Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud

Abstract

The basic oxygen steelmaking process is based on the CaO-FeO-SiO2 ternary slag system, characterized by a high melting point and low lime dissolution rate, often becoming one of the key factors limiting the efficiency of the converter. The bulk solid waste red mud, produced by the Bayer alumina process and rich in Fe2O3/Al2O3/Na2O, significantly reduces the melting point of the steelmaking slag system and enhances the efficiency of lime dissolution. This study utilized red mud as the main raw material to prepare a fluoride-free flux. An in situ online observation system was used to measure the melting point of the flux and the dissolution rate of lime in the flux. The results indicate that the melting point of the red mud-based flux is below 1200 °C, and under the same conditions, the lime dissolution rate is 10 to 15 times higher than when this flux is not used. Experiments in a 10 kg induction furnace show that using this flux, the dephosphorization rate under conditions without oxygen blowing is close to 40%, far higher than the rate achieved using CaF2. Under oxygen-blowing conditions, the dephosphorization rate using the red mud-based flux is comparable to that of CaF2, and significantly higher than without any flux, especially under high [C] content conditions. The data show that the red mud-based flux has the potential to be widely used as a fluoride-free flux in the steelmaking process.