Comparison of stress relief by PWHT and VSR in large-dimension straight welded pipe

Post-weld heat treatment (PWHT) and vibratory stress relieving (VSR) were used to control the residual stress in large-dimension welded pipes.The results show that both PWHT and VSR are able to relieve the residual stress effectively in large-dimension straight welded pipe and make the distribution of residual stress more uniform.Their effect in weld zone is more obvious than these in base metal.The results of stress relieving of VSR of as-cast microstracture are qualified but not acceptable in cold plastic deformation zone.The effect of PWHT on the stress relieving and stress uniform ability is better than that of VSR.However, considered of economy factor and technique convenience, VSR is confirmed as stress relieving technique to control the residual stress in large-dimension straight welded pipe.