GB754495A - Improvements in method of an apparatus for hot forging toothed wheels - Google Patents

Abstract

754,495. Forging gear-wheels. BAYERISCHES LEICHTMETALLWERK AKT.- GES. June 30, 1954 [July 1, 1953], No. 19255/54. Classes 83 (2) and 83 (4). In the manufacture of a toothed gear by forging a metal blank 16 between a stationary bottom die 6, a tooth forming matrix 9 and a movable punch 2 which are maintained at a temperature within the range 400-500‹ C., the blank is heated to a temperature near the upper forging temperature limit for the metal and is then placed on the surface of an ejector 12 out of contact with the punch, die and matrix, the punch is then moved quickly to press the blank and cause the metal thereof to flow into the tooth forming spaces 8 of the matrix, and the punch and ejector are then raised, thereby removing the forged blank. The punch and die are made of tungsten steel and have co-operating circular projections 5, 5<SP>1</SP> which form an annular nozzle for the metal flowing radially outwards and give it an increased velocity of flow into the tooth spaces. The matrix which is made of high-grade steel is shrunk into a support-block 11 and has a recess 24 for receiving a spigot portion of the bottom die or for receiving a guide-plate (not shown) for the ejector. The bottom die, punch and matrix are sprayed with castor oil before the forging operation. The punch is shrunk in the body 1 of the press ram which has a central bore 3 which enables the punch to be removed and which may also receive a cooling agent. The matrix is cooled by blowing with cool compressed air. Recesses 14, 21 are provided for excess metal which thus forms fins; the latter may be removed subsequently by turning. The forging is cooled slowly in a bed of hot sand to which small quantities of graphite may be added. The matrix 9 may alternatively be carried by the punch. Working at specified temperatures.-The blank is heated to a temperature within the range 1050-1100‹ C., preferably 1080‹ C., and the tools are maintained at an initial temperature of 400‹ C. Making dies.-The steel matrix 9 is finishetched with the aid of a master bevel gear in which shrinkage is allowed for, and the matrix may also be cold worked to obtain a favourable grain distribution in the metal thereof.