Effect of CO2 and O2 Mixed Injection on the Decarburization and Manganese Retention in High-Mn Twinning-Induced Plasticity Steels

In order to achieve decarburization and manganese retention simultaneously, CO2 was introduced in the smelting process of high-Mn twinning-induced plasticity (TWIP) steel. The effect of CO2 and O-2 mixed injection on the decarburization and manganese retention was carried out based on the thermodynamics calculation and experimental research. The calculation results showed that the evaporation loss of manganese decreased dramatically with increasing CO2 blowing proportion, from the value close to 38 kg/t at pure O-2 blowing to the value close to 4.4 kg/t at 40 vol pct CO2 proportion. The oxidation loss of manganese decreased from 70.5 to 41.7 kg/t when the CO2 blowing proportion increased from 0 to 40 vol pct. Additionally, the obtained data of the present experiments indicated that the introduction of CO2 could significantly lower the manganese loss and improve decarburization efficiency. The decarburization and manganese retention could be achieved simultaneously by replacing the partial oxygen with CO2 in the injected gas. Moreover, increasing the flow rate of the CO2-O-2 gas mixture and increasing the melt temperature would improve decarburization efficiency but deteriorate the retention of manganese in the meantime.