Calcium fluoride, known as fluorspar is a very good flux in steel making and also has been reported to increase the alloy yield and metal recovery in aluminothermic melts for production of ferrochrome. The present investigation is therefore carried out to study the effect of CaF₂ additions on the viscosity of synthetically prepared aluminothermic slags pertaining to the production of ferrochrome, with the composition approximating that of ferrochrome slag generated in the industry. The viscosities of these slags have been measured at four different Al₂O₃/CaO ratios with the broad composition of the slags varying between 50–62 mass% Al₂O₃, at various temperatures.
Calcium fluoride additions decreased the viscosity of aluminothermic ferrochrome slags at all temperatures. It is observed that the decrease in viscosity is different at different Al₂O₃/CaO ratios and that at all temperatures there is fast decrease in viscosity initially at lower CaF₂ contents, the rate of decrease diminishing at higher mole percent of CaF₂. The viscosity is found to obey the Arrhenius equation of viscous flow at two different temperature ranges and not throughout the temperature range above liquidus.
The activation energy at the two temperature ranges have been estimated and it is found to be stronglydependent not only on the CaF₂ content but also on the Al₂O₃/CaO ratio.
From the analysis of results it is suggested that the decrease of viscosity with increasing additions of CaF₂ content may be due to both depolymerisation and decreasing intensity of interactions among various anions and cations in the melt.