Phase Evolution Behavior and Oxidation Induration Mechanism of High-Chromium Vanadium–Titanium Magnetite Flux Pellets

The quality of vanadium–titanium magnetite sinters is poor. The high-pellet operation of the blast furnace ironmaking process is a feasible method for utilization of the High-chromium Vanadium–titanium magnetite (HVTM). To ensure the basicity of the burden, flux pellets need to be investigated. In this study, HVTM concentrate and CaCO3 were used to prepare flux pellets. The phase transition and oxidation induration mechanism of flux pellets were studied separately and analyzed by scanning electron microscopy and energy dispersive spectroscopy. Solid-phase and solid–liquid-phase experiments were used to verify the phase transition behavior. The results indicated that the basicity (CaO/SiO2) increased from 0.4 to 1.4, and the compressive strength of HVTM concentrate flux pellets first increased to 4916 N and then decreased to 2399 N at 1523 K for 20 minute. The porosity of the pellets increased from 8.236 to 20.734 pct. Perovskite produced due to increasing basicity reduced the slag content and had a low bonding strength, which reduced the overall compressive strength of the pellets. The increasing basicity was conducive to the solid solution of Ti forming an iron-titanium solid solution. The addition of CaCO3 increased the porosity of the pellets. The oxidation induration of the pellets changed from oxide-bonded to slag-bonded.