Numerical simulation on welding residual stresses of X80 pipeline girth weld joint

Based on thermal elastic-plastic theory,X80 pipeline steel welding temperature fields and stress fields were simulated with SYSWELD and double ellipsoid thermal source model. Residual stress distributions were obtained. The residual stresses are rather large in the welded seam zones and the adjacent zones and gradually reduce away in the base metal. The cooling velocity difference between the surface and the inner of the pipeline results in opposite directions or different levels of residual stresses. Effects of weld parameters on residual stresses are investigated,and the results show that the residual stress decreases with the increase of heat inputs or preheats. High heat inputs and preheats should be applied to reduce welding residual stresses.