HOLLOW PRODUCT MANUFACTURING METHOD Russian patent published in 1994 - IPC

FIELD: plastic working of metals. SUBSTANCE: method involves producing tube billet with section area less than maximum section area of forging part adjacent hexagonal part by 15-20%; locating billet in die with hexagonal and cylindrical surfaces; drop forging for one pass by punch with conical outer surface; preliminary forming of hexagon and inner surface by expansion combined with upsetting; final forming of hexagon, outer cylindrical and inner surfaces by extrusion with simultaneous conveyance of metal adjacent hexagon in radial direction towards outer surface. EFFECT: reduced metal usage and improved quality of products. 3 dwg, 2 tbl