Structural characteristics and viscous behaviors of Al2O3-CaO-SiO2-Fe2O3 slags

The high temperature properties of the Al2O3-CaO-SiO2-Fe2O3 basic slag had significant influences on the steelmaking operation and the waste slag utilization process. To further clarify the structural characteristics and properties of Al2O3-CaO-SiO2-Fe2O3 slags, the structures and viscosities of the slags were researched. The slag liquidus temperature was determined, which reduced from 1365°C to 1287°C with adding Al2O3 in slags from 4.16wt% to 8.52wt%, and then increased to 1356°C with further adding Al2O3 to 17.07wt%. Structure analysis indicated increasing temperature depolymerized the structure of the 4.16wt%Al2O3-CaO-SiO2-Fe2O3 slag by decreasing the amount of complex AlO4 units and promoting the formation of simplified silicate monomers. The addition of Al2O3 in slags could polymerize the slag structure by increasing the quantities of complex AlO4 tetrahedral units and the complicated Si-O units. The variation trends of the structure polymerization degree were similar for the slag at the same superheat degree and the same quenching temperature, and both samples could be applied to analyze the impact of Al2O3 on slag structures. Finally, the viscous behavior of the slag was evaluated. Increasing Al2O3 content could increase the slag viscosity, and the apparent activation energy increased from 132.13 to 174.83 kJ/mol with raising the content of Al2O3 from 4.16wt% to 17.07wt%.