Cracking Reasons of Stainless Steel Elbow of Medium Temperature Shift Cooling System in Hydrogen Plant

Several penetrated cracks occurred in the heat affecting zone of austenitic stainless steel elbow of medium temperature shift cooling system in a hydrogen plant.Cracking reasons were analyzed by macroscopic examination,hardness test,chemical compositions analysis,X-ray test,metallographic structure and SEM testing,etc.The nature of cracking was determined to be intergranular stress corrosion cracking.Some precautions and suggestions were proposed.