FREE-CUTTING COPPER ALLOY AND METHOD FOR MANUFACTURING FREE-CUTTING COPPER ALLOY

摘要

A free-cutting copper alloy comprising more than 59.7% but less than 64.7% of Cu, more than 0.60% but less than 1.30% of Si, more than 0.001% but less than 0.20% of Pb, more than 0.001% but less than 0.10% of Bi, and more than 0.001% but less than 0.15% of P, the remaining portion being Zn and unavoidable impurities, wherein the total amount of Fe, Mn, Co, and Cr is less than 0.45%, the total amount of Sn and Al is less than 0.45%, 56.7≤Cu-4.7×Si+0.5×Pb+0.5×Bi-0.5×P≤59.7 and 0.003≤Pb+Bi<0.25 are satisfied, 0.02≤Bi/(Pb+Bi)≤0.98 is satisfied if 0.003≤Pb+Bi<0.08 is satisfied, 0.01≤Bi/(Pb+Bi)≤0.40 or 0.85≤Bi/(Pb+Bi)≤0.98 is satisfied if 0.08≤Pb+Bi<0.13 is satisfied, 0.01≤f3=Bi/(Pb+Bi)≤0.33 is satisfied if 0.13≤Pb+Bi<0.25 is satisfied, the metal structure of the alloy comprises an α phase and a β phase, and 17≤β≤75, 7.0≤(Bi+Pb-0.001)^1/2×10+(P-0.001)^1/2×5+(β-8)^1/2×(Si-0.2)^1/2×1.3≤16.0 are satisfied.