Causes of leakage at T-joint of 304 austenitic stainless steel pipe

Leakage occurred in the weld position of T-type welding reinforcement sleeve on the outer ring surface of a 304 austenitic stainless steel pipe. The causes were studied by means of macroscopic observation, chemical composition analysis, liquid penetration test, metallographic examination and scanning electron microscope analysis. The results show that there were a large number of welding defects such as pores, incomplete penetration and longitudinal cracks in the weld, and the cracks had penetrated the pipe wall. Austenitic stainless steel and reinforced casing were dissimilar metal welding, resulting in high welding residual stress. At the same time, excessive welding heat input led to the weakening of grain boundary properties of stainless steel, which caused cracking.