The reaction mechanism of CO/CO2 with low-carbon aluminium-killed molten steel in ladle furnace was investigated through thermodynamic analysis, simulation, and experiments. When a[O]×a[C] in molten steel is less than pCO/(pΘ × KΘCO), CO/CO2 gas is dissolved in the metal phase and decomposed into oxygen and carbon. When a[O] × a[C] is equal to or close to pCO/(pΘ × KΘCO), CO no longer reacts with molten steel, part of CO2 is decomposed to CO, and oxygen atoms selectively oxidise other elements. The experimental results showed that the CO reaction rate increases with an increase in the aluminium content in molten steel, whereas the opposite occurs for the decomposition rate of CO2. The industrial test of the CO2 bottom blowing was conducted in a 100 t LF. Compared with argon, the stirring effect was weakened, and carburisation and selective oxidation of the elements were noted.
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