Development of a Quasi-chemical Viscosity Model for Fully Liquid Slags in the Al2O3–CaO–‘FeO’–MgO–SiO2 System: The Revised Model to Incorporate Ferric Oxide

A model has been developed that enables the viscosities of the fully liquid slag in the multi-component AlO-CaO-FeO-FeO-MgO-SiO system close to and at metallic iron saturation to be predicted within experimental uncertainties over a wide range of compositions and temperatures based on the Eyring equation to express viscosity. The model links both the activation and pre-exponential energy terms to the slag internal structure through the concentrations of various SiO, Me2/nO and Me 1/nSiO viscous flow structural units, of which the concentrations are derived from a quasi-chemical thermodynamic model of the liquid slag. The model describes a number of slag viscosity features including the chargecompensation effect specific for the AlO-containing systems. The present paper describes application of recent significant improvements in the model formalism to the multi-component system AlO-CaO-FeO- FeO-MgO-SiO, where both Fe and Fe effects on viscosity are individually evaluated. The present model reproduces viscosities of slags equilibrated with metallic iron, which mainly reflects Fe effects on viscosity including the charge compensation effect of the Fe as well as Ca and Mg2+ cations on the formation of tetrahedrally-coordinated Al3+. The model can also reproduce the compositional tendency of viscosity of the SiO-free CaO-FeO-FeO slag in air by incorporating the charge compensation effect of Fe to form tetrahedral coordination by basic cations such as Ca and Fe and to indicate viscosity maximum at an intermediate composition. Further analysis of the behaviour of the Fe cation in the silicate structure to describe corresponding effect on viscosities and to improve viscosity predictions is essential.