Viscosity-Structure Relationship of CaO-Al2O3-FetO-SiO2-MgO Ruhrstahl-Heraeus (RH) Refining Slags

Abstract

The effects of iron oxide on the viscosity of the CaO-Al2O3-FetO-SiO2-MgO system Ruhrstahl-Heraeus (RH) refining slags with different CaO/Al2O3 ratios (C/A = 1.0 to 2.0) and various iron oxide contents (T.Fe = 4 to 18 wt%) were investigated. Iron oxide generally decreases the viscosity of the slags. In the relatively low iron oxide content region (i.e., T.Fe < 10 wt%), the increase in the C/A ratio decreases the viscosity of the slags, whereas it has less significant effect on the modification of the aluminate structure in the relatively high iron oxide content region. The addition of iron oxide to the slags with C/A < 1.3 effectively breaks the aluminate networks, while the network structure is less affected by the iron oxide in the slags with C/A 1.6. From the semi -quantitative analysis of Raman scattering data, the addition of iron oxide into the relatively acidic slags (C/A s 1.3) modifies the aluminate networks, which means that the [FeO4]-tetrahedra substitute for the [AlO4] -tetrahedra. Thus, the degree of polymerization of the melts decreases with increasing content of iron oxides. However, the effect of iron oxides is less significant in the relatively basic compositions (C/A 1.6). The activation energy for the viscous flow of the slags has a good linear correlation with the fraction of polymerized aluminate species, i.e., In OA,. However, the network-modifying role of iron oxide is limited within a critical concentration, which is also dependent on the C/A ratio of the CaO-Al2O3-FetO-SiO2-MgO slags.