Patent ID: 11136648

Abstract:
This free-cutting copper alloy contains 76.0%-79.0% Cu, 3.1%-3.6% Si, 0.36%-0.84% Sn, 0.06%-0.14% P, 0.022%-0.10% Pb, with the remainder being made up of Zn and unavoidable impurities. The composition satisfies the following relations: 74.4≤f1=Cu+0.8×Si−8.5×Sn+P+0.5×Pb≤78.2, 61.2≤f2=Cu−4.4×Si−0.7×Sn−P+0.5×Pb≤62.8, 0.09≤f3=P/Sn≤0.35. The area ratio (%) of the constituent phases satisfies the following relations: 30≤κ≤65, 0≤γ≤2.0, 0≤β≤0.3, 0≤μ≤2.0, 96.5≤f4=α+κ, 99.4≤f5=α+κ+γ+μ, 0≤f6=γ+μ≤3.0, 36≤f7=1.05×κ+6×γ1/2+0.5×μ≤72. The κ phase is present within the α phase, the long side of the γ phase does not exceed 50 μm, and the long side of the μ phase does not exceed 25 μm.