超低碳钢RH混合喷吹Ar-CO2冶金反应特性

 钢铁生产过程CO₂的资源化利用对中国“碳达峰,碳中和”目标的实现起着重要作用。氩气驱动的RH(ruhrstahl-heraeus)真空装置是超低碳钢精炼的关键设备,利用高真空下钢水循环流动可有效脱碳、脱气和去除夹杂物。由于真空条件下CO₂可直接与钢水中碳反应生成CO,在实现脱碳的同时可促进熔池搅拌。因此,尝试将Ar-CO₂混合气体作为提升气体引入超低碳钢RH脱碳过程。首先,针对CO₂在RH脱碳条件下的冶金反应行为,通过热力学理论分析了不同压力下Fe-C-O熔体与Ar-CO₂的反应特性。其次,搭建了Ar-CO₂混合气体作为RH提升气体的工业试验平台,通过工业性试验研究了超低碳钢RH脱碳过程混合喷吹Ar-CO₂对钢水脱碳、脱氮和温降的影响。Fe-C-O熔体与Ar-CO₂反应热力学表明,在低于100 kPa和超低碳条件下,Ar-CO₂混合气体中的CO₂仍可能与钢水中碳反应,从而促进RH脱碳和脱气。工业性试验表明,喷吹100% CO₂、50% Ar+50% CO₂和100% Ar炉次出站平均碳质量分数分别为0.001 50%、0.001 57%和0.001 19%,因而混合喷吹Ar-CO₂并不会显著影响RH脱碳效率。同时,由于CO₂与钢水中碳反应十分有限,与喷吹100% Ar相比,喷吹100% CO₂和50% Ar+50% CO₂对RH脱氮效率和钢水温降没有明显影响。因此,超低碳钢RH脱碳时,完全可采用CO₂取代部分或全部氩气作为提升气体,尽管无法提高精炼效率,但仍具有显著的经济价值和环保优势。

Metallurgical reaction behavior of Ar-CO2 mixed injection during RH refining process

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.