NUMERICAL SIMULATION OF WELD POOL KEYHOLING PROCESS IN STATIONARY PLASMA ARC WELDING
NUMERICAL SIMULATION OF WELD POOL KEYHOLING PROCESS IN STATIONARY PLASMA ARC WELDING
复制标题
DOI：
10.3724/sp.j.1037.2010.00021
复制
发表时间：
2010-08
影响因子：
2.3
通讯作者：
WU Zhuan-Song
中科院分区：
文献类型：
--
作者：
WU Zhuan-Song
小孔的形成行为在很大程度上决定了中厚板深熔焊接工艺和焊缝深宽比。深入研究等离子弧焊接熔池中的动态穿孔过程，对于拓宽等离子弧焊接工艺参数范围，提高等离子弧焊接过程的鲁棒性和焊接质量的稳定性具有重要意义。基于Level-Set理论，建立了描述稳态等离子弧焊接熔池小孔行为的数值模型，并用于跟踪小孔边界的演化过程。本文根据已有文献中的实验和模拟数据，构造了等离子体区和小孔区的流体流场。采用组合体积热源模型对焊接过程中的瞬态温度场进行数值分析，进而确定熔池的几何形状。采用Level-Set理论结合瞬态热传导模型的算法，确定了小孔和熔池几何形状在不同时间步的演化。通过对不锈钢板焊接穿孔现象的数值模拟，获得了几种工艺条件下熔池和穿孔几何形状和尺寸的动态信息。据发现，一个完整的锁孔建立在2.7和2.5秒的电流水平为170和180 A，分别。在稳态等离子弧焊接过程中，小孔的截面形状由初始的U形逐渐转变为V形，形成完整的小孔后，小孔的截面形状逐渐变为双曲线形。通过测量小孔形成时刻的射流等离子体电压信号，验证了小孔形成的数值分析。
The behaviors of keyhole formation determine to a great degree the deep penetration welding process and the weld depth-width ratio in welding of medium and large thickness plates. Obtaining a deep insight into the dynamic keyholing process in the weld pool in plasma arc welding is of great significance for widening the process parameter-widow and improving the process robustness as well as weld quality stability. Based on the Level-Set theory, a numerical model is developed to describe the keyhole behaviors in the weld pool in stationary plasma arc welding (PAW), and employed to track the evolution process of keyhole boundary. In this paper, the fluid flow fields in both the plasma and the keyhole regions are constructed according to the experimental and simulation data in the previous literatures. The combined volumetric heat source model is used to numerically analyze the transient temperature field and then to determine the weld pool geometry. The algorithm of Level-Set theory combined with the transient thermal conduction model is used to determine the evolution of both keyhole and weld pool geometry at different time steps. The dynamic information on the weld pool and keyhole geometry and sizes under a few process conditions is obtained by the numerical simulation of keyholing phenomena in welding of stainless steel plates. It is found that a complete keyhole is established at 2.7 and 2.5 s for the current levels of 170 and 180 A, respectively. During the stationary PAW process, the cross-section geometry of keyhole transforms from U-shape at initial stage to V- shape later and shows finally a hyperbola shape after a complete keyhole is formed. The numerical analysis of keyhole formation is verified by measuring the efflux plasma voltage signals at the moment of keyholing.