鉛フリー黄銅63Cu–1Si–Znのドリル切削性に及ぼす送りの影響

抄録

In response to a move of enacting lead–restricting regulations in Europe, demand for lead–free, free–cutting brass is growing. Amidst such circumstances, the authors developed a lead–free brass C68370 (63Cu–1Si–0.07P–Z) in 2020 consisting of two phases, alpha and beta phases, and containing Si. In order to examine the machinability of this alloy, the authors compared its behavior when drilled using an NC lathe with that of C3604 and CW510L. The result was that C68370 exhibited magnificent machinability, excelling C3604, particularly when drilled at a high feed. This is indicated by the fine vertical grooves generated over the entire surface of its fan–shaped cutting chips. Further, it was revealed that the required power to cut the new alloy was small, and the surface of the inner wall of drill holes was smooth and good since the chips were less likely to get stuck in the holes. It is considered that this improvement in machinability when drilled at a high feed derives from the superb machinability that C68370’s beta phase has due to an addition of Si, and the precipitates present in the alloy that trigger fragmentation of chips, neither of which CW510L or C3604 has.