Research On The Welding Temperature Field And Residual Stress Of Bifurcation Region In Combined Welds Of Crescent-RIB Reinforced Bifurcation Of Hydropower Station

The steel bifurcated pipe is a large welded structure. The combined weld of the crescent-rib reinforced bifurcation combined by butt weld and fillet weld is connected crescent rib stiffened inside and the shell plate of branch pipe. It requires strict welding procedure. The main quality problems often occur in it. The most sensitive areas of combined weld is the bifurcation region, because it is difficultly welded, the stress is complex, and it is a welding defect prone areas. In this paper, the welding temperature field and residual stress of bifurcation region in combined weld of crescent-rib reinforced bifurcation was researched by SYSWELD which is a welding professional software. It has important engineering significance to guarantee obtain high quality crescent-rib reinforced bifurcation.In order to reveal the distribution of temperature field at different times and typical nodes’ thermal cycles, discuss the influence of welding sequence on welding residual stress, the welding field and residual stress of bifurcation region in combined weld were simulated numerically. The results show that he distribution of temperature field at different times and typical nodes’thermal cycles are similar to the actual welding situation. The thermal cycles of nodes which are on the same section perpendicular to the weld direction are different. They are the first layer of weld node, the near the weld nodes, and the far away from the weld node respectively. The welding sequence affects the distribution of residual stress of the weld. The maximum Von Mises residual stress of the selected nodes is minimum in the welding sequence, which the smaller groove is welded firstly then the larger groove is welded.Introducing the method of orthogonal design to investigate the influence of the factors of the joint of bifurcation region in combined weld on the peak residual stress of the weld, such as the bifurcation angle, the groove, the asymmetry size, the truncated edge. The results show bifurcation angle is the most important factor to the peak residual stress, the second is groove, the third is asymmetry size, the last is truncated edge. The bifurcation angle, the groove and the asymmetry size have significant influence on the peak residual stress of bifurcation region in combined weld. But the truncated edge has no significant influence. The influence of two different subsection welding on the residual stress of bifurcation region in combined weld was discussed in this paper. The results show the piecewise regression welding is better than the subsection welding simultaneously, because the residual stress of bifurcation region in combined weld is smaller and uniformer.