Decarburization and desilication behavior by CO₂-O₂ mixed gas injection in Fe-C-(Si) molten alloys

Abstract

In the steelmaking industry, the utilization of CO₂ as a resource has become one of the important research projects. The decarburization and desilication mechanism were investigated to the extension range of low carbon condition and in Fe-C-Si ternary system in 1873K. ¹³CO₂ and ¹⁸O₂ dual isotope gases were use to clarify the complicated oxidation process. The results showed that in Fe-1.0 mass%C-0.5 mass%Si molten alloy, CO₂ substitution part of O₂ within 40% slightly reduced the decarburization rates in the advantage area of decarburization, and after reaching the oxidation equilibrium curve, the decarburization rates were basically stable and low even 100% CO₂. However, with introducing CO₂ from 0 to 40%, the desilication rates were dropped a lot. CO₂ replacing part of O₂ was beneficial to reducing the loss of silicon during decarburization process at 1873 K. The critical value of carbon content was around 0.3 mass%, that the main limiting rate step was transformed to the diffusion of carbon in molten under the correspondindg condition of 1.2 to 3.2 Nm³/t·min gas supply intensity in the present experiments. When the gas supply was sufficient, CO₂ participation ratio was decreased and that of O₂ was increased with the carbon content decreasing. When the gas supply was insufficient, both CO₂ and O₂ participation ratios were relatively stable until the carbon transfer limiting the reactions.