Experimental study on crack propagation characteristics of welded high-strength steel Q690CFD joints

Abstract

High-strength steel typically refers to steel with a yield strength greater than or equal to 460 MPa. The heterogeneity caused by welding could impact the mechanical properties base material, weld metal and heat-affected zone. In this study, the welding sequence and crack propagation characteristics of welded high-strength steel joints were experimentally analyzed. It is found that the distribution of residual stresses in both the transverse and longitudinal directions exhibit highly nonlinear characteristics. The magnitude of longitudinal residual stresses can exceed 60 % of the nominal yield stress and the magnitude of transverse residual stresses can exceed 50 % of the nominal yield stress in the regions adjacent to the weld. In the early stage of crack propagation, the crack propagation rate in the HAZ and WM regions is significantly faster than in the base metal. The main differences in crack propagation between the base metal, weld metal, and HAZ occur in the initial and final stages of crack growth. In the stable crack propagation stage, there are no significant differences for the base metal, weld metal, and HAZ. Finally, a normalized crack growth prediction model was proposed with validated accuracy.