RH精炼过程增氮行为探讨

Discussion on nitrogen increasing behavior in RH refining process

为了在RH精炼过程对氮的质量分数进行稳定控制,通过热力学计算分析钢水成分、RH真空度等对理论平衡氮质量分数的影响,分析RH提升气体从吹入上升管到进入真空室过程中压力的变化对平衡氮质量分数的影响。从动力学角度分析气相中的传质阻力、界面化学反应阻力、液相中的传质阻力共同作用于钢液的增氮、脱氮过程。提出RH处理过程的3种增氮途径及其对应的平衡氮质量分数。当钢种要求氮质量分数大于真空度下的理论平衡氮质量分数时,RH处理过程存在增氮、脱氮共存的状态。在氮质量分数变化过程中,当脱氮速度等于增氮速度时,钢液中氮质量分数达到动态平衡,不再发生变化。在真空度为5kPa的条件下,RH钢液中氮质量分数达到动态平衡,不再发生变化时对应的氮质量分数为0.010 0%。

In order to control the quality of nitrogen in the RH refining process,the theoretical equilbrium nitrogen mass fraction is analyzed by thermodynamic calculation considering the influence of liquid steel composition and RH vacuum degree,and the effect of the pressure change of circulation gas ware blowed tube to into the vacuum chamber on the equilbrium nitrogen mass fraction is also analyzed.Through the dynamics analysis,the adding and removing nitrogen process was affected by the mass transfer resistance in the gas phase,the interfacial chemical reaction resistance,and the mass transfer resistance in the liquid phase.Three kinds of nitrogen increasing pathway of RH process are proposed,and the corresponding equilbrium nitrogen mass fraction are calculated.When the nitrogen mass fraction of steel grade is greater than the equilibrium nitrogen mass fraction,two states in RH treatment process,increasing nitrogen and decreasing nitrogen,are coexistence.In the process of the variation of nitrogen concentration in liquid steel,when the rate of removing nitrogen is equal to the rate of adding nitrogen,the concentration of nitrogen in liquid steel reaches the dynamic equilibrium.For the vacuum degree of 5 kPa,the theoretical equilbrium nitrogen mass fraction in RH is 0.010 0%.