Removal of Residual Element Antimony from Molten Steel by CaC2-Containing Refining Slag

Abstract

Increasing the use of steel scrap and enhancing its recycling utilization are important strategies for fostering the low-carbon and environmental-friendly growth of the iron and steel industry in China. However, the current steelmaking processes cannot efficiently remove the residual elements in the scrap, such as Cu, Sn, As, and Sb. As a result, the above elements are recycled and accumulate in the scrap, which will eventually have a negative impact on the properties of steel. Currently, there are few studies on Sb removal from molten steel. To remove the residual element Sb in molten steel, the CaO-SiO2-Al2O3 refining slag system containing CaC2 was used, and the effect of the CaC2 content in the molten slag, slag quantity, smelting temperature, and initial Sb and C contents in molten steel on the Sb removal ratio in the steel was investigated, and the mechanism of Sb removal by the aforementioned refining slag system was discussed in order to provide some experimental and theoretical basis for industrialization practice. When the smelting time is 5~10 min, the removal ratio of Sb from molten steel is at its peak and can reach 45.8%. The ”Sb-reversion” phenomenon will appear in the molten steel when the smelting period is progressively extended. In molten steel, CaC2 will preferentially react with O and S, and as the smelting temperature decreases, the distribution ratio of Sb, LSb, improves. An increased initial Sb content in molten steel and slag quantity are beneficial to improving the removal ratio of Sb, but an increased initial C content in molten steel is detrimental to the progress of the Sb removal reaction. The removal reaction of Sb from molten steel by CaC2 is a reversible reaction, and the diffusion of the products from the interface is the limiting factor of the overall reaction.