Reduction of welding residual stress in the head-cylinder joint of a large rectifying tower by finite element method and experimental study.

The welding residual stresses (WRS) in a cracked head-cylinder joint of a large rectifying tower were studied by finite element method (FEM) and experimental study. The effects of welding layer sequence, cover welding direction and weld reinforcement have been fully studied. The results showed that the stress concentration and plastic strain accumulation caused by unreasonable welding process and structural discontinuity are the main reasons of cracking. Furthermore, the order of welding layers has a significant influence on the distribution of axial stress: the inside and outside alternating welding process is superior to non-alternating welding process. The direction of cover welding markedly influences the hoop stress: the location of maximum stress is related to the welding start-end position. Besides, the removal of weld reinforcement after welding helps to release sub-surface tensile stress and solve the stress concentration problem. • Recommendations regarding welding procedure in large pressure vessels were proposed by FEM and experiment study. • High tensile WRS and large PEEQ at the weld toe directly contributed to the cracking. • The axial stresses can be effectively reduced by alternating welding. • The position of peak stress is related to the cover welding direction. • Removing the weld reinforcement helps to further control WRS. [ABSTRACT FROM AUTHOR]