Welding flanges are non-deformable, provide good sealing, and have wide applications. They meet the requirements for both rigidity and elasticity, with a reasonable transition in weld thinning. The weld joint is far from the joint surface, preventing deformation due to welding temperature. They feature a complex trumpet-shaped structure, suitable for pipelines with significant fluctuations in pressure or temperature, as well as high-temperature, high-pressure, and low-temperature pipelines. Typically used for pipe and valve connections with PN over 2.5 MPa, and also for pipelines transporting expensive, flammable, and explosive substances.