2020 Volume 61 Issue 8 Pages 1684-1688
C6932 is a lead-free 75.5Cu–3Si–Zn alloy (hereinafter, “C6932”) which is excellent in machinability, strength, corrosion resistance, hot workability, and castability. C6932 is widely used for water-related products and in automobile and electricity fields, and over 40,000 tons of this alloy is distributed world-wide under the brand name of ECOBRASS®.
In the United States, a law to restrict lead in drinking water was put into force across the nation in 2014. Lead is going to be restricted in Europe also in the automobile field as well as electronic and electrical field. Considering this trend, more free-cutting copper alloys are likely to be free of lead. Concurrently, in the automobile field, for instance, there is a higher demand for improved fuel efficiency by reducing component weight and improved reliability by using components of higher strength.
Based on these backgrounds, we have developed a lead-free, high-strength free-cutting copper alloy by optimizing the composition of a Cu–Si–Zn alloy and controlling its metallographic structure. The developed alloy shows significantly higher strength compared to C6932 without sacrificing its machinability and ductility. The alloy we have developed is a lead-free, high strength free-cutting copper alloy with tensile strength of 650 MPa and an elongation of 43%, which can be realized by annealing a 76.3Cu–3.2Si–0.2Sn–Zn alloy and controlling the grain size to 8 µm.
This Paper was Originally Published in Japanese in J. Japan Inst. Copper 58 (2019) 40–44. Captions of Figures and Tables were slightly modified.
