Development of lead-free copper alloy graphite castings. Annual report for the period January through December 1996

Abstract

Centrifugal casting of Copper alloys containing graphite particles established the feasibility of making hollow cylindrical castings. In theses castings, the graphite particles are segregated to the inner periphery making them well suited for bearing applications because of the lubricity of the graphite particles. The recovery of graphite is found to be around 90%. Chemical analysis shows that the average concentration of graphite particles near the inner periphery is 13 vol.% (3.5 wt.%) and 16.3 vol.% (4.54 wt.%) for castings made from melts originally containing 7 vol.% (2 wt.%) and 13 vol.% (3.5 wt. %) graphite particles, respectively. Hardness tests show that as the volume fraction of graphite particles increases, the hardness values in the graphite rich zone is found to be widely scattered. The results indicate that it is feasible to centrifugally cast copper alloys containing dispersed graphite particles to produce cylindrical components with graphite rich inner periphery for bearing and plumbing applications.