Evolution of Interface Characteristic between Quicklime and CaO–SiO₂–Fe_tO–MgO Melt during Slag‐Forming Procedure in Converter under Different Times

Abstract

In 2022, China produced 1.018 billion tons of crude steel, with steel slag accounting for 10–15% of the output. The presence of 10–20% f‐CaO in steel slag causes volume instability, hindering comprehensive utilization. The generation of f‐CaO is closely associated with the dissolution of quicklime during the converter slag‐forming procedure. This study focuses on investigating the evolution of the lime–slag interface and the variations in lime dissolution rate under different slag conditions using the electron probe microanalyzer and ImageJ. The results reveal that the formation of the CaO–FeO solid solution, (Ca, Mg, Fe) olivine, and low‐melting point (Ca, Mg) olivine at 1400 °C. As the FeO content decreases, a dense and high‐melting‐point 2CaO·SiO2 layer is formed. A maximum thickness of the 2CaO·SiO2 layer is precipitated at a dissolution time of 180 s. Additionally, the average dissolution rate of lime in different slags shows an initial increase followed by a subsequent decrease. Among the slag studied, the highest average dissolution rate is in slag A3 at 2.24 × 10−6 m s−1, while the lowest rate is in slag A4 at 1.49 × 10−6 m s−1. The presence of the 2CaO·SiO2 layer hinders the mass transfer, thereby further inhibiting the reaction.