Abstract: Oxidation behavior of the metallic iron reduced by the ore-coal pellets during the grinding process and its influence on magnetic separation were studied by low intensity magnetic separation， laser particle size analysis， Scanning Electronic Microscope (SEM)、X-ray diffraction(XRD) and X-ray photo-electroscope(XPS) using a low - grade hematite ore of low temperature fast direct reduction pellets as research object. The results of investigation demonstrated: ①The iron grade of the reduced pellet is 31.18%，while the metal iron content is 26.45%，silica is 43.63%， and metallization ratio of the pellet is 84.43%. Metal iron is mostly aggregate， which is worm like or star shaped dispersed in gangue minerals. Crystal size is fine. The particle size of the metal iron is generally 10~30 μm and the maximum is 400 μm. ②When the grinding time was prolonged， the metallization rate of iron in grinding products was obviously reduced. The metallization is 82.24% when milling 10 min，the metallization reduced to 71.67% when grinding 40 min. The iron grade of magnetic concentrates decreased slightly after an obvious increase， the iron recovery took the lead in a small increase and then decreased obviously， the iron metallization decreased obviously； the magnetic concentrate average volume size， D50 and D10 all showed a slow downward trend， and the dissolution of the metal iron increased fast at first， then slowly. When the grinding time is 10 min， the metallization rate of iron of magnetic concentrate is 81.10%， and the metallization rate of iron decreases to 62.99% when grinding 40 min. ③The diffraction peaks of metallic iron weakened with the increase the milling time， while the diffraction peaks of Fe3O4 appeared from nothing and then strengthened. The binding energy of Fe 2p3/2 was promoted with the increase of grinding time，the onidation of the iron on the surface of the particles increased. ④SEM-EDS analysis showed that the surface of iron particles in magnetic separation concentrate was bound to oxygen， and the longer the grinding time， the higher the oxygen content， and the flocculent iron-bearing area also showed the same characteristics. In summary， the metal iron in reduced pellets will be oxidized in the grinding process， and the longer the grinding time， the higher the oxidation degree.

Key words: Reduced pellet, Grinding, Oxidation of metallic iron, Magnetic separation