JP2019007031A - Cu-Ni-Si-BASED COPPER ALLOY - Google Patents

Abstract

To provide a Cu-Ni-Si-based copper alloy having suppressed generation of deformation, while securing Young modulus and flexure processability.SOLUTION: There is provided a Cu-Ni-Si-based copper alloy containing, by mass%, at least one or more kind selected from Ni and Co of 3.0 to 5.0% as total and Si:0.6 to 1.1%, and the balance Cu with inevitable impurities, and having 0.2% bearing force in a rolling parallel direction of 1000 MPa or more, Young modulus in a rolling right angle direction of 115 GPa or more, and MBR/t, which represents flexure processability Badway in the rolling right angle direction at sheet thickness t (mm) with sheet width of 0.2 mm, of 2.5 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a Cu—Ni—Si based copper alloy suitable for conductive spring materials such as connectors, terminals, relays, switches and the like.

  In recent years, miniaturization of electrical / electronic components has progressed, and copper alloys used for these components are required to have high strength, electrical conductivity, and bending workability. In response to this demand, demand for precipitation strengthened copper alloys such as Corson alloys having high strength and conductivity is increasing instead of conventional solid solution strengthened copper alloys such as phosphor bronze and brass. A Corson alloy is an alloy in which an intermetallic compound such as Ni-Si, Co-Si, Ni-Co-Si is precipitated in a Cu matrix, and has high strength, high electrical conductivity, and good bending workability. .

  For example, the connector is composed of a female terminal and a male terminal, and electrical connection is obtained by fitting both terminals. In the electrical contact, the female terminal holds the male terminal by its spring force and obtains a desired contact force. However, if the strength of the female terminal is low, permanent deformation (sagging) occurs in the female terminal when the male terminal is inserted. When the sagging occurs, the contact force at the electrical contact portion decreases and the electrical resistance increases.

  Sag is more likely to occur as the 0.2% proof stress is lower and the Young's modulus is higher. A Cu—Ni—Si based copper alloy having a 0.2% proof stress of 500 MPa or more and an improved spring limit value has been developed (Patent Document 1). Further, Cu—Ni—Si based copper alloys have been developed in which the spring displacement of the connector is increased by setting the 0.2% proof stress to 500 MPa or more and the bending deflection coefficient (Young's modulus) in the rolling direction to 105 GPa or less. (Patent Document 2). Further, a Cu—Ni—Si based copper alloy for an autofocus camera module having a proof stress in the rolling parallel direction of 1000 MPa or more has been developed (Patent Document 3).

JP 2004-131829 A International Publication No. WO2011 / 068134 JP 2017-43789 A

However, in the case of the technique described in Patent Document 2, the sag characteristics when repeated stress is applied are not sufficient. In order to improve the sag characteristics of the copper alloy material, it is effective to increase the yield strength and decrease the Young's modulus. However, when the Young's modulus is lowered, the contact force at the electrical contact portion when the copper alloy material is used as a terminal is lowered. Further, when the proof stress is improved, the bending workability is lowered.
In particular, in the case of the technology described in Patent Document 3, a copper alloy is manufactured by performing low temperature annealing after finish cold rolling following aging treatment. To improve strength while performing low temperature annealing after finish cold rolling, Since it is necessary to perform cold rolling by strong rolling, bending workability may be reduced.

  The present invention has been made to solve the above-mentioned problems, and is a Cu-Ni-Si system that improves strength and Young's modulus, ensures bending workability, and suppresses occurrence of sag (residual strain). The purpose is to provide a copper alloy.

In order to improve the sag characteristics of the Cu—Ni—Si based copper alloy, the present inventor studied to improve the yield strength without reducing the Young's modulus from the viewpoint of suppressing the decrease in contact pressure. In addition, as a method for improving the proof stress, an improvement in the workability can be mentioned, but the bending workability decreases as the strength increases.
Therefore, as a method for improving the yield strength while ensuring the bending workability, a method other than the strong rolling was examined, and attention was paid to low-temperature annealing hardening in strain relief annealing. Low-temperature annealing hardening is a phenomenon in which when rolling strain is introduced into a structure by cold rolling after aging, solid solution elements are fixed to the strain by subsequent strain relief annealing and are strengthened by preventing dislocation. This low-temperature annealing hardening increases the strength of the material and reduces the elongation.

  In the low-temperature annealing hardening, the degree of hardening varies depending on the degree of cold rolling after aging just before strain relief annealing and the degree of precipitation of solid solution elements during the cold rolling. As mentioned above, increasing the workability of cold rolling after aging deteriorates the bending workability, so pay attention to the degree of solid solution element precipitation just before strain relief annealing, and perform heat treatment at a low temperature before strain relief annealing. By defining the relationship between the degree of processing at the time of manufacture and the degree of precipitation (conductivity EC), we succeeded in improving the 0.2% yield strength to 1000 MPa or more.

  In order to achieve the above object, the Cu—Ni—Si based copper alloy of the present invention is, in mass%, at least one selected from the group of Ni and Co in a total amount of 3.0 to 5.0%, Si: 0.6 to 1.1% contained, balance is Cu and inevitable impurities, 0.2% proof stress in the rolling parallel direction is 1000 MPa or more, Young's modulus in the direction perpendicular to the rolling is 115 GPa or more, MBR / t representing the bending workability Badway in the direction perpendicular to the rolling direction at 0.2 mm and a sheet thickness t (mm) is 2.5 or less.

The Cu—Ni—Si based copper alloy of the present invention preferably further contains at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr in a total amount of 0.005 to 1.0 mass%.
The Cu—Ni—Si based copper alloy of the present invention further contains at least one selected from the group of P, B, Ti, Zr, Al, Fe and Ag in a total amount of 0.005 to 1.0 mass%. It is preferable.

  According to the present invention, it is possible to obtain a Cu—Ni—Si based copper alloy that improves the strength and Young's modulus and secures bending workability while suppressing the occurrence of sag (residual strain).

It is a figure which shows the correlation with the electrical conductivity before strain relief annealing, and the processing rate RE of cold rolling after aging. It is a figure which shows the measuring method of a drooping characteristic.

  Hereinafter, the Cu—Ni—Si based copper alloy according to the embodiment of the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

(composition)
[Ni, Co and Si]
The total amount of at least one selected from the group of Ni and Co in the copper alloy is 3.0 to 5.0%, and Si: 0.6 to 1.1%. Ni, Co, and Si form an intermetallic compound by performing an appropriate heat treatment, and improve strength without deteriorating conductivity.
When the content of Ni, Co and Si is less than the above range, the effect of improving the strength cannot be obtained, and when the content exceeds the above range, the electrical conductivity is lowered and the hot workability is lowered.
Moreover, since a large amount of solid solution elements are required to develop the above-described low-temperature annealing hardening, the contents of Ni (Co) and Si are increased in the present invention.

[Other additive elements]
The alloy may further contain 0.005 to 1.0% by mass in total of at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr.
Mg improves strength and stress relaxation resistance. Mn improves strength and hot workability. Sn improves the strength. Zn improves the heat resistance of the solder joint. Since Cr forms a compound with Si like Ni, it improves the strength without deteriorating conductivity by precipitation hardening.
Further, the alloy may further contain at least one selected from the group consisting of P, B, Ti, Zr, Al, Fe and Ag in a total amount of 0.005 to 1.0% by mass. When these elements are contained, product characteristics such as conductivity, strength, stress relaxation characteristics, and plating properties are improved.
In addition, when the total amount of each element described above is less than the above range, the above effect cannot be obtained, and when it exceeds the above range, the conductivity may be lowered.

[0.2% yield strength]
The 0.2% proof stress YS of the Cu—Ni—Si based copper alloy in the rolling parallel direction and the direction perpendicular to the rolling is 1000 MPa or more. When YS is 1000 MPa or more, the sag characteristics, particularly the sag characteristics when repeated stress is applied, are improved. The upper limit of YS is, for example, 1300 MPa.
YS is obtained by a tensile test according to JIS-Z2241.

[Bending workability]
As a bending workability, when a W-bending test is performed so that the bending axis is parallel to the rolling direction when the sheet width is 0.2 mm (bending workability Badway in the direction perpendicular to the rolling direction), the minimum bending radius (where no crack occurs) The ratio (MBR / t) of MBR (mm)) to the plate thickness (t (mm)) is 2.5 or less. Good bendability can be secured when (MBR / t) is 2.5 or less. The lower limit of (MBR / t) is not limited, but is, for example, 1.0.
(MBR / t) is a W-bend test in Badway (the direction perpendicular to rolling) according to JIS-H3130, and measures the minimum radius (MBR) at which no cracks occur with respect to the plate thickness (t). The test piece was strip-shaped with a width of 0.2 mm and a length of 30 mm.
[Young's modulus]
The Young's modulus in the direction perpendicular to the rolling of the Cu—Ni—Si based copper alloy is 115 GPa or more. When the Young's modulus is 115 GPa or more, the contact pressure is improved. The upper limit of the Young's modulus is not limited, but is 140 GPa, for example.
The Young's modulus is measured according to the Japan Copper and Brass Association (JACBA) technical standard “Method of measuring bending deflection coefficient by cantilever of copper and copper alloy strip JCBA T312: 2002”. However, the technical standard is also used when it is different from the thickness of the application range of the technical standard.
The sample has a strip shape with a plate thickness t (mm), a width w (= 10 mm), and a length of 100 mm, and the longitudinal direction of the sample is the direction perpendicular to the rolling. One end of this sample is fixed, a load of P (= 0.15 N) is applied to a position L (= 100 t) from the fixed end, and the Young's modulus E is obtained from the deflection d at this time using the following equation.
E = 4 × P × (L / t) ³ / (w × d)

<Manufacturing method>
The Cu—Ni—Si based copper alloy of the present invention is usually produced by performing ingot in the order of hot rolling, cold rolling, solution treatment, aging treatment, low temperature heat treatment, cold rolling after aging, and strain relief annealing. can do. Cold rolling and recrystallization annealing before solution treatment are not essential, and may be performed as necessary.

<Cold rolling after aging>
In order to improve the strength (0.2% proof stress) of the Cu—Ni—Si based copper alloy, it is important to improve the strength by strain relief annealing, which is the final annealing. For this purpose, it is necessary to increase the processing rate of post-aging cold rolling immediately before strain relief annealing and increase the amount of solid solution elements (Ni (Co) and Si) immediately before strain relief annealing. This is because when a rolling strain is introduced into the structure by cold rolling after aging, a mechanism (low temperature annealing hardening) in which solid solution elements are fixed to this strain and strengthened as dislocation obstacles by subsequent strain relief annealing. This is to cause it to occur.

In order to develop the low temperature annealing hardening, the post-aging cold rolling processing rate RE is set to 70% or more and less than 90%, and the post-aging cold rolling processing rate RE is represented by the formula (1): Re ≧ −0.3074. It is preferable to satisfy (EC) 2 + 15.06EC-86.549. EC (% IACS) is the electrical conductivity before strain relief annealing (after aging and after cold rolling).
When the processing rate RE is less than 70%, the low-temperature annealing hardening is insufficient and the 0.2% yield strength is less than 1000 MPa. If the processing rate RE is 90% or more, the bending workability deteriorates.
The processing rate RE is the rate (%) of change in the plate thickness of the alloy before and after cold rolling after aging.

Moreover, since the minimum processing rate required also changes with the degree of precipitation strengthening (solid solution) of the alloy at the time of cold rolling after aging, it is necessary to set a processing rate according to the degree of solid solution. Then, as the degree of this solid solution, the electrical conductivity EC (% IACS) in the direction perpendicular to the rolling direction after cold rolling after aging and before strain relief annealing is used as an index, and it is necessary in the formula (1) calculated from the electrical conductivity. By defining the processing rate, the strength of the alloy can be stably improved.
Here, by setting the above-described conductivity EC (% IACS) to 30% or more and less than 40%, the conditions for aging treatment and strain relief annealing are both appropriate, and the strength increases in both treatments, resulting in high strength. Is obtained. When the electrical conductivity EC is 40% or more, the strength increases by aging treatment, but the amount of solid solution decreases, so even if the processing rate RE is increased, the strength is not sufficiently increased by strain relief annealing, and the desired strength is increased. It may not be obtained. On the other hand, if the electrical conductivity EC is less than 30%, the strength is increased by strain relief annealing, but the strength is not increased by the aging treatment, and a desired strength may not be obtained.
Note that the electrical conductivity EC (% IACS) of the final product after strain relief annealing is about 30 to 40%.

And, as the electrical conductivity EC before strain relief annealing is lower, the increase in strength due to the aging treatment is smaller. Therefore, unless the processing rate RE is increased and a larger number of rolling strains are introduced, the required strength cannot be improved. Therefore, it is preferable to set the processing rate RE so as to satisfy the formula (1): Re ≧ −0.3074 × (EC) ² + 15.06 × EC−86.549. This equation (1) is obtained from a prior experiment as shown in Table 1 and FIG.

In this preliminary experiment, an ingot having a composition shown in Table 1 was subjected to hot rolling, cold rolling, solution treatment, aging treatment, low temperature heat treatment, cold rolling after aging, and strain relief annealing in the order of 0.05 mm thickness. The samples were manufactured and their characteristics were evaluated. Hot rolling was performed at 1000 ° C. for 3 hours, and solution treatment was performed at 800 to 1000 ° C. The aging treatment was performed at 400 ° C. to 550 ° C. for 1 to 15 hours.
The low-temperature heat treatment was performed in the range of 550 to 650 ° C., and the heating time was adjusted in the range of 1 to 250 seconds so that ΔEC described later was 2.0%. Then, prior experiments 1 to 7 were performed by changing the electrical conductivity EC before strain relief annealing and the processing rate RE of cold rolling after aging as shown in Table 1.

Next, the relationship between the processing rate RE and the electrical conductivity EC shown in Table 1 is plotted in FIG. 1, and each plot is passed by the least square method for Experiments 1 to 3 in which the 0.2% proof stress YS is 1000 MPa or more. A quadratic curve was obtained to obtain equation (1).
On the other hand, in Experiments 6 and 7, the 0.2% yield strength YS was less than 1000 MPa, and the RE was lower than that in the formula (1). Experiments 5 and 8 are on the formula (1) or in a region where the RE is higher than that of the formula (1), but the experiment 5 has a processing rate RE of less than 70% and a 0.2% proof stress YS of less than 1000 MPa. In No. 8, the processing rate RE was 90% or more, and the bending workability deteriorated.
In Experiment 4, the processing rate RE was approximately the same (70%) as in Experiment 1, the conductivity EC was increased, and the 0.2% proof stress YS was 1000 MPa or more. Experiment 4 is data for indicating that a region where the RE is higher than that of the formula (1) is a preferable range of the present invention.
From the above results, in order to achieve the target of 0.2% proof stress and bending workability, it is necessary to set the working rate RE of the cold rolling after aging to a condition satisfying the formula (1) by 70% or more and less than 90%. is there.

  When the processing rate RE does not satisfy the formula (1), the processing rate RE is too small with respect to the strength after the aging treatment, and the required strength may not be improved.

<Low temperature heat treatment>
Further, low-temperature heat treatment is performed in order to increase the amount of dissolved elements immediately before the strain relief annealing. The low-temperature heat treatment is performed at a temperature below the initial solution temperature and above the aging temperature. In the low-temperature heat treatment, the solid solution element precipitated by the aging treatment is again dissolved in the matrix, so that the amount of the solid solution element immediately before the strain relief annealing increases.
Then, as an index representing the amount of the solid solution element immediately before the strain relief annealing, the change amount ΔEC of the conductivity after the aging treatment (that is, before the low temperature heat treatment) and after the low temperature heat treatment is used. ΔEC = (conductivity after aging treatment) − (conductivity after low-temperature heat treatment). Low temperature heat treatment is performed at 550 to 800 ° C. for 1 to 250 seconds so that ΔEC = 2 to 4% (IACS).
If the amount of the solid solution element is increased by the low-temperature heat treatment immediately before the strain relief annealing as compared with that after the aging treatment, the conductivity is lowered.

When ΔEC is less than 2% IACS, it indicates that the amount of solid solution elements in the material after low-temperature heat treatment (before strain relief annealing) is small. When the amount of the solid solution element is small during the strain relief annealing, the amount of the solid solution element fixed to the dislocation by the strain relief annealing is reduced, and the degree of curing in the low temperature annealing hardening is reduced or is not cured.
When ΔEC exceeds 4% IACS, it indicates that the amount of the solid solution element in the material is too large after the low-temperature heat treatment (before strain relief annealing). For this reason, the degree of hardening in low-temperature annealing hardening at the time of strain relief annealing increases too much, and the 0.2% proof stress of the material after strain relief annealing decreases due to an increase in solid solution elements that do not contribute to strength.

  Further, the electrical conductivity EC (% IACS) before strain relief annealing is set to 30% to less than 40%. The reason for this is as already described.

<Strain relief annealing>
Thereafter, strain relief annealing is performed at 200 to 500 ° C. for 1 to 1000 seconds. When the temperature or annealing time of the strain relief annealing is less than the above range, the strain relief annealing is insufficient, the strength is improved by the low-temperature annealing hardening described above, and the softening by heating after the stress relief annealing is insufficient. It is difficult to make the 2% proof stress 1000 MPa or more.
When the temperature or annealing time of strain relief annealing exceeds the above range, the above-described low temperature annealing hardening by strain relief annealing becomes excessive, the alloy is softened, and the strength (0.2% proof stress) cannot be improved.

The electrolytic copper was melted in an atmospheric melting furnace, and a predetermined amount of the additive elements shown in Table 2 was added as necessary, and the molten metal was stirred. Thereafter, the molten metal was poured into a mold at a casting temperature of 1200 ° C. to obtain a copper alloy ingot having the composition shown in Table 2. The ingot was hot rolled to a plate thickness of 10 mm. Thereafter, chamfering, cold rolling, solution treatment, aging treatment, low temperature heat treatment, and cold rolling after aging were performed in this order to obtain a sample having a thickness of 0.05 to 0.4 mm. After cold rolling after aging, strain relief annealing was performed.
In addition, hot rolling was performed at 1000 degreeC for 3 hours, and the solution treatment was performed at 800-1000 degreeC. The aging treatment was performed at 400 to 550 ° C. for 1 to 15 hours, the low temperature heat treatment was performed at 650 ° C., and the strain relief annealing was performed at 200 to 500 ° C. for 1 to 1000 seconds. The aging treatment and the strain relief annealing were performed at a temperature and a time at which the tensile strength after each treatment was maximized.

<Evaluation>
The following items were evaluated for the obtained samples.
[conductivity]
Volume resistance obtained by a four-terminal method using a double bridge apparatus in accordance with JISH0505 for samples in the rolling parallel direction after aging treatment and after low-temperature heat treatment, and samples in the rolling parallel direction of the final product after strain relief annealing. The electrical conductivity (% IACS) was calculated from the rate.
[Strength]
About the final product after strain relief annealing, the JIS13B test piece was produced using the press so that the tension direction might become parallel to the rolling direction. The specimen was subjected to a tensile test according to JIS-Z2241, and 0.2% yield strength YS was measured.
The tensile test conditions were a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, a gauge length L = 50 mm, and a tensile test in the rolling direction of the copper foil.

[Bending workability]
(MBR / t) was measured by the method described above for a test material having a plate width of 0.2 mm.
[Young's modulus]
Measurement was performed by the method described above.
[Sag characteristics]
As shown in FIG. 2, one end of a strip-shaped sample having a width of 12.7 mm was fixed to form a horizontal cantilever. A punch whose tip was processed into a knife edge was pressed to a position at a distance L = 5 mm from the fixed end to give a downward deflection d (mm), and then the punch was returned to the initial position and unloaded. The moving speed of the punch was 1 mm / min. The sag δ, which was permanently deformed in the vertical direction after unloading, was determined. If the 0.2% proof stress is 1000 MPa or more, the amount of sag is less than 0.025 mm. The sag characteristics were measured in the direction parallel to the rolling and the direction perpendicular to the rolling, and the value with the larger sag amount was adopted.
The deflection d (mm) is performed so that the deflection (mm) / plate thickness (mm) = 100.

  The obtained results are shown in Tables 2 and 3. “0.5Zn” in Table 2 means that 0.5% by mass of Zn is contained.

  As is clear from Tables 2 and 3, in each Example in which YS was 1000 MPa or more and Young's modulus was 115 GPa or more, the bending workability and sag characteristics were excellent.

On the other hand, in Comparative Example 1 in which ΔEC was less than 2% IACS, the 0.2% proof stress in the rolling parallel direction was less than 1000 MPa, the Young's modulus was less than 115 GPa, and the sag characteristics were inferior. This is thought to be due to insufficient low-temperature annealing hardening.
In the case of Comparative Example 2 in which the low-temperature heat treatment was excessively performed and ΔEC exceeded 4% IACS, the 0.2% proof stress in the rolling parallel direction was less than 1000 MPa, the Young's modulus was less than 115 GPa, and the sag characteristics were inferior.

  In the case of Comparative Example 3 in which the electrical conductivity before strain relief annealing exceeded 40%, low-temperature annealing hardening did not appear, 0.2% proof stress in the rolling parallel direction was less than 1000 MPa, and Young's modulus was less than 115 GPa. The characteristics were inferior.

In the case of Comparative Example 4 in which the processing rate RE does not satisfy the formula (1), low temperature annealing hardening does not occur, the 0.2% proof stress in the rolling parallel direction is less than 1000 MPa, and the Young's modulus is less than 115 GPa. The characteristics were inferior.
On the other hand, in the case of Comparative Example 5 in which the processing rate RE before strain relief annealing was 90% or more, the sag characteristics were good, but the bendability was inferior.

In the case of Comparative Example 6 in which ΔEC exceeds 4%, the electrical conductivity before strain relief annealing is less than 30%, and the processing rate RE does not satisfy the formula (1), sufficient strength increase due to low-temperature annealing hardening cannot be obtained, The setting characteristics were inferior.
In the case of Comparative Example 7 in which ΔEC is less than 2% and the electrical conductivity before strain relief annealing exceeds 40%, and Comparative Example 8 in which ΔEC is less than 2% and the processing rate RE is less than 70%, both are low-temperature annealing. Hardness was insufficient, strength was not improved, and sag characteristics were inferior.
In the case of Comparative Example 9 in which the electrical conductivity before strain relief annealing exceeds 40% and the processing rate RE is less than 70%, the low-temperature annealing hardness is insufficient, the strength is not improved, and the sag characteristics are inferior.

  In the case of Comparative Example 10 containing Mg, Mn, Sn, Zn, Co, and Cr in a total amount exceeding 1.0%, cracking occurred during hot rolling, and the alloy could not be manufactured.

  In the case of Comparative Example 11 in which the total content of Ni and Co is less than 3.0%, the degree of precipitation strengthening is small, precipitation strengthening by these elements becomes insufficient, sufficient strength cannot be obtained, and sag characteristics are obtained. inferior.

Reference Example 1 simulates Example (1) of Patent Document 3, performs slab heating 1030 ° C. × 3 h, hot rolling and cold rolling, and then performs a solution treatment (solution treatment) 1000 ° C. × 1 h. , Pretreatment of aging treatment is 700 ° C. × 20 sec, aging treatment is 375 ° C. × 7 h (ECage / ECmax: 0.68), post-aging cold rolling is performed 90% and low temperature annealing is performed at 375 ° C. × 120 sec. did.
The low temperature annealing of Reference Example 1 is different from the embodiment of the present invention in the range of low temperature heat treatment and cold rolling after aging, and the degree of work of cold rolling after aging has increased to 90% or more. The 2% yield strength was 1000 MPa or more and the Young's modulus was 115 GPa or more, but the bendability was inferior.

Claims (3)

Containing at least one or more selected from the group of Ni and Co by mass% in a total amount of 3.0 to 5.0%, Si: 0.6 to 1.1%, the balance consisting of Cu and inevitable impurities,
The bending workability Badway in the direction perpendicular to the rolling when the 0.2% proof stress in the rolling parallel direction is 1000 MPa or more, the Young's modulus in the direction perpendicular to the rolling is 115 GPa or more, the sheet width is 0.2 mm, and the sheet thickness is t (mm). A Cu—Ni—Si based copper alloy having an MBR / t of 2.5 or less.   Furthermore, the Cu-Ni-Si type | system | group copper alloy of Claim 1 which contains 0.005-1.0 mass% of at least 1 sort (s) chosen from the group of Mg, Mn, Sn, Zn, and Cr in a total amount.   Furthermore, Cu-Ni-Si of Claim 1 or 2 which contains at least 1 sort (s) chosen from the group of P, B, Ti, Zr, Al, Fe, and Ag by 0.005-1.0 mass% in total amount. Copper alloy.

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