Exploring the Efficiency of Post-Welding Vibratory Stress-Relief Treatment Applied on Multi-Pass Butt-Welded Thick Sheet of High-Strength Low-Alloy Steel

Post-welding vibratory stress relief (VSR) has been studied extensively for its capability of decreasing welding residual stresses (RS). This study examines the effectiveness of VSR applied on butt-welded thick sheets of high-strength low-alloy steel. The effect of thermal stress relief (TSR) was examined simultaneously. X-ray diffractometry (XRD), hole drilling method (HDM), and instrumented indentation technique (IIT) were employed for evaluating RS distribution. Global mechanical properties of the weld joint were assessed using tensile tests, bending tests, and Charpy impact tests. Hardness was employed to assess local variation in mechanical properties. The microstructure was observed through light optical microscopy (LOM) and electron back-scatter diffraction (EBSD). It was found that RS redistributed after VSR. The overall decrease in RS could be seen after VSR; however, the scatter in RS increased. TSR, on the other hand, resulted in the decrease in both magnitude and scatter of RS. Peak values of the post-welding RS were evaluated in the range of −200 to 200 MPa; meanwhile, the mean RS was within the range of −100 to 100 MPa. After TSR, RS was mostly within the range of −50 to 50 MPa. After VSR, RS was found to lie mostly within the range of −100 to 200 MPa with peak values being close to the yield strength. VSR had no adverse effect on the structural integrity of the weld joint. No significant differences in the microstructure were seen among as-welded, TSR, and VSR conditions.