GB806387A - Improvements in or relating to the cold working of metal - Google Patents

Abstract

806,387. Making cupped articles; extruding. AMERICAN RADIATOR & STANDARD SANITARY CORPORATION. Feb. 24, 1956, No. 5727/56. Classes 83 (2) and 83 (4). A method of cold forming a cup-shaped steel article 72, Fig. 7, having an internal shoulder 76 and a thin terminal wall 71, comprises backwardly extruding the upper portion of the wall 50 of a cup-shaped blank 47, Fig. 5, to produce the thin wall 71. A disc-shaped blank of up to 0.4 per cent carbon steel, which may be a scrap slug from a punching operation or may be cut from bar stock, is pressed in die cavity 5, Fig. 3, by a punch 16, having a flat or slightly crowned end 20, to form a sized blank 24 of reduced diameter having a concavity 26 caused by radial compression of the metal due to a die shoulder 10 which closes the grain structure of the blank. The latter has an upper flatbottomed recess 21; work-hardening is effected on the flat surface 21 and on the lower side wall of the blank. The latter is ejected by a member 14 and inserted in a second die 29, Fig. 5, where it is backwardly extruded by a nose-ended punch 39 to produce a cup-shaped blank 47 work hardened on its portions 48, 49, 45 and having an upper annular shoulder 53. The blank 47 may be formed in a two-stage operation with intermediate annealing, normalising, pickling, washing and bonderizing. After ejection by a member 37, the blank is drawn through a die 57, Fig. 7, by a punch 65 to first elongate the blank until its shoulder 53 engages an abrupt shoulder 67 on the punch, whereupon the wall of the blank is backwardly extruded between the punch shank 66 and the parallel bore 60 of the die to form the thin wall 71. As the punch shoulder 67 passes through the die bore 60, the backward extrusion changes to drawing and finally the blank 72 passes completely through the bore 60 where the relaxation of compression causes a slight enlargement in diameter which enables the blank to be stripped from the punch, as the latter is withdrawn, by engagement with die shoulder 61. The blank 72 has now been work-hardened on its wall 73. This blank may constitute the finished pressed article or the thin wall 71 may be closed in by a nosing punch 80, Fig. 9. Alternatively, the thin wall may be flanged outwardly to form a flanged member 86, Fig. 16 (not shown). Subsequently, the pressed article may be threaded internally and undercut adjacent its closed end to form a hollow plug, Fig. 15 (not shown). Alternatively, the article may be threaded externally. Annealing or normalising may take place between successive pressing operations and final stress relief heating at 750‹ F. before or after the nosing operation of Fig. 9. Die lubricants are used and the blanks are bonderized or provided with a phosphate coating before each pressing operation.