Grain growth and cleavage characteristics of metallic phase in direct reduction of a low-grade iron ore

The grain growth and cleavage characteristics of metallic phase were studied in direct reduction of a low-grade iron ore. The effects of reducing agent dosage and roasting time on the grain growth were discussed. The results of X-ray diffraction and scanning electron microscopy show that decreasing the reducing agent dosage can limit the reducing atmosphere and restrict the generation of crystallization centers, thereby it is conducive to the grain growth of metallic phase, but the further grain growth is confined due to the partly losing of iron in gangue. Prolonging the roasting time can promote the grain agglomeration and growth, which can decrease the activity of metallic products and thus prohibit the reoxidation reaction. The generation of amorphous substances and the hardness differ-ence between metallic phase and gangue are beneficial to the cleavage of metallic iron when the grinding fineness is coarse.