Copper alloy sheet

Abstract

To provide a Cu-Ni-Si based copper alloy sheet capable of achieving high proof stress and excellent flexure workability, and a manufacturing method thereof.SOLUTION: A copper alloy sheet includes 1.50 to 3.00 mass% Ni, 0.10 to 1.00 mass% Si, and balance Cu with inevitable impurities. In the copper alloy sheet, a surface density of Ni2Si particles with a grain diameter 30 nm or more included in a metallographic structure is 1.0×10-6 pieces / nm2 or less, 0.2% proof stress at a right angle to a rolling direction is 680 MPa or more, and no cracks are caused by G.W. adhesion bending.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a copper alloy sheet, and in particular to a copper alloy sheet having high yield strength and excellent bending workability. [Background technology]

[0002] Copper alloys for electrical and electronic components are required to have high electrical conductivity, high proof stress (yield stress), high tensile strength, excellent bending workability, excellent fatigue resistance, excellent stress relaxation resistance, high Young's modulus, etc. In order to satisfy these properties, the metal structure of copper alloy sheets is controlled. In particular, since it is difficult to achieve both high strength (high yield strength and high tensile strength) and excellent bending workability, various efforts have been made to achieve this.

[0003] Among copper alloys, Cu-Ni-Si based copper alloys have a relatively high 0.2% yield strength and good bending workability (i.e., a good balance between yield strength and bending workability), and further have a relatively high electrical conductivity and good stress relaxation resistance. Therefore, Cu-Ni-Si based copper alloys are considered suitable for use in electrical and electronic components (for example, Patent Documents 1 to 3).

[0004] Patent Document 1 discloses a Cu-Ni-Si based copper alloy sheet and a method for manufacturing the same. The copper alloy sheet has a yield strength of 450 N / mm in both directions parallel and perpendicular to the rolling direction. 2 More than 670N / mm 2 The following are considered to have excellent bending workability: a ratio of proof stress to tensile strength of 0.85 or more and 0.95 or less, a ratio of uniform elongation to total elongation of 0.5 or more and 0.88 or less, and a work hardening index (n value) of 0.05 or more and 0.12 or less.

[0005] Patent Document 2 discloses a method for manufacturing a copper alloy sheet for electrical and electronic components of the Cu-Ni-Si system. When the conductivity at the time of maximum solid solution amount is X, the conductivity Y after solution annealing satisfies X < Y ≤ 1.5X, and the yield strength in both the rolling parallel direction and the rolling perpendicular direction is 150 MPa or more. Heating is performed to a solid temperature of 700 to 1000 °C at a heating rate of 10 °C / second or more, held at that temperature for less than 3 seconds, and then air-cooled at a cooling rate of 30 °C / second or more to perform continuous solution annealing. Subsequently, finish cold rolling and aging annealing are performed at a processing rate of 50% or less. It is characterized by this. By this manufacturing method, it is said that a copper alloy sheet for electrical and electronic components with little anisotropy in both yield strength and bending workability can be obtained.

[0006] Patent Document 3 discloses a Cu-Ni-Si-based copper alloy sheet and a method for manufacturing the same. The average crystal grain size is 10 μm to 40 μm, and in the measurement result by the SEM-EBSP method, the average area ratio of the Cube orientation {001}<100> is 20% or more, and the difference in the area ratio of the Cube orientation between the 1 / 4t (t is the plate thickness) part and the 1 / 2t part is within 5%, and a Cu-Ni-Si-based copper alloy having a KAM value of 1.00 or more and 3.00 or less and a method for manufacturing the same are disclosed. It is said that a Cu-Ni-Si-based copper alloy having such characteristics has both high strength, excellent bending workability, and excellent stress relaxation characteristics.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the automotive field, various types of electronic devices are being implemented and their number is increasing due to compliance with environmental regulations, the pursuit of comfort and safety, and the recent trend toward advanced driver assistance systems based on CASE (Connected, Autonomous, Shared & Services, Electric). This has led to demand for further miniaturization of terminals, connectors, relay components, etc. To manufacture small components, it is necessary to achieve high yield strength equivalent to that of Patent Documents 1 to 3, as well as even better bending workability (particularly tight bending workability).

[0009] An object of an embodiment of the present invention is to provide a Cu-Ni-Si based copper alloy sheet that can achieve high proof stress and excellent bending workability, and a method for producing the same. [Means for solving the problem]

[0010] Aspect 1 of the present invention is Ni: 1.50 to 3.00 mass%; and Si: 0.10 to 1.00 mass% the balance being Cu and unavoidable impurities, The surface density of Ni2Si particles with a diameter of 30 nm or more contained in the metal structure is 1.0 × 10 -6 pieces / nm 2 is as follows: This copper alloy sheet has a 0.2% yield strength of 680 MPa or more in the direction perpendicular to the rolling direction, and does not crack when subjected to GW close bending.

[0011] Aspect 2 of the present invention is The copper alloy sheet according to aspect 1 satisfies one or more of the following (a) to (c): (a) further containing one or more of Sn and Mg, Sn: more than 0% by mass and not more than 1.00% by mass, Mg: contained in the range of more than 0 mass% and not more than 0.20 mass%; (b) Zn: contained in the range of more than 0 mass% and not more than 2.00 mass%, (c) The alloy further contains more than 0 mass % and 0.50 mass % in total of one or more elements selected from the group consisting of Al, Mn, Cr, Ti, Zr, Fe, P, and Ag.

[0012] Aspect 3 of the present invention is a copper alloy ingot containing 1.50 to 3.00 mass% of Ni and 0.10 to 1.00 mass% of Si, with the balance being Cu and unavoidable impurities, the ingot being subjected to hot rolling, cold rolling, solution treatment, aging treatment, and finish cold rolling in this order; The solution treatment is carried out under conditions in which the cold-rolled material after the solution treatment satisfies the following formula (1): The finish cold rolling is performed at a rolling ratio of 40 to 70%. This is a method for manufacturing a copper alloy sheet. X≦Y<1.13X (1) where X is the electrical conductivity when the amounts of Ni and Si in solid solution are maximum in a copper alloy material having the same chemical composition as that of the copper alloy ingot, Y is the electrical conductivity of the cold-rolled material after the solution treatment.

[0013] A fourth aspect of the present invention is In the method for producing a copper alloy sheet according to aspect 3, the copper alloy ingot satisfies one or more of the following (a) to (c): (a) further containing one or more of Sn and Mg, Sn: more than 0% by mass and not more than 1.00% by mass, Mg: contained in the range of more than 0 mass% and not more than 0.20 mass% (b) Zn: contained in the range of more than 0 mass% and not more than 2.00 mass% (c) The alloy further contains more than 0 mass % and 0.50 mass % in total of one or more elements selected from the group consisting of Al, Mn, Cr, Ti, Zr, Fe, P, and Ag. [Effects of the Invention]

[0014] According to the embodiments of the present invention, it is possible to provide a Cu—Ni—Si based copper alloy sheet that can achieve high proof stress and excellent bending workability, and a method for manufacturing the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1(a) to 1(c) are schematic cross-sectional views of the jig used in the close contact bending test. [Figure 2] Figures 2(a) and (b) are optical microscope photographs of the cross section (observation surface) of a test piece that was subjected to close contact bending in a close contact bending test. [Figure 3] Figure 3 shows FE-TEM images of sample No. 3, where (a) is a bright-field image and (b) is a dark-field image. DETAILED DESCRIPTION OF THE INVENTION

[0016] Cu-Ni-Si copper alloys (hereinafter sometimes simply referred to as "copper alloys") are precipitation-strengthened copper alloys strengthened by Ni and Si precipitates (Ni-Si compounds). By increasing the Ni and Si contents and the amount of precipitated Ni-Si compounds, the strength of the copper alloy sheet (high yield strength and high tensile strength) can be increased. On the other hand, an increase in the Ni-Si compounds can cause a decrease in the bendability of the copper alloy sheet. Therefore, it has been considered difficult to achieve both high yield strength and excellent bending workability (i.e., an improvement in the balance between yield strength and bending workability).

[0017] The present inventors have intensively studied the relationship between Ni-Si compounds and the strength and bending workability of copper alloy sheets, and as a result have found that the strength of copper alloy sheets can be increased by reducing the average particle size of Ni2Si particles, which are Ni-Si compounds, and that the bending workability can be improved by keeping the content (areal density) of Ni2Si particles, which have large particle sizes, low. By utilizing these findings, the present inventors have completed an invention relating to a copper alloy sheet having an excellent balance between proof stress and bending workability.

[0018] The chemical composition, structure, and manufacturing method of the copper alloy sheet according to this embodiment will be described below.

[0019] 1.Chemical composition (1)Ni: 1.50~3.00% by mass The Ni content is set to 1.50 to 3.00 mass %. Ni can improve strength without significantly reducing electrical conductivity by aging and precipitating Ni-Si compounds (intermetallic compounds) with Si. If Ni is less than 1.50% by mass, these effects are not fully exhibited. If Ni is more than 3.00% by mass, Ni-Si compounds crystallize or precipitate during casting or hot rolling, reducing hot workability. Furthermore, subsequent heat treatment (e.g., solution treatment) can cause the particles of the Ni-Si compounds to coarsen, potentially reducing the bending workability of the copper alloy sheet. The lower limit of Ni is preferably 1.60 mass %, more preferably 1.70 mass %, and the upper limit of Ni is preferably 2.80 mass %, more preferably 2.60 mass %.

[0020] (2)Si:0.10~1.00% by mass The Si content is set to 0.10 to 1.00 mass %. As described above, Si can improve strength without significantly reducing electrical conductivity by aging and precipitating Ni-Si compounds (intermetallic compounds) with Ni. If the Si content is less than 0.10% by mass, these effects are not fully achieved. If the Si content is more than 1.00% by mass, Ni-Si compounds crystallize or precipitate during casting or hot rolling, reducing hot workability. Furthermore, subsequent heat treatment (e.g., solution treatment) can cause the particles of the Ni-Si compounds to coarsen, potentially reducing the bending workability of the copper alloy sheet. The lower limit of Si is preferably 0.20 mass %, more preferably 0.30 mass %, and the upper limit of Si is preferably 0.80 mass %, more preferably 0.60 mass %.

[0021] (3) Remainder In a preferred embodiment, the balance is Cu and unavoidable impurities. The unavoidable impurities include trace elements introduced due to the conditions of raw materials, materials, manufacturing facilities, etc.

[0022] The copper alloy sheet is not limited to this embodiment, and may further contain any other elements as long as the properties of the copper alloy sheet of the present invention can be maintained. Examples of other elements that can be selectively contained in this way are listed below.

[0023] (4) Contains one or more of Sn and Mg in the range of Sn: more than 0 mass% and not more than 1.00 mass%, Mg: more than 0 mass% and not more than 0.20 mass% When Sn is added, the Sn content is preferably more than 0 mass % and 1.00 mass % or less. The addition of Sn is expected to increase the strength of the copper alloy sheet through solid solution strengthening and improve stress relaxation resistance. To achieve these effects, the Sn content is preferably greater than 0% by mass. Furthermore, by keeping the Sn content at 1.00% by mass or less, high electrical conductivity, a property required for copper alloys for terminals, can be maintained. The lower limit of Sn is more preferably 0.005 mass%, further preferably 0.010 mass%, and particularly preferably 0.020 mass%, and the upper limit of Sn is more preferably 0.60 mass%, and further preferably 0.30 mass%.

[0024] When Mg is added, the Mg content is preferably more than 0 mass % and 0.20 mass % or less. The addition of Mg is expected to increase the strength of the copper alloy sheet through solid solution strengthening and improve stress relaxation resistance. To achieve the above effects, the Mg content is preferably greater than 0% by mass. Furthermore, by setting the Mg content to 0.20% by mass or less, high electrical conductivity, a property required for copper alloys for terminals, can be maintained. The lower limit of Mg is more preferably 0.005% by mass, and the upper limit of Mg is more preferably 0.15% by mass, and even more preferably 0.05% by mass.

[0025] (5) Zn: More than 0% by mass and 2.00% by mass or less When Zn is added, the Zn content is preferably more than 0 mass % and 2.00 mass % or less. Electronic components using copper alloy sheets are sometimes incorporated into semiconductor devices by soldering. Furthermore, the copper alloy sheets may be Sn-plated to improve corrosion resistance. Adding Zn within the above range can improve the solder heat peel resistance of the copper alloy sheet and the heat peel resistance of the Sn plating. Furthermore, by setting the Zn content to 2.00 mass% or less, high electrical conductivity, a property required for copper alloys for terminals, can be maintained. The lower limit of Zn is more preferably 0.01 mass%, even more preferably 0.05 mass%, and particularly preferably 0.10 mass%, and the upper limit of Zn is more preferably 1.70 mass%, and even more preferably 1.50 mass%.

[0026] (6) One or more selected from the group consisting of Al, Mn, Cr, Ti, Zr, Fe, P, and Ag, in a total amount of more than 0 mass% and 0.50 mass% or less The addition of these elements is expected to increase the strength of the copper alloy sheet through solid solution strengthening, improve the heat resistance, and improve the press-punchability of the copper alloy sheet. To achieve the above effects, the total content of these elements is preferably more than 0% by mass. Furthermore, by setting the total content of these elements to 0.50% by mass or less, the copper alloy sheet can have good hot workability, cold workability, and bending workability.

[0027] 2.Metal structure The copper alloy sheet according to this embodiment contains Ni2Si particles, which are Ni-Si compounds, in the metal structure. In particular, the surface density of the Ni2Si particles having a particle size of 30 nm or more is 1.0 × 10 -6 pieces / nm 2 The following is the result.

[0028] Furthermore, since coarse Ni2Si particles can become the starting point for cracks during processing of the copper alloy sheet, cracks during processing such as bending are suppressed by reducing the number of Ni2Si particles with large particle diameters. The inventors first discovered that Ni2Si particles with a particle diameter of 30 nm or more are likely to induce cracks in the copper alloy sheet because they are incompatible with the lattice of the parent phase. As a result of further investigation, it was found that the surface density of Ni2Si particles with a particle diameter of 30 nm or more is 1.0 × 10 -6 pieces / nm 2 It has been found that cracking during close bending can be effectively suppressed by controlling the following: In addition, since Ni2Si particles with a particle size of 30 nm or more have a low effect of improving strength, even if the surface density of such Ni2Si particles is kept low, it does not cause a significant decrease in the strength of the copper alloy sheet. In other words, by reducing the content of Ni2Si particles with a particle size of 30 nm or more, it is possible to maintain the strength of the copper alloy sheet while suppressing cracking during close bending.

[0029] The copper alloy sheet can be strengthened by the precipitation of Ni2Si particles. In this embodiment, it is preferable to suppress the average particle size of the Ni2Si particles to 5 nm or less, thereby enhancing the effect of precipitation strengthening.

[0030] The average particle size of the Ni2Si particles is determined as follows. The rolled surface of the copper alloy sheet is measured by XRD. The scattering intensity of the X-rays obtained from the measurement and the relationship between the structure factor and shape factor are parameter-fitted with experimental values ​​to determine the particle size when the Ni2Si particles are assumed to be spherical.

[0031] The surface density of Ni2Si particles with a particle size of 30 nm or more is determined by the following method. Using thin-film deposition methods such as electrolytic thinning, copper alloy sheets are thinned to allow observation of the central portion of the sheet thickness. The thin-film deposition is then observed using a field-emission transmission electron microscope (FE-TEM). The "electrolytic thin-film deposition" method is a common method in which an observation material is thinned using an electrolyte to a thickness that allows the electron beam emitted from the electron gun of an electron microscope to penetrate. A thin-film deposition device, such as a TenuPol manufactured by Struers, is used. First, the observation material is placed on a sample holder equipped with electrodes so that both sides of the observation material are exposed. The sample holder is then placed in the thin-film deposition device, and the exposed surface of the observation material is polished by spraying electrolyte from both sides of the holder (twin-jet polishing). The electrolyte is composed of, for example, 30% nitric acid and 70% distilled water. The current and flow rate of the spray are adjusted appropriately during polishing.

[0032] Bright-field and dark-field images are acquired for the same field of view and compared, and particle images that appear black in the bright-field image and white in the dark-field image are judged to be Ni2Si particles. Ni2Si particles with a particle size of 30 nm or more are identified and counted within the specified observation range, and this number is divided by the area of ​​the observation range to determine the surface density (particles / nm 2 ) is calculated. Since Ni2Si particles are approximately spherical particles, the particle size measured in any direction can be regarded as the particle size. In particular, in this embodiment, the particle size measured from an observation image obtained from a cross section perpendicular to the rolling direction is regarded as the particle size of the Ni2Si particles.

[0033] 3.Characteristics The copper alloy sheet according to this embodiment has a 0.2% yield strength in the direction perpendicular to the rolling direction (TD direction) of 680 MPa or more, and also has the property that cracks do not occur due to GW close bending.

[0034] - 0.2% yield strength in the transverse direction (TD direction) is 680 MPa or more A test piece for a tensile test is prepared from the copper alloy plate, and a tensile test is performed. The tensile test is performed using a JIS No. 5 test piece with the longitudinal direction perpendicular to the rolling direction (TD) using a tensile testing device (for example, Shimadzu AG-IS (100kN)) at room temperature, a test speed of 5mm / min, and a rating distance of 50mm, to measure the 0.2% yield strength (MPa).From the tensile test results, the 0.2% yield strength (YS) in the direction perpendicular to the rolling direction (TD) is measured. The copper alloy sheet of this embodiment has a 0.2% yield strength of 680 MPa or more, which is equal to or higher than that of conventional Cu-Ni-Si based copper alloys.

[0035] · No cracks caused by bending with GW The GW close bending test is a close bending test in which the bending axis is set perpendicular to the rolling direction. In the close-contact bending test, a V-shaped bending jig (reference numerals 11 and 12 in Fig. 1(a) and 21 and 22 in Fig. 1(b)) and a block-shaped jig (reference numerals 31 and 32 in Fig. 1(c)) are used. First, the test piece S is sandwiched between the jigs 11 and 12 as shown in Fig. 1(a) and bent to R = 0.05 and θ = 90° with a load of 200 N. Next, the test piece S is sandwiched between the jigs 21 and 22 as shown in Fig. 1(b) and bent to R = 0.05 and θ = 150° with a load of 200 N. Finally, the V-shaped bent test piece S is sandwiched between the block-shaped jigs 31 and 32 as shown in Fig. 1(c) and crushed with a load of 200 N to perform close-contact bending.

[0036] The presence or absence of cracks is confirmed by observing the cross section of the bent part. The test piece (bending test piece) that has been subjected to close contact bending is polished so that the plane perpendicular to the bending axis becomes the cross section (observation surface), and the observation surface is prepared. The cross section (observation surface) is observed using an optical microscope (magnification: 200x) to determine the presence or absence of cracks on the outer surface of the bent part. "Cracks" refer to thin cracks that are observed extending from the surface of the outer surface of the bent part toward the inside of the test piece. In the copper alloy sheet of this embodiment, even when GW close bending is performed, no cracks occur on the outer surface of the bent portion.

[0037] 3. Manufacturing method Next, a method for producing a copper alloy sheet according to the present invention will be described.

[0038] The copper alloy sheet can be produced by subjecting a copper alloy ingot to the steps of hot rolling, cold rolling, solution treatment, aging treatment, finish cold rolling, and low-temperature annealing in this order, with no cold rolling being performed between the solution treatment and the aging treatment.

[0039] The copper alloy of the present invention is basically a rolled copper alloy sheet, and strips obtained by slitting the copper alloy sheet in the width direction, and coils of such sheets or strips are also included in the copper alloy sheet of the present invention.

[0040] (hot rolling, cold rolling) First, a copper alloy ingot having a desired chemical composition (i.e., a chemical composition substantially equal to the chemical composition of the copper alloy sheet described above) is produced. The copper alloy ingot is heated (homogenized) at 800 to 1000°C for 0.5 to 4 hours, and then hot-rolled at 800 to 1000°C. After hot-rolling, the ingot is water-cooled or naturally cooled. Thereafter, the ingot is cold-rolled to a target thickness (e.g., 0.2 to 1 mm). The target thickness is appropriately changed taking into account the finishing reduction ratio and final thickness of the copper alloy sheet. Intermediate annealing may be performed as appropriate during cold rolling.

[0041] (solution treatment) The subsequent solution treatment is carried out under the condition that the cold-rolled material after the solution treatment satisfies the following formula (1). X≦Y<1.13X (1) where X is the electrical conductivity when the amounts of Ni and Si in solid solution are maximum in a copper alloy material having the same chemical composition as that of the copper alloy ingot, Y is the electrical conductivity of the cold-rolled material after the solution treatment.

[0042] The conductivity X is calculated as follows. First, a copper alloy material containing Ni and Si is subjected to solution treatment (holding at the solution treatment temperature for a predetermined time and then quenching). The higher the solution treatment temperature, the more the solution progresses (i.e., the amount of Ni and Si dissolved in solid solution increases). The more the Ni and Si dissolved in solid solution progresses, the lower the electrical conductivity of the copper alloy material. Therefore, when a copper alloy material having the same chemical composition as that of a copper alloy ingot is subjected to solution treatment at various solution treatment temperatures, and the conductivity no longer decreases, this conductivity is the "electrical conductivity when the amount of solid solution of Ni and Si is at its maximum" (electrical conductivity X).

[0043] As described above, in a copper alloy material containing Ni and Si, the electrical conductivity of the copper alloy material decreases as the solid solution of Ni and Si progresses. Therefore, electrical conductivity can be an index for knowing the solid solution state of Ni and Si in the copper alloy material. It can be said that the closer the electrical conductivity Y of the cold-rolled material after solution treatment is to the electrical conductivity X calculated as above, the more the solid solution of Ni and Si in the cold-rolled material progresses. In particular, when Y = X, it can be determined that Ni and Si in the cold-rolled material are completely dissolved. On the other hand, when Y is significantly larger than X (for example, when Y≧1.13X), the solution treatment is insufficient, and the GW adhesion bendability of the final copper alloy sheet product decreases.

[0044] In this embodiment, the solution treatment is performed so that the electrical conductivity Y satisfies the formula (1). By performing solution treatment under the condition that satisfies formula (1), the surface density of Ni2Si particles with a particle size of 30 nm or more becomes 1.0 × 10 -6 pieces / nm 2 or less, and a copper alloy sheet excellent in GW adhesion and bendability can be obtained.

[0045] Preferably, the solution treatment is carried out so that the electrical conductivity Y satisfies the following formula (2): where X and Y are the same as the electrical conductivity X and Y in formula (1). X≦Y<1.1X (2)

[0046] Specific solution treatment conditions include heating to 700 to 1000°C at a heating rate of 10°C / sec or more and holding at that temperature for 10 seconds or more but less than 60 seconds. The copper alloy sheet is then cooled (rapidly cooled) at a cooling rate of 30°C / sec or more. The heating rate is preferably 30°C / sec or more, and the cooling rate is preferably 100°C / sec or more. By increasing the heating rate and cooling rate, Ni2Si can be suppressed during heating and cooling. This allows for a copper alloy sheet with well-balanced improvements in GW adhesion bendability, electrical conductivity, and 0.2% yield strength to be obtained.

[0047] The higher the Ni and Si contents in the copper alloy sheet, the higher the solution treatment temperature is preferred. This can promote the solid solution of Ni and Si. The optimal solution treatment temperature can also vary depending on the heating rate, holding time, and cooling rate. When the Ni and Si contents are in a relatively high range (for example, Ni: 2.20 to 3.00 mass%, Si: 0.50 to 1.00 mass%), the solution treatment temperature is preferably generally higher than 800°C and lower than 1000°C, and more preferably higher than 850°C and lower than 950°C. When the Ni and Si contents are in a relatively low range (Ni: 1.50 mass% or more and less than 2.20 mass%, Si: 0.10 mass% or more and less than 0.50 mass%), the solution treatment temperature is preferably generally 700 to 800°C. It is preferable to adjust the solution treatment temperature within the preferred temperature range, taking the Ni and Si contents into consideration.

[0048] In Patent Document 3, the solution treatment temperature rise time is as long as 4 to 8 hours and the holding time is as long as 5 minutes, which may reduce productivity and cause excessively large crystal grains, resulting in reduced bendability after final cold rolling.

[0049] (Aging treatment) After the solution treatment, an aging treatment is carried out. The aging treatment may be carried out under the same conditions as in the past, for example, by heating to 350 to 600°C and holding at that temperature for 1 to 20 hours. This treatment causes Ni-Si to precipitate by aging (aging treatment). If the holding temperature is less than 350°C, the precipitation of Ni2Si becomes insufficient, and if it exceeds 600°C, the sheet material softens, and in either case, the yield strength required for the copper alloy sheet cannot be obtained. The holding temperature is more preferably 400 to 500°C. If the holding time is less than 1 hour, the precipitation of Ni2Si becomes insufficient, and if it exceeds 20 hours, productivity is hindered.

[0050] (finish cold rolling) Finish cold rolling is performed at a reduction ratio of 40 to 70%. If cold rolling is performed at a reduction ratio exceeding 70%, the GW tight bending workability of the copper alloy sheet product deteriorates.

[0051] In Patent Documents 1 and 2, finish cold rolling is performed after solution annealing, and then aging annealing is performed. On the other hand, the present embodiment is different in that aging annealing is performed after solution annealing, and then finish cold rolling is performed. Due to this difference, the copper alloy sheet of the present embodiment can have improved bending workability compared to the copper alloy sheets of Patent Documents 1 and 2.

[0052] (low temperature annealing) After the finish cold rolling, low-temperature annealing may be performed to reduce the residual stress of the sheet material and improve its spring limit and stress relaxation resistance. The heating temperature is preferably 200 to 400°C, and the holding time is preferably 10 to 60 seconds. Annealing at such a low temperature reduces the residual stress inside the sheet material, improving the bending workability and breaking elongation with almost no reduction in strength. It also increases the electrical conductivity of the sheet material. If the heating temperature during low-temperature annealing exceeds the upper limit of the heating temperature for aging treatment (600°C), the sheet material will significantly soften. Therefore, the upper limit of the heating temperature for low-temperature annealing is set to 400°C, which is significantly lower than the upper limit of the heating temperature for aging treatment. On the other hand, if the heating temperature is lower than 200°C, the effects of improving the above-mentioned properties are less likely to be fully realized.

[0053] A person skilled in the art who has come into contact with the manufacturing method of the copper alloy sheet according to the embodiment of the present invention described above may be able to obtain the copper alloy sheet according to the present invention by trial and error using a manufacturing method different from the above-described manufacturing method. [Example]

[0054] (Preparation of copper alloy plate) Copper alloys having the chemical compositions shown in Table 1 were air-melted in an induction furnace under a charcoal cover to produce ingots measuring 5000 mm x 640 mm x 260 mm. These ingots were heated at 900 to 970°C for 3 hours or more, then hot-rolled to a thickness of approximately 20 mm and water-cooled from 700°C or higher to obtain hot-rolled materials with a thickness of 20 mm. The hot-rolled sheets were then faced to remove surface oxide scale and cold-rolled.

[0055] In the subsequent solution treatment, Sample No. 1 was subjected to solution treatment in a continuous annealing furnace at the furnace temperature and strip threading speed shown in Table 2. The continuous annealing furnace conditions used for Sample No. 1 corresponded to laboratory conditions of a holding temperature of 770°C and a holding time of 30 seconds. Samples Nos. 2 to 4 were subjected to solution treatment at the temperature and time shown in Table 3. Next, the solution-treated plate material was subjected to an aging treatment described below.

[0056] After the solution treatment, a portion of the plate material was cut out, and the electrical conductivity (electrical conductivity Y) of each sample after the solution treatment was measured. In addition, the electrical conductivity X (i.e., the electrical conductivity when the amount of Ni and Si in solid solution is at its maximum) of copper alloy sheets having the chemical composition of Samples No. 1 to 4 was determined in a separate test. Four test pieces were cut out from each of the cold-rolled materials (before solution treatment) of Samples No. 1 to 4, and the electrical conductivity was measured after different solution treatments (solution treatment temperature: 720°C to 820°C, holding time: 10 to 60 seconds). The change in electrical conductivity versus solution treatment temperature was graphed, and the value at which the electrical conductivity no longer decreased was designated as "electrical conductivity X." The electrical conductivity X and Y of each sample are shown in Tables 2 and 3. In addition, each sample was evaluated for its sufficiency in the following formula (1), and the results are shown in Tables 2 and 3 as "Good" if it was satisfied and "Poor" if it was not. X≦Y<1.13X (1)

[0057] The solution-treated sheets were then subjected to aging treatment. The aging conditions for Sample No. 1 are shown in Table 2, and the aging conditions for Samples Nos. 2 to 4 are shown in Table 3. The aging-treated sheets were then finish cold-rolled at a rolling reduction of 40 to 60%. The thickness after finish cold rolling was 0.1 mm for Sample No. 1 and 0.15 mm for Samples Nos. 2 to 4, respectively. After the finish cold rolling, low-temperature annealing was performed at a heating temperature of 200 to 400° C. and a holding time of 10 to 60 seconds. For the low-temperature annealing, a continuous annealing furnace was used for sample No. 1, and a saltpeter furnace was used for samples Nos. 2 to 4.

[0058] Various measurements were carried out on the sheet material after low-temperature annealing.

[0059] (Metal structure) Surface density of Ni2Si particles with a particle size of 30 nm or more A 3 mm diameter disk was punched out of the plate material, and then the plate material was thinned by the electrolytic thin film method to prepare a sample for observation so that the center of the plate thickness could be observed. The thinning treatment device used was a TenuPol manufactured by Struers. First, the observation material was placed in a sample holder equipped with electrodes so that both sides of the observation material were exposed. The sample holder was then placed in the thinning treatment device, and electrolyte was sprayed from both sides of the holder toward the exposed surface of the observation sample to polish the observation material (twin-jet polishing). The electrolyte consisted of 30% nitric acid and 70% distilled water, and the current and spray flow rate during polishing were adjusted appropriately.

[0060] The prepared observation specimen was observed using a TalosF200X field emission transmission electron microscope (manufactured by Japan FI) at an acceleration voltage of 200 kV and a magnification of 50,000 times. The specimen was positioned so that the left and right direction of the observation area was the rolling direction. <110> The interior of crystal grains within a depth range of 50 to 100 nm was observed using bright-field and dark-field images. By comparing the acquired bright-field and dark-field images, particle images that appeared black in the bright-field image and white in the dark-field image were determined to be Ni2Si particles. Figure 3(a) is a bright-field image, with arrows indicating black particles (Ni2Si particles). Figure 3(b) is a dark-field image of the same area as Figure 3(a), and it can be seen that white particles are observed in the area pointed to by the arrow in Figure 3(a).

[0061] At any point within the field of view, an additional 3100 nm × 3100 nm (= 9.61 × 10 6 nm 2 ) was defined as an observation area. Of the Ni2Si particles present in the observation area, particles with a vertical dimension (particle size) of 30 nm or more (direction perpendicular to the rolling direction) were identified and counted. Ni2Si particles with a particle size of 30 nm were identified manually by visual inspection. Image analysis software may also be used for identification. The number of Ni2Si particles with a particle size of 30 nm was divided by the area of ​​the observation area to calculate the areal density of Ni2Si particles.

[0062] (characteristic evaluation) The properties of the copper alloy sheet samples were evaluated by measuring the tensile test (0.2% yield strength in the TD direction), electrical conductivity, and adhesive bendability.

[0063] Tensile test: Test pieces for tensile tests were prepared from the copper alloy plate samples and used in the tensile tests. Tensile test specimens were cut out from copper alloy sheets to form JIS No. 5 test specimens specified in JIS 2241, with the longitudinal direction of the test specimen at 90 degrees to the rolling direction (hereinafter referred to as TD). The test specimens were processed by milling. The 0.2% yield strength was determined by performing a tensile test according to JIS Z2241 at room temperature using a Shimadzu 100kN autograph, and determining the strength at which the strain was 0.2% as the 0.2% yield strength. A 0.2% yield strength of 680 MPa or more was evaluated as passing.

[0064] ·conductivity: Test pieces for measuring electrical conductivity were prepared from the copper alloy plate samples, and the electrical conductivity was measured. A test piece measuring 180 mm in length and 10 mm in width was cut out from the copper alloy plate so that the longitudinal direction was the rolling direction. At this time, the longitudinal side was milled to prevent burrs generated during cutting from changing the contact area between the terminal and the test piece. The conductivity is measured in accordance with the non-ferrous metal material conductivity measurement method specified in JISH0505, and the volume resistivity measured by the four-terminal method using a double bridge is the volume resistivity of International Annealed Copper Standard, 1.7241 x 10 -8 Calculated by dividing by Ω·m. Those with a conductivity of 65% IACS or higher were evaluated as passing.

[0065] GW Adhesion Bendability: The adhesion bending test of the copper alloy plate samples was carried out by the following method. A bending test piece measuring 30 mm in length and 10 mm in width was cut from the copper alloy plate so that the longitudinal direction was the rolling direction. At this time, the longitudinal side was milled to prevent burrs generated during cutting from affecting the bending process. The bending test piece was subjected to a close contact bending test using GoodWay (bending axis perpendicular to the rolling direction).

[0066] In the close contact bending test, a V-shaped bending jig (reference numerals 11 and 12 in Fig. 1(a) and 21 and 22 in Fig. 1(b)) and a block-shaped jig (reference numerals 31 and 32 in Fig. 1(c)) were used. First, the polished test piece S was clamped between the jigs 11 and 12 as shown in Fig. 1(a) and bent to R = 0.05 and θ = 90° with a load of 200 N. Next, the test piece S was clamped between the jigs 21 and 22 as shown in Fig. 1(b) and bent to R = 0.05 and θ = 150° with a load of 200 N. Finally, the V-shaped bent test piece S was clamped between the block-shaped jigs 31 and 32 as shown in Fig. 1(c) and crushed with a load of 200 N to perform close contact bending.

[0067] The close bendability was judged by observing the cross section of the bent part to check for the presence or absence of cracks. Of the surfaces of the bent part, the surfaces that face each other when bent with close contact were designated the "inner surface," and the surface opposite the inner surface was designated the "outer surface" (see Figures 2(a) and (b)). The close bendability was judged by the presence or absence of cracks on the outer surface of the bent part (the area surrounded by the dashed line in Figures 2(a) and (b)).

[0068] The test piece (bending test piece) that had been subjected to close contact bending was embedded in resin, and the observation surface was prepared by mechanical polishing and buffing so that the plane perpendicular to the bending axis would be the cross section (observation surface). The cross section (observation surface) was observed using an optical microscope (magnification: ×200) to determine whether or not there were cracks on the outer surface of the bent part. "Cracks" were observed as thin cracks extending from the surface of the outer surface of the bent part toward the inside of the test piece.

[0069] The example shown in Figure 2(a) (Sample No. 1) had no cracks on the outer surface of the bent portion and was judged to be "suitable for close bending (○)." The example shown in Figure 2(b) (Sample No. 3) had cracks on the outer surface of the bent portion and was judged to be "unsuitable for close bending (×)." The judgment results are shown in the "GW close bending" column in Table 3.

[0070] [Table 1]

[0071] [Table 2]

[0072] [Table 3]

[0073] [Table 4]

[0074] The copper alloy sheets of Samples 1 and 2, which are examples of the present invention, have high yield strength and excellent GW adhesion bendability, and are excellent in balance between yield strength and bendability, because they satisfy the chemical composition and metal structure (average grain size and areal density of Ni2Si) specified in this embodiment. Furthermore, it was found that the copper alloy sheets of Samples 1 and 2 have high electrical conductivity and are suitable for use in electrical and electronic components.

[0075] In the comparative example, sample No. 3, the electrical conductivity Y after solution treatment did not satisfy formula (1), and therefore the solution treatment was insufficient, and the surface density of Ni2Si particles with a particle size of 30 nm or more exceeded the range specified in this embodiment. As a result, the GW adhesion bendability was low and cracks occurred.

[0076] In sample No. 4, which is a comparative example, the Ni content was low, so the precipitation effect of Ni2Si particles was low, and the 0.2% proof stress was lower than 680 MPa. [Industrial Applicability]

[0077] The copper alloy sheet of the present disclosure has high strength and excellent GW adhesion bendability, and is therefore suitable for mating terminals and other terminal materials for automotive applications, as well as current-carrying parts for electric and electronic components such as relays, switches, and sockets.

Claims

1. Ni: 1.50 to 3.00 mass%; and Si: 0.10 to 1.00 mass %, the balance being Cu and unavoidable impurities; Ni with a grain size of 30 nm or more contained in the metal structure ２ The surface density of Si particles is 1.0 × 10 －６ pieces / nm ２ is as follows: A copper alloy sheet having a 0.2% yield strength of 680 MPa or more in the direction perpendicular to the rolling direction and free from cracks due to G.W. close bending.

2. The copper alloy sheet according to claim 1, which satisfies one or more of the following (a) to (c): (a) further containing one or more of Sn and Mg, Sn: more than 0% by mass and not more than 1.00% by mass, Mg: contained in the range of more than 0 mass% and not more than 0.20 mass%; (b) Zn: more than 0 mass% and 2.00 mass% or less; (c) The steel further contains more than 0 mass % and 0.50 mass % in total of one or more elements selected from the group consisting of Al, Mn, Cr, Ti, Zr, Fe, P, and Ag.

3. A copper alloy ingot containing 1.50 to 3.00 mass% of Ni and 0.10 to 1.00 mass% of Si, with the balance being Cu and unavoidable impurities, is subjected to hot rolling, cold rolling, solution treatment, aging treatment, and finish cold rolling in this order; The solution treatment is carried out under conditions in which the cold-rolled material after the solution treatment satisfies the following formula (1): The finish cold rolling is performed at a rolling ratio of 40 to 70%. Manufacturing method of copper alloy sheet. X≦Y<1.13X (1) where X is the electrical conductivity when the amounts of Ni and Si dissolved in a copper alloy material having the same chemical composition as that of the copper alloy ingot are at their maximum, Y is the electrical conductivity of the cold-rolled material after the solution treatment.

4. The method for producing a copper alloy sheet according to claim 3, wherein the copper alloy ingot satisfies one or more of the following (a) to (c): (a) further containing one or more of Sn and Mg, Sn: more than 0% by mass and not more than 1.00% by mass, Mg: More than 0 mass% and not more than 0.20 mass% (b) Zn: more than 0 mass% and not more than 2.00 mass% (c) The steel further contains more than 0 mass % and 0.50 mass % in total of one or more elements selected from the group consisting of Al, Mn, Cr, Ti, Zr, Fe, P, and Ag.

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