Residual Stress in 347H Weldments: Influence of Various Thermal Treatment on Residual Stress Reduction

Residual stresses play a pivotal role in influencing the structural integrity of welded structures, a consequence inherent to the welding process itself. In scenarios involving cyclic thermal and mechanical loading during operation, the dynamic transformation of residual stress patterns arises from multiple influencing factors. In addition to thermomechanical considerations, the evolution of the microstructure significantly contributes to this intricate and interconnected phenomenon. The selection of 347H austenitic stainless steel stands out as an optimal choice due to its exceptional resistance to creep and corrosion. Nonetheless, unforeseen failures continue to pose significant challenges in meeting design criteria. Residual stress remains the primary factor for predicting the lifetime of welded components, and a reliable measurement method for this purpose is still lacking. In this research paper, we present a comprehensive series of measurements conducted on lab-made plate welds subjected to different thermal treatment conditions. Simultaneously, we employ and compare two distinct calculation methodologies to assess the disparities and the feasibility of applying the plane stress methodology to thick service pipe welds. Through a meticulous measurement plan encompassing both As-Welded and post-weld heat treatment (PWHT) lab-made plate welds, which aim to determine the impact of PWHT on the redistribution and relaxation of the residual stress field. Additionally, both plate welds undergo 361.5 hours of thermal aging (TA) at 650℃ to mimic as practical as possible service conditions. The validation of both methodologies is subsequently established across four distinct thermal treatment conditions. Consequently, the reliable application of the plane stress methodology to service-grade thin/thick pipes becomes apparent.