Manufacturing method of free-cutting copper alloy and free-cutting copper alloy

摘要

The free-cutting copper alloy contains 75.0 to 78.5% of Cu, 2.95 to 3.55% of Si, 0.07 to 0.28% of Sn, 0.06 to 0.14% of P and 0.022 to 0.25% of Pb, Inevitable impurities, the composition satisfying the following relationship, Pb = Cu-4.3 x Si-0.7 x Sn-P + 0.5 x Pb / = 63.3, The area ratio (%) in the composition satisfies the following relationship, ? 25, 0??? 65, 0?? 1.5, 0??? 0.2, 0?? 2.0, 97.0? F3 =? + ?, 99.4? F4 =? +? +? + ?, 0? μ≤2.5, 27≤f6 = κ + 6 × γ 1/2 + 0.5 × μ≤70, the long side of the γ phase is 40 μm or less, the long side of the μ phase is 25 μm or less, and the κ phase is present in the α phase.