1. It is allowed to use grade I forgings for carbon steel and austenitic stainless steel forgings with a nominal pressure of PN 0.25MP-1.0MPa.

2. Except for the following provisions, forgings with a nominal pressure of PN 1.6MPa-6.3MPa shall meet the requirements of Class II or Class II forgings.

3. If one of the following conditions is met, it should meet the requirements of III and forgings: (1) flange forgings with a 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 below -20 ℃.

4. The flange is generally made by forging or forging process. When manufacturing steel or section steel, the following requirements must be met:

5. The butt welding of the ring should be full penetration welding.

After the butt welding of the ring, it should undergo heat treatment and undergo 100% radiographic or ultrasonic testing. Radiographic inspection meets the Level II requirements of JB4730. Ultrasonic inspection meets the I requirements of JB4730.

7. The flange should undergo ultrasonic testing and have no delamination defects.

8. The steel should be cut into strips along the rolling direction, bent to form a ring, and the surface of the steel will form a cylindrical shape of the ring. Steel plates shall not be directly processed into welded neck flanges.