Effect of FeO on Spinel Crystallization and Chromium Stability in Stainless Steel-Making Slag

Chromium alloy is a key ingredient in stainless steel production, and slag forms a significant proportion of the production process’s output. To investigate how to avoid the leaching of Cr(VI) from stainless steel slag into the environment, we examined the effect of the FeO content on the stability of chromium in the CaO-SiO2-MgO-Al2O3-Cr2O3 system in laboratory experiments. The solidification process was then studied using FactSage 7.0. The results indicate that the leaching of Cr(VI) can be reduced. As the content of FeO increases in the slag, the content of chromium in the matrix decreases significantly. In our experiments, the concentration of the Cr(VI) leaching was decreased from 0.1434 mg/L to 0.0021 mg/L, and the size of spinel crystals in the slag increased from 5.77 μm to 8.40 μm. The content of calcium and silicon was reduced and the level of ferrum improved in the spinel crystals after the addition of FeO. FeO promotes the formation of a core–shell heterostructure in spinel crystals, with the Fe-enriched shell notably improving the stability of the chromium.