Low stress welding technology without post-weld heat treatment

摘要

In order to assure the tightness and the service life of a full welded body ball valve, the temperature of grommet cannot exceed 150°C. Therefore, post-weld heat treatment cannot be used to relieve the welding residual stresses. In this study, a low stress welding technology was studied. The type of welding joint was optimised through the finite element method and vibratory welding was employed to decrease the residual stress. At the same time, the fracture toughness behaviour of weld zone and heat affected zone in terms of crack tip opening displacement was investigated to assess the safety of valve without PWHT in the active service. Finally, the results are discussed and analysed.