Slag Formation Behaviour at Interface between Pre-reduced Lump Iron Ore and CaO under Load Conditions

Oxygen blast furnace technology is expected to expand the selectivity of iron burden materials owing to its superior productivity compared to present blast furnace technology. To evaluate the possibility of utilising lump ore in an oxygen blast furnace, slag formation behaviour at the lump ore and limestone interface was investigated in this study. To focus on the slag formation behaviour in the cohesive zone, where low gas permeability can be an issue for blast furnaces, the softening behaviour between pre-reduced lump ore and a CaO substrate in an inert atmosphere was measured under loading conditions using a softening simulator. Simultaneously, cross-sectional observation and EDS analysis of quenched samples at intermediate temperatures were conducted. From the results, the following conclusions were drawn. When melt intrusion from the lump ore to the CaO substrate occurs, the lump ore penetrates into the CaO substrate with deformation of the CaO substrate, and the greater the degree of melt intrusion, the more lump ore penetrates. The intrusion behaviour of the melt into the CaO substrate is largely related to the presence or absence of Ca₂SiO₄ formation at the initial melt formation start temperature. At 1 300°C or lower, the gangue composition at the outer part of the lump ore is the key factor. Whereas at 1 300°C or higher, where all the gangue components melt, the average gangue component of the entire lump ore is the key factor.