Free-cutting copper alloy processed material and method for producing free-cutting copper alloy processed material

摘要

This free-cutting copper alloy casting contains 75.0-78.5% Cu, 2.95-3.55% Si, 0.07-0.28% Sn, 0.06-0.14% P, 0.022-0.20% Pb, with the remainder being made up of Zn and unavoidable impurities. The composition satisfies the following relations: 76.2≤f1=Cu+0.8×Si-8.5×Sn+P+0.5×P=0.5×Pb≤80.3, 61.2≤f2=Cu-4.4×Si-0.8×Sn-P+0.5×Pb≤62.8. The area ratios (%) of the constituent phases satisfy the following relations: 25≤κ≤65, 0≤γ≤2.0, 0≤β≤0.3, 0≤µ≤2.0, 96.5≤f3=α+κ, 99.2≤f4=α+κ+γ+µ, 0≤f6=γ+µ≤3.0, 29≤f6=κ+6×γ+0.5×µ≤66. The long side of the γ phase does not exceed 50 pm, the long side of the µ phase does not exceed 25 µm, and the κ phase is present within the α phase.