Original Article

Mechanistic study of decarburization kinetics and specific stirring power in molten steel under bottom-blown CO₂/Ar gas

School of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063210, Hebei, PR China

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Received: 3 April 2026
Accepted: 22 June 2026

Abstract

To achieve efficient utilization of CO₂ in molten steel refining, this study systematically investigated the molten pool stirring power density and decarburization kinetics under bottom-blown CO₂/Ar conditions by combining theoretical analysis with high-temperature tubular furnace experiments. The effects of CO₂ fraction, initial carbon content, temperature, and blowing flow rate on CO₂ utilization, decarburization rate, and stirring power density were analyzed in detail. The results indicate that CO₂ utilization exhibits a significant positive linear correlation with stirring power density, forming a positive feedback mechanism through “bubble generation–mass transfer enhancement–reaction promotion”. When CO₂ utilization increases from approximately 30% to 80%, the stirring intensity is markedly enhanced, and for utilization above 50%, the stirring power density per ton of steel must exceed 4.5 × 10⁻⁴ W·t⁻¹. Increasing the initial carbon content from 0.2% to 0.6%–0.7% raises CO₂ utilization from ∼30% to 80%, shifting the controlling step of decarburization from liquid-phase mass transfer to gas supply or interfacial reaction control. Increasing the CO₂ fraction strengthens the reaction driving force, but under high CO₂ conditions, the growth of the decarburization rate is limited by CO partial pressure and mass transfer. Blowing flow rate is the dominant factor: tripling the flow rate increases the stirring power density by ∼3–7 times; in contrast, raising the temperature from 1550 °C to 1650 °C increases CO₂ utilization by only ∼11.3% and stirring power density by ∼67.76 W t⁻¹, indicating that the overall process is largely mass-transfer-controlled. In summary, specific stirring power is synergistically governed by gas supply, reaction efficiency, and gas–liquid mass transfer, with blowing flow rate playing the primary role, initial carbon content determining the reaction stage, and temperature exerting a regulatory effect. These findings provide a theoretical basis for the efficient utilization of CO₂ in ladle refining.