Butt welding flange is a type of pipe fitting, which refers to a flange with a neck and a round pipe transition and connected to the pipe by butt welding.

Butt welding flange is not easy to deform, has good sealing, is widely used, has corresponding rigidity and elasticity requirements and reasonable butt welding thinning transition, the distance between the welding junction and the joint surface is large, and the joint surface is free from welding temperature deformation. Trumpet-shaped body structure, suitable for pipelines with large fluctuations in pressure or temperature or pipelines with high temperature, high pressure and low temperature, generally used for the connection of pipelines and valves with PN greater than 2.5MPa; also used for transportation of expensive, flammable and explosive on the medium line.

1. The level and technical requirements of butt welding flanges should meet the corresponding requirements of JB4726-4728. 1. Carbon steel and austenitic stainless steel forgings with nominal pressure PN of 0.25MP-1.0MPa are allowed to use grade I forgings. 2. In addition to the following regulations, forgings with a nominal pressure PN of 1.6MPa-6.3MPa should meet the requirements for forgings of Class II or above. 3. Those who meet one of the following conditions shall meet the requirements of III and forgings: (1) Forgings for flanges with nominal pressure PN ≥ 10.0MPa; (2) Chrome-molybdenum steel forgings with nominal pressure PN>4.0MPa; (3) Nominal Ferritic steel forgings with pressure PN>1.6MPa and working temperature ≤-20 degrees Celsius.

2. Butt welding flanges are generally made of forgings or forgings. When it is made of steel plate or section steel, it must meet the following requirements: 1. The butt welding flange shall be ultrasonically inspected, and there shall be no delamination defects; 2. It shall be cut into strips along the rolling direction of the steel, and bent into a ring by butt welding. , and make the surface of the steel form the cylinder of the ring. It is not allowed to use steel plate to directly machine into butt welding flange with neck; 3. The butt weld of the ring should be full penetration weld; 4. The butt weld of the ring should be subjected to post-weld heat treatment and 100% radiation or Ultrasonic flaw detection, and radiographic flaw detection meets the requirements of Class II of JB4730, and ultrasonic flaw detection meets the requirements of Class I of JB4730.

3. The outside slope of the neck of the butt welding flange should not be greater than 70°. Welding flanges strictly control technical parameters during production and welding to ensure that they can fully play their role and value in production and use.