Metallurgical reaction behavior of Ar-CO2 mixed injection during RH refining process
CHEN Gu-jun1, YANG Jiang2, LI Long3, ZHANG Min3, HE Sheng-ping2
1. School of Materials Science and Engineering, Yangtze Normal University, Chongqing 408100, China; 2. School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; 3. Institute of Material Engineering and Technology, Pangang Group Research Institute Co., Ltd., Panzhihua 617000, Sichuan, China
Abstract:The resource utilization of CO2 during iron and steel production process makes a valuable contribution towards achieving the target of “carbon peak and carbon neutralization”. Ar-driven RH (ruhrstahl–heraeus) vacuum device is the key equipment for decarburization of ultra-low carbon steel, and the decarburization, degassing and inclusion removal can be effectively achieved by circulation flow of liquid steel in high vacuum. Since CO2 can directly react with carbon in the liquid steel to form CO, the decarburization can be realized and the bath stirring can be strengthened. Therefore, an attempt was made to introduce the Ar-CO2 mixed gas, as the lifting gas, into the RH decarburization process of ultra-low carbon steel. Firstly, the thermodynamic analysis between Fe-C-O melt and Ar-CO2 was carried out to study the metallurgical reaction behavior under different pressures in RH refining conditions. Then, an industrial test platform for taking Ar-CO2 mixed gas as RH lifting gas was built, and the effect of Ar-CO2 mixed injection on decarburization, denitrification and temperature drop of liquid steel during RH decarburization process of ultra-low carbon steel was investigated by industrial tests. Thermodynamic analysis between Fe-C-O melt and Ar-CO2 shows that CO2 can react with carbon in the molten steel under conditions of low atmospheric pressure and ultra-low carbon content, and RH decarburization and degassing can be accelerated. Industrial test indicates that the average carbon content in molten steel after RH treatment with 100% CO2, 50% Ar+50% CO2 and 100% Ar injection are 0.001 50%, 0.001 57% and 0.001 19%, respectively, and thus the decarburization efficiency is not significantly affected by Ar-CO2 mixed injection. Meanwhile, compared with 100% Ar injection, 100% CO2 and 50% Ar+50% CO2 injection have slight effect on RH denitrification efficiency and temperature drop of molten steel because the reaction of CO2 with carbon is quite limited. Therefore, CO2 can be used to partially or completely replace the Ar during RH decarburization process of ultra-low carbon steel based on economic and environmental considerations, although the refining efficiency cannot be improved.
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