Determination of Density and Surface Tension of CaO–SiO2–Al2O3 Molten Slag by Pendant Drop Method

Surface tension is an important physical property of molten metallurgical slag. In recent years, the determination of slag surface tension by pendant drop method has received increasing attention, but the corresponding density data are required during its calculation. For this reason, researchers have to use the density data from literature or other experiments, which limits the application of the pendant drop method. In this work, a novel ring-shaped pendant drop forming device was made of PtIr alloy. A 40 pct CaO–40 pct SiO2–20 pct Al2O3 (mass percentages) slag was taken as an example, the density and surface tension data of the slag at high temperatures were tried to obtain in one experiment by the pendant drop method under different atmospheres including high-purity argon, air, and purified argon. In the temperature range of 1450 °C to 1650 °C, the measurement results are comparable with literature data of the slags with the same or similar compositions, which confirms that it is feasible to obtain the slag density and surface tension in one experiment by the pendant drop method based on the pendant drop forming device. The measured density of the molten slag slightly decreases with an increase in temperature, while the surface tension slightly increases; the temperature coefficients of both the density and the surface tension are relatively small. In addition, it is found that the obtained density values under the three atmospheres are highly consistent at the same temperature, and the surface tension values under high-purity argon and purified argon are also relatively consistent; however, the surface tension value under air is slightly larger than that under argon.