JP5153949B1 - Cu-Zn-Sn-Ni-P alloy - Google Patents

Abstract

The purpose of the present invention is to provide a Cu-Zn-Sn-Ni-P-based alloy which contains Zn, which is a raw material cheaper than Cu or Ni, in an amount of 3 mass% or more, in which Sn is allowed to be contained in a copper scrap, and which can be produced at a low cost, has excellent strength, bendability and stress relaxation resistance properties and also has low anisotropy. For achieving the purpose, a Cu-Zn-Sn-Ni-P-based alloy is produced, which contains, in mass%, 0.2 to 0.8% of Sn, 3 to 18% of Zn, 0.3 to 1.2% of Ni, 0.01 to 0.12% of P, and a remainder made up by Cu and unavoidable impurities, wherein the crystal particle diameter ratio (a/b) is 0.9 to 1.4 wherein a represents a crystal particle diameter as measured in the direction parallel to the rolling direction and b represents a crystal particle diameter as measured in the direction orthogonal to the rolling direction, and wherein the number density of Ni-P-based compound particles in a cross section taken in the direction parallel to the rolling direction is as follows: (1) the number density of Ni-P-based compound particles each having a particle diameter of 2.0 mum or more (A) is 10 particles/mm2 or less; and (2) the number density of Ni-P-based compound particles each having a particle diameter of 100 to 500 nm inclusive (B) is 50 to 500 particles/mm2 inclusive.

Description

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

Conventionally, brass and phosphor bronze, which are solid solution strengthened alloys, have been used as materials for terminals and connectors. By the way, with the reduction in weight and size of electronic devices, terminals and connectors are made thinner and smaller, and high strength and high bendability are desired for materials used for these. Further, in a connector used in a high temperature environment such as in the vicinity of an engine room of an automobile, the connector contact pressure is reduced due to the stress relaxation phenomenon, and therefore, a material having good stress relaxation resistance is required.
However, since brass and phosphor bronze do not have sufficient strength and stress relaxation resistance, precipitation strengthened alloys have been widely used in recent years. In particular, among precipitation strengthening alloys, Cu-Ni-Si alloy is called Corson alloy and has high strength, high bendability and good stress relaxation resistance due to precipitation of Ni ₂ Si fine compound. Are used for consumer and in-vehicle connectors (Patent Documents 1 to 8).

JP 2009-185341 A JP 2009-62610 A JP-A-11-293367 JP 2003-306732 A JP 2005-163127 A JP-A-5-33087 JP 2007-84923 A JP 2007-107087 A

However, the precipitation alloy is strengthened by solid solution of the solute element and precipitation by aging treatment, so that higher temperature solution treatment and longer aging treatment are required compared with the solid solution alloy, and an increase in manufacturing cost is avoided. I can't. In addition, due to the recent rise in copper and nickel prices, development of low-cost copper alloys that can replace these with inexpensive raw materials is desired. In addition, terminals and connectors are manufactured by stamping and bending from copper alloy strips with a press. However, as electronic components become smaller and more functional, flexibility is required in the direction of material removal during pressing. As a result, it is required that the material has a small anisotropy.
The present invention has been made in order to solve the above-mentioned problems. The raw material cost is lower than that of Cu or Ni, and Zn that may be mixed into copper scrap is contained in an amount of 3% by mass or more and mixed into copper scrap. The object is to provide a Cu—Zn—Sn—Ni—P based alloy that allows Sn to be contained, is low in cost, excellent in strength, bendability and stress relaxation resistance, and has low anisotropy.

  In order to achieve the above object, the inventor has intensively studied, and as a result, in the Cu-Zn-Sn-Ni-P alloy, the crystal grain size a in the rolling parallel direction is set to the crystal grain size b in the direction perpendicular to the rolling. By appropriately controlling the crystal grain size ratio a / b and the number density of Ni-P compound particles in the cross section in the rolling parallel direction, anisotropy can be achieved without impairing strength, bendability and stress relaxation resistance. I succeeded in making it smaller.

That is, the Cu-Zn-Sn-Ni-P based alloy of the present invention contains, in mass%, Sn: 0.2 to 0.8%, Zn: 3 to 18%, Ni: 0.3 to 1.2%, P: 0.01 to 0.12% And the balance consists of Cu and inevitable impurities, the crystal grain size a in the rolling parallel direction a, the crystal grain size ratio a / b when the crystal grain size b in the perpendicular direction of rolling is 0.9 to 1.4, and in the cross section in the rolling parallel direction The number density of the Ni-P compound particles is in the following range.
(1) Ni-P compound particles A of 2.0μm or more are 10 particles / mm2 or less (2) Ni-P compound particles B of 100nm to 500nm are 50 particles / mm2 to 500 particles / mm2

The tensile strength of GW and BW is 500 MPa or more, the difference in tensile strength of GW and BW is 50 MPa or less, the minimum bending radius MBR / t of GW and BW is 1 or less, and the deflection coefficient of GW and BW is The difference is preferably 10 GPa or less.
Furthermore, it is preferable to contain 0.02 to 0.25% by mass in total of at least one selected from the group consisting of Mg, Mn, Ti, Cr and Zr.

  According to the present invention, the cost of raw materials is cheaper than Cu and Ni, and it contains 3% by mass or more of Zn that may be mixed into copper scrap, while allowing the inclusion of Sn mixed into copper scrap, at low cost and strength In addition, a Cu—Zn—Sn—Ni—P alloy having both excellent bendability and stress relaxation resistance and low anisotropy can be obtained.

  Hereinafter, a Cu—Zn—Sn—Ni—P alloy according to an embodiment of the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

(composition)
[Sn and Zn]
The Sn concentration in the alloy is 0.2 to 0.8%, and the Zn concentration is 3 to 18%. Sn and Zn improve the strength and heat resistance of the alloy, Sn further improves the stress relaxation resistance, and Zn improves the heat resistance of the solder joint. Further, by containing 3% by mass or more of Zn, the tensile strength can be improved to 500 MPa or more, and the manufacturing cost can be reduced by using copper scrap mixed with Zn for alloy production. As will be described later, even if Zn is contained in an amount of 3% by mass or more, if the recrystallization temperature is not lowered (480 ° C. or less), the crystal grain size is significantly coarsened and the strength is reduced to 500 MPa or more. The tensile strength cannot be obtained stably.
If the content of Sn and Zn is less than the above range, the above-mentioned effect cannot be obtained, and if it exceeds the above range, the conductivity is lowered. Further, when the Sn content exceeds the above range, the hot workability decreases, and when the Zn content exceeds the above range, the bending workability decreases.
[Ni and P]
The concentration of Ni in the alloy is 0.3 to 1.2%, and the concentration of P is 0.01 to 0.12%. When both Ni and P are contained, Ni ₃ P fine precipitates are precipitated in the alloy even during a short heat treatment for the purpose of recrystallization, which improves strength and stress relaxation resistance.
When the contents of Ni and P are less than the above ranges, the precipitation of Ni ₃ P is not sufficient, and the desired strength and stress relaxation improvement effect cannot be obtained. When the content of Ni and P exceeds the above range, the electrical conductivity is remarkably lowered, and the bending workability and the hot workability are lowered.

[Other additive elements]
In order to improve the strength, the alloy may further contain 0.02 to 0.25% by mass in total of at least one selected from the group consisting of Mg, Mn, Ti, Cr and Zr. Further, Mg and Mn improve stress relaxation resistance, and Cr and Mn improve hot workability.
However, these elements have lower free energy of formation of oxides than Zn, and if the total amount of these elements exceeds the above range, they will oxidize during dissolution in the atmosphere during ingot casting, resulting in unnecessary increase in raw material costs. Then, the generated oxide is involved at the time of casting, resulting in a decrease in ingot quality.

[Crystal grain size]
The crystal grain size ratio a / b is 0.9 to 1.4 when the crystal grain size a in the rolling parallel direction and the crystal grain size b in the direction perpendicular to the rolling are taken. When a / b exceeds the above range, the difference in crystal grain size between the rolling parallel direction and the rolling perpendicular direction becomes large, and the bending workability in the BW direction is significantly deteriorated. The reason for this is not clear, but it is considered to be a difference in workability when a fibrous structure facing in one direction is bent in the fiber direction and in a direction perpendicular to the fiber direction. In other words, since the size of the crystal grain crossing the bending axis is larger in the BW direction than in the GW direction, the strain at the time of plastic deformation cannot be absorbed by the slip deformation of each crystal grain, and propagates through the grain boundary. It is considered that cracks occur.
The crystal grain size a is measured in accordance with the cutting method of JIS-H0501 with respect to the rolling parallel section (cross section cut along a plane parallel to the rolling direction). The crystal grain size b is measured in accordance with the cutting method of JIS-H0501 with respect to the rolling cross section (cross section cut along a plane parallel to the direction perpendicular to the rolling direction).

[Ni-P compounds]
The number density of Ni—P-based compound particles in the rolling parallel section is controlled within the following range.
(1) Ni-P compound particles A of 2.0 μm or more 10 particles / mm2 or less (2) Ni-P compound particles B of 100 nm to 500 nm or less 50 particles / mm2 to 500 particles / mm2 where Ni -P-based compound particles (hereinafter referred to as Ni-P-based particles) are particles containing Ni at 50 at% or more and containing P at 10 at% or more. Is defined as the diameter of the smallest circle that encloses (and so on). The above-mentioned particle A is a crystallized product, and the bendability of GW and BW deteriorates when the number density exceeds 10 / mm2. The above-mentioned particle B is a precipitate, and if it is less than 50 particles / mm 2, the precipitation of Ni—P-based particles of less than 100 nm that contributes to the improvement of the stress relaxation resistance becomes insufficient, so that the desired stress relaxation resistance can be obtained. Absent. On the other hand, when the number is 500 particles / mm 2 or more, the Ni—P-based particles grow, and thus the above-mentioned particles of less than 100 nm are reduced, so that desired stress relaxation resistance characteristics cannot be obtained.
The above-mentioned components of the particles A and B are Ni-P-based particles, which means that in a predetermined field of view of an FE-SEM (electrolytic emission scanning electron microscope), particles having a typical form (diameter) are converted into EDS [energy dispersive X It is confirmed by analyzing using [Line Analysis]. For the particles A and B, the rolling parallel cross section of the sample is observed with an FE-SEM, and the number of particles in the above-mentioned particle size range is measured with the particle analysis software attached to the FE-SEM to obtain the number density. .

  The Cu—Zn—Sn—Ni—P alloy of the present invention is usually manufactured by hot rolling and chamfering an ingot, first cold rolling and recrystallization annealing, and finally cold rolling. Can do. After final cold rolling, strain relief annealing is performed.

The casting temperature of the ingot is 1250 ° C or less. If the casting temperature of the ingot exceeds 1250 ° C, the cast structure becomes coarse, and even after dynamic recrystallization at the end of hot rolling, the coarse structure remains without being sufficiently eliminated. As a result, even in the product, grains elongated in the longitudinal direction remain, the crystal grain size ratio a / b is out of the range of 0.9 to 1.4, and at least one of the minimum bending radii MBR / t of GW and BW is bent beyond 1. Deteriorates.
The casting mold for casting the ingot is made of copper. If the mold is made of a material other than copper (for example, cast iron, graphite, brick, etc.), coarse crystals remain in the ingot and eventually the number density of particles A exceeds 1 / mm2, so GW and BW The bendability is degraded.
Adjust the pass schedule so that the temperature at the end of hot rolling is 600 ℃ or higher. When the end temperature of hot rolling is less than 600 ° C., dynamic recrystallization does not occur and a coarse structure remains in the rolling direction. For this reason, the crystal grain size ratio a / b is out of the range of 0.9 to 1.4, and at least one of the minimum bending radii MBR / t of GW and BW exceeds 1, and the bendability deteriorates.
The degree of processing in the final pass of hot rolling is 25-40%. If the degree of work is less than 25%, dynamic recrystallization does not occur and a coarse structure remains in the rolling direction. For this reason, the crystal grain size ratio a / b is out of the range of 0.9 to 1.4, and at least one of the minimum bending radii MBR / t of GW and BW exceeds 1, and the bendability deteriorates. If the degree of processing exceeds 40%, hot rolling may occur.

  The working degree of the first cold rolling is set to 95% or more. When the workability of the first cold rolling is less than 95%, the precipitation of Ni-P during recrystallization annealing is insufficient, the number of particles B is less than 50 / mm2, and the stress relaxation resistance is deteriorated.

In batch annealing, the recrystallization annealing temperature is preferably 380 to 500 ° C., and the annealing time is preferably 25 to 70 minutes. When the recrystallization annealing temperature is lower than 380 ° C., unrecrystallized grains remain, and at least one of the minimum bending radii MBR / t of GW and BW exceeds 1, and the bendability deteriorates. Further, the precipitation of the Ni—P compound is insufficient, the number of particles B is less than 50 / mm 2, and the stress relaxation resistance is deteriorated. When the recrystallization annealing temperature exceeds 500 ° C., the crystal grain size exceeds 10 μm and coarsens, the strength decreases, and the Ni-P precipitates also coarsen, so that the particle B exceeds 500 particles / mm2, Precipitates that contribute to stress relaxation are reduced, and the stress relaxation resistance is deteriorated.
If the annealing time for recrystallization annealing is less than 25 minutes, the precipitation of Ni—P compound is insufficient, the number of particles B is less than 50 / mm 2, and the stress relaxation resistance is deteriorated. When the annealing time for recrystallization annealing exceeds 70 minutes, the crystal grain size exceeds 10 μm and coarsens, the strength decreases, and the Ni-P precipitates also coarsen, so that the particle B becomes 500 particles / mm 2. The precipitate that contributes to stress relaxation is reduced, and the stress relaxation resistance is deteriorated.
In order to further reduce the production cost, recrystallization annealing can be performed in a continuous annealing furnace. At that time, the annealing temperature is set to 550 to 800 ° C., and the residence time of the material in the furnace (synonymous with the sheet feeding speed) is adjusted so that the crystal grain size is equal to or less than the target size (10 μm).

  The degree of work of the final cold rolling can be arbitrarily set in consideration of desired tensile strength and bending workability, but is preferably 20% or more and 50% or less. The strain relief annealing is performed under conditions of 250 ° C. or higher, and the conditions are adjusted so that the difference in tensile strength before and after annealing is within 50 MPa.

In addition, the present invention contains Ni and P in the alloy, and even if the recrystallization annealing time is set to a short time as described above, Ni ₃ P fine precipitates are precipitated, reducing the production cost, Strength and stress relaxation resistance can be improved.
On the other hand, in order to reduce the stress relaxation rate to 25% or less, it is necessary to disperse Ni3P having an appropriate size that contributes to stress relaxation as a precipitate in the matrix. When the cooling after hot rolling is gradually cooled, the precipitation of Ni3P proceeds, but the size of Ni3P becomes coarse compared to the precipitate size at a level that contributes to stress relaxation. For this reason, by suppressing precipitation after the end of hot rolling and sufficiently dissolving Ni and P in the matrix, Ni3P precipitates in the material during subsequent strip annealing and recrystallization annealing. Adjust the state of Ni and P. In order to dissolve Ni and P, the end temperature of hot rolling is 600 ° C. or higher, and the material is water-cooled after the end of hot rolling to suppress precipitation.

<Experiment A (Invention Examples 1-16, Comparative Examples 1-8)
Electrolytic copper was melted in an air melting furnace, a predetermined amount of additive elements shown in Table 1 were added, and the molten metal was stirred. Thereafter, the hot water was poured into a copper mold at a casting temperature of 1170 ° C. to obtain a copper alloy ingot having a composition shown in Table 1 having a thickness of 30 mm × width of 60 mm × length of 120 mm. The ingot was shaved 2.5 mm per side and then subjected to hot rolling, cold rolling and heat treatment in the following order to obtain a sample having a thickness of 0.2 mm.
(1) After annealing the ingot at a holding temperature of 850 ° C. for 3 hours (holding time), hot rolling to a sheet thickness of 11 mm, the material temperature at the end of hot rolling (end temperature of hot rolling) is 660 ° C. (error ± 10 ° C.) and then water-cooled.
(2) In order to remove the oxide scale on the surface layer after hot rolling, one side of 0.5 mm was chamfered.
(3) The first cold rolling was performed until the plate thickness became 0.36 mm (working degree 97%).
(4) Recrystallization annealing was performed at 380 ° C. for 30 minutes.
(5) After removing the oxidized scale on the surface after recrystallization annealing by pickling and buffing, final cold rolling was performed until the thickness became 0.25 mm (working degree 33.3%).
(6) After final cold rolling, strain relief annealing at 300 ° C. × 0.5 h was further performed.

<Experiment B (Invention Examples 21 to 32, Comparative Examples 11 to 25)
An ingot was obtained in the same manner as in Experiment A except that the composition of the ingot was Cu-0.4% Sn-10% Zn-1.0% Ni-0.05% P. However, ingot melting and casting conditions, hot rolling conditions, first cold rolling workability, and recrystallization annealing conditions were changed as shown in Table 3. Final cold rolling was performed on the 0.3 mm thick material after recrystallization annealing until it reached 0.2 mm (working degree: 33.3%). Further, after the final cold rolling, a strain relief annealing of 300 ° C. × 0.5 h was further performed.

<Evaluation>
The following items were evaluated for the materials after strain relief annealing in Experiments A and B. In this experiment, the copper alloy with small anisotropy shown in the inventive examples refers to a copper alloy in which the difference in tensile strength between the rolling parallel direction and the direction perpendicular to the rolling direction and the difference in deflection coefficient are small according to the following criteria. .
[Average crystal grain size and crystal grain size ratio a / b]
A sample having a width of 20 mm and a length of 20 mm was electropolished, and then a reflected electron image was observed with a FE-SEM manufactured by Philips. The observation magnification was set to 1000 times, and the crystal grain size was determined by the cutting method defined in JISH0501 for images of five fields of view, and the average value was calculated. The above average values were obtained for the crystal grain size a in the rolling parallel direction and the crystal grain size b in the direction perpendicular to the rolling, and the crystal grain size ratio a / b was calculated.

[Average crystal grain size and crystal grain size ratio a / b]
In order to measure the number density of the Ni-P compound particles, the rolled parallel section of the sample was mirror-finished by mechanical polishing using diamond abrasive grains having a diameter of 1 μm, and then electropolished with a phosphoric acid type polishing solution. Using FE-SEM (Electrolytic Emission Scanning Electron Microscope: manufactured by PHILIPS), the sample surface after electropolishing was 65 fields at a magnification of 500 times for Particle A, and 67 fields at a magnification of 8000 times for Particle B. Observed, the number of compound particles in the above-mentioned particle size range was measured with the particle analysis software attached to the FE-SEM, and the number density was determined. The fact that the components of the particles A and B described above are Ni-P-based particles, in each field of view, analyze particles having a representative form (diameter) using EDS (energy dispersive X-ray analysis) of FE-SEM. Was confirmed.

[Tensile strength]
About each sample, the tensile test was done about GW and BW and the tensile strength (TS) was calculated | required based on JISZ2241. When the tensile strength was 500 MPa or more, the strength was judged to be good, and when the difference in tensile strength between GW and BW was 50 MPa or less, the strength difference was judged to be small.
[conductivity]
About each sample, based on JISH0505, the electrical conductivity (% IACS) was computed from the volume resistivity calculated | required by the four-terminal method using the double bridge apparatus.
[W bendability]
A strip specimen having a width of 10 mm and a length of 30 mm was taken so that the sample longitudinal direction was parallel to the rolling direction (GW direction) or perpendicular (BW direction). The test piece was subjected to a W bending test (JCBA-T307), and the minimum bending radius at which cracks did not occur was defined as MBR (Minimum Bend Radius), and evaluation was performed based on the ratio MBR / t to the plate thickness t (mm). In both directions, when MBR / t was 1 or less, it was determined that the bendability was good.

[Deflection coefficient]
About each sample of GW and BW, the deflection coefficient was measured based on Japan Copper and Brass Association technical standard (JCBAT312: 2002). When the difference in deflection coefficient between GW and BW was 10 GPa or less, it was determined that the difference in deflection coefficient was small.
[Stress relaxation resistance]
A strip-shaped test piece having a width of 10 mm and a length of 100 mm was collected so that the longitudinal direction of the test piece was parallel to the rolling direction. Fix one end of the test piece, give a deflection of y _{0 to} the test point at a position 50 mm from the fixed position (l = 50 mm), and apply a stress (σ ₀ ) equivalent to 80% of 0.2% proof stress did. y ₀ was determined by the following equation.
y ₀ = (2/3) · l ² · σ ₀ / (E · t)
Here, E is the deflection coefficient (value measured by the above method), and t is the thickness of the sample. Unloading after 1000 hours of heating at 150 ° C with y ₀ deflection applied to the test piece, measuring permanent deformation (height) y, stress relaxation rate {[y (mm) / y0 (mm) ] × 100 (%)} was calculated. When the stress relaxation rate was 25% or less, it was determined that the stress relaxation resistance was good.

  The obtained results are shown in Tables 1 to 4. Tables 1 and 2 show the results of Experiment A, and Tables 3 and 4 show the results of Experiment B.

About Experiment A
The content of Sn, Zn, Ni, P is within the specified range, the crystal grain size ratio a / b satisfies 0.9 to 1.4, and the number density of the particles A and B that are Ni-P compounds is within the specified range. In each of the examples, the strength, bendability, and stress relaxation resistance were maintained satisfactorily and the anisotropy was reduced.
On the other hand, in Comparative Example 1 where Zn is less than 3% and Comparative Example 3 where Sn is less than 0.2%, the tensile strengths of GW and BW were both less than 500 MPa, and the strength deteriorated.
In Comparative Example 2 where Zn exceeded 18%, the minimum bending radius MBR / t of BW exceeded 1, and the stress relaxation rate deteriorated beyond 25%.
In Comparative Example 4 in which Sn exceeded 0.8% and in Comparative Example 8 in which P exceeded 0.12%, cracks occurred during hot rolling, and an alloy could not be produced.
In the case of Comparative Example 5 in which Ni is less than 0.3%, the precipitation of Ni—P-based particles was insufficient, and the stress relaxation rate deteriorated by exceeding 25%.
In Comparative Example 6 in which Ni exceeded 1.2%, the minimum bending radius MBR / t of BW exceeded 1.
In the case of Comparative Example 7 where P is less than 0.01%, the precipitation of Ni—P-based particles was insufficient, and the stress relaxation rate deteriorated by exceeding 25%.

About Experiment B In each example in which the conditions of melt casting of ingot, hot rolling, first cold rolling, and recrystallization annealing satisfy the specified range, the crystal grain size ratio a / b satisfies 0.9 to 1.4, In addition, the number density of the particles A and B, which are Ni-P compounds, was within the specified range, and the strength, bendability and stress relaxation resistance were maintained well, and the anisotropy was reduced.

On the other hand, in the case of Comparative Example 11 in which the casting temperature of the ingot was less than 1150 ° C., the casting surface of the ingot became rough, and surface abnormalities occurred, which prevented further production. In the case of Comparative Example 12 where the casting temperature of the ingot exceeded 1250 ° C., the cast structure became coarse, the crystal grain size ratio a / b was out of the range of 0.9 to 1.4, the anisotropy increased, and GW and BW The minimum bend radius MBR / t of both exceeded 1 and the bendability deteriorated.
Further, in Comparative Examples 13 to 15 in which the mold for casting the ingot was made of a material other than copper (cast iron, graphite, brick, etc., respectively), coarse crystals remained in the ingot, and the number density of particles A was 10 The bendability deteriorated when the minimum bending radius MBR / t of GW and BW exceeded 1 and exceeded pcs / mm2.

In the case of Comparative Example 16 in which the end temperature of hot rolling was less than 600 ° C., dynamic recrystallization did not occur and a coarse structure remained in the rolling direction. For this reason, the crystal grain size ratio a / b was out of the range of 0.9 to 1.4, the anisotropy was increased, and the minimum bending radius MBR / t of BW exceeded 1, and the bendability deteriorated. Further, since the amount of Ni and P to be dissolved was insufficient, the precipitation of Ni—P-based particles was insufficient, the number density of particles B was less than 50 / mm2, and the stress relaxation resistance was deteriorated.
In the case of Comparative Example 17 in which the degree of processing of the final pass of hot rolling was less than 25%, dynamic recrystallization did not occur and a coarse structure remained in the rolling direction. For this reason, the crystal grain size ratio a / b was out of the range of 0.9 to 1.4, the anisotropy was increased, and the minimum bending radius MBR / t of BW exceeded 1, and the bendability deteriorated. On the other hand, in the case of Comparative Example 18 in which the final pass degree of hot rolling exceeded 40%, hot-rolling cracking occurred and no further production was possible.

In the case of Comparative Example 19 in which the workability of the first cold rolling is less than 95%, the precipitation of Ni—P during recrystallization annealing becomes insufficient, and the number density of particles B is less than 50 / mm2, Stress relaxation characteristics deteriorated.
In the case of Comparative Example 20 in which the temperature of recrystallization annealing is less than 380 ° C., recrystallization does not occur sufficiently, an unrecrystallized region remains in most of the observation region, and the minimum bending radius MBR / t of GW and BW is In both cases, the bendability deteriorated exceeding 1.
In the case of Comparative Example 21 in which the recrystallization annealing temperature exceeded 500 ° C., the crystal grain size exceeded 10 μm and the tensile strength of GW and BW decreased to less than 500 MPa. Furthermore, the number density of particles B exceeded 500 particles / mm2, and fine precipitates contributing to stress relaxation decreased, resulting in deterioration of stress relaxation resistance.
In the case of Comparative Example 22 in which the annealing time for recrystallization annealing is less than 25 minutes, the precipitation of Ni-P-based particles is insufficient, the number density of particles B is less than 50 / mm2, and the stress relaxation resistance is deteriorated. . In the case of Comparative Example 23 in which the annealing time for recrystallization annealing exceeded 70 minutes, the crystal grain size became larger than 10 μm, and the tensile strength of GW was reduced to less than 500 MPa. In addition, the number density of particles B was 500 particles / mm 2 or more, and as a result of the reduction of fine precipitates contributing to stress relaxation, the stress relaxation resistance was deteriorated.

Claims (3)

In mass%, Sn: 0.2-0.8%, Zn: 3-18%, Ni: 0.3-1.2%, P: 0.01-0.12%, the balance consists of Cu and inevitable impurities,
The crystal grain size ratio a / b is 0.9 to 1.4 when the crystal grain size a in the rolling parallel direction and the crystal grain size b in the perpendicular direction of rolling are 0.9, and the number density of Ni-P compound particles in the cross section in the rolling parallel direction is as follows: Cu-Zn-Sn-Ni-P based alloys that are in the range.
(1) Ni-P compound particles A of 2.0μm or more are 10 particles / mm2 or less (2) Ni-P compound particles B of 100nm to 500nm are 50 particles / mm2 to 500 particles / mm2   The tensile strength of GW and BW is 500 MPa or more, the difference in tensile strength of GW and BW is 50 MPa or less, the minimum bending radius MBR / t of GW and BW is 1 or less, and the deflection coefficient of GW and BW is The Cu-Zn-Sn-Ni-P alloy according to claim 1, wherein the difference is 10 GPa or less.   The Cu-Zn-Sn-Ni-P alloy according to claim 1 or 2, further comprising 0.02 to 0.25 mass% in total of at least one selected from the group consisting of Mg, Mn, Ti, Cr and Zr.