2020 Volume 59 Issue 1 Pages 314-318
Review of End–of Life Vehicles Directive and Restriction of Hazardous Substances Directive was postponed to July 2021, and discussion is ongoing in each of the relevant industries as to whether further postponement is necessary. Assuming that C6932, a lead–free, Cu–Zn–Si copper alloy, will be used for small components in the automobile, electronic, and electric fields, we have examined machinability of the alloy when drilling small holes of 1.0 mm in diameter and 10 mm in depth. And, we have confirmed that 10000 holes can be continuously drilled with a carbide drill available in the market by adjusting drilling speed to 94 m/min, feed rate to 0.1 mm/rev, and drilling depth per stroke to 2.0 mm.
Thin rods are manufactured by a repeated process of annealing and drawing. We have studied the influence of annealing on drilling small holes of 1.0 mm in diameter and 10 mm in depth in C6932 materials to find out whether drilling such small holes in an annealed material was possible, the results of which are reported in this paper. It was able to drill 10000 small holes continuously both in a simply extruded material and an extruded and annealed material. Gamma phase is eliminated in the course of annealing, which causes stress concentration sources to reduce. If stress concentration sources are reduced, cutting chips become less brittle, and eventually, they become slightly larger. However, they do not turn into a kind of mass which may cause the thrust resistance to rise, i.e., the influence of annealing is not to the extent that dischargeability of cutting chips is seriously affected, and an addition of annealing process does not cause deterioration in machinability when drilling small holes.
We believe that application of C6932 can be well expanded to small components which include drilling small holes in their production process.
