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

A free-cutting copper alloy comprising:

• higher than or equal to 58.5 mass % and lower than or equal to 64.0 mass % of Cu;
• higher than 0.35 mass % and lower than 1.15 mass % of Si;
• higher than or equal to 0.003 mass % and lower than or equal to 0.095 mass % of Pb;
• higher than or equal to 0.12 mass % and lower than or equal to 0.49 mass % of Bi;
• and
• higher than or equal to 0.010 mass % and lower than or equal to 0.15 mass % of P,
• with the balance being Zn and inevitable impurities,
• wherein among the inevitable impurities, the total content of Fe, Mn, Co, and Cr is 0.35 mass % or lower and the total content of Sn and Al is 0.35 mass % or lower,
• when a Cu content is represented by [Cu] mass %, a Si content is represented by [Si] mass %, a Pb content is represented by [Pb] mass %, a Bi content is represented by [Bi] mass %, and a P content is represented by [P] mass %, relationships of
• 56.3≤f1=[Cu]−4.8×[Si]+0.5×[Pb]+0.5×[Bi]−0.5×[P]≤59.5 and
• 0.15≤f2=[Pb]+[Bi]<0.50
• are satisfied,
• in constituent phases of a metallographic structure excluding non-metallic inclusions, when an area ratio of α phase is represented by (α)%, an area ratio of 7 phase is represented by (γ)%, and an area ratio of β phase is represented by (β)%, relationships of
• 28≤f3=(α)≤75,
• 25≤f4=(β)≤72,
• 0≤f5=(γ)<2,
• 10.0≤f6=([Bi]+[Pb])1/2×10+[P]1/2×6+(β)1/2×[Si]1/2×0.8+(γ)1/2×0.5≤16.0, and
• 0.6≤f7=(([Bi]+[Pb])1/2−0.05)×((β)1/2−3)×([Si]1/2−0.2))≤2.4
• are satisfied,
• particles mainly composed of Bi are present in α phase, and
• P-containing compounds are present in β phase.

A free-cutting copper alloy, comprising:

• higher than 57.5 mass % and lower than 64.5 mass % of Cu;
• higher than 0.20 mass % and lower than 1.20 mass % of Si;
• higher than 0.001 mass % and lower than 0.20 mass % of Pb;
• higher than 0.10 mass % and lower than 1.00 mass % of Bi;
• and
• higher than 0.001 mass % and lower than 0.20 mass % of P,
• with the balance being Zn and inevitable impurities,
• wherein among the inevitable impurities, the total content of Fe, Mn, Co, and Cr is lower than 0.45 mass % and the total content of Sn and Al is lower than 0.45 mass %,
• when a Cu content is represented by [Cu] mass %, a Si content is represented by [Si] mass %, a Pb content is represented by [Pb] mass %, a Bi content is represented by [Bi] mass %, and a P content is represented by [P] mass %, relationships of
• 56.3≤f1=[Cu]−4.8×[Si]+0.5×[Pb]+0.5×[Bi]−0.5×[P]≤59.5 and
• 0.12≤f2=[Pb]+[Bi]<1.0
• are satisfied,
• in constituent phases of a metallographic structure excluding non-metallic inclusions, when an area ratio of α phase is represented by (α)%, an area ratio of γ phase is represented by (γ)%, and an area ratio of β phase is represented by (β)%, relationships of
• 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×[Si]1/2×0.8+(γ)1/2×0.5≤18.0, and
• 0.45≤f7=(([Bi]+[Pb])1/2−0.05)×((β)1/2−3)×([Si]1/2−0.2))≤3.6
• are satisfied,
• particles mainly composed of Bi are present in α phase,
• electrical conductivity is 15% IACS or higher and at least tensile strength S (N/mm2) is 430 N/mm2 or higher, and
• f8=S×(100+E)/100 representing the balance between the tensile strength S and elongation E (%) is 580 or higher.

A free-cutting copper alloy comprising:

• higher than or equal to 58.5 mass % and lower than or equal to 64.0 mass % of Cu;
• higher than 0.35 mass % and lower than 1.15 mass % of Si;
• higher than or equal to 0.003 mass % and lower than or equal to 0.095 mass % of Pb;
• higher than or equal to 0.12 mass % and lower than or equal to 0.49 mass % of Bi;
• and
• higher than or equal to 0.010 mass % and lower than or equal to 0.15 mass % of P,
• with the balance being Zn and inevitable impurities,
• wherein among the inevitable impurities, the total content of Fe, Mn, Co, and Cr is 0.35 mass % or lower and the total content of Sn and Al is 0.35 mass % or lower,
• when a Cu content is represented by [Cu] mass %, a Si content is represented by [Si] mass %, a Pb content is represented by [Pb] mass %, a Bi content is represented by [Bi] mass %, and a P content is represented by [P] mass %, relationships of
• 56.3≤f1=[Cu]−4.8×[Si]+0.5×[Pb]+0.5×[Bi]−0.5×[P]≤59.5 and
• 0.15≤f2=[Pb]+[Bi]<0.50
• are satisfied,
• in constituent phases of a metallographic structure excluding non-metallic inclusions, when an area ratio of α phase is represented by (α)%, an area ratio of γ phase is represented by (γ)%, and an area ratio of β phase is represented by (β)%, relationships of
• 28≤f3=(α)≤75,
• 25≤f4=(β)≤72,
• 0≤f5=(γ)<2,
• 10.0≤f6=([Bi]+[Pb])1/2×10+[P]1/2×6+(β)1/2×[Si]1/2×0.8+(γ)1/2×0.5≤16.0, and
• 0.6≤f7=(([Bi]+[Pb])1/2−0.05)×((β)1/2−3)×([Si]1/2−0.2))≤2.4
• are satisfied,
• particles mainly composed of Bi are present in α phase,
• P-containing compounds are present in β phase,
• electrical conductivity is 15% IACS or higher and at least tensile strength S (N/mm2) is 430 N/mm2 or higher, and
• f8=S×(100+E)/100 representing the balance between the tensile strength S and elongation E (%) is 580 or higher.