New insights on consolidation behavior of Fe2O3 in the Fe3O4-CaO-MgO-SiO2 system for fluxed pellet production: Phase transformations and morphology evolution

A systematic study of the preparation and metallurgical properties of magnesia flux pellets was used to elucidate the mechanism for oxidation and consolidation occurring during oxidative roasting. The compressive strength of the finished pellets was 3545 N/P. With sufficient basicity and MgO contents, magnetite (Fe) x [Fe] 2 O 4 and maghemite γ-Fe 2 O 3 with spinel-type crystal structures combined with MgO/CaO to form nonstoichiometric Mg x Fe 1-x Fe 2 O 4 (0 < x < 1) and Ca y Fe 1-y Fe 2 O 4 (0 < y < 1). With higher basicity and MgO contents, the participation of CaO/MgO was the driving force for gradient conversion from olivine Fe 2 SiO 4 to olivine Mg x Ca 2-x SiO 4 . The CaO/MgO combined with magnetite (Fe) x [Fe] 2 O 4 and maghemite γ-Fe 2 O 3 to form stable (Ca, Mg) x Fe 1-x Fe 2 O 4 , CaFe 2 O 4 and CaFe 3 O 5 , thereby inhibiting recrystallization of the pellets and resulting in poorer metallurgical properties of the magnesia flux pellets.