Reduction behavior and microstructure evolution of iron oxides under hydrogen atmosphere

Owing to the importance of hydrogen metallurgy for the low-carbon and green iron and steel industries, the reduction behavior and microstructure evolution of two iron oxides (hematite and magnetite) at various temperatures were investigated in a pure hydrogen environment (99.999%). The weight loss ratio, total oxygen content, reduction degree, and phase composition of the iron oxides were also discussed. The hematite shows a better reducibility compared to magnetite. It is indicated that hematite and magnetite transform into iron metal with total oxygen contents below 6790 and 25,200 ppm, respectively, when the reduction temperature exceeds 800 °C. Simultaneously, a porous iron skeleton was formed at 800 °C, and the densification of the porous iron occurred with increasing temperature. The impurities in iron oxides significantly affect the microstructure evolution, weight loss ratio, and total oxygen content.