Effect of magnetite on mineral phase formation in sintering process

Mineral phase formation behavior in the sintering process is one of the most important factors for quality and productivity of iron ore sinter. As resource of high-grade hematite ore is exhausting, it is expected that hematite ore can replaced by magnetite in iron-making. So that, the purpose of this study is to investigate the effect of magnetite on mineral phase formation. To clarify the effects of magnetite on mineral phases formation, sintering experiments using hematite and magnetite reagent were carried out. To research the effects of atmosphere and temperature, samples were sintered under oxidizing (air) and reducing (CO–CO₂) atmosphere at 1 250°C and 1 350°C respectively. The results were analyzed by microscopic observation and image processing. Under both oxidizing and reducing atmosphere, the shapes of each phase after sintering of magnetite samples are likely to hematite samples. From the image processing results, the ratio of each phases formed after sintering of samples were at the same level. So, it is expected that magnetite can be used as raw material instead of hematite in sintering process. Under Air atmosphere, both hematite and magnetite samples formed more calcium ferrite phase when the sintering temperature was higher. Moreover, under Air atmosphere, the calcium ferrite formation ratio of both hematite and magnetite samples was larger than that of under CO–CO₂ atmosphere. Therefore, it is very important to keep oxidation state in sintering process.