Understanding the Properties of Slags

Abstract

Understanding of the properties of slags is a pre-requisite in optimizing their functions towards the making and refining of steel. Important contributions towards this objective have been made over the past half a century, in different parts of the world, especially in USA, UK, Germany and most of all in Japan. Knowledge of the slag properties enables in understanding the slag structure as well. The present review paper summarizes the contributions made in this field by the Division of Materials Process Science, Royal Institute of Technology, Stockholm, Sweden.The paper deals with the measurement and modeling of (a) thermochemical properties of slags, (b) thermophysical properties and (c) inter-property correlations. Some important contributions during recent years, such as the determination of the valence states of Cr and V in slags, wetting characteristics related to hot-metal desulphurization, diffusion of sulphide ions in slags, partition of phosphorus between slag and metal phases and studies on process phenomena such as foaming are highlighted. The research work has led to the evolution of a new basicity concept. Dynamic physical property measurements are pointed out to be an experimental tool towards understanding of reaction mechanisms. Developments with respect to slag/metal interfacial phenomena, viz. the concept of surface velocity and surface viscosity and quantification of these properties are presented.

Visualization of Slag Data for Efficient Monitoring and Improvement of Steelmaking Slag Operation in Electric Arc Furnaces, with a Focus on MgO Saturation

“…The viscosity of the basic EAF slag is increased to the required range using finely dispersed periclase crystals, i.e., when the slag composition is MgO saturated [4,5]. Consistently, optimum slag foaming is observed at EAF slag compositions with basicity B 2 = x CaO /x SiO2 ≈ 2 [4,5], i.e., heterogeneous slag foaming [9,13], in order to compensate the viscosity decreasing effect of FeO (e.g., [14]). The complex behavior of FeO in slag foaming was clarified by considering the composition dependence of the Fe 3+ /Fe 2+ ratio on the surface tension [15].…”

Treatments and Recycling of Metallurgical Slags

“…The presence of impurities and possible reactions between the crucible material and the slag produces a transportation problem in the interface that can reduce the values of the properties and can occasionally modify wettability. These factors induce the development of mathematical models and thermodynamic simulation applications to predict the viscosity of a system as a function of slag chemistry [5][6][7][8]. The Urbain theoretical model is being one of those more used for the steelmaking slags [5], being the Urbain model one of the most widely used for industrial slags.…”

“…Slag foaming constitutes another alternative to use the converter slags to protect MgO-C bricks below the trunnion line [8,10]. It is important to take into account that in order to enhance the performance of this industrial practice, it is necessary to understand deeply the associated fundamental phenomena.…”

Previsão De Viscosidade Dos Sistemas De Escórias C-a-S E C-a-S-M Por Meio De Uma Rede Neural Artificial

“…This feature was incorporated into the commercially available software FactSage (developed by CRCT and GTT), whichdelivers viscosity directly as an output [3]. Yet another thermodynamically-related method is cited in the literature(based on the Gibbs activation energy for viscosity), and is incorporated in the software Thermoslag (developed at the Royal Institute of Technology, KTH) [4]. Accurate viscosity estimates, however, are still difficult to obtain, despite the advancement of the mathematical models, or the use of thermodynamic computational tools.…”