Technical requirements for pipe flange forgings (including forged and rolled pieces).
1. The grade and technical requirements of forgings (including forged and rolled pieces) shall meet the corresponding requirements of JB4726-4728.
2. Nominal pressure PN 0.25 MP 1.0 MPa carbon steel and austenitic stainless steel forgings allowed the use of level Ⅰ forgings.
3. In addition to the following provisions, nominal pressure of PN 1.6 MPa to 6.3 MPa forgings shall conform to Ⅱ level or above level Ⅱ forgings levels.
4. In one of the following should accord with the requirement of Ⅲ and forgings: (1) nominal pressure PN acuity 10.0 MPa flange forging;(2) chromium-molybdenum steel forgings with nominal pressure PN>4.0MPa;(3) ferritic steel forgings with nominal pressure PN>1.6MPa and operating temperature ≤-20 ℃.
Butt welding with neck, flat welding with neck, socket welding and threaded flange are generally made by forging or forging rolling process.When steel plate or section steel is used, the following requirements must be met:
1. The steel plate shall be inspected by ultrasonic without stratification defect;
2. It shall be cut into strips along the rolling direction of the steel, and welded into a ring by bending, and make the surface of the steel form a cylinder of the ring.Steel plates shall not be directly machined into flanges with necks;
3. Full penetration weld shall be adopted for the butt weld of the ring;
4. The butt weld of the ring shall undergo post-weld heat treatment and perform 100% X-ray or ultrasonic flaw detection, and the X-ray flaw detection shall meet the class II requirements of JB4730 and the ultrasonic flaw detection shall meet the class I requirements of JB4730.
Post time: Nov-16-2020