Free-machining copper alloys and their manufacturing methods

Abstract

The free-machining copper alloy of the present invention is characterized in that it contains specific amounts of Cu, Si, Pb and P, and contains a specific amount of Bi as an arbitrary element. The remaining portion contains Zn and unavoidable impurities. The total content of Fe, Mn, Co and Cr in the aforementioned unavoidable impurities does not reach a specific amount, and the Al content does not reach a specific amount. The compositional relationship f1 defined by the composition of each element and the microstructure relationship f2, f3 and f4 defined by the area ratio of the constituent phases of the metal microstructure are respectively set within a specific range. When the modified β1 phase is etched in a mixture of hydrogen peroxide and ammonia, grain boundaries can be observed.