Study on Decarburization and Dehydrogenation of Molten Steel under CO₂/Ar Mixed Blowing

Abstract

To investigate the application potential of CO2 in molten steel refining, CO2/Ar mixed-gas bottom blowing experiments were conducted using a high-temperature tubular furnace. The effects of gas mixing ratio, initial carbon content, blowing flow rate, and refining temperature on the decarburization, oxygen control, and dehydrogenation behaviors of molten steel were systematically studied, and the purification mechanism induced by CO bubbles was analyzed. The results show that CO2/Ar mixed blowing effectively promotes molten steel decarburization, with the optimal comprehensive purification effect achieved at 1600 ℃ under 50% CO2–50%Ar conditions. As the initial carbon content increased from 0.15% to 0.65%, the decarburization amount increased from approximately 0.045% to 0.129%. When the blowing flow rate increased from 10 mL/min to 40 mL/min, the decarburization rate increased by approximately 2.21 times. Fine CO bubbles generated by the CO2–C reaction not only enhanced decarburization, but also reduced the total oxygen content by adsorbing and entraining oxide inclusions. The average total oxygen content stabilized within 32-35 ppm, with the minimum value of 32.7 ppm obtained at 1600 ℃. Meanwhile, CO bubble flotation promoted molten steel dehydrogenation, and the lowest average hydrogen content of 32.2 ppm was achieved at 30 mL/min. The results indicate that CO2/Ar mixed blowing has promising potential as a novel green refining process for clean steel production with both low reoxidation and deep purification capabilities.