Reasons Analysis on Cracks of TP321 Stainless Steel Piping Welding Seam on Hydrogenation Unit

The cracking causes of welding seam of TP321 austenitic stainless steel piping on reaction system of hydrogenation unit were analyzed by means of surface nondestructive testing,chemical components analysis,hardness test,metallographic examination combined with operating mode analysis of the piping.The results show that the welding material with high content of carbon and low content of chromium easily led to form high crack sensitivity full austenitic microstructure with austenite solidification pattern.High temperature,high pressure and hydrogen medium conditions promoted the initiation and propagation of cracks.