Development of a Powder Metallurgical Self Cooling Forging Die with Inner Cavities

Abstract

Powder metallurgy is known for its high potential for producing near net-shape products. A material utilization of up to 95%, paired with comparably low energy costs, allows powder metallurgy to fulfil the requirements of modern manufacturing processes. By combining different powders, a wide range of products can be manufactured. An innovative powder metallurgical method currently being investigated at the Institute of Forming Technology and Machines (IFUM) within the subproject E3 of the Collaborative Research Centre 653 is the generation of controlled cavities inside a sintered part. For this purpose, a foreign element with a lower melting point than the base powder is embedded inside the green body. Depending on the sintering temperature, the foreign element can be firmly bonded with or melted out of the base powder, creating a defined cavity. Being attached to an external cooling system, the cavity can be applied as a closed circuit for circulating a cooling medium within the tool. The approach in this work is the development of a sintered forging die, equipped with an active temperature regulation which can react autonomously to process variations. The cooling temperature is controlled by measuring the operating temperature within the forging die. For measuring purposes, the cavities can also be used for integrating temperature sensors. The main aspect of these studies is the characterization of the compaction and melting behavior of the foreign material. Since the location of the foreign element within the base powder can differ due to the pressing force, the prediction of its final position based on the initial position and the process conditions is of high importance. For this aim, numerical simulations are employed to develop an optimized cooling layout. A numerical model is used to describe the compaction behaviour of the powder as an elastoplastic compressible continuum and its interdependency with the integrated elements. The studies also cover the influence of surface contours of the foreign elements (corrugated, plain) on their melting behavior as well as the resulting inner surface of the cooling channel.