JP5507635B2 - Copper alloy sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a copper alloy sheet and a method for manufacturing the same, and more particularly to a Cu—Zn-based copper alloy sheet used for electrical and electronic parts such as connectors, lead frames, relays, and switches, and a method for manufacturing the same.

  Materials used for electrical and electronic parts such as connectors, lead frames, relays, and switches must have good electrical conductivity to suppress the generation of Joule heat due to energization, as well as during assembly and operation of electrical and electronic equipment. A high strength that can withstand the stress sometimes applied is required. In addition, since electrical and electronic parts such as connectors are generally formed by bending, excellent bending workability is also required. Furthermore, in order to ensure contact reliability between electrical and electronic components such as connectors, it is also required to have durability against a phenomenon (stress relaxation) in which the contact pressure decreases with time, that is, excellent stress relaxation characteristics. .

  In recent years, electrical and electronic parts such as connectors tend to be highly integrated, miniaturized, and lightened, and accordingly, there is an increasing demand for thinning of copper and copper alloy plate materials. For this reason, the strength level required for the material is becoming stricter. Further, in order to cope with the downsizing and complicated shape of electrical and electronic parts such as connectors, it is required to improve the shape and dimensional accuracy of the bent product. Therefore, recently, a so-called post-notching bending method in which notching is performed on a portion of a material to be bent (notching) and then bending along the notch is often applied. However, in this post-notching bending method, the vicinity of the notch portion is work-hardened by notching, so that cracking is likely to occur in subsequent bending. For this reason, the post-notching bending method is a very severe bending process for materials.

  In addition, as electrical and electronic parts such as connectors are often used in harsh environments, demands for stress relaxation resistance have become stricter. For example, when used in an environment exposed to high temperatures, such as an automobile connector, the stress relaxation resistance is particularly important. Note that stress relaxation means that under a relatively high temperature (for example, 100 to 200 ° C.) environment, even if the contact pressure of the spring portion of the material constituting the electrical / electronic component such as the connector is kept constant at room temperature. It is a kind of creep phenomenon that decreases with time. In other words, stress relaxation is given by the fact that dislocations move due to self-diffusion of atoms constituting the matrix or diffusion of solute atoms in the state where stress is applied to the metal material, resulting in plastic deformation. This is a phenomenon in which the stress is relaxed.

  In recent years, there has been a tendency to reduce the environmental burden and save resources and energy, and in connection with this, with copper and copper alloy plates, which are raw materials, reduction of raw material costs and manufacturing costs, product recyclability, etc. The demand for is increasing.

  However, since there is a trade-off relationship between the strength and conductivity of the plate material, between the strength and the bending workability, and between the bending workability and the stress relaxation resistance characteristic, conventionally, the electrical power of such a connector or the like has been used. As a plate material for an electronic component, a plate material having good conductivity, strength, bending workability or stress relaxation resistance and a relatively low cost is appropriately selected and used depending on the application.

  Conventionally, brass, phosphor bronze, and the like are used as general-purpose materials for electrical and electronic parts such as connectors. Phosphor bronze has a relatively good balance of strength, corrosion resistance, stress corrosion cracking resistance, and stress relaxation resistance. For example, in the case of two types of phosphor bronze (C5191), the conductivity is as small as about 15% IACS. Moreover, it cannot be hot-worked and contains about 6% of expensive Sn, which is disadvantageous in terms of cost.

On the other hand, brass (Cu—Zn-based copper alloy) is widely used as a material with low raw material and manufacturing costs and excellent product recyclability. However, the strength of brass is lower than that of phosphor bronze, and brass having the highest strength is EH (H06). For example, in the case of a plate product of one type of brass (C2600), the tensile strength is generally 550 N / mm. The tensile strength is about ² , and this tensile strength corresponds to the tensile strength of two types of phosphor bronze H (H04). In addition, in the type 1 brass product (C2600), the stress relaxation rate is about twice that of the grade 2 H (H04) of phosphor bronze, and the stress relaxation resistance is also inferior.

Further, in order to improve the strength of brass, it is necessary to increase the finish rolling rate (increased by grade), and accordingly, the bending workability in the direction perpendicular to the rolling direction (that is, the bending axis is rolled). Bending workability which is a direction parallel to the direction) is significantly deteriorated. Therefore, even brass with a high strength level may not be processed into electrical and electronic parts such as connectors. For example, if the finish rolling rate of one kind of brass is increased and the tensile strength is higher than 570 N / mm ² , it becomes difficult to press-mold small parts.

  In particular, in the case of a simple alloy brass made of Cu and Zn, it is not easy to improve the bending workability while maintaining the strength. Therefore, a device has been devised to increase the strength level by adding various elements to brass. For example, a Cu—Zn-based copper alloy to which a third element such as Sn, Ni, Mn, and Si is added has been proposed (see, for example, Patent Documents 1 to 3). However, the addition of Sn or the like is not preferable because it increases the raw material and manufacturing cost of the Cu-Zn-based copper alloy, which is inherently inexpensive, and reduces the recyclability of the product. Moreover, even if Sn or the like is added, the bending workability may not be sufficiently improved.

  Generally, crystal grain refinement is performed in order to improve the bending workability of a copper alloy. However, the smaller the crystal grain size, the larger the area of the crystal grain boundary that exists per unit volume. Therefore, the refinement of crystal grains becomes a factor that promotes stress relaxation, which is a kind of creep phenomenon. In particular, when used in a high-temperature environment such as an in-vehicle connector, the diffusion rate along the grain boundary of atoms is significantly faster than in the grains. It is easy to become.

  In addition, since there is no large amount of fine precipitates in the Cu-Zn-based copper alloy, it is difficult to control grain refinement, and the final recrystallization treatment conditions and the preceding cold rolling conditions are strictly controlled. However, variations in crystal grain size during mass production are likely to occur.

  Further, brass having a two-phase mixed structure composed of a fine α phase and a β phase has been proposed as copper that improves strength without degrading bending workability (see, for example, Patent Document 4). However, generally used brass for terminals is brass having an α-phase single-phase structure, and when a large amount of Zn is contained in such a two-phase mixed structure brass, properties such as corrosion resistance may differ. .

JP-A-5-33087 (paragraph numbers 0006-0008) JP 2000-38628 A (paragraph numbers 0009-0012) JP 2001-164328 A (paragraph numbers 0013 and 0022) JP 2000-129376 A (paragraph numbers 0007-0009)

  The Cu—Zn-based copper alloy is a typical solid solution strengthened alloy, and in order to improve the strength, it is necessary to increase the finish rolling rate (increased quality). However, due to the increase in finish rolling rate (increased by grade), the bending workability in the direction parallel to the rolling direction (that is, the bending workability in which the bending axis is perpendicular to the rolling direction) is not bad, but rolling The bending workability in the direction perpendicular to the direction (that is, the bending workability in which the bending axis is parallel to the rolling direction) is significantly deteriorated.

Therefore, when the bending workability of the Cu—Zn-based copper alloy is required, only a low-quality (approximately H or less) Cu—Zn-based copper alloy having a tensile strength of 500 N / mm ² or less can be used. In addition, the spring property tends to be low due to insufficient strength. On the other hand, Cu-Zn based copper alloys of high quality (generally EH or higher) having a tensile strength of 570 N / mm ² or higher are used only for components that are almost flat and do not undergo bending.

  As described above, general methods for improving bending workability while maintaining strength include a method of adding a large amount of elements such as Sn and a method of refining crystal grains. However, when elements such as Sn are added in a large amount, raw materials and production costs are increased, product recyclability tends to be lowered, and bending workability cannot be sufficiently improved. Moreover, in the case of crystal grain refinement, the stress relaxation resistance of a Cu—Zn-based copper alloy having poor stress relaxation resistance may be further reduced.

  Further, applying the notching after bending method to the copper alloy sheet is effective in improving the shape and dimensional accuracy of the bent product, but the Cu-Zn copper alloy is generally parallel to the rolling direction. Even good directional bendability is not sufficient to withstand severe bending such as post-notching bending.

  Therefore, in view of such a conventional problem, the present invention is not only excellent in ordinary bending workability but also in bending workability after notching while maintaining high strength, and inexpensive with excellent stress relaxation resistance. An object of the present invention is to provide a copper alloy sheet and a method for producing the same.

As a result of diligent research to solve the above problems, the inventors of the present invention have prepared a copper alloy sheet having a composition containing 15 to 37% by mass of Zn and the balance being Cu and inevitable impurities. Assuming that the X-ray diffraction intensity of the {420} crystal plane at I {420} and the X-ray diffraction intensity of the {420} crystal plane of pure copper standard powder is I ₀ {420}, I {420} / I ₀ {420 If the crystal orientation satisfies the condition of> 0.8, not only the normal bending workability but also the bending workability after notching is excellent while maintaining high strength, and the stress relaxation resistance is low. The present inventors have found that a copper alloy sheet can be obtained and have completed the present invention.

That is, the copper alloy sheet according to the present invention contains 15 to 37% by mass of Zn, with the balance being Cu and inevitable impurities. The copper alloy sheet has a composition of X of {420} crystal plane in the plate surface of the copper alloy sheet. A crystal satisfying I {420} / I ₀ {420}> 0.8, where the line diffraction intensity is I {420} and the X-ray diffraction intensity of the {420} crystal plane of pure copper standard powder is I ₀ {420}. It has an orientation.

In this copper alloy sheet, the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy sheet is I {220}, and the X-ray diffraction intensity of the {220} crystal plane of the pure copper standard powder is I ₀ {220}. Then, it is preferable to have a crystal orientation satisfying 1.0 ≦ I {220} / I ₀ {220} ≦ 3.5. Moreover, it is preferable that the average crystal grain diameter of a copper alloy board | plate material is 10-60 micrometers. Further, one copper alloy sheet, which is selected from the group consisting of 2.0 wt% or less of Sn, 2.0 mass% of Ni, 2.0 mass% of Fe and 1.0 mass% of Si You may have the composition which further contains the above element. Further, the copper alloy plate material further includes a composition that further includes one or more elements selected from the group consisting of Co, Cr, Mg, Al, B, P, Zr, Ti, Mn, and V in a total range of 3% by mass or less. You may have. The copper alloy sheet preferably has a tensile strength of 580 MPa or more, an electrical conductivity of 20% IACS or more, and a stress relaxation rate of 35% or less.

A method of manufacturing a copper alloy sheet according to the invention comprises a 15 to 37 mass% of Zn, optionally 2.0 wt% or less of Sn and 2.0 mass% of Ni and 2.0 wt% It contains one or more elements selected from the group consisting of the following Fe and 1.0% by mass or less of Si, and further contains Co, Cr, Mg, Al, B, P, Zr, Ti, Mn and V as required. After melting and casting a raw material of a copper alloy having a composition containing at least one element selected from the group consisting of 3% by mass or less and the balance being Cu and inevitable impurities, 900 ° C. to 300 ° C. After performing the first rolling pass at 900 ° C. to 600 ° C. as the hot rolling in, rolling at a rolling rate of 40% or more is performed at less than 600 ° C. to 300 ° C., and then cold rolling is performed at a rolling rate of 85% or more, Then, recrystallization annealing at 350 to 650 ° C., A copper alloy sheet is produced by sequentially performing finish cold rolling at a rolling rate of 30 to 80%.

  In this method for producing a copper alloy sheet, it is preferable to perform rolling at a rolling rate of 60% or more in a rolling pass at 900 ° C. to 600 ° C. Moreover, in recrystallization annealing, it is preferable to perform heat treatment by setting a holding time and an ultimate temperature at 350 to 650 ° C. so that the average crystal grain size after recrystallization annealing is 10 to 60 μm. Furthermore, it is preferable to perform low-temperature annealing at 150 to 350 ° C. after finish cold rolling.

  The connector terminal according to the present invention is characterized by using the above-described copper alloy sheet as a material.

  According to the present invention, while maintaining high strength, an inexpensive copper alloy sheet material excellent in not only normal bending workability but also bending workability after notching and excellent in stress relaxation resistance, and a method for producing the same are provided. can do.

It is a standard inverse pole figure showing distribution of the Schmid factor of a face centered cubic crystal. It is a figure which shows typically the cross-sectional shape of a notch formation jig | tool. It is a figure explaining the method of notching. It is a figure which shows typically the cross-sectional shape of the notch formation part vicinity of a bending test piece with a notch. It is a figure which shows typically the shape of the intermediate product of the stage which formed the connector terminal part by carrying out the continuous press molding of the strip | belt of a copper alloy board | plate material.

The embodiment of the copper alloy sheet according to the present invention contains 15 to 37 mass% of Zn, and if necessary, 2.0 mass% or less of Sn, 2.0 mass% or less of Ni, and 2.0 mass% or less. And one or more elements selected from the group consisting of Si and 1.0% by mass or less, and optionally Co, Cr, Mg, Al, B, P, Zr, Ti, Mn and V. In a copper alloy sheet having a composition of one or more elements selected from the group consisting of 3% by mass or less and the balance being Cu and unavoidable impurities, the {420} crystal plane of the plate surface of the copper alloy sheet When the X-ray diffraction intensity is I {420} and the X-ray diffraction intensity of the {420} crystal plane of the pure copper standard powder is I ₀ {420}, I {420} / I ₀ {420}> 0.8 is satisfied. , X-ray diffraction intensity of {220} crystal plane on the copper alloy sheet And I {220}, the X-ray diffraction intensity of the {220} crystal plane of standard pure copper powder When _I 0 {220}, satisfy _{1.0 ≦ I {220} / I} 0 {220} ≦ 3.5 crystals Has an orientation. Hereinafter, this copper alloy sheet and its manufacturing method will be described in detail.

[Alloy composition]
The embodiment of the copper alloy sheet material according to the present invention is a sheet material composed of a Cu-Zn based copper alloy containing Cu and Zn, preferably a sheet material composed of a binary copper alloy of Cu-Zn. A small amount of Sn, Ni, Si, Fe, and other elements may be contained.

  Zn has the effect of improving the strength and springiness of the copper alloy sheet. Since Zn is cheaper than Cu, it is preferable to add a large amount of Zn. However, when the Zn content exceeds 37% by mass, the cold workability of the copper alloy sheet material is remarkably lowered due to the formation of the β phase, and the stress corrosion cracking resistance is also lowered. And solderability is also reduced. On the other hand, if the Zn content is less than 15% by mass, the strength and springiness such as 0.2% proof stress and tensile strength of the copper alloy sheet are insufficient, the Young's modulus increases, and the copper alloy sheet is dissolved. The amount of hydrogen gas occluded increases, ingot blowholes are easily generated, and the amount of inexpensive Zn is small, which is economically disadvantageous. Therefore, the Zn content is preferably 15 to 37% by mass, and more preferably 20 to 35% by mass.

  Sn has the effect of improving the strength, stress relaxation resistance and stress corrosion cracking resistance of the copper alloy sheet. In order to reuse the material surface-treated with Sn such as Sn plating, the copper alloy sheet preferably contains Sn. However, if the Sn content exceeds 2.0% by mass, the electrical conductivity of the copper alloy sheet material is drastically reduced, and grain boundary segregation becomes severe in the coexistence with Zn, so that the hot workability is remarkably lowered. . On the other hand, when the Sn content is less than 0.1% by mass, the effect of improving the mechanical properties of the copper alloy sheet is reduced, and it is difficult to use press scraps subjected to Sn plating as a raw material. Therefore, when the copper alloy sheet contains Sn, the Sn content is preferably 0.1 to 2.0% by mass, and more preferably 0.2 to 1.0% by mass.

  Ni has the effect of improving the solid solution strengthening effect and stress relaxation resistance of the copper alloy sheet, and in particular, the zinc equivalent of Ni is a negative value. There is an effect of suppressing the variation of the. In order to fully exhibit these effects, the Ni content is preferably 0.1% by mass or more. On the other hand, if the Ni content exceeds 2.0% by mass, the conductivity will be significantly reduced. Therefore, when the copper alloy sheet contains Ni, the Ni content is preferably 0.1 to 2.0% by mass, and more preferably 0.2 to 1.0% by mass.

  Si has the effect of improving the stress corrosion cracking resistance of the copper alloy sheet even in a small amount. In order to sufficiently obtain this effect, the Si content is preferably 0.01% by mass or more. However, if the Si content exceeds 1.0% by mass, the conductivity tends to decrease, and Si is an element that easily oxidizes, and the castability tends to decrease, so the Si content should not be too much. Good. Therefore, when the copper alloy sheet contains Si, the Si content is preferably 0.01 to 1.0% by mass, and more preferably 0.05 to 0.5% by mass.

  Fe has a solid solution strengthening effect of a copper alloy sheet, a deoxidation effect during casting, and a refinement effect of the cast structure. In order to sufficiently exhibit these effects, the Fe content is preferably set to 0.01% by mass or more. However, Fe is an element that is easily oxidized, and when the Fe content exceeds 2.0 mass%, the castability is significantly lowered. Therefore, when the copper alloy sheet contains Fe, the Fe content is preferably 0.01 to 2.0% by mass, more preferably 0.01 to 1.0% by mass, Most preferably, it is 0.1-0.5 mass%.

  Other elements added to the copper alloy sheet as necessary include Co, Cr, Mg, Al, B, P, Zr, Ti, Mn, and V. For example, Co, Cr, B, P, Zr, Ti, Mn, and V have the effect of further increasing the alloy strength and reducing the stress relaxation. In addition, Cr, Zr, Ti, Mn, and V easily form a high melting point compound with S and Pb, which are unavoidable impurities, and B, P, Zr, and Ti have an effect of refining the cast structure. And has the effect of improving hot workability. When the copper alloy sheet contains one or more elements selected from the group consisting of Co, Cr, Mg, Al, B, P, Zr, Ti, Mn and V, the effect of adding each element is In order to obtain sufficiently, the total amount of these is preferably 0.01% by mass or more. However, when there is too much content of these elements, it will have a bad influence on hot workability or cold workability, and will become disadvantageous also in cost. Therefore, the total amount of these elements is preferably 3% by mass or less, more preferably 2% by mass or less, and most preferably 1% by mass or less.

[Organization]
An X-ray diffraction pattern from a plate surface (rolled surface) of a Cu—Zn based copper alloy is generally composed of diffraction peaks of four crystal planes {111}, {200}, {220}, and {311}. The X-ray diffraction intensities from other crystal planes are much smaller than the X-ray diffraction intensities from these crystal planes. Moreover, in the Cu—Zn-based copper alloy plate produced by a normal production method, the X-ray diffraction intensity from the {420} plane is weakened to a negligible level, but the method for producing a copper alloy plate according to the present invention According to the embodiment, it is possible to manufacture a Cu—Zn-based copper alloy sheet having a texture having {420} as a main orientation component. It was also found that the stronger the texture, the more advantageous the bending workability as follows.

  There is a Schmid factor as an index indicating the ease of plastic deformation (slip) when an external force is applied in a certain direction of the crystal. When the angle between the direction of the external force applied to the crystal and the normal of the slip surface is φ, and the angle between the direction of the external force applied to the crystal and the slip direction is λ, the Schmid factor is expressed as cos φ · cos λ. The value is in the range of 0.5 or less. The larger the Schmid factor (that is, the closer to 0.5), the greater the shear stress in the slip direction. Therefore, when an external force is applied to a certain crystal from a certain direction, the larger the Schmid factor (that is, closer to 0.5), the easier the crystal is to be deformed. The crystal structure of the Cu—Zn-based copper alloy is face-centered cubic (fcc), but the face-centered cubic slip system is the slip plane {111} and the slip direction <110>. It is known that the larger the factor, the easier it is to deform and the lower the degree of work hardening.

  A standard reverse pole figure showing the Schmid factor distribution of face-centered cubic crystals is shown in FIG. As shown in FIG. 1, the Schmid factor in the <120> direction is 0.490, which is close to 0.5. That is, when an external force is applied in the <120> direction, the face-centered cubic crystal is very easily deformed. The Schmid factors in the other directions are 0.408 in the <100> direction, 0.445 in the <113> direction, 0.408 in the <110> direction, 0.408 in the <112> direction, and 0 in the <111> direction. .272.

  In the case of a crystal whose main orientation plane in a general rolling texture of a Cu—Zn-based copper alloy is a {110} plane, LD (rolling direction) is in the <112> direction, TD (in the rolling direction and the plate thickness direction). (The vertical direction) is the <111> direction, and the Schmitt factors are LD of 0.408 and TD of 0.272. Therefore, the higher the finish rolling ratio, the higher the density of the {110} plane, which is the main orientation plane in the rolling texture, and the higher the strength (particularly the strength of TD), but the TD bending workability becomes significantly worse.

  Further, the texture having {420} as the main orientation component means a texture having a large abundance of crystals in which the {420} plane, that is, the {210} plane is substantially parallel to the plate surface (rolled surface). In the case of a crystal whose principal orientation plane is the {210} plane, there are another <120> direction and <100> direction in the plate plane, that is, in the {210} plane, which are orthogonal to each other. In practice, LD is in the <100> direction and TD is in the <120> direction, and the Schmitt factors are LD of 0.408 and TD of 0.490.

  Thus, when looking at the Schmid factor of LD and TD, when the texture has {420} as the main orientation component, the bending workability of the LD is higher than that of the rolling texture with {220} as the main orientation component. Although it is almost equivalent, the bending workability of TD is remarkably excellent.

  Moreover, in the crystal whose principal orientation plane is the {210} plane, the direction (ND) perpendicular to the plate plane is the <120> direction, and its Schmitt factor is close to 0.5. It is easy and the degree of work hardening is small. On the other hand, the general rolling texture of the Cu—Zn-based copper alloy has {220} as the main orientation component, and in this case, the {220} plane, that is, the {110} plane is substantially parallel to the plate surface (rolling surface). There are many existing ratios of crystals. A crystal whose principal orientation plane is the {110} plane has ND in the <110> direction and its Schmitt factor is about 0.4, so that it is ND compared to a crystal whose principal orientation plane is the {210} plane. The degree of work hardening associated with the deformation to becomes larger. Moreover, the general recrystallization texture of the Cu—Zn-based copper alloy has {311} as the main orientation component. A crystal whose principal orientation plane is the {311} plane has ND in the <113> direction and its Schmitt factor is about 0.45. Therefore, when compared with a crystal whose principal orientation plane is the {210} plane, ND The degree of work hardening associated with the deformation to becomes larger.

In the post-notching bending method, the degree of work hardening in the deformation to ND is extremely important. This is because notching is a deformation to ND, and the degree of work hardening of the portion where the plate thickness is reduced by notching largely governs the bending workability when bent along the notch. If the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet is I {420}, and the X-ray diffraction intensity of the {420} crystal plane of the pure copper powder is I ₀ {420}, I {420} / I ₀ {420}> In the case of a texture that satisfies {420} as a main orientation component, notching compared to a conventional rolled texture or recrystallized texture of a Cu—Zn based copper alloy It is considered that the degree of work hardening due to is reduced, and this significantly improves the bending workability after notching.

In the bending process of the metal plate, the crystal orientation of each crystal grain is different, so that there is a crystal grain that is easily deformed and a crystal grain that is not easily deformed during the bending process. As the degree of bending increases, the deformable crystal grains are preferentially deformed, and the surface of the bent portion of the metal plate has minute irregularities due to uneven deformation between the crystal grains. , This develops into wrinkles and in some cases leads to cracks (breaks). As described above, in the metal plate having a texture satisfying I {420} / I ₀ {420}> 0.8, each crystal grain is easily deformed to ND as compared with a metal plate having a conventional texture. It is easy to be deformed in the plate surface. Thus, it is considered that the bending workability after notching and the normal bending workability can be remarkably improved without particularly refining the crystal grains.

Such crystal orientation is such that the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet is I {420}, and the X-ray diffraction intensity of the {420} crystal plane of the pure copper standard powder is I ₀ {420. }, I {420} / I ₀ {420}> 0.8 is satisfied. In the face-centered cubic X-ray diffraction pattern, {420} plane reflection occurs but {210} plane reflection does not occur, so the {210} plane crystal orientation is evaluated by {420} plane reflection. The Further, it is more preferable to satisfy I {420} / I ₀ {420}> 1.0.

Further, the texture having {420} as the main orientation component is formed as a recrystallized texture by recrystallization annealing. However, in order to increase the strength of the copper alloy sheet, it is necessary to cold-roll after recrystallization annealing. As the cold rolling rate increases, a rolling texture with {220} as the main orientation component develops. As the {220} orientation density increases, the {420} orientation density decreases, but I {420} / I ₀ {420}> 0.8, preferably I {420} / I ₀ {420}> 1. What is necessary is just to adjust a cold rolling rate so that 0.0 may be maintained. However, if the texture having {220} as the main orientation component develops too much, the workability may deteriorate, so the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy plate material is I {220. and}, the X-ray diffraction intensity of the {220} crystal plane of standard pure copper powder When _I 0 {220}, preferably satisfy _{1.0 ≦ I {220} / I} 0 {220} ≦ 3.5. In order to further improve both strength and bending workability, it is preferable to satisfy 1.5 ≦ I {220} / I ₀ {220} ≦ 3.0.

[Average crystal grain size]
As described above, the smaller the average crystal grain size, the better the bending workability. However, if the average crystal grain size is too small, the stress relaxation resistance is likely to deteriorate. When the average crystal grain size is 10 μm or more, it is easy to ensure a satisfactory level of stress relaxation resistance even when a copper alloy sheet is used for the connector. However, when the average crystal grain size becomes too large and exceeds 60 μm, the surface of the bent portion tends to become rough, and the bending workability may be lowered. Therefore, the average crystal grain size is preferably 10 to 60 μm, and more preferably 15 to 30 μm. Such control of the average crystal grain size can be performed by adjusting recrystallization annealing conditions.

[Characteristic]
In order to further reduce the size and thickness of electrical and electronic parts such as connectors, it is preferable that the tensile strength of the copper alloy plate material, which is a material, be set to 580 MPa or more, and more preferably 600 MPa or more. Moreover, in order to suppress the generation of the Joule heat due to energization as electrical and electronic parts such as connectors become highly integrated, it is preferable that the conductivity of the copper alloy sheet is 20% IACS or more.

  In addition, as an evaluation of the bending workability of the copper alloy sheet material, a bending test piece cut out from the copper alloy sheet material so that the longitudinal direction is LD (rolling direction) is used as a bending axis with respect to TD (rolling direction and sheet thickness direction). When the 90 ° W bending test is performed in the vertical direction) and the 90 ° W bending test is performed on the bending test piece cut out so that the longitudinal direction becomes TD, the bending axis is set to LD. In any case, the ratio R / t of the minimum bending radius R to the sheet thickness t in the 90 ° W bending test is preferably 1.0 or less, and more preferably 0.5 or less. Further, in order to improve the shape and dimensional accuracy of the bent product, it is preferable that R / t is 0 as an evaluation of the bending workability after notching of the LD.

  Regarding the stress relaxation resistance, when using a copper alloy sheet material for an in-vehicle connector, etc., the stress relaxation resistance of TD is particularly important, so the stress relaxation rate using a test piece whose longitudinal direction is TD It is preferable to evaluate the stress relaxation characteristics. Moreover, when the maximum load stress on the surface of the copper alloy sheet is 80% of the 0.2% proof stress and held at 150 ° C. for 1000 hours, the stress relaxation rate is less than half of the conventional brass type ( It is preferably about 2 types of phosphor bronze), more preferably 35% or less, and most preferably 30% or less.

  Further, as will be described later, the female connector terminal 100 having the shape shown in FIG. 5 is produced in a horizontal chain manner by continuous pressing, and the surface and cross section of the box bending portion 124 of the obtained female connector terminal 100 are examined by an optical microscope. It is preferably a copper alloy plate material having connector terminal formability that is observed at a magnification of 100 times and no cracks are observed. In the box bending portion 124 of the female connector terminal 100, notching (installation) is performed before bending to form a substantially trapezoidal cross-sectional notch 12′a having a depth of 30 μm as shown in FIG. After that, bending was performed.

[Production method]
The copper alloy sheet as described above can be produced by the embodiment of the method for producing a copper alloy sheet according to the present invention. An embodiment of a method for producing a copper alloy sheet according to the present invention includes a melting / casting step of melting and casting a copper alloy raw material having the above-described composition, and 900 ° C. to 600 ° C. after the melting / casting step. A first rolling pass is performed, and then a hot rolling process in which rolling is performed at a rolling rate of 40% or more at less than 600 ° C. to 300 ° C., and cold rolling is performed at a rolling rate of 85% or more after the hot rolling process. A cold rolling step, a recrystallization annealing step for performing recrystallization annealing at 350 ° C. to 650 ° C. after this cold rolling step, and a finish cold rolling with a rolling rate of 30 to 80% after this recrystallization annealing step And a finish cold rolling process, and after this finish cold rolling process, a low temperature annealing process is performed to perform low temperature annealing as necessary. Hereinafter, these steps will be described in detail. In addition, after hot rolling, chamfering may be performed as necessary, and after each heat treatment, pickling, polishing, and degreasing may be performed as necessary.

(Melting and casting process)
A slab is produced by continuous casting or semi-continuous casting after melting the raw material of the copper alloy by a method similar to a general brass melting method. In addition, the atmosphere at the time of melt | dissolving a raw material is enough for an air atmosphere.

(Hot rolling process)
Usually, the hot rolling of Cu-Zn based copper alloy is performed at a high temperature range of 650 ° C or higher or 700 ° C or higher, for the purpose of breaking the cast structure and softening the material by recrystallization during rolling and between rolling passes. Done. However, under such general hot rolling conditions, it is difficult to produce a copper alloy sheet having a specific texture as in the embodiment of the copper alloy sheet according to the present invention. That is, under such general hot rolling conditions, it is difficult to produce a copper alloy sheet having {420} in the main azimuth direction even if the post-process conditions are changed over a wide range. Therefore, in the embodiment of the method for producing a copper alloy sheet according to the present invention, in the hot rolling process, the first rolling pass is performed in the temperature range of 900 ° C. to 600 ° C., and the rolling is performed in the temperature range of less than 600 ° C. to 300 ° C. Rolling is performed at a rate of 40% or more (so-called hot rolling and warm rolling are combined).

  When the slab is hot-rolled, by performing the first rolling pass at a temperature higher than 600 ° C. where recrystallization is likely to occur, the cast structure can be destroyed and the components and structure can be made uniform. However, rolling at a high temperature exceeding 900 ° C. is not preferable because cracking may occur in a portion where the melting point is lowered, such as a segregated portion of an alloy component. Therefore, in order to ensure complete recrystallization during the hot rolling process, it is preferable to perform rolling at a rolling rate of 60% or more in a temperature range of 900 ° C. to 600 ° C., thereby making the structure uniform Is further promoted. Since a large rolling load is necessary to obtain a rolling rate of 60% in one pass, a total rolling rate of 60% or more may be secured by dividing into multiple passes. Moreover, in embodiment of the manufacturing method of the copper alloy board | plate material by this invention, the rolling rate of 40% or more is ensured in the temperature range of less than 600 degreeC-300 degreeC which a rolling distortion tends to produce. In this way, it becomes easy to form a recrystallized texture having {420} as the main orientation component by a combination of the subsequent cold rolling and recrystallization annealing. In this case as well, several passes of rolling can be performed in a temperature range of less than 600 ° C. to 300 ° C. The final pass temperature of hot rolling is preferably 500 ° C. or less, and the total rolling rate in hot rolling may be about 80 to 95%.

The rolling rate ε (%) in each temperature range is ε = (t ₀ −t) where t _{0 is} the thickness of the slab before hot rolling and t ₁ is the thickness of the slab after hot rolling. ₁ ) / t ₀ × 100. For example, the final rolling performed at a temperature of 600 ° C. or higher is performed by rolling in a temperature range of 600 ° C. or higher, with the plate thickness of the slab provided for the first rolling pass performed between 900 and 600 ° C. being 120 mm. At the end of the pass, the plate thickness became 30 mm, and then the rolling was continued, and the final pass of the hot rolling was performed in a range of less than 600 ° C. to 300 ° C., and finally a hot rolled material having a plate thickness of 10 mm was obtained. To do. In this case, the rolling rate of the rolling performed in the temperature range of 900 ° C. to 600 ° C. is (120−30) / 120 × 100 = 75 (%), and the rolling rate in the temperature range of less than 600 ° C. to 300 ° C. Is (30-10) /30×100=66.7 (%).

(Cold rolling process)
In the cold rolling process performed before recrystallization annealing, the rolling rate needs to be 85% or more, and preferably 90% or more. A recrystallized texture having {420} as the main orientation component can be formed by performing recrystallization annealing on the material processed at such a high rolling rate in the next step. In particular, the recrystallization texture greatly depends on the cold rolling rate before recrystallization. Specifically, the crystal orientation having {420} as the main orientation component hardly generates when the cold rolling rate is 60% or less, and gradually increases with the increase of the cold rolling rate in the region of about 60 to 80%. However, when the cold rolling rate exceeds about 80%, it suddenly increases. In order to obtain a crystal orientation in which the {420} orientation is sufficiently dominant, it is necessary to achieve a cold rolling rate of 85% or more, and preferably 90% or more. Note that the upper limit of the cold rolling rate is inevitably restricted by mill power and the like, and thus need not be specified. However, from the viewpoint of preventing edge cracking and the like, good results can be obtained at about 98% or less. it can.

  In the embodiment of the method for producing a copper alloy sheet according to the present invention, as is performed in the ordinary method for producing a copper alloy sheet, when intermediate annealing is performed after hot rolling and before recrystallization annealing, Since the recrystallization texture having {420} as the main orientation component formed by recrystallization annealing is significantly weakened, intermediate annealing is not performed between hot rolling and recrystallization annealing.

(Recrystallization annealing process)
In the conventional method for producing a copper alloy sheet, recrystallization annealing is performed for recrystallization, but in the embodiment of the method for producing a copper alloy sheet according to the present invention, it is further performed to control the texture. This recrystallization annealing is preferably performed at a furnace temperature of 350 to 650 ° C. When this temperature is too low, recrystallization becomes incomplete, recrystallized grains become fine (for example, 5 μm or less), and a rolling texture having {220} as the main orientation component remains. On the other hand, if the temperature is too high, the {220} orientation component becomes strong as the crystal grains become coarse. In any of these cases, it becomes difficult to finally obtain a high-strength material excellent in bending workability.

  Further, this recrystallization annealing is performed at 350 to 650 ° C. so that the average grain size of recrystallized grains (a twin boundary is not regarded as a grain boundary) is 10 to 60 μm, preferably 15 to 40 μm. It is preferable to perform the heat treatment by setting the holding time and the reached temperature. When the grain size of the recrystallized grains becomes too fine, a rolling texture having {220} as a main orientation component remains, a recrystallization texture having {420} as a main orientation component becomes weak, and stress resistance Relaxation characteristics are difficult to improve. On the other hand, when the grain size of the recrystallized grains becomes too large, the surface of the bent portion tends to become rough. The grain size of the recrystallized grains varies depending on the cold rolling rate and chemical composition before the recrystallization annealing, but the relationship between the recrystallized annealing heat pattern and the average crystal grain size is determined in advance for each alloy by experiment. In this case, the holding time and the reached temperature can be set at 350 to 650 ° C. Specifically, in the chemical composition of the copper alloy sheet according to the present invention, appropriate conditions can be set in the heating condition of holding at 350 to 650 ° C. for several seconds to several hours.

(Finish cold rolling process)
Finish cold rolling is performed to improve the strength level. If the finish cold rolling rate is too low, the strength is low, but a rolling texture having {220} as the main orientation component develops as the finish cold rolling rate increases. On the other hand, if the finish cold rolling rate is too high, the rolling texture in the {220} orientation becomes relatively dominant, and crystal orientation with improved strength and bending workability cannot be realized. Therefore, the finish cold rolling is preferably 20 to 70%, and more preferably 30 to 60%. By performing such finish cold rolling, the crystal orientation satisfying I {420} / I ₀ {420}> 0.8 can be maintained. The final plate thickness is preferably about 0.05 to 1.0 mm, and more preferably 0.1 to 0.8 mm.

(Low temperature annealing process)
After finish cold rolling, in order to improve the stress corrosion cracking characteristics and bending workability by reducing the residual stress of the copper alloy sheet material, and to improve the stress relaxation characteristics by reducing dislocations on the pores and slip surface, Low temperature annealing may be performed. In particular, in the case of a Cu—Zn copper alloy, it is preferable to perform low temperature annealing at a heating temperature of 150 to 350 ° C. By this low temperature annealing, strength, stress corrosion cracking resistance, bending workability and stress relaxation resistance can be improved at the same time, and the electrical conductivity can be increased. If this heating temperature is too high, it softens in a short time, and variations in characteristics are likely to occur in both batch and continuous systems. On the other hand, if the heating temperature is too low, the effect of improving the above characteristics cannot be obtained sufficiently. The holding time at this heating temperature is preferably 5 seconds or longer, and usually good results can be obtained within 1 hour.

  Hereinafter, examples of the copper alloy sheet material and the manufacturing method thereof according to the present invention will be described in detail.

[Examples 1 to 11]
A copper alloy (Example 1) containing 16.1% by mass of Zn, 0.14% by mass of Zr and 0.12% by mass of Co, with the balance being Cu, 19.8% by mass of Zn, and the balance A copper alloy (Example 2) comprising Cu, 25.2% by mass of Zn, the remainder comprising Cu (Example 3), 30.4% by mass of Zn, the remainder comprising Cu Copper alloy (Example 4), containing 34.8% by weight of Zn, the balance comprising Cu (Example 5), containing 36.7% by weight of Zn and 0.44% by weight of Ni, the balance A copper alloy (Example 6), in which 29.8% by mass of Zn, 0.12% by mass of Mg and 0.03% by mass of P are contained, with the balance being Cu (Example 7). , 26.2% by mass of Zn, 0.23% by mass of Fe and 0.003% by mass of B, with the balance being Cu Example 8), a copper alloy (Example 9) containing 24.6% by mass of Zn, 0.52% by mass of Sn and 0.04% by mass of Ti with the balance being Cu, 28.3% by mass of A copper alloy (Example 10) containing Zn, 0.34% by mass of Si and 0.04% by mass of Al, the balance being Cu, 28.9% by mass of Zn, 0.07% by mass of Mn and 0 Each of the copper alloys (Example 11) containing 11 mass% Cr and the balance being Cu was melted and cast using a vertical compact continuous casting machine to obtain slabs each having a thickness of 50 mm. It was.

  Each slab was extracted after heating to 850 ° C., and hot rolling was started. In this hot rolling, the pass schedule was set so that the rolling rate in the temperature range of 850 ° C. to 600 ° C. was 60% or more and the rolling was performed in the temperature range of less than 600 ° C. In addition, the hot rolling rate in less than 600 degreeC-300 degreeC is 45% (Example 1), 50% (Example 2), 42% (Example 3), 47% (Example 4), 43% ( Example 5), 52% (Example 6), 45% (Example 7), 45% (Example 8), 52% (Example 9), 46% (Example 10), 42% (Example) 11), and the final pass temperature of hot rolling was between 500 ° C and 300 ° C. Moreover, the total hot rolling rate from the slab was about 90%. After hot rolling, the surface oxide layer was removed (faced) by mechanical polishing.

  Next, the rolling ratios are 90% (Example 1), 92% (Example 2), 86% (Example 3), 95% (Example 4), 87% (Example 5), 85% (Example), respectively. After cold rolling at 6), 85% (Example 7), 90% (Example 8), 94% (Example 9), 91% (Example 10), 86% (Example 11) Recrystallization annealing was performed at a furnace temperature of 350 to 650 ° C. The temperature change during recrystallization annealing was monitored by a thermocouple attached to the sample surface. The ultimate temperature is adjusted within the range of 350 to 650 ° C. according to the alloy composition so that the average crystal grain size after recrystallization annealing (a twin boundary is not regarded as a grain boundary) is 10 to 40 μm. The holding time in the temperature range of ˜650 ° C. was adjusted in the range of 10 seconds to 10 minutes.

  Next, the rolling rate of 55% (Example 1), 50% (Example 2), 45% (Example 3), 50% (Example 4), and 40% of the plate material after recrystallization annealing, respectively. (Example 5), 45% (Example 6), 50% (Example 7), 35% (Example 8), 35% (Example 9), 45% (Example 10), 40% (implemented) In Example 11), finish cold rolling was performed, and then low temperature annealing was performed in a furnace at 250 ° C. for 30 minutes.

  Thus, the copper alloy board | plate material of Examples 1-11 was obtained. In addition, chamfering was performed in the middle as needed, and the thickness of the copper alloy sheet was adjusted to 0.2 mm.

  Next, samples were taken from the copper alloy sheet materials obtained in these examples, and the average crystal grain size, X-ray diffraction strength, conductivity, tensile strength, stress relaxation rate, and normal bending workability of the crystal grain structure were obtained. The bending workability after notching and the connector terminal formability were examined as follows.

The average grain size of the grain structure is determined by polishing the surface (rolled surface) of the copper alloy sheet, etching it, and observing the surface with an optical microscope.
It was measured by the cutting method of H0501. As a result, the average crystal grain sizes were 22 μm (Example 1), 18 μm (Example 2), 16 μm (Example 3), 24 μm (Example 4), 18 μm (Example 5), and 15 μm (Example 6), respectively. ), 24 μm (Example 7), 18 μm (Example 8), 25 μm (Example 9), 20 μm (Example 10), and 12 μm (Example 11).

X-ray diffraction intensity (X-ray diffraction integrated intensity) is measured by preparing a sample obtained by polishing the surface (rolled surface) of a copper alloy sheet with # 1500 water-resistant paper, and using an X-ray diffractometer (XRD). Under the conditions of Mo-Kα ray, tube voltage 20 kV, and tube current 2 mA, the X-ray diffraction intensity I {420} on the {420} plane and the X-ray diffraction intensity I {220} on the {220} plane are obtained for the polished surface of the sample. This was done by measuring. On the other hand, using the same X-ray diffractometer under the same measurement conditions, standard pure copper powder {420} plane X-ray diffraction intensity _I 0 and {420} of the {220} plane X-ray diffraction intensity _I 0 {220} is also a It was measured. Using these measured values, an X-ray diffraction intensity ratio I {420} / I ₀ {420} and an X-ray diffraction intensity ratio I {220} / I ₀ {220} were obtained. As a result, I {420} / I ₀ {420} and I {220} / I ₀ {220} are 1.4 and 2.5 (Example 1), 1.6 and 2.2 (Example), respectively. 2) 1.7 and 2.0 (Example 3), 1.4 and 2.3 (Example 4), 1.3 and 1.9 (Example 5), 1.1 and 2.7 ( Example 6), 1.5 and 2.1 (Example 7), 1.8 and 1.8 (Example 8), 1.9 and 2.1 (Example 9), 1.4 and 2. 2 (Example 10), 1.3 and 1.8 (Example 11).

The electrical conductivity of copper alloy sheet is JIS
It was measured according to the H0505 conductivity measurement method. As a result, the electrical conductivity was 36.6% IACS (Example 1), 31.7% IACS (Example 2), 30.1% IACS (Example 3), and 27.7% IACS (Example 4), respectively. ), 26.6% IACS (Example 5), 25.6% IACS (Example 6), 28.3% IACS (Example 7), 27.7% IACS (Example 8), 23.8% IACS (Example 9), 24.6% IACS (Example 10), and 24.8% IACS (Example 11).

As tensile strength as a mechanical property of the copper alloy sheet material, a specimen for tensile test of LD (rolling direction) and TD (direction perpendicular to the rolling direction and sheet thickness direction) of the copper alloy sheet material (JIS).
Three Z2201 No. 5 test pieces) were sampled, and a tensile test based on JIS Z2241 was performed on each test piece, and the tensile strengths of LD and TD were determined by average values. As a result, the tensile strengths of LD and TD were 586 MPa and 602 MPa (Example 1), 603 MPa and 615 MPa (Example 2), 614 MPa and 626 MPa (Example 3), 619 MPa and 636 MPa (Example 4), and 624 MPa, respectively. And 639 MPa (Example 5), 635 MPa and 645 MPa (Example 6), 624 MPa and 635 MPa (Example 7), 598 MPa and 603 MPa (Example 8), 617 MPa and 623 MPa (Example 9), 626 MPa and 642 MPa (Example) 10), 617 MPa and 628 MPa (Example 11).

In order to evaluate the stress relaxation characteristics of the copper alloy sheet, a bending test piece (width 10 mm) whose longitudinal direction is TD (direction perpendicular to the rolling direction and the plate thickness direction) is collected from the copper alloy sheet. It was fixed in an arch-bent state so that the surface stress at the center in the longitudinal direction was 80% of the 0.2% proof stress. The surface stress is determined by the surface stress (MPa) = 6 Etδ / L ₀ ² (where E is the elastic modulus (MPa), t is the thickness (mm) of the sample, and δ is the deflection height (mm) of the sample). Determined. From the bending habit after holding the test piece in this state at 150 ° C. in the atmosphere for 1000 hours, the stress relaxation rate (%) = (L ₁ −L ₂ ) / (L ₁ −L ₀ ) × 100 (provided that L ₀ is the length of the jig, that is, the horizontal distance (mm) between the sample ends fixed during the test, L ₁ is the sample length (mm) at the start of the test, and L ₂ is the distance between the sample ends after the test. The horizontal stress (mm) was used to calculate the stress relaxation rate. As a result, the stress relaxation rates were 33.4% (Example 1), 32.8% (Example 2), 31.4% (Example 3), 30.9% (Example 4), 33, respectively. 3% (Example 5), 32.5% (Example 6), 28.7% (Example 7), 30.4% (Example 8), 31.4% (Example 9), 31 It was 0.7% (Example 10) and 32.6% (Example 11).

In order to evaluate the normal bending workability of the copper alloy sheet, the bending test piece whose longitudinal direction is LD (rolling direction) from the copper alloy sheet and the longitudinal direction is TD (direction perpendicular to the rolling direction and the plate thickness direction). Three bend test pieces (each 10 mm wide) were collected, and JIS was used for each test piece.
A 90 ° W bending test in accordance with H3110 was performed. With respect to the test piece after this test, the surface and cross section of the bent portion were observed with an optical microscope at a magnification of 100 times to obtain a minimum bending radius R at which no cracks occurred, and this minimum bending radius R was obtained from a copper alloy sheet. By dividing by the thickness t, each R / t value of LD and TD was determined. Among the three test pieces of LD and TD, the result of the worst test piece was adopted to obtain the R / t value. As a result, R / t of LD and TD are 0.0 and 0.5 (Examples 1, 2, 7 to 9, 11), 0.0 and 0.8 (Examples 3 and 4), 0, respectively. 0.0 and 1.0 (Examples 5 and 6) and 0.0 and 0.6 (Example 10).

In order to evaluate the bending workability after notching of a copper alloy sheet, a strip sample (width 10 mm) whose longitudinal direction is LD (rolling direction) is taken from the copper alloy sheet, and is approximately as shown in FIGS. As shown in FIG. 3, using a notch forming jig 10 having a trapezoidal cross-sectional convex portion formed on the upper surface (flat surface width 0.1 mm, both side angle 45 ° at the tip of the convex portion) A notch extending over the entire width of the sample 12 was formed by applying a load of 10 kN. Note that the direction of the notch (that is, the direction parallel to the groove) was a direction perpendicular to the longitudinal direction of the sample (the direction of arrow B). When the depths of the notches 12′a of the three notched bending test pieces 12 ′ prepared in this manner were measured, the depth δ of the notches 12′a schematically shown in FIG. It was about 1/4 to 1/6 of t. Each of these three notched bending specimens 12 'is JIS.
A 90 ° W bending test in accordance with H3110 was performed. In this 90 ° W bending test, a notched bending test piece 12 ′ was placed with the notch forming surface facing downward using a jig whose R at the tip of the lower mold central projection was 0 mm, and the lower middle mold projection The tip was set so as to match the notch. For the three test pieces after this test, the result of the worst test piece was adopted by observing the surface and cross section of the bent part with an optical microscope at a magnification of 100 times and judging the presence or absence of cracks. The bending workability after notching of the copper alloy sheet was evaluated. As a result, in any of the examples, no cracks were observed on the surface and cross section of the bent portion after notching, and the bendability after notching was good.

  In order to evaluate the connector terminal formability of the copper alloy sheet material, a female connector terminal (caliber 0.64 mm) 100 having a shape shown in FIG. However, the box bending portion 124 of the female connector terminal 100 is notched (assembled) before bending to form a notch having a substantially trapezoidal cross section as shown in FIG. Went. In FIG. 5, reference numeral 110 denotes a pilot part, 120 denotes a box part, 122 denotes a crimping part, and 126 denotes a spring part. By observing the surface and cross section of the box bending portion 124 of the female connector terminal 100 obtained with an optical microscope at a magnification of 100 times and judging the presence or absence of cracks, the result of the worst connector terminal is adopted, and the copper The connector terminal formability of the alloy sheet was evaluated. As a result, in any of the examples, no cracks were observed on the surface and cross section of the box bending portion 124 of the female connector terminal 100, and the connector terminal moldability was good.

[Comparative Examples 1-5]
Copper alloys having the same composition as in Examples 1 to 5 were used, and the hot rolling ratios at temperatures below 600 ° C. to 300 ° C. were 15% (Comparative Example 1), 0% (Comparative Example 2), and 0% (Comparative Example), respectively. 3), 22% (Comparative Example 4), 22% (Comparative Example 5), the cold rolling rate before recrystallization annealing was 90%, and the final cold rolling rate was 25% (Comparative Example 1). A copper alloy was produced in the same manner as in Examples 1 to 11 except that 50% (Comparative Example 2), 15% (Comparative Example 3), 30% (Comparative Example 4), and 25% (Comparative Example 5). A board was obtained. In these comparative examples, as an ordinary method for producing a copper alloy sheet, in the cold rolling after hot rolling and before recrystallization annealing, intermediate annealing is performed at 500 ° C. for 3 hours when the sheet thickness is reduced by 50%. gave. In Comparative Examples 2 and 3, the final hot rolling pass temperature was 600 ° C. or higher.

  Samples were taken from the copper alloy sheets obtained in the respective comparative examples, and the average crystal grain size, X-ray diffraction strength, conductivity, tensile strength, stress relaxation rate, normal bending workability, after notching of the grain structure The bendability and connector terminal formability were examined by the same method as in Examples 1-11.

As a result, the average crystal grain sizes were 6 μm (Comparative Example 1), 5 μm (Comparative Example 2), 3 μm (Comparative Example 3), 5 μm (Comparative Example 4), and 4 μm (Comparative Example 5), respectively. The X-ray diffraction intensity ratios I {420} / I ₀ {420} and I {220} / I ₀ {220} are 0.6 and 3.7 (Comparative Example 1), 0.4 and 5. 1 (Comparative Example 2), 0.2 and 3.9 (Comparative Example 3), 0.5 and 4.2 (Comparative Example 4), 0.5 and 3.7 (Comparative Example 5). Further, the electrical conductivity was 37.1% IACS (Comparative Example 1), 32.2% IACS (Comparative Example 2), 30.6% IACS (Comparative Example 3), and 28.1% IACS (Comparative Example 4), respectively. 26.9% IACS (Comparative Example 5). The tensile strengths of LD and TD are 502 MPa and 533 MPa (Comparative Example 1), 621 MPa and 654 MPa (Comparative Example 2), 555 MPa and 596 MPa (Comparative Example 3), 556 MPa and 586 MPa (Comparative Example 4), and 562 MPa, respectively. It was 591 MPa (Comparative Example 5). Furthermore, the stress relaxation rates were 48.4% (Comparative Example 1), 57.4% (Comparative Example 2), 59.4% (Comparative Example 3), 52.9% (Comparative Example 4), and 53. 3% (Comparative Example 5). In addition, as an evaluation of ordinary bending workability, R / t of LD and TD are 0.0 and 1.5 (Comparative Example 1), 1.0 and 4.0 (Comparative Example 2), and 0.0, respectively. And 2.0 (Comparative Example 3), 0.5 and 1.5 (Comparative Example 4), and 0.5 and 1.5 (Comparative Example 5). In Comparative Examples 1 and 3 to 5, cracks were observed on the surface and cross section of the bent portion after notching, and in Comparative Example 2, the bent portion was broken. Furthermore, in Comparative Examples 1 and 3 to 5, cracks were observed on the surface and cross section of the box bent portion of the female connector terminal, and in Comparative Example 2, the box bent portion was broken.

[Comparative Example 6]
The molten copper alloy contains 9.3% by mass of Zn, and the balance is made of Cu. The hot rolling rate at less than 600 ° C. to 300 ° C. is 45%, and the cold rolling rate before recrystallization annealing is A copper alloy sheet was obtained in the same manner as in Examples 1 to 11 except that 85% and the finish cold rolling rate were 80%.

  A sample is taken from the obtained copper alloy sheet, and the average grain size of the grain structure, X-ray diffraction strength, conductivity, tensile strength, stress relaxation rate, normal bending workability, bending workability after notching, The connector terminal moldability was examined by the same method as in Examples 1-11.

As a result, the average crystal grain size was 15 μm, the X-ray diffraction intensity ratio I {420} / I ₀ {420} was 0.5, and I {220} / I ₀ {220} was 3.8. The electrical conductivity was 41.4% IACS, and the tensile strengths of LD and TD were 518 MPa and 566 MPa, respectively. Moreover, the stress relaxation rate was 39.6%, and R / t of LD was 0.0 and R / t of TD was 2.0 as evaluation of normal bending workability. Furthermore, cracks were observed on the surface and cross section of the bent part after notching, and cracks were observed on the surface and cross section of the box bent part of the female connector terminal.

[Comparative Example 7]
A copper alloy sheet was produced in the same manner as in Examples 1 to 11 except that the melted copper alloy contained 41.7% by mass of Zn and 0.37% by mass of Co, and the balance was made of Cu. Got. In this comparative example, since there was too much Zn content, cracks did not occur during hot rolling due to the formation of β phase, but it was possible to take a sample that could be evaluated because cracking was severe in the latter stage of finish rolling. could not.

[Comparative Examples 8-12]
The melted copper alloy contains 30.4% by mass of Zn, and the balance is made of Cu. The hot rolling rate at less than 600 ° C. to 300 ° C. is 47%, and cold before recrystallization annealing. Each of the rolling rates was 95%, and the finish cold rolling rates were 50% (Comparative Example 8), 50% (Comparative Example 9), 50% (Comparative Example 10), 10% (Comparative Example 11), and 85% ( A copper alloy sheet was obtained in the same manner as in Examples 1 to 11 except that Comparative Example 12) was used. In Comparative Example 8, the recrystallization annealing temperature is 700 ° C., which is higher than those in Examples 1 to 11, and in Comparative Example 9, the recrystallization annealing temperature is 300 ° C., which is lower than those in Examples 1 to 11. In Comparative Example 10, the holding time during recrystallization annealing was adjusted so that the average crystal grain size became fine crystal grains of about 3 μm.

  Samples were taken from the copper alloy sheets obtained in the respective comparative examples, and the average crystal grain size, X-ray diffraction strength, conductivity, tensile strength, stress relaxation rate, normal bending workability, after notching of the grain structure The bendability and connector terminal formability were examined by the same method as in Examples 1-11.

As a result, the average crystal grain sizes were 90 μm (Comparative Example 8), mixed grains (Comparative Example 9), 3 μm (Comparative Example 10), 24 μm (Comparative Example 11), and 24 μm (Comparative Example 12), respectively. The X-ray diffraction intensity ratios I {420} / I ₀ {420} and I {220} / I ₀ {220} are 0.7 and 3.8 (Comparative Example 8), 0.2 and 4. 5 (Comparative Example 9), 0.5 and 4.0 (Comparative Example 10), 2.1 and 1.6 (Comparative Example 11), and 0.6 and 4.4 (Comparative Example 12). Also, the electrical conductivity was 27.4% IACS (Comparative Example 8), 28.9% IACS (Comparative Example 9), 28.1% IACS (Comparative Example 10), and 28.6% IACS (Comparative Example 11), respectively. 27.1% IACS (Comparative Example 12). The tensile strengths of LD and TD are 564 MPa and 601 MPa (Comparative Example 8), 654 MPa and 697 MPa (Comparative Example 9), 632 MPa and 661 MPa (Comparative Example 10), 401 MPa and 423 MPa (Comparative Example 11), and 676 MPa, respectively. It was 721 MPa (Comparative Example 12). Furthermore, the stress relaxation rates were 26.4% (Comparative Example 8), 67.8% (Comparative Example 9), 59.5% (Comparative Example 10), 29.1% (Comparative Example 11), and 39. 6% (Comparative Example 12). Also, as a normal evaluation of bending workability, the R / t of LD and TD are 1.0 and 2.5, 1.5 and 4.0, 0.5 and 3.0, 0.0 and 0, respectively. 0.0, 1.0 and 3.0. In Comparative Example 11, no cracks were observed on the surface and cross section of the bent part after notching, but in Comparative Examples 8 and 10, cracks were observed on the surface and cross section of the bent part after notching. In Examples 9 and 12, fracture occurred at the bent portion. Further, in Comparative Example 11, no crack was observed on the surface and cross section of the female connector terminal box bending portion, but in Comparative Example 8, cracks were observed on the surface and cross section of the female connector terminal box bending portion. In Comparative Examples 9, 10 and 12, fracture occurred at the box bend.

[Comparative Examples 13 and 14]
As comparative example 13, a commercially available representative brass type (C2600-H06, plate thickness 0.2 mm) plate material and as comparative example 14 two types of phosphor bronze (C5191-H06, plate thickness 0.2 mm) plate material are prepared. Samples are taken from these copper alloy sheet materials, the average grain size of the grain structure, X-ray diffraction strength, conductivity, tensile strength, stress relaxation rate, normal bending workability, bending workability after notching, The connector terminal moldability was examined by the same method as in Examples 1-11.

As a result, the average crystal grain sizes were 6 μm (Comparative Example 13) and 4 μm (Comparative Example 14), respectively. The X-ray diffraction intensity ratios I {420} / I ₀ {420} and I {220} / I ₀ {220} are 0.6 and 3.9 (Comparative Example 13), 0.4 and 0. 4 (Comparative Example 14). The electrical conductivities were 28.2% IACS (Comparative Example 13) and 14.2% IACS (Comparative Example 14), respectively. The tensile strengths of LD and TD were 544 MPa and 583 MPa (Comparative Example 13), 628 MPa and 653 MPa (Comparative Example 14), respectively. Furthermore, the stress relaxation rates were 51.4% (Comparative Example 13) and 37.6% (Comparative Example 14), respectively. Moreover, as evaluation of normal bending workability, R / t of LD and TD were 0.5 and 1.2 (Comparative Example 13) and 0.5 and 1.5 (Comparative Example 14), respectively. Furthermore, cracks were observed on the surface and cross section of the bent part after notching, and cracks were observed on the surface and cross section of the box bent part of the female connector terminal.

  The compositions and production conditions of these examples and comparative examples are shown in Table 1 and Table 2, respectively, and the results on the structure and properties are shown in Table 3 and Table 4, respectively.

  In addition, in the column of evaluation of the bending workability after notching of the copper alloy sheet material in Table 4, “◯” indicates that no cracks are observed on the surface and cross section of the bent part after notching, and indicates that cracks are observed. "X", the one that breaks at the bending part is displayed as "Break", and the result of the worst test piece among the three test pieces is adopted, and "○", "X", "Break" Evaluation was made, and those with ○ evaluation were determined to be acceptable. Moreover, in the column of evaluation of connector terminal formability of the copper alloy plate material in Table 4, “◯” indicates that no crack is observed on the surface and cross section of the box-bending portion of the female connector terminal, and indicates that crack is recognized. "X", the one that breaks at the box bending part is displayed as "Break", and the result of the worst connector terminal among the three connector terminals is adopted, and "○", "X", "Break" Evaluation was made, and those with ○ evaluation were determined to be acceptable.

As can be seen from Tables 3 and 4, all of the copper alloy sheet materials of Examples 1 to 11 have a crystal orientation satisfying I {420} / I ₀ {420}> 0.8, and the conductivity is 20%. It has a high bending strength of not less than IACS, a tensile strength of not less than 580 MPa, and an R / t value of LD and TD of not more than 1.0. In addition, regarding the bending workability after notching of the LD, which is practically important, no cracking occurred despite severe bending at R / t = 0 in the 90 ° W bending test. Moreover, it has the characteristic which the stress relaxation rate of TD which becomes important in uses, such as a vehicle-mounted connector, has the characteristic which is not in the conventional brass that is 35% or less. Further, the connector terminal formability having a box bending portion is also excellent.

  On the other hand, in Comparative Examples 1-5, about the alloy of the same composition as Examples 1-5, it manufactures with a normal manufacturing method (In Comparative Examples 2 and 3, a hot rolling final pass temperature shall be 600 degreeC or more, and comparison. In Examples 1 to 5, an intermediate annealing process is performed after hot rolling and before recrystallization annealing. In all of these comparative examples, the X-ray diffraction intensity of the {420} crystal plane was weak, and a trade-off relationship was observed between the strength and the bending workability, and between the bending workability and the stress relaxation resistance. In all of these comparative examples, the bending workability after notching was poor.

  Comparative Examples 6 and 7 are examples in which the Zn content is too low and too high, respectively. In Comparative Example 6, since the Zn content was too small, the strength level was low even when the finish cold rolling rate was increased to 80% or more. Moreover, although the crystal orientation with {420} as the main orientation component was weak and the strength level was low, the bending workability after notching could not be improved. In Comparative Example 7, since there was too much Zn content, cracks did not occur during the hot rolling due to the formation of the β phase, but cracking was severe in the latter stage of finish rolling, and a sample that could be evaluated could not be taken. .

  In Comparative Example 8, since the recrystallization annealing temperature was too high at 700 ° C., the crystal grains were coarsened, and good bending workability was not obtained. Further, the crystal orientation having {420} as the main orientation component was weak, and the bending workability after notching was also inferior. In Comparative Example 9, since the recrystallization annealing temperature was too low at 300 ° C., the recrystallization itself did not proceed sufficiently to form a mixed grain structure, and all of the tensile strength, bending workability, and stress relaxation resistance were poor. As a result. In Comparative Example 10, in order to improve bending workability, the holding temperature during recrystallization annealing was adjusted to make the average crystal grain size as fine as about 3 μm, but the normal bending workability is not bad, but {420 } Has become a main orientation component, and the bending workability after notching was inferior. Further, since the crystal grains became fine, the stress relaxation resistance was deteriorated.

  In Comparative Example 11, since the finish cold rolling rate was low, good characteristics could not be obtained. In Comparative Example 12, since the finish cold rolling rate was too high, the crystal orientation having {420} as the main orientation component was weakened, and the bending workability was remarkably deteriorated although the strength was high.

  In addition, the copper alloy sheet of Example 4 has improved tensile strength, bending workability, stress relaxation resistance, and the like compared to brass (Comparative Example 13), which is a conventional electrical and electronic material such as a connector. You can see that Moreover, compared with phosphor bronze (Comparative Example 14), the strength is almost the same and the conductivity is excellent. Further, phosphor bronze contains 6% of expensive Sn, and the raw material cost is likely to increase and cannot be hot-rolled. Therefore, the manufacturing method is limited and the total cost including the manufacturing cost is inferior. . Therefore, the copper alloy of Example 4 is sufficiently superior to conventional brass and phosphor bronze.

DESCRIPTION OF SYMBOLS 10 Notch formation jig | tool 12 Sample 12 'Bending test piece with a notch 12'a Notch 100 Connector terminal 110 Pilot part 120 Box part 122 Crimp part 124 Box bending part 126 Spring part

Claims (9)

Selected from the group consisting of 15 to 37 mass% Zn, 2.0 mass% or less Sn, 2.0 mass% or less Ni, 2.0 mass% or less Fe and 1.0 mass% or less Si. In a copper alloy sheet having a composition containing one or more elements and the balance being Cu and inevitable impurities, the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet is I {420}, and pure copper When the X-ray diffraction intensity of the {420} crystal plane of the standard powder and _I 0 {420}, have a crystal orientation satisfying _{I {420} / I 0 {} 420}> 0.8, a tensile strength of more than 580MPa a conductivity of 20% IACS or more, the stress relaxation rate is characterized der Rukoto 35% or less, the copper alloy sheet. When the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy sheet is I {220} and the X-ray diffraction intensity of the {220} crystal plane of the pure copper standard powder is I ₀ {220}, 2. The copper alloy sheet according to claim 1, having a crystal orientation satisfying 0 ≦ I {220} / I ₀ {220} ≦ 3.5. The copper alloy sheet according to claim 1 or 2, wherein the copper alloy sheet has an average crystal grain size of 10 to 60 µm. The copper alloy sheet has a composition further including one or more elements selected from the group consisting of Co, Cr, Mg, Al, B, P, Zr, Ti, Mn, and V in a total range of 3% by mass or less. The copper alloy sheet material according to any one of claims 1 to 3, wherein Containing 15 to 37% by mass of Zn, and if necessary, from 2.0% by mass or less of Sn, 2.0% by mass or less of Ni, 2.0% by mass or less of Fe and 1.0% by mass or less of Si. A total of one or more elements selected from the group consisting of Co, Cr, Mg, Al, B, P, Zr, Ti, Mn, and V, if necessary. After melting and casting the raw material of the copper alloy having a composition containing 3% by mass or less and the balance being Cu and inevitable impurities, the first hot rolling at 900 ° C. to 300 ° C. is performed at 900 ° C. to 600 ° C. After performing the rolling pass, rolling is performed at a rolling rate of 40% or more at a temperature less than 600 ° C. to 300 ° C., followed by cold rolling at a rolling rate of 85% or more, and then recrystallization annealing at 350 to 650 ° C., rolling 30% to 80% finish cold rolling A method for producing a copper alloy sheet material, comprising producing a copper alloy sheet material having a tensile strength of 580 MPa or more, an electrical conductivity of 20% IACS or more, and a stress relaxation rate of 35% or less . The method for producing a copper alloy sheet according to claim 5 , wherein rolling is performed at a rolling rate of 60% or more in the rolling pass at 900 ° C to 600 ° C. In the recrystallization annealing, heat treatment is performed by setting a holding time and an ultimate temperature at 350 to 650 ° C so that an average crystal grain size after recrystallization annealing is 10 to 60 µm. 5. A method for producing a copper alloy sheet according to 5 or 6 . The method for producing a copper alloy sheet according to any one of claims 5 to 7 , wherein low-temperature annealing is performed at 150 to 350 ° C after the finish cold rolling. Characterized by using the copper alloy sheet according to any one of claims 1 to 4 as a material, connector terminals.

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