Influence of post-weld heat treatment on welding residual stress in U-rib-to-deck joint

Welding residual stress (WRS) significantly influences the fatigue life and safety of welded steel structures. Postweld heat treatment (PWHT) is a common method employed to mitigate WRS. In present study, the WRS evolution law and relaxation mechanism of U-rib-to-deck joints was investigated during PWHT. High-temperature heat treatment tests with varying holding times were conducted on U-rib-to-deck joints to reduce WRS. The WRS distributions were measured using the hole-drilling method before and after PWHT. ABAQUS software, incorporating the Norton-Bailey creep constitutive model, was employed to simulate the WRS evaluation during both welding and PWHT processes. The simulated values were validated against the measured data, and the effects of different holding times, holding temperatures, and heating and cooling rates during PWHT on WRS relaxation were discussed. The results demonstrate that PWHT effectively reduces WRS and leads to a more uniform distribution. Extending the PWHT holding time from 0.5 h to 1 h and 2 h results in a gradual decrease in WRS relaxation at 600 degrees C, primarily occurring in the high-value stress region of the weld zone with a small amplitude. Elevating the PWHT temperature from 500 degrees C to 550 degrees C and subsequently to 600 degrees C amplifies the significance of WRS relaxation. Variations in heating and cooling rates (200 degrees C/h and 80 degrees C/h, 100 degrees C/h and 40 degrees C/h, 50 degrees C/h and 20 degrees C/h) lead to a gradual decrease in WRS relaxation across the entire model. Furthermore, considering the creep effect, the stress relaxation rate in the weld is approximately 70 %-80 %, which found to be about 2-3 times higher than that without considering the creep effect. By understanding the evolution law and relaxation mechanism, this study provides valuable insights for designing PWHT processes and assessing their impact on structural safety and fatigue life.