Experimental study on deep denitrogenation of molten steel via vacuum coupled with carbon-oxygen reaction
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摘要: 钢中氮含量过高会显著劣化钢材力学性能及后续加工性能，实现稳定、高效的深度脱氮是转炉与电弧炉炼钢流程中生产高品质钢的关键技术难题。利用10 kg真空感应炉试验，提出并验证了一种真空条件下耦合碳氧反应内生CO气泡强化钢液深度脱氮的方法，系统研究了碳氧反应强度及初始氮含量对脱氮行为的影响，并从热力学与动力学角度进行了分析。结果表明，在真空条件下，碳氧反应生成的内生CO气泡可显著增加气–液反应界面，从而大幅提升脱氮效率；随着碳氧反应强度的提高，钢液脱氮速率显著增加，在初始碳含量为
1500 ×10-6时，钢液氮含量可在10 min内降至10 ×10-6以下。相同碳氧反应强度条件下，初始氮含量对脱氮速率影响不显著，但对终点氮含量具有决定作用。热力学计算表明，试验获得的最低氮含量已接近30 Pa真空条件下的平衡溶解度。动力学分析结果表明，脱氮过程受液相传质与界面化学反应的混合控制，并在试验尺度下建立了脱氮速率与脱碳速率之间的2/3次方定量关系。研究还发现，在超低氮区间内，随着碳氧反应减弱，钢液脱氮易向吸氮行为转变，需在脱氮后期严格控制真空条件。试验结果可为真空精炼过程的深度脱氮工艺优化提供理论依据和试验参考。Abstract: Excessively high nitrogen content in steel significantly deteriorates its mechanical properties and subsequent processing performance. Achieving stable and efficient deep denitrogenation is a key technical challenge in producing high-quality steel during the converter and electric arc furnace steelmaking processes. This study, utilizing experiments in a 10 kg vacuum induction furnace, proposes and validates a method to enhance deep denitrification in molten steel by coupling carbon-oxygen reactions to generate endogenous CO bubbles under vacuum conditions. The effects of carbon-oxygen reaction intensity and initial nitrogen content on the denitrification behavior were systematically investigated and analyzed from both thermodynamic and kinetic perspectives. The results indicate that under vacuum conditions, the endogenous CO bubbles generated by the carbon-oxygen reaction significantly increase the gas-liquid reaction interface, thereby greatly enhancing the denitrification efficiency. As the intensity of the carbon-oxygen reaction increases, the denitrification rate of the molten steel accelerates markedly. With an initial carbon content of 1500×10-6, the nitrogen content in the steel can be reduced to below 10×10-6 within 10 minutes. Under the same carbon-oxygen reaction intensity, the initial nitrogen content does not significantly affect the denitrification rate but plays a decisive role in determining the final nitrogen content. Thermodynamic calculations show that the minimum nitrogen content achieved in the experiments is close to the equilibrium solubility under a vacuum of 30 Pa. Kinetic analysis reveals that the denitrification process is controlled by a mixed mechanism involving liquid-phase mass transfer and interfacial chemical reactions. A quantitative relationship was established at the experimental scale, showing that the denitrification rate is proportional to the 2/3 power of the decarburization rate. The study also found that in the ultra-low nitrogen range, as the carbon-oxygen reaction weakens, the molten steel's behavior can easily shift from denitrification to nitrogen absorption, necessitating strict control of vacuum conditions during the later stages of denitrification. The findings of this paper provide a theoretical basis and experimental reference for optimizing deep denitrification processes in vacuum refining processes.-
Key words:
- denitrogenation /
- carbon-oxygen reaction /
- kinetics /
- internal bubbles /
- vacuum
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图 2 不同配碳量下氮含量随时间的变化
Figure 2. Variation of nitrogen content over time with different carbon additions
图 3 不同配碳量下碳含量随时间的变化
Figure 3. Variation of carbon content over time with different carbon additions
图 4 不同初始氮含量下氮含量随时间的变化
Figure 4. Variation of nitrogen content over time with different initial nitrogen levels
图 9 脱氮速率和脱碳速率关系
Figure 9. Relationship between denitrification rate and decarburization rate
表 1 试验钢母料成分
Table 1. Chemical composition of experimental steel
C Si Mn P S Alt Ti O 0.002 0.01 0.12 0.007 0.005 0.032 0.07 0.0012 
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