Investigation on Residual Stress in SA508/Inconel Metal/CF8A Dissimilar Welded Joint for Nuclear Steam Generator Safe End Using Different Processes

The residual stress of a safe-end/nozzle dissimilar metal welded joint in nuclear power plants was investigated by finite element simulation coupled with a measurement method. Cladding, butting, dissimilar metal multipass welding, machinery processes, and in-service condition were all considered to investigate the evolution of residual stress. The numerical simulation matched well with the measured values, validating the effectiveness of the numerical simulation. Tensile residual stress occurred at both inner and outer surfaces due to a double-side-welding sequence. Moreover, the highest stresses in the outer surface were located at the interface between the SA508 and clad layer due to the difference of expansion materials across the welded joint. The machinery process would greatly reduce the residual stress level and produce compressive residual stress in the base metal. When the safe end was subjected to working conditions, the tensile residual stress obviously was reduced especially on the inner surface.