Effect of increasing the proportion of high-alumina iron ore on structures and properties of sinter produced in iron ore blending sintering process

Facing the consumption of high-grade iron ore, high-alumina iron ore emerges as a potential alternative for steel companies aiming to cut costs and address resource shortages. This study systematically investigated the impact of increasing the proportion of high-alumina iron ore on sintering performance through sinter pot tests. The detailed microstructural and morphological analyses of the produced sinter phase, combined with the results of thermodynamic calculation on liquid phase formation, elucidated the transformation mechanism of the sinter properties in varying alumina content. The results show that the yield and quality of sinter undergoes a crucial shift at 2.35% content of Al2O3, where yield, drum index, and low-temperature reduction degradation index reach their lowest, indicating a severe degradation. Al2O3 content up to 2.53% proves beneficial for improving sinter reduction index. The major phases found in all resultant sinters by X-ray diffraction are hematite, magnetite, silicate, spinel, and silico-ferrite of calcium and aluminium (SFCA). Increasing Al2O3 content transforms SFCA from acicular to columnar, while porosity exhibits an increasing and then decreasing trend. It is found that the shape of SFCA and porosity are the main factors affecting the quality of sinter. The research findings are helpful to promote the efficient application of high-alumina iron ores in blast furnace ironmaking.