Study on the reduction degradation behaviour and mechanism of ferrous burden with different characteristics under multiple atmospheres

To meet the development trends towards high-yield, low-carbon, and low-energy consumption in blast furnaces, the demand for high-quality ferrous burden is increasing. However, ferrous burden undergo degradation during reduction, deteriorating the permeability of the blast furnace charge column and thereby influencing the stability of the smelting process. To investigate the reduction degradation mechanism of ferrous burden, reduction degradation experiments were systematically conducted using ferrous burden with different characteristics under simulated atmospheres of traditional blast furnace, hydrogen-rich traditional blast furnace, oxygen blast furnace, and hydrogen-rich oxygen blast furnace. Results indicate that under the simulated blast furnace atmosphere in this study, high basicity sinter exhibits approximately 10% higher degradation performance than low basicity sinter, demonstrating broader applicability. Acidic pellet is suitable for traditional blast furnaces and hydrogen-rich traditional blast furnaces; while fluxed pellet is suitable for oxygen blast furnaces and hydrogen-rich oxygen blast furnaces. Both high reduction potential and hydrogen-rich conditions promote crack propagation. Carbon deposition accelerates iron fragmentation, with iron accumulating within carbon deposits, thereby worsening degradation. Fluxed pellet exhibits improved degradation properties due to its low porosity and toughened slag phase formed by the MgO/CaO stable phase, which suppresses crack initiation and limits carbon deposition.