Free-cutting copper alloy, and method for producing free-cutting copper alloy
This free-cutting copper alloy contains 76.0%-79.0% Cu, 3.1%-3.6% Si, 0.36%-0.84% Sn, 0.06%-0.14% P, 0.022%-0.10% Pb, with the remainder being made up of Zn and unavoidable impurities. The composition satisfies the following relations: 74.4≤f1=Cu+0.8×Si−8.5×Sn+P+0.5×Pb≤78.2, 61.2≤f2=Cu−4.4×Si−0.7×Sn−P+0.5×Pb≤62.8, 0.09≤f3=P/Sn≤0.35. The area ratio (%) of the constituent phases satisfies the following relations: 30≤κ≤65, 0≤γ≤2.0, 0≤β≤0.3, 0≤μ≤2.0, 96.5≤f4=α+κ, 99.4≤f5=α+κ+γ+μ, 0≤f6=γ+μ≤3.0, 36≤f7=1.05×κ+6×γ 1/2 +0.5×μ≤72. The κ phase is present within the α phase, the long side of the γ phase does not exceed 50 μm, and the long side of the μ phase does not exceed 25 μm.
1. A free-cutting copper alloy worked material that is obtained by performing any one or both of cold working and hot working, the free-cutting copper alloy worked material comprising:
76.0 mass % to 79.0 mass % of Cu;
3.1 mass % to 3.6 mass % of Si;
0.36 mass % to 0.84 mass % of Sn;
0.06 mass % to 0.14 mass % of P;
0.022 mass % to 0.10 mass % of Pb; and
a balance including Zn and inevitable impurities,
wherein a total amount of Fe, Mn, Co, and Cr as the inevitable impurities is lower than 0.08 mass %,
when a Cu content is represented by [Cu] mass %, a Si content is represented by [Si] mass %, a Sn content is represented by [Sn] mass %, a P content is represented by [P] mass %, and a Pb content is represented by [Pb] mass %, the relations of
74.4≤ f 1=[ Cu ]+0.8×[ Si ]−8.5×[ Sn ]+[ P ]+0.5×[ Pb ]≤78.2,
61.2≤ f 2=[ Cu ]−4.4×[ Si ]−0.7×[ Sn ]−[ P ]+0.5×[ Pb ]≤62.8, and
0.09≤ f 3=[ P ]/[ Sn ]≤0.35
are satisfied,
in constituent phases of metallographic structure, when an area ratio of α phase is represented by (α)%, an area ratio of β phase is represented by (β)%, an area ratio of γ phase is represented by (γ)%, an area ratio of κ phase is represented by (κ)%, and an area ratio of μ phase is represented by (μ)%, the relations of
30≤(κ)≤65,
0≤(κ)≤2.0,
0 ≤(β)≤0.3,
0(μ)≤2.0,
96.5 ≤f 4=(α)+(κ),
99.4≤ f 5=(α)+(κ)+(γ)+(μ),
0≤ f 6=(γ)+(μ)≤3.0, and
36≤ f 7=1.05×(κ)+6×(γ) 1/2+ 0.5×(μ)≤72
are satisfied,
κ phase is present in α phase,
a length of a long side of γ phase is 40 μm or less, and
a length of a long side of μ phase is 15 μm or less.
2. The free-cutting copper alloy worked material according to claim 1 , further comprising:
one or more element(s) selected from the group consisting of 0.02 mass % to 0.08 mass % of Sb, 0.02 mass % to 0.08 mass % of As, and 0.02 mass % to 0.20 mass % of Bi.
3. A free-cutting copper alloy worked material that is obtained by performing any one or both of cold working and hot working, the free-cutting copper alloy worked material comprising:
76.5 mass % to 78.7 mass % of Cu;
3.15 mass % to 3.55 mass % of Si;
0.41 mass % to 0.78 mass % of Sn;
0.06 mass % to 0.13 mass % of P;
0.023 mass % to 0.07 mass % of Pb; and
a balance including Zn and inevitable impurities,
wherein a total amount of Fe, Mn, Co, and Cr as the inevitable impurities is lower than 0.08 mass %,
when a Cu content is represented by [Cu] mass %, a Si content is represented by [Si] mass %, a Sn content is represented by [Sn] mass %, a P content is represented by [P] mass %, and a Pb content is represented by [Pb] mass %, the relations of
74.6≤ f 1=[ Cu ]+0.8×[ Si ]−8.5×[ Sn ]+[ P ]+0.5×[ Pb ]≤77.8,
61.42≤ f 2[ Cu ]−4.4×[ Si ]−0.7×[ Sn ]−[ P ]+0.5×[ Pb ]62.6, and
0.1≤ f 3=[ P ]/[ Sn ]≤0.3
are satisfied,
in constituent phases of metallographic structure, when an area ratio of α phase is represented by (α)%, an area ratio of β phase is represented by (β)%, an area ratio of γ phase is represented by (γ)%, an area ratio of κ phase is represented by (κ)%, and an area ratio of μ phase is represented by (μ)%, the relations of
33≤(κ)≤62,
0(γ)≤1.5,
0≤(γ)≤0.2,
0≤(μ)≤1.0,
97.5≤ f 4=(α)+(κ),
99.6 f 5=(α)+(κ)+(κ)+(μ),
0≤ f 6=(γ)+(μ)≤2.0, and
40≤ f 7=1.05×(κ)+6×(γ) 1/2 +0.5×(μ)≤70
are satisfied,
κ phase is present in α phase,
a length of a long side of γ phase is 40 μm or less, and
a length of a long side of μ phase is 15 μm or less.
4. The free-cutting copper alloy worked material according to claim 3 , further comprising:
one or more element(s) selected from the group consisting of 0.02 mass % to 0.07 mass % of Sb, 0.02 mass % to 0.07 mass % of As, and 0.02 mass % to 0.10 mass % of Bi.
5. The free-cutting copper alloy worked material according to claim 1 ,
wherein the amount of Sn in κ phase is 0.40 mass % to 0.85 mass %, and
the amount of P in κ phase is 0.07 mass % to 0.22 mass %.
6. The free-cutting copper alloy worked material according to claim 1 ,
wherein a Charpy impact test value is 12 J/cm 2 to 45 J/cm 2 ,
a tensile strength is 540 N/mm 2 or higher, and
a creep strain after holding the material at 150° C. for 100 hours in a state where a load corresponding to 0.2% proof stress at room temperature is applied is 0.4% or lower.
7. The free-cutting copper alloy worked material according to claim 1 , that is used in a device for water supply, an industrial plumbing member, a device that comes in contact with liquid, or an automobile component that comes in contact with liquid.
8. A method of manufacturing the free-cutting copper alloy worked material according to claim 1 , the method comprising:
any one or both of a cold working step and a hot working step; and
an annealing step that is performed after the cold working step or the hot working step,
wherein in the annealing step, the material is held at a temperature of 510° C. to 575° C. for 20 minutes to 8 hours or is cooled in a temperature range from 575° C. to 510° C. at an average cooling rate of 0.1° C./min to 2.5° C./min, and
subsequently the material is cooled in a temperature range from 470° C. to 380° C. at an average cooling rate of higher than 3° C./min and lower than 500° C./min.
9. A method of manufacturing the free-cutting copper alloy worked material according to claim 1 , the method comprising:
a hot working step,
wherein the material's temperature during hot working is 600° C. to 740° C.,
wherein when hot extrusion is performed as the hot working, the material is cooled in a temperature range from 470° C. to 380° C. at an average cooling rate of higher than 3° C./min and lower than 500° C./min in the process of cooling, and
wherein when hot forging is performed as the hot working, the material is cooled in a temperature range from 575° C. to 510° C. at an average cooling rate of 0.1° C./min to 2.5° C./min and subsequently is cooled in a temperature range from 470° C. to 380° C. at an average cooling rate of higher than 3° C./min and lower than 500° C./min in the process of cooling.
10. A method of manufacturing the free-cutting copper alloy worked material according to claim 1 , the method comprising:
any one or both of a cold working step and a hot working step; and
a low-temperature annealing step that is performed after the cold working step or the hot working step,
wherein in the low-temperature annealing step, conditions are as follows:
the material's temperature is in a range of 240° C. to 350° C.;
the heating time is in a range of 10 minutes to 300 minutes; and
when the material's temperature is represented by T° C. and the heating time is represented by t min, 150≤(T-220)x(t) 1/2 ≤1200 is satisfied.
11. The free-cutting copper alloy worked material according to claim 2 ,
wherein the amount of Sn in κ phase is 0.40 mass % to 0.85 mass %, and
the amount of P in κ phase is 0.07 mass % to 0.22 mass %.
12. The free-cutting copper alloy worked material according to claim 2 ,
wherein a Charpy impact test value is 12 J/cm 2 to 45 J/cm 2 ,
a tensile strength is 540 N/mm 2 or higher, and
a creep strain after holding the material at 150° C. for 100 hours in a state where a load corresponding to 0.2% proof stress at room temperature is applied is 0.4% or lower.
13. The free-cutting copper alloy worked material according to claim 2 , that is used in a device for water supply, an industrial plumbing member, a device that comes in contact with liquid, or an automobile component that comes in contact with liquid.
14. The method of manufacturing a free-cutting copper alloy worked material according to claim 8 ,
wherein the manufactured free-cutting copper alloy worked material further comprises:
one or more element(s) selected from the group consisting of 0.02 mass % to 0.08 mass % of Sb, 0.02 mass % to 0.08 mass % of As, and 0.02 mass % to 0.20 mass % of Bi.
15. The method of manufacturing a free-cutting copper alloy worked material according to claim 9 ,
wherein the manufactured free-cutting copper alloy worked material further comprises:
one or more element(s) selected from the group consisting of 0.02 mass % to 0.08 mass % of Sb, 0.02 mass % to 0.08 mass % of As, and 0.02 mass % to 0.20 mass % of Bi.
16. The method of manufacturing a free-cutting copper alloy worked material according to claim 10 ,
wherein the manufactured free-cutting copper alloy worked material further comprises:
one or more element(s) selected from the group consisting of 0.02 mass % to 0.08 mass % of Sb, 0.02 mass % to 0.08 mass % of As, and 0.02 mass % to 0.20 mass % of Bi.