Experimental studies of viscosities of some CaO–CaF 2 –SiO 2 slags

In the present work, the viscosities of some CaO–CaF₂–SiO₂ slags were measured using the rotating cylinder method. The effects of various volatile fluorine compounds on the change in slag composition are discussed on the basis of thermodynamic calculations. The kinetic factors concerning the escape of the volatile fluorides under the experimental conditions were also examined. It was found that the formation of gaseous species SiF₄ was the main source for compositional changes during the viscosity measurements. In the case of CaO–CaF₂–SiO₂slags, the formation of SiF₄ would be somewhat limited owing to the existence of CaO. The composition change during the measurements was only about ±1 wt-% for all components in most cases. Viscosity measurements are reported for slags, based on the post-measurement compositions. It was found that the addition of CaF₂ causes a significant decrease in viscosity.