The heavy welding neck flanges

　　The heavy welding neck flanges are also named heavy WN flanges, which are hot formed from a circular section of steel plate having a very small co-axial hole in the flange center. The steel around the hole is shear-formed downward and outward by a tapered die plug which is forced by the small hole forming an integral neck on the weld neck flange. A supporting ring die is radiused at its inner corner to form a suitable fillet radius at the junction of the neck with the flange proper. A suitable pre-forming or post-forming operation may be required to compensate for any deflection in the work piece out of planar configuration.