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众所周知,由于焊缝收缩,焊接温差以及焊件的刚性,在厚壁管焊接接头中将形成残余应力。这种应力对15X1M1φ和12XM1φ钢特别危险。此外,焊接接头还承受固定的工作应力:由介质压力引起的拉应力,由管道位移引起的胀缩应力和由于管子加热不均匀而引起的热应力。在某些情况下,裂缝出现的部位并非是工作应力最大处,其原因之一是该处存有高水平的残余应力,它和外载的合力导致了焊接接头的破坏。
It is well-known that due to the shrinkage of the weld, the temperature difference of the welding and the rigidity of the weldment, residual stresses will form in the welded joints of the thick-walled pipe. This stress is particularly dangerous for 15X1M1φ and 12XM1φ steel. In addition, the welded joint also withstands a fixed working stress: tensile stress caused by medium pressure, expansion and contraction stress caused by pipe displacement and thermal stress due to uneven heating of the pipe. In some cases, the part where the crack appears is not the maximum work stress. One of the reasons is that there is a high level of residual stress in the place, and the resultant force with the external load leads to the destruction of the welded joint.