Density, viscosity and surface tension of high-silicate CaO–SiO2 and CaO–SiO2–Fe2O3 slags derived by aerodynamic levitation. The behavior of Fe3+ in high-silicate melts

Thermophysical data for liquid slag are required for the optimization and control of metallurgical processes. The density, surface tension and viscosity were measured by employing aerodynamic levitation under contactless conditions. The high-silicate slag (44 and 63 mass-% of SiO2) of the CaO–SiO2 and CaO–SiO2–Fe2O3 systems (with 5 and 10 mass-% Fe2O3) was investigated under (80% Ar + 20% O2) gas atmosphere. The temperature ranges were between 800 °C and 2000 °C for the density and 1500 °C–2000 °C for surface tension and viscosity measurements. The influence of the CaO/SiO2 ratio on the investigated properties and the behavior of Fe3+ ions in high-silicate melts were examined. The density of the CaO–SiO2 melt was lower than that of the CaO–SiO2–Fe2O3 systems. The surface tension of all compositions tested decreased with temperature and showed compositional dependence. The viscosity measured was higher in the Fe2O3-containing slag. The Raman spectroscopy analyses confirmed the increase in the degree of polymerization with the addition of Fe2O3 for the silicate-rich slag. The formation of a complex anion of a ferric ion and contribution to the silicate network were assumed. The trends observed were related to the structural properties and different interionic bonding. Urbain's viscosity model and FactSage™ 7.3 were applied for the assessment of the experimental data.