Corrosion behaviour and corrosion mechanism of corundum block and mullite block in hearth of blast furnace

Abstract

A ceramic cup is often used to prolong the hearth life of a blast furnace (BF). Corundum blocks and mullite blocks are two kinds of refractories widely used for building ceramic cups in China. Therefore, research on the corrosion resistance of these two kinds of refractories is beneficial to realize the BF longevity. In this study, the corrosion behaviours and corrosion mechanisms of molten slag and molten iron on corundum block and mullite block samples were investigated by corrosion tests. The results show that the slag corrosion resistance of corundum block was better than that of mullite block, and the corrosion mechanisms of molten slag on corundum block and mullite block were different. The aggregates fell from the matrix of the corundum sample when the matrix was corroded to a certain degree by slag, and the corrosion rate of slag on the corundum sample was controlled by the diffusive transport rate of a substance and the chemical reaction rate between slag and matrix. However, the aggregate and matrix of the mullite sample was corroded by slag at the same time, and the corrosion rate of slag on the mullite sample was controlled by the diffusive transport rate of Ca through the newly formed reaction layer. Moreover, the corundum block and mullite block had excellent iron corrosion resistance. The high temperature of molten iron led to an in situ reaction to generate a mullite phase in the corundum sample, and the high temperature affected the microstructure of the corundum block and mullite block.