US 11,814,712 B2
Free-cutting copper alloy and method for producing free-cutting copper alloy
Keiichiro Oishi, Sakai (JP); Kouichi Suzaki, Sakai (JP); and Hiroki Goto, Sakai (JP)
Assigned to MITSUBISHI MATERIALS CORPORATION, Tokyo (JP)
Appl. No. 17/611,195
Filed by MITSUBISHI MATERIALS CORPORATION, Tokyo (JP)
PCT Filed Mar. 16, 2020, PCT No. PCT/JP2020/011343
§ 371(c)(1), (2) Date Nov. 15, 2021,
PCT Pub. No. WO2020/261666, PCT Pub. Date Dec. 30, 2020.
Claims priority of application No. 2019-116914 (JP), filed on Jun. 25, 2019; application No. 2019-130143 (JP), filed on Jul. 12, 2019; application No. 2019-141096 (JP), filed on Jul. 31, 2019; application No. 2019-163773 (JP), filed on Sep. 9, 2019; application No. PCT/JP2019/048438 (WO), filed on Dec. 11, 2019; and application No. PCT/JP2019/048455 (WO), filed on Dec. 11, 2019.
Prior Publication US 2022/0259711 A1, Aug. 18, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 9/04 (2006.01); C21D 9/00 (2006.01); C22F 1/08 (2006.01)
CPC C22C 9/04 (2013.01) [C21D 9/00 (2013.01); C22F 1/08 (2013.01)] 21 Claims
OG exemplary drawing
 
1. 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 a 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, and
particles mainly composed of Bi are present in a phase.