Assessment of Physicochemical Properties of Electrical Arc Furnace Slag and Their Effects on Foamability

Abstract

The composition of slags of an electric arc furnace (EAF) in a commercial melt shop was systematically analyzed with a focus on slag foaming. Basic behavior of FeO in an EAF slag was confirmed using fundamental thermodynamics. Monoxide ([Mg,Fe,Mn]O = M'O) and spinel ([Mg,Fe]Al2O4) phases in EAF slag were confirmed by X-ray diffraction analysis, and these results were interpreted in the context of equilibrium cooling calculation using FactSage (TM) software. Furthermore, the distribution of MgO with respect to the M'O-saturation limit at different basicity ratios (=CaO/SiO2=C/S) and temperatures was evaluated. In particular, the relationship between MgO and FeO for C/S ratios ranging from 1.3 to 1.6 was considered with reference to phase equilibria. Foam height was affected by slag viscosity (eta) and gas generation according to changes in C/S ratio and FeO content. Foaming index (Sigma) decreased with the increasing C/S ratio and FeO content. The measured foam heights were relatively higher than the calculated values, and the result indicates that the effect of M'O on slag foaming in commercial process is remarkable. Therefore, slag chemistry should be optimized based on thermodynamic considerations and thermophysical properties to achieve good foaming characteristics. (C) The Minerals, Metals Materials Society and ASM International 2019