Reduction Reactions in Al₂O₃–C–Fe and Al₂O₃–Fe₂O₃–C Systems at 1823 K

Abstract

With a view to produce Fe–Al alloys for deoxidation during steel refining, chemical reactions were investigated in Al₂O₃–C–Fe and Al₂O₃–Fe₂O₃–C systems at 1823 K. Using a horizontal tube furnace and argon atmosphere, interactions were investigated for time periods up to 2 hours. Two sets of blends were prepared from initial constituents, which were later used to prepare two types of substrates. Alumina and synthetic graphite powders were blended in a 70: 30 proportion (blend I), and in the second set, Fe₂O₃ was blended with C in a proportion of 75:25 (blend II). In one case, blend I was mixed thoroughly with iron powder (Fe (2.7 pct C)) in a ratio of 80:20; in the second case, blend I was mixed with blend II in the ratio of 70:30. We report significant reduction reactions in both cases. SEM/EDS studies on the Al₂O₃–C–Fe system showed unambiguous evidence for the pick-up of aluminium by molten iron after 1 hour. Levels of aluminium in molten iron were found to increase significantly with time. Due to in-situ reduction of Fe₂O₃, the generation of CO gas and associated turbulence, the reactions were quite fast in the Al₂O₃–Fe₂O₃–C system. X-ray diffraction studies showed the presence of additional diffraction peaks belonging to Fe₃AlC and Fe₃Al systems. Molten iron was found to act as a reducing agent and a metallic solvent in both cases. This study provides evidence for the carbothermic reduction of alumina at 1823 K and for the formation of ferroalloys directly from mixed oxides of aluminium and iron.