First, the level of welding flange and its technical requirements should meet the corresponding requirements of jb4726-4728.
1, the nominal pressure pn for 0.25mp-1.0mpa carbon steel, austenitic stainless steel forgings allow the use of Ⅰ grade forgings.
2, in addition to the following provisions, the nominal pressure pn for 1.6mpa-6.3mpa forgings should meet the Ⅱ level or ⅱ level of the requirements of the forging level.
3, in accordance with the following circumstances, should meet the requirements of Ⅲ and forgings:
(1) The nominal pressure Pn≥10.0mpa flange forgings;
(2) CR-Mo steel forgings with nominal pressure pn>4.0mpa;
(3) Ferritic steel forgings with nominal pressure Pn>1.6mpa and working temperature ≤-20 Celsius.
Second, the welding flange is generally made of forged or forged rolling process. When using steel or steel, the following requirements must be met:
1, butt welding flange should be ultrasonic flaw detection, no delamination defects;
2, should be along the steel rolling direction cut into strips, by bending to weld into a ring, and make the surface of steel to form a ring on the cylinder surface. shall not be machined into a neck butt welding flange by the direct machine of steel plate;
3. The butt weld of the ring should be full penetration weld;
4, the butt weld of the ring should be after welding heat treatment, and for 100% X-ray or ultrasonic flaw detection, and radiographic inspection in line with JB4730 II requirements, ultrasonic flaw detection in line with the JB4730 level I requirements.
Third, the butt welding flange of the lateral slope of the neck should not be less than 7o. Welding flange in the production and welding strict control of technical parameters, to ensure that the production and use of the full play of the role and value.