Corrosion Fatigue Behavior of Welded Joints in 304L Stainless Steel Drain Pipe

Cracking failure occurred at the welded joints of two 304L stainless steel drain pipes. The failed pipes were investigated by metallographic microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). And Ansys software was used to simulate and analyze the influence of fluid rate on the stress distribution in the pipes. The results show that the failure modes of the two drain pipes were corrosion fatigue cracking. All cracks were initiated at the weld toes of the welded joints with several crack sources. When water flew, a negative pressure area was formed near the welded joint, leading to cavitation corrosion at many places in the area. Corrosion pits generated by cavitation corrosion were the stress concentration points and became sources of fatigue cracks. The tremendous impact stress caused by cavitation blasting could induce pipe vibration, which finally led to corrosion fatigue cracking.