J55 oil jacket fusion zone defect:
After the ERW oil jacket, the welded pipe in the heat affected zone of the fusion line was found to be unqualified. Metallographic analysis, scanning electron microscopy and process research were carried out. The results show that the J55 welded pipe is on the fusion line. There is a certain depth of crack defect at the edge of the original plate in the heat affected zone. During the pipe making process, the user has a small pipe diameter and insufficient trimming amount, resulting in a significant increase in crack defects. The crack at the edge of the hot rolled original sheet originates from the corners of the cast slab and the subcutaneous bubbles.