等离子弧焊匙孔对电弧物理特性影响规律的研究

匙孔是等离子弧焊的重要特征。建立等离子弧焊电弧数值模型,对比分析含匙孔和不考虑匙孔的两种情况下,电弧温度场、流场、电磁场等物理特性的差异性,揭示匙孔对等离子弧物理特性的影响规律。采用光谱诊断方法计算电弧温度分布,从而验证模拟结果。数值模拟研究结果表明,匙孔的出现,导致电弧体积增大,弧柱区平均电流密度下降,从而导致电弧最高温度降低约2 400 K,等离子体最大流速从437 m/s降低到349 m/s。匙孔直径沿匙孔深度方向减小,对电弧产生附加的机械压缩作用,使匙孔底部电弧的温度和速度上升。数值模拟与光谱诊断获取的轴线上温度大小及变化规律相接近,证明电弧数值模型的可靠性,也说明建立等离子弧数值模型时,应当考虑匙孔的影响。

Influence Mechanisms of Keyhole on the Arc Characteristics in Plasma Arc Welding

The generation of keyhole is an important feature of plasma arc welding. To elucidate the influence of a preset keyhole on the arc, numerical models of plasma arcs are established, and physical properties such as temperature field, fluid flow field, electromagnetic field are analyzed. A spectrum analysis system is developed to obtain the plasma arc temperature distribution. The numerical results show that the existence of a keyhole causes an expansion of the plasma arc and the decrease of average current density; therefore, the maximum temperature of the plasma arc is decreased by about 2 400 K, which is consistent with experimental result. The maximum plasma velocity is decreased from 437 m/s to 349 m/s. The keyhole diameter shrinks along its depth, producing additional mechanical compression on the arc, which increases the temperature and speed of the arc at the bottom of the keyhole. All of these effects prove that an effective numerical model of an arc ought to consider keyhole effects.