Distribution of Residual Stresses in Dissimilar Ferritic Steel Weld Joints and Their Modification via Mechanical Hammer Peening

Dissimilar steel welding is a necessary means for engineering structures to meet complex service conditions. However, residual stress becomes a challenge for the service properties of dissimilar welded joints (DWJs), as it can reduce fatigue strength and trigger cracking in welded components. Therefore, accurately estimating the distribution of residual stress and efficiently eliminating it is of great importance. This study investigated the evolution of residual stress during the welding process of two commonly used ferritic steels through experimental and numerical analyses. The results show that different thermal cycle behaviors between DWJs have a significant impact on the formation of residual stress. Longitudinal tensile residual stress is predominant in the weld and heat-affected zone (HAZ), with higher longitudinal tensile and compressive stresses in the Q390 side than in the Q690 side, while the maximum transverse tensile stress occurs in the HAZ of the Q690 side. Hammer peening shows excellent ability to eliminate residual stress after welding, with a maximum elimination rate of approximately 62%, and converts the stress state from tensile to compressive at a certain welding depth. The analysis of process parameters reveals that peening velocity is the most influential factor. Under the present experimental configuration, the peening velocity should be set between 4.5 m/s and 5.5 m/s.