Résumé
Residual stress is a well-known consequence of welding which may promote cold cracking, stress-corrosion cracking, or fatigue cracks growth phenomena of steel pressure vessels. Residual stresses can be reduced by post weld heat treatment (PWHT). However, such treatments may not be usable on-site for welding repair of pressure vessels. "Temper bead welding" (TBW) techniques have been developed and introduced as substitution to PWHT for steel structures in construction codes because of their abilities to temper or to refine the heat affected zone (HAZ). Then TBW techniques reduce cracking risks related to the initial presence of brittle or hard metallurgical phases in the HAZ of steels. Nevertheless, reduction of residual stresses is not clearly made evident with TBW techniques. In this context, residual stresses induced by deposition of weld beads following a TBW technique were investigated with neutron diffraction carried out at SINQ instrument, Villigen, Switzerland. This communication describes the experiment and the resulting evolution of residual stresses up to five adjacent beads deposited on the surface of 20 mm thick P355 NH steel plates. The results show that the zone under tensile stress along longitudinal direction expands. For the five plates, the peak of transverse stress is equal to half of the maximal longitudinal stress.