Carbothermal reduction process of the Fe-Cr-O system

Abstract

Understanding the reduction behaviors and characteristics of the end products of Fe-Cr-O systems is very important not only for maximizing the recovery of metals from stainless steel dust but also for the subsequent reuse in metallurgical process. The present work first predicted the possible products thermodynamically when FeCr₂O₄ was reduced by C. The reduction behaviors by graphite of three kinds of Fe-Cr-O systems, i.e., FeCr₂O₄, Fe₂O₃+Cr₂O₃, and Fe+Cr₂O₃, were then investigated in 1350–1550°C. Further, the microstructures of final products and element distribution conditions were examined. The results suggest that, thermodynamically, the mass of products for the carbothermal reduction of FeCr₂O₄ is a strong function of temperature, and the initial carbon content is used. More Fe-Cr-C solution and less residual carbon content are obtained at higher temperatures and lower n _C:n _O ratios (the initial molar ratio of C to O in the sample). Experimental data show that the sample amount tends to affect the reduction rate, and the residual carbon content strongly depends on n _C:n _O. With regard to the phases present in products during the reaction process, metal carbides tend to form in the initial stage, whereas Fe-Cr-C solution forms when the degree of reduction is sufficiently high.

Keywords

stainless steel / dust / ternary systems / carbothermal reduction / reaction kinetics

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