Weld neck flanges are resistant to deformation, provide good sealing, and have wide applications. They meet the requirements for both rigidity and elasticity and feature a reasonable weld thinning transition. The weld joint is far from the mating surface, ensuring the mating surface is not deformed by welding temperatures. They adopt a more 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. Generally used for pipeline and valve connections with PN greater than 2.5 MPa; also used in pipelines for transporting expensive, flammable, and explosive media.