Free-cutting copper alloy and method for manufacturing free-cutting copper alloy

摘要

This free-cutting copper alloy has Cu: more than 57.5% and less than 64.5%, Si: more than 0.20% and less than 1.20%, Pb: more than 0.001% and less than 0.20%, Bi: 0. .10% and less than 1.00%, P: more than 0.001% and less than 0.20%, the balance consists of Zn and unavoidable impurities, and the total amount of Fe, Mn, Co and Cr is less than 0.45%. , Sn, Al is less than 0.45%, and 56.3 ≦ f1 = [Cu] -4.8 × [Si] + 0.5 × [Pb] + 0.5 × [Bi] −0. It has a relationship of 5 × [P] ≦ 59.5 and 0.12 ≦ f2 = [Pb] + [Bi] <1.0, and the constituent phases of the metal structure are 20 ≦ f3 = (α) ≦ 85, 15 ≦ f4 = (β) ≦ 80, 0 ≦ f5 = (γ) <4, 8.5 ≦ f6 = ([Bi] + [Pb]) ^1/2 × 10 + [P] ^1/2 × 6 + (β) ) ^1/2 x [Si] ^1/2 x 0.8 + (γ) ^1/2 x 0.5 ≦ 18.0, 0.45 ≦ f7 = (([Bi] + [Pb]) ^1/2 − A particle having a relationship of 0.05) × ((β) ^1/2 -3) × ([Si] ^1/2 −0.2)) ≦ 3.6 and having Bi as a main component in the α phase. Exists.