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What are the technical requirements for welding neck flange

2022-02-21 14:46:02   COMMENT:0 HITS:
1.The grade and technical requirements of welding neck flange shall meet the corresponding requirements of jb4726-4728.
1. Grade I forgings are allowed for carbon steel and austenitic stainless steel forgings with nominal pressure PN of 0.25mp-1.0mpa.
2. In addition to the following provisions, forgings with nominal pressure PN of 1.6mpa-6.3mpa shall meet the requirements of grade II or above.
3. If one of the following conditions is met, it shall meet the requirements of III and Forgings:
(1) Forgings for flanges with nominal pressure PN ≥ 10.0MPa; (2) Chromium molybdenum steel forgings with nominal pressure PN > 4.0Mpa; (3) Ferritic steel forgings with nominal pressure PN > 1.6Mpa and working temperature ≤ - 20 ℃.
2、 Butt welding flanges are generally made of forgings or forging and rolling process. When made of steel plate or section steel, the following requirements must be met:
1. Butt welding flange shall be subject to ultrasonic flaw detection without delamination defect;
2. The steel shall be cut into strips along the rolling direction, bent and butt welded into a ring, and the surface of the steel shall form the cylindrical surface of the ring. It is not allowed to directly machine the steel plate into a neck butt welding flange;
3. The butt weld of the ring shall be full penetration weld;
4. The butt weld of the ring shall be subject to post weld heat treatment and 100% radiographic or ultrasonic flaw detection. The radiographic flaw detection shall meet the class II requirements of JB4730 and the ultrasonic flaw detection shall meet the class I requirements of JB4730.

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