Influence of the atmosphere on the mechanical properties and slag resistance of magnesia-chrome bricks

Abstract

Magnesia-chrome bricks are commonly used as the lining of smelters in copper and lead industry because of their resistance against the thermal, mechanical and chemical loads in the pyrometallurgical production process. In fact, the pyrometallurgical production process of lead-copper matte is generally a reducing process with plenty of coke and iron fillings as reducing agent, which implies that the magnesia-chrome bricks service in stronger reducing atmosphere. In this work, the microstructure, mechanical properties and slag resistance of such materials were investigated in reducing atmosphere to simulate the influence of the atmosphere on the properties of magnesia-chrome refractories. The results show that obvious increase in porosity and decrease in strength occurred to the magnesia-chrome samples after treating in reducing atmosphere. This is related to the structural damage of samples, in which Fe3+/Fe2+ within spinel (Mg, Fe)(Cr, Al, Fe)2O4 were partly reduced to metallic Fe under reducing atmosphere. Consequently, the slag penetrated much easily into the matrix of the samples. Moreover, the slag corrosion also aggravated due to the aggressive FeO in slag and the formation of magnesiowüstite in the penetration layer. Nevertheless, the high melt phases of spinel and forsterite were formed when the slag corrosion test was conducted in air atmosphere, thereby preventing further slag corrosion and penetration.