Research on Selective Oxidation of Carbon and Aluminum with Introduction of CO₂ in RH Refining of Low-Carbon Steel Process

The injection of CO₂ during the Rheinstahl–Heraeus (RH) refining process as a lifting gas is a new attempt for the steel industry, and can promote refining effect and realize the utilization of CO₂ as a resource. In the present study, the thermodynamic equilibrium of the RH refining process through CO₂ injection instead of Ar was calculated using FactSage software. A selective oxidation sequence of [C] and [Al] with CO₂ was studied and analyzed under the RH refining temperature and vacuum degree. In addition, the oxidation zones of carbon and aluminum were both defined. Industrial trials were preliminarily conducted to verify the above theory. The results show that CO₂ has the potential to be used to refine low-carbon steel in RH, but its refining effect is affected by the [Al] content in steel. By reducing the additive amount of aluminum alloy in the ladle furnace and replenishing the aluminum during the late stage of the RH refining process, CO₂ injection can achieve a lower temperature drop of molten steel and a better refining effect than Ar during the RH degassing process.