Development of a modern theory for metallurgical slag

Abstract

A new theory of metallurgical slag has been developed based on a detailed study of the thermodynamic properties of various slag systems having various complexity levels, as well as various ideas regarding associativity. This theory has, for the first time, enabled: the reactivity (component activities), phase equilibrium conditions, and important physical and chemical properties such as viscosity, surface tension, and thermal conductivity to be described to an accuracy level consistent with, or better than that of the experimental results (2-3%); enabled slag vitrification capacity to be predicted; and enabled precipitation of fluorides (which are considered environmentally undesirable) to be predicted. This has enabled us to develop new, environmentally-friendly slag generation mixtures for continuous casting of steel having excellent operational characteristics, develop appropriate methods for calculation of equilibria and reaction yields for the metal-slag-gas system, and develop appropriate methods for management of slag conditions during in-ladle steel processing. This in turn led to the development of efficient processes for production of high-quality bulk steels with excellent service characteristics and low levels of continuouscast billet and rolled-stock rejection based on surface defects and ultrasonic defectoscopy results.