Powder forging of high-strength brass and its application to automobile parts

Abstract

This paper deals with the work — from basic technical experimentation through to application to automobile parts — which was carried out in connection with the development of a new powder-forging process using high-strength brass machining swarf. Powder forging techniques were used to successfully consolidate the high-strength brass powder, which cannot be sintered easily because of the presence of aluminium in the brass. The compacted preform, of simple shape, is hot-forged to produce a complicated shell, with large metal flow. Powder particles are consolidated to provide a solid product by mutual adhesion under high compressive force and high temperature, where the large metal flow compensates for the poor sinterability of the material. The brass powder was produced by pulverizing machining swarf from expensive high-strength brass containing Al and Mn, the swarf price of which is the cheapest amongst that of all kinds of brass. The size of this powder is not necessarily as fine as that of conventional metal powder for sintering. Mechanical properties of hot-forged products — such as strength and wear resistance — were confirmed to be almost equal to those of wrought high-strength brass. An automobile transmission part was manufactured experimentally by this process and passed a comprehensive range of performance tests without any trouble. Further, the cost of the forged part was found to be only 74% of that of the current component, due to drastic reduction in material cost. The production of a transmission thrust washer will now be changed from the present conventional forging to powder forging.