The fatigue behaviors of butt welds ground flush in the super-long life regime

► Fracture may still occur for butt welds ground flush during 10 8–0 10 cycles. ► A new kind of “fish-eye” was found in the butt welds ground flush. ► Fatigue crack sources of butt welds ground flush often issued from the fusion face. ► The relation between fatigue life and area of defects for welded joint was confirmed. The fatigue properties of EH36 steel and butt welds ground flush in the super-long life regime were studied in this paper. Experimental results indicate that fatigue fracture may still occur during 10 8–10 10 cycles, which is incompatible with conventional method of using the fatigue strength corresponding to 1 × 10 7 cycles to design welding structure serving in the super-long life regime. Scanning electron microscope analysis shows that fatigue crack mainly initiates from internal defects in the fusion face for butt welds ground flush. A new kind of “fish-eye” is found in welded joints. The relation between fatigue life and area of defects in the butt welds ground flush is confirmed.