Isothermal Forging of Large Gears by P/M Techniques

The objective of this program was to extend the development of isothermal forging of steel powder parts to near-net shapes with plan areas larger than 100 square inches .0645 sq. m.. Previously, it had been determined that the application of isothermal forging to near-net shape parts production reduces the forging pressure needed to achieve both full density and a completely filled die cavity. Thus, larger parts may be forged with existing equipment. The prototype component in this project was the final drive gear of the M60 tank PN 19207-7364141. This gear has an outside diameter of 19.4 inches .493 sq. m. and a plan area of 296 square inches .191 sq. m.. The 66 teeth were to be forged to shape, allowing 0.005 to 0.010 inches .00013 to . 00025 sq. m. per tooth face for grinding and crowning after carburizing. Prealloyed 4600 grade steel powder was to be used. Based on the finished part dimensions, a forging was designed, a hot die set for isothermal forging was designed, and a segmented preform and compaction tooling were designed. At this point quotations from tool builders indicated serious cost and time overruns. Coupling these problems with lubricationdie release problems experienced in a sister program, a decision was made to halt this program until such problems were overcome or a suitable redirection option could be formulated. This report covers the design steps completed on the program, the tooling quotations, alternative action possibilities, and concludes with a recommendation for redirection.