First, the level of welding flange and its technical requirements should be consistent with the corresponding requirements of JB4726-4728.
1, nominal pressure PN of 0.25MP-1.0MPa of carbon steel, austenitic stainless steel forgings allow the use of grade Ⅰ forging. In the case of
2, in addition to the following provisions, the nominal pressure PN 1.6MPa-6.3MPa forging should be consistent with Ⅱ or Ⅱ grade forging level requirements. In the case of
3, meet one of the following circumstances, should meet the requirements of Ⅲ and forgings:
(1) nominal pressure PN ≥10.0MPa flange forging;
(2) nominal pressure PN> 4.0MPa chrome molybdenum steel forgings;
(3) nominal pressure PN> 1.6MPa and the working temperature ≤ 20 degrees Celsius ferritic steel forgings.
Second, the welding flange generally used forging or forging process made. When using steel or profiled steel, must meet the following requirements:
1, butt welding flange should be ultrasonic testing, no stratification defects;
2, should be cut along the direction of steel rolling into strips, the bending of the ring into a ring, and the surface of the steel to form a ring cylinder. Shall not be directly machined with steel plate with a neck welded flange;
3, the ring of the butt weld should be used through the weld;
4, the butt weld of the ring should be post-weld heat treatment, and for 100% ray or ultrasonic testing, and ray detection in line with JB4730 II requirements, ultrasonic testing in line with JB4730 I level requirements.
Third, the butt weld flange outside the slope should not be greater than 7o. The butt welding flange in the production and welding strict control of technical parameters to ensure that the production and use can play a full role and value.