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A mathematical model incorporating dynamic parameters is proposed to investigate the overall decarburization process during the vacuum oxygen refining (VOD) process for ultrapure ferritic stainless steel. This paper also conducted a precise theoretical calculation of the C‐Cr equilibrium. Moreover, the top‐blowing oxygen distribution is categorized into six directions: [C] oxidation, alloy component oxidation, CO bubble oxidation above the bath surface, bath surface oxidation (FeO), dissolution in the molten steel ([O]), and escape into the exhausted gas. The FeO and Cr2O3 oxide are intermediate product of oxygen to oxidize [C] remaining in the molten steel during the VCD stage. The modified approach of Gibbs free energies determines the critical carbon concentration by the distribution ratio of carbon to the top‐blowing oxygen. The top‐blowing oxygen primarily consumed by CO‐CO2 bubble (49–55%) and Cr2O3 (26–33%). Additionally, the model considered operational aspects, the system's heat balance, and changes in overall metal‐slag conditions during the refining process. The exhausted gas composition and end‐point carbon concentration align well with industrial data. Within a certain range (approximately up to 0.50%), increasing initial carbon concentration can enhance overall decarburization efficiency. [ABSTRACT FROM AUTHOR]

The total oxygen in 304L stainless steel produced by the VOD-LF-CC process is investigated in this research. The equilibrium oxygen content in the molten steel during the smelting process is calculated based on the ion-molecule coexistence theory. The results show that it is feasible to use the developed thermodynamic model for calculating the equilibrium oxygen content in CaO–SiO2–Al2O3–MgO–FeO–Cr2O3 slags equilibrated with 304L molten steel. The variation law for total oxygen is in good agreement with the equilibrium oxygen content. The oxygen content of the oxide-inclusion decreases with the number density of inclusions, which decrease at different stages in the process. The content of FeO and Cr2O3 in the slag has no obvious effect on the equilibrium oxygen content when the basicity of the slag remains constant. Combining the proposed method with industrial practice, the optimum VOD process parameters for obtaining a low equilibrium oxygen content are as follows: 1600–1650 °C of the temperature after the VOD stage, 0.4–0.5% of the Si content after reduction, and 2.2–2.5 of the slag basicity. [ABSTRACT FROM AUTHOR]