Stress Redistribution During Annealing of a Multi-Pass Butt-Welded Pipe

The reduction of welding stresses during some standard post-weld heat treatments (PWHT) is numerically determined for a multi-pass butt-welded pipe made of a micro-alloyed C-Mn steel. Most of the stress reduction is found to occur during heating to the holding temperature. The further reduction obtained during the subsequent holding period is significant only for holding temperatures above 550°C. Both welding stresses and stresses during annealing were calculated by use of the FE-method assuming rotational symmetry. Experiments performed on a welded pipe indicate that the assumption of rotational symmetry is justified for the welding residual stress field, but not for the transient stress field present during welding of each pass.