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

摘要

This free-cutting copper alloy has Cu: more than 77.0% and less than 81.0%, Si: more than 3.4% and less than 4.1%, Sn: 0.07% to 0.28%, P: 0.00. 06% to 0.14%, and Pb: more than 0.02% and less than 0.25%, the balance is made of Zn and inevitable impurities, and the composition satisfies the following relationship: 1.0 ≦ f0 = 100 × Sn /(Cu+Si+0.5×Pb+0.5×P−75.5)≦3.7, 78.5 ≦ f1 = Cu + 0.8 × Si−8.5 × Sn + P + 0.5 × Pb ≦ 83.0, 61.8 ≦ f2 = Cu−4.2 × Si−0.5 × Sn−2 × P ≦ 63.7, the area ratio (%) of the constituent phases satisfies the following relationship: 36 ≦ κ ≦ 72, 0 ≦ γ ≦ 2.0, 0 ≦ β ≦ 0.5, 0 ≦ μ ≦ 2.0, 96.5 ≦ f3 = α + κ, 99.4 ≦ f4 = α + κ + γ + μ, 0 ≦ f5 = γ + μ ≦ 3.0, 38 f6 = κ + 6 × γ1 / 2 + 0.5 × μ ≦ 80, the long sides of the γ phase is not more 50μm or less, the long side of the mu phase is 25μm or less.