Viscosities of Some Fayalitic Slags Containing CaF_2
In an effort to systematize the knowledge of the viscosities of slags containing CaF<sub>2</sub> and to enable the prediction of the change of viscosities of mould flux slags, viscosity measurements of synthetic slags in the system "FeO"-SiO<sub>2</sub>-CaF<sub>2</sub> were carried out in the temperature range 1450-1763 K. Five different fayalite slag compositions with "FeO" contents varying between 55-65 mass% in the homogeneous liquid range were chosen for the studies. The CaF<sub>2</sub> content was varied between 5 and 15 mass%. Due to the reactions between the slag components and CaF<sub>2</sub>, some CaO was formed during the premelting of the slags. Through analysis, it was found that, compositional changes due to fluoride evaporation occurred during the long premelting period. The libration of the volatile components SiF<sub>4</sub> and FeF<sub>2</sub> during sample preparation was the main source for compositional changes. DTA experiments were carried out in order to determine the liquidus points of the slags studied. CaF<sub>2</sub> was found to decrease the liquidus temperatures.<br> The viscosities were measured by the rotating cylinder method using spindles and crucibles made of iron in an argon atmosphere. The results showed the effect of the CaF<sub>2</sub> content on viscosity. The activation energy for viscous flow was generally dependent on the "FeO"/SiO<sub>2</sub> ratio and viscosity increased with decreasing temperature. The effect on the viscosities of "FeO"-SiO<sub>2</sub> slags due to CaF<sub>2</sub> additions was not found to be as significant as in the case of CaO-SiO<sub>2</sub> slags.
- ISIJ international
ISIJ international 39(7), 687-696, 1999-07-15
The Iron and Steel Institute of Japan