激光焊接顺序对钛合金U型材残余应力与变形的影响

Effect of Laser Welding Sequence on Residual Stress and Deformation of Titanium Alloy U-beam

TC4钛合金U型材由1块面板和2块腹板焊接而成,采用激光自熔焊实现两条长焊缝的焊接。为研究激光焊接顺序对该U型材残余应力与变形的影响,使用有限元仿真方法,采用高斯面热源与柱状热源组合的热源模型,对比分析了不同焊接顺序下U型材的应力与变形。结果表明,U型材在不同焊接顺序下残余应力与变形分布情况不同。2条焊缝同向顺序焊接的方案在型材中部焊缝位置的残余应力保持稳定,其他在中部分段焊接的方案(4条焊缝)在该位置的应力有所降低。这主要是由于型材中部位于前面焊缝的起弧或收弧部分,其受到了后面焊缝的热处理作用,残余应力得到了释放。2条焊缝同向顺序焊接方案的变形量最大,从中间向两端同侧顺序、对称焊接的方案与从两端向中间不同侧顺序、对称焊接的方案产生的最大变形量最小。考虑实际焊接时,在U型材两端起弧可设置引弧板,更有利于保证焊缝成型质量,因此适宜采用两端向中间不同侧顺序、对称焊接的方案。

The TC4 titanium alloy U-beam was welded by 1 panel and 2 webs, the welding of the two long welds was carried out by using laser self-melting welding. In order to study the effect of laser welding sequence on the residual stress and deformation of the U-beam, the stress and deformation of the U-beam under different welding sequences were compared and analyzed by using finite element simulation and the heat source model combined Gaussian surface heat source and cylindrical heat source. The results show that the distribution of residual stress and deformation of the U-beam is different under different welding sequences. In the sequential welding scheme of two welds with same direction, the residual stress of the weld in the middle of the U-beam remains stable, and the stress of the position under the other schemes of four welds with segmented welding at the U-beam center decreases. Because the U-beam center position is located at the arc starting or arc ending of the front weld, and it is subjected to the heat treatment of the rear weld, therefore the residual stress is released. The deformation of the sequential welding of two welds with same direction is the largest. For the scheme of sequential welding from the middle to the end at same side and symmetry welding for both sides and the scheme of sequential welding from the center to the end at different sides and symmetry welding for both sides, the maximum deformation is the minimum. Considering the actual welding process, arc striking plates can be set at both ends of the U-beam, which is more conducive to ensuring the weld forming quality. Therefore, the sheme of sequential welding from the center to the end at different sides and symmetry welding for both sides is suitable.