大型管板结构焊接残余应力的预测与消除

Prediction and Elimination of Welding Residual Stress in Large Pipe-sheet Structure

基于有限元软件MSC.Marc开发了2D轴对称热-弹-塑性有限元模型,用于预测其大型管板结构多层多道焊的焊接温度场和残余应力。之后以此焊接残余应力为初始条件,利用所开发的模型,研究了焊后热处理对焊接残余应力的消除情况;同时研究了在热处理过程的保温阶段是否考虑蠕变对焊后热处理后残余应力消除情况的影响。结果表明,该大型管板结构的焊缝及热影响区附近存在较大的焊接残余应力;通过焊后热处理工艺,可以显著地降低焊接产生的高拉伸应力,但对于焊接压缩应力的影响较小;以环向应力为例,在考虑蠕变的情况下,可以使高拉伸应力的峰值降低86%,而在不考虑蠕变的情况下,只能降低60%;焊接残余应力的释放主要发生在升温阶段,而在降温阶段应力有所升高;在考虑蠕变时,保温阶段焊接残余应力得到一定的释放,在不考虑蠕变时,保温阶段应力保持不变。

Based on MSC. Marc software, a 2D axisymmetric thermo-elastic-plastic finite element model was developed to predict the welding temperature field and residual stress of multi-pass welding in a large pipe-sheet structure. Then using the welding residual stress as the initial condition, the effect of post-weld heat treatment(PWHT) on welding residual stress elimination was studied by using the developed model. At the same time, the effect of creep on the residual stress elimination after post-weld heat treatment was studied in the heat preservation stage of heat treatment process. The results show that there is large welding residual stress near the weld and heat affected zone of the large pipe-sheet structure. The post-weld heat treatment process can significantly reduce the high tensile stress generated during welding, but the effect on welding compressive stress is almost none. Taking the circumferential stress as an example, in the case of considering creep, the peak value of high tensile stress can be reduced by 86%, and only 60% can be reduced without considering creep. The release mainly occurs in the stage of heating, and the stress increases in the cooling stage. When the creep is considered, the welding residual stress in the heat preservation stage is released to a certain extent. However, without considering the creep, the stress in the heat preservation stage remains unchanged.