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.