等离子弧定点焊熔池穿孔过程的数值分析

来源期刊：金属学报2010年第8期

论文作者：王小杰 武传松 陈茂爱

文章页码：984 - 990

关键词：等离子弧定点焊； 小孔； 熔池； 数值分析

Key words：stationary plasma arc welding； keyhole； weld pool； numerical simulation

摘    要：利用Level-Set理论与方法追踪小孔界面的演变过程,建立了等离子弧定点焊熔池与小孔的数学模型,对不锈钢试件等离子弧定点焊熔池的穿孔过程进行数值模拟,获得了多种工艺条件下熔池与小孔形状和尺寸的动态变化数据.结果表明,6 mm厚度不锈钢试件等离子弧定点焊,当焊接电流为170和180 A时,分别在2.7和2.5 s形成贯穿工件厚度的小孔;等离子弧定点焊过程中,小孔断面的形状由开始的U字型转为V字型,穿透工件后又呈现类似双曲线型.通过测量熔池穿孔时刻的等离子弧尾焰电压信号,对数值分析结果进行了实验验证.

Abstract: 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 Vshape 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.