高速GMAW驼峰形成过程的数值分析

Numerical analysis of humping formation in high speed GMAW process

文中通过数值模拟来研究常速、高速熔化极气体保护焊的温度场和流场,并利用高速摄影观察熔池流动,分析了驼峰形成过程.结果表明,常速焊接熔池纵截面同时存在逆时针向内和顺时针向外两种流动方式,但随着焊接速度的提高,熔池纵截面仅存在逆时针向内单一流动方式.高速焊接时,较大动量的后向液体流和足够大的表面张力促进液态金属在熔池尾部不断堆积、变大.沿焊接方向,熔池受到不均匀的表面张力法向力作用而收缩,这是驼峰形成的两个重要因素.任何能降低表面张力的措施,都能抑制驼峰的形成.

The convection difference between normal speed and high speed GMAW processes was investigated using the numerical simulation,a high speed photography system was used to capture the transient images of the weld pool,and the humping formation in high speed GMAW process was also discussed. The results show that at the longitudinal sectional view of the weld pool behind the arc,both counterclockwise circulation and outward fluid flow pattern exist in normal speed GMAW process,only counterclockwise circulation exists in high speed GMAW process. Two main factors are responsible for the humping formation,one is that the high momentum of the backward fluid flow causes the initiation and growth of swelling,and the other is that the unbalance of normal surface tension force in the welding direction promotes the shrinkage of liquid channel. Any measures that help reduce the surface tension can inhibit the formation of humping.