Hot metal erosion behavior of Al2O3-SiC-SiO2-C castable hot surface in blast furnace hearth

Abstract

An ASSC-type cast-type blast furnace with a vertical stage of about 2500 m3 was dissected in present study. There is an iron penetration erosion area with a thickness of about 170 mm in the hot side castable on the hearth sidewall. Iron penetration erosion is concentrated on the hottest surface of the castable. Along the radial direction, from the hot to cold surface, the erosion is different, divided into a metamorphic layer, an erosion layer, and a transition layer. The phase composition and microstructure of the hot surface of the castable after service were studied by chemical analysis and SEM-EDS. The penetration model was applied to calculate the critical pore size of molten iron penetrating the castable, and the universality of molten iron penetrating the castable was proved. Combined with the thermodynamic calculation results, it is shown that in the hearth environment, the molten iron penetrating the castable will react with SiO2 and C to form ferrosilicon and CO gas. CO reacts with SiC and Al2O3 in the castable, and the products are mullite phase and C phase. The two reactions occur at the same time, resulting in the continuous erosion of the aggregate silicon-containing phase of the castable. The Al2O3 in the castable will gradually disintegrate under the erosion of high-temperature molten iron and periodic thermal shock and finally form the erosion phenomenon in the hot surface area of the castable.