Cold extrusion process to produce enclosing screw ring for steel tank as packing container

During the production of the helicoid, the hem part is formed through cold extrusion in a press, rather than cutting, and this can raise the smoothness of the hem part and result in long service lifeof the enclosing helicoid. The technological process includes blanking and drawing, cutting upper end mouth, leveling flange and chamfering the inner part of the upper end mouth, and extrusion to form hem, and features that drawing the chamber of inner part of the upper mouth replenishes material to the transitional outer part and reaming the hem replenishes material to the lower inner thread part.