Effect of Erosion Behavior of FeO-CaO-SiO2-MgO-Al2O3 Blast Furnace Primary Slag on Al2O3 Substrate

Al2O3 substrate is widely used as a lining refractory material throughout the blast furnace (BF) process. Accordingly, the erosion of Al2O3 refractory by molten slag has a negative influence on the running cost and smooth operation of BFs. The effect of the erosion behavior of BF primary slag containing FeO-CaO-SiO2-MgO-Al2O3 on Al2O3 substrate refractory was fundamentally investigated using the high-temperature contact angle method and FactSage thermodynamic software based on the composition of BF primary slag in a typical iron and steel enterprise of China. The results showed that the primary slag mentioned above was easily wetted with Al2O3 substrate, and the observed contact angles were 24.5° and 22.0°, when the FeO mass fraction (w(FeO)) was maintained at 10% and 15% of the primary slag, respectively. Moreover, the starting melting temperature of the primary slag with high FeO content, of 1263 °C, was lower. The erosion thickness between the slag and Al2O3 substrate increased from 19.23 to 23.17 μm as the added w(FeO) increased from 10% to 15%. In addition, it was observed via SEM-EDS analysis that the interface layer was formed, and high-melting-point compounds were generated during the wetting process. This was attributed to the interaction between the molten slag and Al2O3 existing in the substrate, which may have inhibited the continuous dissolution of the Al2O3 in the substrate into slag. Good surface wettability and the dissolution of the Al2O3 substrate refractory into the primary slag of the BF are two dominant factors leading to the erosion of the refractory.