Investigation of Basicity on Compressive Strength and Oxidation Induration Mechanism of Vanadium-Titanium Magnetite Pellets

Currently, the typical charge structure for blast furnace smelting of vanadium-titanium magnetite (VTM) is the addition of acidic pellets, high-basicity sinters, and lumps. To increase the percentage of pellets entering the blast furnace, it is necessary to transfer the basicity burden to the pellets. In this study, the effect of basicity on the phase transition and oxidation hardening mechanism of VTM pellets is investigated. In the results, it is indicated that when the preheating temperature is 950 degrees C, the preheating time is 15 min, the roasting temperature is 1260 degrees C, and the roasting time is 15 min, with the basicity (CaO/SiO2) increasing from 0.08 to 1.3, the compressive strength of pellets shows a trend of "increasing first and then decreasing," with the highest value reaching 3159 N pellet-1 at basicity of 0.5. As the basicity increases, calcium ferrate can be generated by CaO in the liquid phase with Fe2O3 in addition to silicate with SiO2, which will increase the amount of the liquid phase. With the increase of basicity, the oxide-bonded induration is gradually weakened, and the slag-bonded induration is gradually enhanced. A moderate amount of liquid phase can play the role of bonding and filling, thereby improving compressive strength. With the increase of basicity, the content of recrystallized hematite decreases, and the oxide-bonded induration is gradually weakened; while with the larger amount of CaO added, it will generate low-melting-point silicate and calcium ferrate with SiO2 and Fe2O3 and transform into the liquid phase at high temperature, and the slag-bonded induration is gradually enhanced.image (c) 2024 WILEY-VCH GmbH