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 °C, the preheating time is 15 min, the roasting temperature is 1260 °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.