Metallurgical Slag

Abstract

Along with valuable metals, pyrometallurgical methods of extraction also produce an appreciable proportion of a relatively unwanted material called slag. The slag comprising simple and/or complex compounds consists of solutions of oxides from gangue minerals, sulfides from the charge or fuel, and, in some cases, halides added as flux. Slag being immiscible and lighter than the metallic phase, it covers the metallic bath. The specific gravity of slag ranges between 3 and 4 as compared to 5.5 for sulfide matte and 7–8 for iron and steel. The slag cover protects the metal and matte from oxidation and prevents heat losses due to its poor thermal conductivity. In an electric furnace, slag may be employed as a heat resistor. It protects the melt from contamination from the furnace atmosphere and from the combustion products of the fuel. In pyrometallurgy, slags play a very important role in carrying out a number of physical and chemical functions. © 2021, The Minerals, Metals & Materials Society.