The isothermal kinetics of fluoride evaporation from CaF 2-cao-Al 2 o 3-Mgo-tio 2-(Li 2 O) slag with varying Li 2 O content were investigated in the temperature range 1743-1803 K by thermogravimetric analysis. Thermodynamic calculations and viscosity measurements were applied for studying the evaporation mechanism of fluoride. The results showed that the evaporation ratio increases with increasing Li 2 O content and temperature. The volatile constituents from the molten slags, mainly LiF and CaF 2 , were detected and their concentrations calculated. The fluoride evaporation is primarily affected by the vapour pressure of LiF and CaF 2 , viscosity of the slags, and melt-component activities under given experimental conditions. On the other hand, mass transfer of the gas is not the ratecontrolling step that affects fluoride evaporation from the slags. The activation energy for fluoride evaporation gradually decreased from 193 ± 11 to 113 ± 3 kJ mol −1 as the Li 2 O content in the slags increases from 0 to 5.48 wt%. These results hold great theoretical significance for developing lowfluoride slags for electroslag remelting. The slags in electroslag remelting (ESR) process serve as a heat source, a barrier to the atmosphere, and a medium for liquid metals refining 1-5. To perform the intended functions, the slags must have some well-defined properties such as low electrical conductivity and suitable viscosity at remelting temperature 6,7. The traditional ESR slags are CaF 2-CaO-Al 2 O 3-based slags with a high CaF 2 content, and an additive such as MgO, TiO 2 or SiO 2 is commonly used to meet specific material requirements. However, fluoride evaporation from high CaF 2-content slags is a potential health-and safety hazard. Furthermore, it would alter the chemical composition and cause changes in the metallurgical properties of the slags 8-11. Therefore, it is important to develop low-fluoride slags and study their effect on fluoride evaporation during the ESR process. The most common approach for developing low-fluoride slags is to control the CaO/Al 2 O 3 mass ratio and substitute a small amount of oxides for CaF 2 to keep the physicochemical properties stable. Several oxides including Na 2 O, B 2 O 3 , and Li 2 O are considered as potential substitutes for CaF 2 12-14. Among them, a small addition of Li 2 O could effectively regulate the viscosity and melting temperature of the slags; thus, the partial substitution of CaF 2 with Li 2 O retains the performance of the slags. Several works reported by Shi et al. 15 have researched the effect of Li 2 O on the viscosity of CaF 2-CaO-Al 2 O 3-MgO slags, which suggested that the viscosity of slags decreased with Li 2 O content increasing from 0 to 4.5 wt%. Kim et al. 16 measured the viscosity of CaO-Al 2 O 3-12 wt% Na 2 O-12 wt% CaF 2-based slags and concluded that the addition of Li 2 O depolymerized the large aluminate structures and decreased the slag viscosity. Additionally, Liu et al. 17 studied the effect of Li 2 O on the properties of CaF 2-CaO-Al 2 O 3-SiO 2-Na 2 ...
