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.