4、 Conclusion
1) There is stress concentration in the assembly gap on the root structure of the welded joint, so it is necessary to conduct CTOD test to investigate the fracture toughness of the joint.
2) The test results show that the minimum CTOD value of the weld and heat affected zone is 0.196mm, which is greater than the requirements of 0.125mm in Appendix A of API 1104 and 0.15mm in DNV-OS-C401. The weld itself meets the requirements of Class 1 pressure vessel in JB4730-94 through NDT, so it can be recognized that the welded joint has sufficient fracture toughness value, which is sufficient as the basis for post weld heat treatment free.

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