Study on fatigue fracture of SW400 fine-grained high-strength steel T-lap joint

Abstract

The SW400 fine-grained high-strength steel T-lap joints were welded by submerged arc welding. The influence of welding technology on the geometrical characteristics of welds and fatigue performance of the joints were studied by radial fatigue test with different welding parameters. The numerical analysis was used to study the characteristics of the stress distribution. And the fatigue fracture morphology was analyzed by scanning electron microscope. The results show that with the increase of welding line energy, the thickness of the weld increased, and the propagation direction of the fatigue crack changed from the weld to the base metal. When the thickness was less than 4 mm, the high-stress region was in the area of the weld around the weld root, and the fatigue crack propagated to the weld. When the thickness was greater than 4.5 mm, the high-stress region of AE and AS were in the weld around the root, where the crack propagated to the weld, while in the middle of the weld high-stress region was in the area of base metal around the weld root, crack propagated to the base metal. With the increase in the thickness of the weld, the maximum mises stress decreased, and the crack propagation rate decreased. The time of crack initiation was very short, which occurred in the high-stress region of the weld root in the middle of the weld.