Abstract: By studying the characteristics of stainless steel forgings and ultrasonic forgings detection of heat exchangers used in hydrogenation units, the ultrasonic detection technology is flexibly applied to the quality problems of finished stainless steel forgings in circular steel joints, and the sensitivity of ultrasonic detection to area defect direction under the influence of restricted space and special factors is successfully verified. It proves that radiography can judge the existence and orientation characteristics of internal defects, and it plays a role in guiding the precise location and removal of defects in the process of auxiliary repair, ensuring the efficient completion of repair work, and providing a case reference for the construction and installation of pressure vessels or in-service maintenance.