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

Abstract

A model has been developed that enables the viscosities of the fully liquid slag in the multi-component Al2O3-CaO-FeO-Fe2O3-MgO-SiO2 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 Si0.5O, Men+2/nO and Men+ 1/nSi0.25O 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 Al2O3-containing systems. The present paper describes application of recent significant improvements in the model formalism to the multi-component system Al2O3-CaO-FeO- Fe2O3-MgO-SiO2, where both Fe2+ and Fe3+ effects on viscosity are individually evaluated. The present model reproduces viscosities of slags equilibrated with metallic iron, which mainly reflects Fe2+ effects on viscosity including the charge compensation effect of the Fe2+ as well as Ca2+ and Mg2+ cations on the formation of tetrahedrally-coordinated Al3+. The model can also reproduce the compositional tendency of viscosity of the SiO2-free CaO-FeO-Fe2O3 slag in air by incorporating the charge compensation effect of Fe3+ to form tetrahedral coordination by basic cations such as Ca2+ and Fe2+ and to indicate viscosity maximum at an intermediate composition. Further analysis of the behaviour of the Fe3+ cation in the silicate structure to describe corresponding effect on viscosities and to improve viscosity predictions is essential.