Effects of High-Temperature Characteristics of Calcium Ferrites on the Sinter Strength

Iron ore sinter is the main burden charged into the blast furnace. The liquid phase formed during the sintering process plays an important role in the agglomeration process, which affects the quality of the final product. The current study aims to clarify the effect of iron ores on the high-temperature characteristics of calcium ferrites (CFs). It was attempted to use two of the most common iron ores being used in the steel companies worldwide as the raw materials to prepare three kinds of CFs. The gangue components (SiO₂, Al₂O₃) in the iron ores significantly affected the high-temperature characteristics of CF. By changing the CF used to assimilate with the sinter mix, the phases formed in the assimilated region were not significantly modified. For all the CFs, ‘SFCA-related’ phases were found to exist, which is believed that the sinter mix played the main role in the phase formation. Among several high-temperature characteristics, a melt index was newly suggested where its linear relationship coefficient with the penetration length of CFs was calculated to be 0.863. CFs containing a significant amount of gangue showed a low fluidity index and high dissolution of sinter mix, which resulted in the decrease in melt index. This CF consequently had low penetration depth into the sinter mix, which might jeopardize the agglomeration process of the sinter mix. The addition of all kinds of CFs to the standard sinter mix improved the compressive strength of the sinter. However, the strengthening behavior depends on the type and amount of CF.