Research progress on resource utilization of steel casting residue in recycling to production process

For the casting residual slag generated during the steelmaking and continuous casting processes, this paper systematically reviews the relevant research progress and industrial practices of its recycling into the production processes for resource utilization, and summarizes the source, compositional characteristics of casting residual slag as well as its recycling methods and application effects in different steelmaking procedures. Comprehensive analysis shows that casting residual slag is dominated by the CaO-Al₂O₃-SiO₂ system, featuring high basicity and certain metallurgical activity, thus being applicable as a secondary resource in steelmaking slag formation and refining processes. Among them, hot casting residual slag, by virtue of its sensible heat and molten state, is more suitable for direct recycling to converters and refining processes. This contributes to shortening the slag formation time, reducing the consumption of fluxes such as lime and dolomite, and improving the final slag structure. After undergoing crushing, magnetic separation and composition homogenization treatment, cold tailing slag can be stably applied in converters, ladle furnace, Ruhrstahl-Heraeus degasser and tundishes, replacing part of the slag-forming agents or covering agents and extending its metallurgical functions. In general, the recycling of casting residual slag into production processes can achieve comprehensive benefits such as flux saving, metal recovery and indirect carbon reduction without a significant increase in energy consumption. However, its further promotion and application are still confronted with challenges including large composition fluctuation, complex pretreatment processes for cold tailing slag and insufficient cross-process adaptability. In the future, it is necessary to improve the technical system consisting of source classification, on-line composition detection and graded recycling, so as to promote the large-scale and high-efficiency resource utilization of casting residual slag in iron and steel production.