporization of slag under vacuum condition at 1823 K was also studied. The results show that the fluoride vaporization products are CaF2 and AlF3. The weight loss caused by fluoride vaporization reduces with increasing Ce2O3 content. The Ce2O3 addition lowers the breaking temperature of viscosity, which leads to the decrease of viscosity at 1673 K with the increase in Ce2O3 content. It implies the viscosity change is not the reason inhibiting fluoride vaporization because a lower viscosity will promote the fluoride vaporization. The vapor pressure of CaF2 and AlF3 decreases with increasing Ce2O3 content due to activity change, which contributes to the suppression effect on the fluoride vaporization in investigated slags. The fluoride vaporization of slag under vacuum is inhibited because of Ce2O3 addition as well.