Viscosity Property and Melt Structure of CaO–MgO–SiO2–Al2O3–FeO Slag System

For the purpose to describe the change of the viscosity properties of the converter slag during smelting reduction process using aluminum ash as reductant and provide basis for technology development, the viscosity of CaO–MgO–SiO2–Al2O3–FeO slag system at a fixed basicity of 3 was measured with the various ratio of A/(A+F) (w(Al2O3)/w(Al2O3+FeO)) by the cylinder method, and the structural of the melt was analyzed based on the FTIR and Raman spectroscopy to further explain the evolution behavior of viscosity. The results showed that viscosity of the slag was increased with increasing the ratio of A/(A+F). When this ratio increased from 0.17 to 0.5, the simple network units of the molten slag were polymerized into more complex network structure, resulting in a slow increase in viscosity from 0.65 dPa·s to 0.91 dPa·s at 1873 K. With further increasing this ratio to 1.0, the main structure was converted from silicate structure to aluminate structure. In addition, the polymerization degrees of aluminate units and silicate units both increased, which eventually led to an rapid increase in the viscosity from 0.91 dPa·s to 1.94 dPa·s.