As a traditional and effective method to improve and re […]
As a traditional and effective method to improve and restore metal properties, heat treatment has always been a relatively weak link in the design and manufacturing of pressure vessels. Pressure vessels involve four kinds of heat treatment: post-weld heat treatment (stress relief heat treatment); heat treatment to improve material properties; heat treatment to restore material properties; post-weld hydrogen elimination treatment. The focus here is to discuss the issues related to the widely used post-weld heat treatment in the design of pressure vessels.
1. Purpose of post-weld heat treatment (stress relief heat treatment)
1. Relaxation welding participates in stress
2. Stabilize the shape and size of the structure and reduce distortion.
3. Improve the performance of the base metal and welding zone, including: a. Improve the plasticity of the weld metal. b. Reduce the hardness of the heat affected zone. c. Improve fracture toughness. d. Improve fatigue strength. e. Restore or increase the yield strength reduced during cold forming.
4. Improve the ability to resist stress corrosion.
5. Further release the harmful gases in the weld metal, especially hydrogen, to prevent the occurrence of delayed cracks. Vacuum heat treatment process and vacuum heat treatment equipment.