Welding flanges are not easily deformed, provide good sealing, and are widely used. They meet the requirements for both rigidity and elasticity, with a reasonable transition in wall thinning at the weld. The weld distance from the mating surface is substantial, preventing deformation due to welding temperatures. They adopt a relatively complex trumpet-shaped structure, suitable for pipelines experiencing significant fluctuations in pressure or temperature, as well as for high-temperature, high-pressure, and low-temperature pipelines. Typically used for piping and valve connections with a PN rating above 2.5 MPa; also used in pipelines transporting expensive, flammable, and explosive substances.