Bi系Pbレス黄銅の切削加工におけるBiが切削機構に及ぼす影響

抄録

Generally, brass with lead added is called free–cutting brass and is used for various parts such as water supply parts. However, lead is regulated in many countries because it has an adverse effect on the human body. Under regulations, various types of lead–free brass have been developed by copper and copper alloy manufacturers. Among them, lead–free Brass with Bi, which has similar characteristics to Pb, has been developed and put into practical use. It has good machinability and has machinability close to that of free–cutting brass. However, there are still many unclear points such as the difference in cutting mechanism between lead–free Brass with Bi and free–cutting brass and the machinability improvement mechanism. In this study, for the purpose of examining the effect of Bi on machinability in cutting of lead–free Brass with Bi, we performed experiments of turning and two–dimensional cutting about lead–free Brass with Bi and free–cutting brass with Pb. As a result, it was found that Bi in lead–free Brass with Bi has almost the same effect of reducing frictional force and shearing force as Pb. Similar to Pb, the Bi system improves chip fragmentation due to Bi stress concentration in the tissue, and the difference in chip fragmentation from the Pb system may be due to the distribution of Bi particles. In addition, there was a difference in the state of additives between Bi and Pb on the newly formed surface of chip. However, in the lubrication action between the tool and the chips, the difference between Bi and Pb in the elongation of the additive on the new chip surface does not affect the friction reduction effect, and it is considered that a sufficient effect is obtained in Bi as well.