Decarburization and Desilication Behavior by CO<sub>2</sub>–O<sub>2</sub> Mixed Gas Injection in Fe–C–(Si) Molten Alloys

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 1873 K. 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.