US 11,788,173 B2
Free-cutting copper alloy, and manufacturing method of 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. 17/436,667
Filed by MITSUBISHI MATERIALS CORPORATION, Tokyo (JP)
PCT Filed Dec. 23, 2019, PCT No. PCT/JP2019/050255
§ 371(c)(1), (2) Date Sep. 7, 2021,
PCT Pub. No. WO2020/261611, 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; and application No. 2019-163773 (JP), filed on Sep. 9, 2019.
Prior Publication US 2022/0186352 A1, Jun. 16, 2022
Int. Cl. C22C 9/04 (2006.01); C21D 9/00 (2006.01); C22F 1/08 (2006.01); B22D 21/00 (2006.01); C22C 9/10 (2006.01)
CPC C22C 9/04 (2013.01) [B22D 21/00 (2013.01); C21D 9/00 (2013.01); C22C 9/10 (2013.01); C22F 1/08 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A free-cutting copper alloy comprising:
higher than 58.0 mass % and lower than 65.0 mass % of Cu;
higher than 0.30 mass % and lower than 1.30 mass % of Si;
higher than 0.001 mass % and lower than or equal to 0.20 mass % of Pb;
higher than 0.020 mass % and lower than or equal to 0.10 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, a total content of Fe, Mn, Co, and Cr is lower than 0.45 mass % and a 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
56.5≤f1=[Cu]−4.7×[Si]+0.5×[Pb]+0.5×[Bi]−0.5×[P]≤59.5 and
0.025≤f2=[Pb]+[Bi]<0.25
are satisfied,
a metallographic structure contains α phase and β phase,
in constituent phases of the metallographic structure excluding non-metallic inclusions that are intermetallic compounds, precipitates, oxides, and sulfides, 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≤(α)<85,
15<(β)≤80,
0≤(γ)<5,
8.0≤([Bi]+[Pb]−0.002)1/2×10+([P]−0.001)1/2×5+((β)−7)1/2×([Si]−0.1)1/2×1.2+(γ)1/2×0.5≤17.0 and
0.9≤([Bi]+[Pb]−0.002)1/2×((β)−7)1/2×([Si]−0.1)1/2≤4.0
are satisfied, and
a particle containing Bi is present in the α phase.