JP5075438B2 - Cu-Ni-Sn-P copper alloy sheet and method for producing the same - Google Patents

Description

  The present invention is a Cu-Ni-Sn-P-based copper alloy sheet suitable for electrical and electronic parts such as connectors, lead frames, relays, switches, etc., and particularly excellent while maintaining high strength and high conductivity. The present invention relates to a copper alloy sheet material exhibiting bending workability and stress relaxation resistance, and a manufacturing method thereof.

  The materials used for current-carrying parts such as connectors, lead frames, relays, and switches that make up electrical and electronic parts are required to have good "conductivity" to suppress the generation of Joule heat due to current flow. High “strength” is required to withstand the stress applied during assembly and operation of electrical and electronic equipment. Moreover, since electric / electronic parts are generally formed by bending, excellent “bending workability” is required. Furthermore, in order to ensure contact reliability between electrical and electronic components, it is also required to have excellent durability against a phenomenon (stress relaxation) in which the contact pressure decreases with time, that is, “stress relaxation resistance”.

  In particular, in recent years, electrical and electronic components have been increasingly integrated, miniaturized, and lightened, and accordingly, copper and copper alloys, which are materials, have been demanded to be thin. For this reason, the “strength” level required for the material has become more severe.

  Further, in order to cope with the downsizing of electric and electronic parts and the complicated shape, it is strongly required to improve the shape and dimensional accuracy of the bent product. Therefore, recently, a method of applying notching to the part of the material to be bent (notching) and then bending along the notch (hereinafter referred to as “bending method after notching”) is applied. A lot is happening. However, in this processing method, since the vicinity of the notch portion is work-hardened by notching, cracking is likely to occur in subsequent bending. Therefore, it can be said that the “bending method after notching” is a very severe bending process for the material.

  Furthermore, the demand for “stress relaxation resistance” has become stricter as the use of electrical and electronic parts in harsh environments increases. For example, when used in an environment exposed to a high temperature such as an automobile connector, the “stress relaxation resistance” is particularly important. Stress relaxation means that even if the contact pressure of the spring portion of the material constituting the electric / electronic component is kept constant at room temperature, it decreases with time in a relatively high temperature (for example, 100 to 200 ° C.) environment. It is a kind of creep phenomenon. In other words, in the state where stress is applied to the metal material, dislocations move due to self-diffusion of atoms constituting the matrix or diffusion of solute atoms, and plastic deformation occurs, thereby relaxing the applied stress. It is a phenomenon.

  However, there is a trade-off relationship between “strength” and “conductivity”, or “strength” and “bending workability”, and “bending workability” and “stress relaxation resistance”. Conventionally, materials having good “conductivity”, “strength”, “bending workability” or “stress relaxation resistance” are appropriately selected and used for such energized parts depending on the application. Also, good manufacturability is an important requirement.

  A Cu-Ni-Sn-P-based alloy is an example of a material that easily realizes these characteristics and manufacturability in a well-balanced manner. In this type of copper alloy, in addition to the solid solution strengthening effect of Sn and Ni, each characteristic is improved by finely dispersing Ni-P-based precipitates, which has been suitable for electric and electronic parts so far. Various things have been developed (Patent Documents 1 to 8).

Japanese Patent Laid-Open No. 4-154944 Japanese Patent Laid-Open No. 4-236736 Japanese Patent Laid-Open No. 10-226835 JP 2000-129377 A JP 2000-256814 A JP 2001-262255 A JP 2001-262297 A JP 2002-294368 A

  Cu-Ni-Sn-P alloys have good "bending workability" and "stress resistance while having relatively high electrical conductivity (35 to 55% IACS) and strength (tensile strength of 500 to 600 MPa). It is a material that exhibits “relaxation properties”. In particular, the “stress relaxation resistance” is remarkably superior to general solid solution strengthened copper alloys such as brass and phosphor bronze, such as Cu—Ni—Si alloys (so-called Corson alloys), Cu—Ti. It surpasses precipitation-strengthened copper alloys, such as alloy alloys.

  The Cu—Ni—Sn—P alloy is basically a solid solution strengthened alloy, and is an easily oxidizable element such as Si, Ti, Mg, Zr for the purpose of precipitation strengthening and refinement of the cast structure. Even in the case of adding, generally it has good castability because the amount added can be reduced. Furthermore, it is possible to omit complicated heat treatment steps such as solution treatment and aging treatment required for the precipitation strengthened copper alloy, and it can be manufactured at a comparatively low cost.

  However, in order to meet the recent strict demands for thinning and downsizing of electric and electronic parts, it is necessary to further increase the level of “strength”. For example, there are cases where the current Cu—Ni—Sn—P based alloys cannot be used in applications that require high strength such as a tensile strength of 600 MPa or more, or even 650 MPa or more.

  General means for increasing the strength of the Cu—Ni—Sn—P alloy include a method of adding a large amount of solute elements such as Ni and Sn and a method of increasing the finish rolling (tempering treatment) rate. However, the former significantly lowers the conductivity and increases the amount of relatively expensive Ni, Sn, etc., which is economically disadvantageous. In the latter, anisotropy of bending workability occurs because work hardening increases. That is, the bending workability in the direction parallel to the rolling direction (LD) is maintained well, but the bending workability in the direction perpendicular to the rolling direction (TD) is significantly deteriorated. For this reason, even if the strength level and the conductivity level are high, it may not be usable for electric / electronic parts.

  In order to improve the “bending workability”, means for refining crystal grains is generally employed. The smaller the crystal grain size, the larger the area of the crystal grain boundary existing per unit volume. The grain boundary functions as an interface that enables grain boundary sliding and crystal grain rotation on both sides of the grain boundary during bending, so the larger the area of the interface, the more local stress concentration is avoided and the bending workability is It tends to improve. However, even when crystal grains are refined, the anisotropy of bending workability cannot be improved significantly. Furthermore, an increase in grain boundary area due to grain refinement becomes a factor that promotes stress relaxation, which is a kind of creep phenomenon. Particularly in applications that are used in a high temperature environment such as an in-vehicle connector, the diffusion rate along the grain boundaries of the atoms is significantly faster than the inside of the grains, so that the deterioration of the “stress relaxation resistance” due to crystal grain refinement becomes a serious problem.

Thus, it is difficult to simultaneously improve the bending workability and the stress relaxation resistance in the Cu—Ni—Sn—P based copper alloy while further increasing the strength. In order to cope with the recent severe usage environment of electric and electronic parts, it is strongly desired to establish a technique that can provide more stable and excellent bending workability and excellent stress relaxation resistance.
An object of the present invention is to provide a copper alloy sheet material in which strength, bending workability and stress relaxation resistance are simultaneously improved to a high level in this alloy system.

The purpose is mass%, Ni: 0.1-5%, Sn: 0.1-5%, P: 0.01-0.5%, and if necessary, Fe: 3% or less, Zn : 5% or less, Mg: 1% or less, Si: 1% or less, Co: 2% or less, or one or more of Cr, B, Zr, Ti, Mn, and V are 3% or less in total. incorporated within a range, it has the composition balance Cu and unavoidable impurities, the following (1) and (2) have a crystal orientation satisfying expression achieved an average crystal grain size of the copper alloy sheet is 5~40μm Is done.
I {420} / I ₀ {420}> 1.0 (1)
1.5 ≦ I {220} / I ₀ {220} ≦ 3.5 (2)

Here, I {420} is the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {420} is the X-ray diffraction intensity of the {420} crystal plane of the pure copper standard powder. Similarly, I {220} is the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {220} is the X-ray diffraction intensity of the {220} crystal plane of the pure copper standard powder .

Average crystal grain size, and etching after polishing the plate surface (rolled surface), the surface and microscopic observation, can be obtained by cutting method of JIS H0501.

As a method for producing such a copper alloy sheet, the copper alloy material (ingot, slab, etc.) adjusted to the above composition is subjected to hot rolling, cold rolling, recrystallization annealing, and then aging treatment. Apply or not, and then use the process of applying the finish cold rolling, after the recrystallization annealing, when producing a copper alloy sheet by a technique that does not give a thermal history higher than the recrystallization temperature, hot rolling in step, the first rolling pass conducted at a temperature range of 950 ° C. to 700 ° C., it is rolling over the rolling ratio of 40% in the temperature range below 700 ° C. to 400 ° C., the raised cold rolling specification 30-80 In the recrystallization annealing step, the ultimate temperature is in the range of 600 to 750 ° C., and the average crystal grain size after recrystallization annealing is in the range of 600 to 750 ° C. Holding time and temperature reached Manufacturing method is provided which comprises carrying out the heat treatment set. Particularly in the hot rolling step, it is preferable to perform rolling at a rolling rate of 60% or more in a temperature range of 950 ° C to 700 ° C.
However, the rolling rate ε (%) in a certain temperature range is the thickness t ₀ (mm) before the first rolling pass among the continuous rolling passes performed in the temperature range, and after the end of the last rolling pass. thickness of the case to t ₁ (mm), determined by the following equation (3).
ε = (t ₀ −t ₁ ) / t ₀ × 100 (3)

More preferably, the rolling rate of the cold rolling performed before the recrystallization annealing is 85% or more . When carrying out the aging treatment time, it is preferable that the holding temperature of the aging treatment and 375-500 ° C.. After the finish cold rolling, low temperature annealing at 150 to 450 ° C. can be performed.

  According to the present invention, a Cu-Ni-Sn-P-based copper alloy sheet material having basic characteristics necessary for electrical and electronic parts such as connectors, lead frames, relays, switches, etc., has a high strength with a tensile strength of 600 MPa or more. And having both excellent bending workability and stress relaxation resistance, and also excellent bending workability even after notching. It has been difficult for the conventional Cu-Ni-Sn-P-based copper alloy manufacturing technology to stably and significantly improve bending workability and stress relaxation resistance while maintaining a tensile strength of 600 MPa or more. . The present invention can meet the needs for downsizing and thinning of electric and electronic parts, which are expected to make further progress in the future.

  A major factor that makes it difficult to simultaneously improve the “strength” and “bending workability” of the Cu—Ni—Sn—P based copper alloy is the influence of the rolling texture that inevitably develops by finish rolling. That is, this type of copper alloy is basically a solid solution strengthened alloy, and in order to improve the strength, it is necessary to increase the finish rolling rate to a certain level (for example, 30% or more). As the finish rolling ratio increases, a rolling texture with {110} <112> as the main orientation component develops, but this texture significantly deteriorates the TD bending workability.

  On the other hand, as a major factor that makes it difficult to simultaneously improve “bending workability” and “stress relaxation resistance” of Cu—Ni—Sn—P-based copper alloys, (i) bending workability when crystal grain size is made finer However, the stress relaxation resistance decreases, that is, it is impossible to improve both of these characteristics at the same time only by controlling the crystal grain size, and (ii) it is advantageous for improving the bending workability and bending work. The crystal orientation (texture) that is advantageous for improving the “anisotropy” of the property is not found.

  As a result of detailed studies, the inventors have determined that a direction (ND) perpendicular to the plate surface (rolling surface) of the copper alloy sheet, a direction parallel to the rolling direction (LD), and a direction perpendicular to the rolling direction within the plate surface (TD) It was found that there are crystal orientations that are easily deformed in the three directions. And the component and manufacturing conditions which can control the ratio of the crystal grain which has such a specific crystal orientation were discovered. Based on such knowledge, the present invention is based on such a texture that increases the existence ratio of crystal grains having a specific crystal orientation to a certain level or more, thereby simultaneously providing “strength”, “bending workability”, and “stress relaxation resistance”. It is possible to improve. Hereinafter, matters for specifying the present invention will be described.

<< Texture
An X-ray diffraction pattern from a plate surface (rolled surface) of a Cu—Ni—Sn—P based copper alloy is generally a diffraction peak of four crystal planes {111}, {200}, {220}, and {311}. The X-ray diffraction intensity from other crystal planes is much smaller than those from these crystal planes. The diffraction intensity of the {420} plane is also weak enough to be ignored in the Cu—Ni—Sn—P based copper alloy plate obtained in the normal manufacturing process. However, according to detailed examinations by the inventors, it has been found that a Cu—Ni—Sn—P based copper alloy sheet having a texture with {420} as the main orientation component can be obtained according to the manufacturing conditions described later. . The inventors have found that the stronger the texture is, the more advantageous the bending workability is. At present, the mechanism for improving the bending workability is considered 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. A larger Schmid factor (that is, closer to 0.5) means a greater 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, the closer to 0.5), the easier the crystal is deformed. The crystal structure of the Cu—Ni—Sn—P based copper alloy is face centered cubic (fcc). The slip system of the face-centered cubic crystal has a slip plane {111} and a slip direction <110>, and it is known that even in an actual crystal, the larger the Schmid factor, the easier the deformation and the less work hardening.

  FIG. 1 shows a standard inverted pole figure representing the Schmid factor distribution of face-centered cubic crystals. The Schmid factor in the <120> direction is 0.490, 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, and 0.272 in the <111> direction.

  The texture having {420} as the main orientation component means a texture having a large amount of crystals in which the {420} plane, that is, the {210} plane is substantially parallel to the plate surface (rolled surface). In a crystal whose principal orientation plane is the {210} plane, the direction (ND) perpendicular to the plate surface is the <120> direction, and its Schmitt factor is close to 0.5, so that the transformation to ND is very easy. There is little work hardening. On the other hand, a general rolling texture of a Cu—Ni—Sn—P based alloy has {220} as the main orientation component. In this case, the {220} plane, that is, the {110} plane is a plate surface (rolled surface). ) And a large proportion of crystals that are almost in parallel. 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 work hardening accompanying the deformation to becomes larger. Further, a general recrystallization texture of a Cu—Ni—Sn—P alloy has {311} as a main orientation component. The crystal whose principal orientation plane is the {311} plane has the ND <113> direction and its Schmitt factor is about 0.45, so that it is still ND compared with the crystal whose principal orientation plane is the {210} plane. The work hardening accompanying the deformation to becomes larger.

  In the “bending method after notching”, the degree of work hardening at the time of deformation in the direction perpendicular to the plate surface (ND) is extremely important. This is because notching is exactly 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. In the case of a texture having {420} as a main orientation component that satisfies the formula (1), work hardening by notching is compared with a rolled or recrystallized texture of a conventional Cu—Ni—Sn—P alloy. This is considered to be a factor that significantly improves the bending workability in the “notched bending method”.

  Further, in the case of a texture having {420} as a main orientation component that satisfies the expression (1), in a crystal whose main orientation plane is a {210} plane, There are <120> direction and <100> direction, which are orthogonal to each other. Actually, it has been confirmed that the rolling direction (LD) is the <100> direction and the direction perpendicular to the rolling direction (TD) is the <120> direction. As a specific crystal direction, for example, in a crystal whose main orientation plane is the (120) plane, LD is the [001] direction and TD is the [−2, 1, 0] direction. The Schmid factor of such crystals is LD of 0.408 and TD of 0.490. On the other hand, in the case of a crystal whose main orientation plane in a general rolling texture of a Cu—Ni—Sn—P based alloy is a {110} plane, LD is in the <112> direction and TD is in the <111> direction. The Schmid factor has an LD of 0.408 and a TD of 0.272. Further, in the case of a crystal whose main orientation plane in the general recrystallization texture of the Cu—Ni—Sn—P based alloy is a {113} plane, LD is in the <112> direction and TD is in the <110> direction, The Schmitt factor is 0.408 for LD and 0.408 for TD. Thus, looking at the Schmid factor of LD and TD, the texture with {420} as the main orientation component is compared with the rolling texture or recrystallized texture of the conventional Cu-Ni-Sn-P alloy. Thus, it can be said that deformation within the plate surface is easy. This point is also considered to be advantageous in preventing cracking in bending 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 not easily deformed but a crystal grain that is easily deformed during bending and a crystal grain that is difficult to deform. As the degree of bending increases, the deformable crystal grains become more preferentially deformed, and micro unevenness is generated on the surface of the bent part of the plate due to uneven deformation among the crystal grains. This develops into wrinkles, and in some cases leads to cracks (breaks). As described above, the metal plate having a texture satisfying the expression (1) is more likely to be deformed into ND and more easily deformed in the plate surface than the conventional metal plate. It can be inferred that this leads to a marked improvement in the bending workability after notching and the normal bending workability even if the crystal grains are not particularly refined.

According to the study by the inventors, such crystal orientation can be specified by the following formula (1). It is more preferable to satisfy the following formula (1) ′.
I {420} / I ₀ {420}> 1.0 (1)
I {420} / I ₀ {420}> 1.5 (1) ′
Here, I {420} is the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {420} is the X-ray diffraction intensity of the {420} crystal plane of the pure copper standard powder. 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 texture having {420} as the main orientation component is formed as a recrystallized texture by recrystallization annealing described later. However, cold rolling after recrystallization annealing is extremely effective for increasing the strength of the copper alloy sheet. As the cold rolling rate of this cold rolling (finished cold rolling described later) increases, a rolling texture with {220} as the main orientation component develops. As the {220} orientation density increases, the {420} orientation density decreases, but the rolling rate may be adjusted so that the expression (1) is maintained.

Along with the increase in the rolling rate of finish cold rolling, a texture with {220} as the main orientation component develops and the strength is improved. However, if this texture is excessively developed, bending workability may be deteriorated. Therefore, it is preferable to satisfy the following expression (2). Further, in order to achieve both “strength” and “bending workability” at a high level with a good balance, it is more preferable to satisfy the following expression (2) ′.
1.5 ≦ I {220} / I ₀ {220} ≦ 3.5 (2)
2.0 ≦ I {220} / I ₀ {220} ≦ 3.0 (2) ′
Here, I {220} is the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {220} is the X-ray diffraction intensity of the {220} crystal plane of the pure copper standard powder.

  In the case of a copper alloy whose main orientation plane is the {110} plane like a conventional Cu—Ni—Sn—P based alloy, LD is in the <112> direction and TD is in the <111> direction as described above. The Schmid factor has an LD of 0.408 and a TD of 0.272. That is, the bending workability of the TD sample is deteriorated. In contrast, in the Cu—Ni—Sn—P based alloy of the present invention, the main orientation plane is the {210} plane, the LD is the <100> direction, the TD is the <120> direction, and the Schmitt factor is that the LD is 0. .408, TD is 0.490. Therefore, in addition to the formula (1), in addition to the texture satisfying the formula (2), the “strength” and the “bending workability” can be balanced at a particularly high level and the anisotropy of the bending workability can be achieved. Can be reduced.

<Average crystal grain size>
As described above, the smaller the average crystal grain size is, the more advantageous the bending workability is. However, when the average crystal grain size is too small, the stress relaxation resistance is likely to deteriorate. As a result of various studies, if the average crystal grain size is finally a value of 5 μm or more, preferably a value exceeding 10 μm, it is easy to secure a stress relaxation resistance level that is satisfactory even for use in a vehicle-mounted connector, which is suitable. . However, likely to occur the HadaAra the bent portion surface so the average crystal grain size is too large, because it may lead to bending lowering of workability shall be the following range 40 [mu] m. It is more preferable to adjust to the range of 10-30 micrometers. The final average crystal grain size is almost determined by the crystal grain size in the stage after recrystallization annealing. Therefore, the average crystal grain size can be controlled by the recrystallization annealing conditions described later.

<Alloy composition>
In the present invention, a Cu—Ni—Sn—P based copper alloy is employed. A copper alloy in which Zn, Fe, and other alloy elements are added to the quaternary basic component of Cu—Ni—Sn—P is also collectively referred to as a Cu—Ni—Sn—P copper alloy in this specification. .

  Ni dissolves in the Cu matrix and contributes to improvement in strength, elasticity, and heat resistance of the base material. In particular, it forms a compound with P and contributes to improvement of electrical conductivity and resistance to stress relaxation. When the Ni content is less than 0.1% by mass, it is difficult to effectively bring out the above effect. On the other hand, when the Ni content is excessive, the conductivity tends to decrease. For this reason, Ni content needs to be 5 mass% or less, it is more preferable to set it as 3 mass% or less, and it is still more preferable to set it as 2 mass% or less. A particularly preferable Ni content range is 0.5 to 1.5% by mass.

  Sn has a large solid solution strengthening action, and the action is further enhanced by the combined addition with Ni. Sn has an effect of improving stress relaxation resistance. In order to sufficiently exhibit these effects, an Sn content of 0.1% by mass or more is preferable. However, when Sn content exceeds 5 mass%, electrical conductivity will fall remarkably. Moreover, since Sn is an element that easily segregates, cracks are likely to occur during hot rolling. For this reason, Sn content needs to be 5 mass% or less, it is more preferable to set it as 3 mass% or less, and it is still more preferable to set it as 2 mass% or less. In particular, it is more preferable to adjust to the range of 0.5 to 2% by mass.

  P contributes to the improvement of strength and electrical conductivity and the improvement of stress relaxation resistance by the formation of precipitates with Ni. Further, P acts as a deoxidizing agent at the time of melting and casting, and brings about a decrease in the oxygen concentration of the molten metal. In order to sufficiently exhibit these effects, it is preferable to secure a P content of 0.01% by mass or more. However, if the P content exceeds 0.5% by mass, the formation of coarse Ni—P-based precipitates and the increase in hydrogen concentration due to excessive deoxidation tend to cause casting defects and cracks during hot rolling. In addition, conductivity and bending workability are also reduced. For this reason, P content needs to be 0.5 mass% or less. The particularly preferable P content range is 0.03 to 0.2% by mass, and more preferably 0.04 to 0.15% by mass.

  In the present invention, since a precipitate of Ni and P is used, it is desirable to optimize the ratio of the content of Ni and P. If P is present excessively, the plating adhesion and the solder corrosion resistance are reduced. On the other hand, when Ni is excessive, the conductivity is lowered. As a result of various studies, it is desirable to adjust the Ni / P ratio expressed in mass% to a range of 3 to 50, and more preferably 5 to 25.

  Fe forms a precipitate with P, and in some cases, a ternary compound containing Ni is also generated. Further, by adding a small amount of Fe, the nucleation sites of the Ni—P compound or Ni—Fe—P compound are dispersed, and a fine precipitation state is easily obtained. However, since excessive Fe content causes aggregation and coarsening of precipitates, when Fe is contained, the content must be 3% by mass or less. The content is more preferably 1% by mass or less, and further preferably 0.5% by mass or less.

  Zn has the effect of improving castability in addition to improving solderability and strength. Furthermore, the addition of Zn has an advantage that inexpensive brass scrap can be used. However, if Zn content exceeds 5% by mass, it tends to cause a decrease in conductivity and stress corrosion cracking resistance. For this reason, when it contains Zn, it is set as the range of 5 mass% or less. It is still more preferable to adjust to the range of 2.0 mass% or less.

  Mg has an effect of improving stress relaxation resistance and a de-S effect. However, Mg is an easily oxidizable element, and if it exceeds 1% by mass, the castability is significantly lowered. For this reason, when it contains Mg, it is set as the range of 1 mass% or less. More preferably, it is 0.5 mass% or less.

  Co is an element that forms a precipitate with P and can be precipitated alone, and it is effective to improve the strength and conductivity at the same time. However, Co is an expensive element, and if it exceeds 2% by mass, it is disadvantageous in cost. For this reason, when Co is contained, it is performed in a range of 2% by mass or less. It is still more preferable to set it as 1.5 mass% or less.

  As other elements, Cr, B, Zr, Ti, Mn, V, and the like can be contained as necessary. For example, Cr, B, Zr, Ti, Mn, and V have the effects of further increasing the alloy strength and reducing the stress relaxation. Cr, Zr, Ti, Mn, and V easily form a high melting point compound with S, Pb, and the like that exist as inevitable impurities, and B, Zr, and Ti have a refinement effect on the cast structure and are hot-worked. It can contribute to improvement of sex.

  When one or more of Cr, B, Zr, Ti, Mn, and V are contained, in order to sufficiently obtain the action of each element, the total amount of these elements is 0.01% by mass or more. It is desirable. However, if it is contained in a large amount, it adversely affects hot or cold workability and is disadvantageous in terms of cost. Accordingly, the total amount of these elements is preferably in the range of 3% by mass or less, more preferably in the range of 2% by mass or less, still more preferably in the range of 1% by mass or less, and in the range of 0.5% by mass or less. Even more preferred.

"Characteristic"
In order to cope with further downsizing and thinning of electric / electronic parts, the tensile strength of the copper alloy sheet material is preferably 600 MPa or more, and more preferably 650 MPa or more. For both LD and TD, 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. . Furthermore, in order to improve the shape and dimensional accuracy of the bent product, it is preferable that R / t is 0 for the bending workability after notching of the LD. For the bending workability after notching, the method shown in the examples described later is adopted. The “LD bending workability” is bending workability evaluated by a bending test piece cut out so that the LD is in the longitudinal direction, and the bending axis in the test is TD. Similarly, “TD bending workability” is bending workability evaluated by a bending work specimen cut out so that TD is in the longitudinal direction, and the bending axis in the test is LD.

  Since the value of TD is particularly important for applications such as in-vehicle connectors, it is desirable to evaluate the stress relaxation resistance with the stress relaxation rate using a test piece whose longitudinal direction is TD. The stress relaxation rate is preferably 5% or less and preferably 3% or less when the maximum load stress on the surface of the plate is 0.2% and 80% of the proof stress and held at 150 ° C. for 1000 hours. Is more preferable.

<Production method>
The copper alloy sheet material of the present invention as described above can be produced, for example, by the following manufacturing process.
“Melting / Casting → Hot Rolling → Cold Rolling → Recrystallization Annealing → (Aging Treatment) → Finishing Cold Rolling → (Low Temperature Annealing)”
However, as described later, it is important to devise manufacturing conditions in several steps. Although not described in the above steps, chamfering is performed as necessary after hot rolling, and pickling, polishing, or further degreasing is performed as necessary after each heat treatment. Hereinafter, each step will be described.

[Melting / Casting]
A general copper alloy melting method can be followed. The slab may be manufactured by continuous casting, semi-continuous casting, or the like.

(Hot rolling)
Normally, hot rolling of a Cu—Ni—Sn—P based copper alloy is performed in a high temperature range of 700 ° C. or higher or 750 ° C. or higher in order not to generate precipitates during rolling, and is rapidly cooled after the end of rolling. This is done by However, it is difficult to produce a copper alloy sheet having a unique texture of the present invention under such common-sense hot rolling conditions. That is, according to the inventors' investigation, when such hot rolling conditions are adopted, a copper alloy sheet having {420} in the main orientation direction can be obtained with good reproducibility even if the conditions of the post-process are changed over a wide range. We couldn't find any conditions that could make it. Therefore, the inventors conducted further detailed studies. As a result, the first rolling pass was carried out in the temperature range of 950 ° C. to 700 ° C., and hot rolling conditions were found in which rolling was performed at a rolling rate of 40% or more in the temperature range of less than 700 ° C. to 400 ° C. .

  When the slab is hot-rolled, by performing the first rolling pass at a temperature higher than 700 ° C. where recrystallization is likely to occur, the cast structure is destroyed, and the components and the structure can be made uniform. However, rolling at a high temperature exceeding 950 ° C. is not preferable because there is a risk of cracking at a location where the melting point is lowered, such as a segregation location of the alloy component. In order to reliably perform complete recrystallization during the hot rolling process, it is extremely effective to perform rolling at a rolling rate of 60% or more in a temperature range of 950 ° C to 700 ° C. This further promotes tissue homogenization. However, in order to obtain 60% in one pass, a large rolling load is required, so that a rolling rate of 60% or more in total can be secured by dividing into multiple passes. In the present invention, it is important to secure a rolling rate of 40% or more in a temperature range of less than 700 ° C. to 400 ° C. at which rolling distortion easily occurs. Thereby, some precipitates are generated, and a recrystallization texture having {420} as a main orientation component is easily formed by a combination of “cold rolling + recrystallization annealing” in the subsequent step. Also at this time, several passes of rolling can be performed in a temperature range of less than 700 ° C to 400 ° C. The final pass temperature for hot rolling is preferably 400 ° C. or higher, and more preferably in the range of 600 to 400 ° C. The total rolling ratio in hot rolling may be approximately 80 to 95%.

Here, the rolling rate ε (%) in each temperature range is calculated by the equation (3).
ε = (t ₀ −t ₁ ) / t ₀ × 100 (3)
For example, the plate thickness of the slab used for the first rolling pass performed between 950 and 700 ° C. is 120 mm, and rolling is performed in a temperature range of 700 ° C. or higher (returning to the furnace during the process may be performed again) The sheet thickness is 30 mm at the end of the last rolling pass carried out at a temperature of 700 ° C. or higher, and the rolling is continued continuously, and the final pass of hot rolling is in the range of less than 700 ° C. to 400 ° C. It is assumed that a hot rolled material having a thickness of 10 mm is finally obtained. In this case, the rolling rate of the rolling performed in the temperature range of 950 ° C. to 700 ° C. is (120−30) / 120 × 100 = 75 (%) according to the equation (3). Moreover, the rolling rate in the temperature range of less than 700 ° C. to 400 ° C. is (30−10) /30×100=66.7 (%) according to the same expression (3).

(Cold rolling)
When rolling the hot-rolled sheet, in cold rolling performed before recrystallization annealing, it is important that the rolling rate is 85% or more, and more preferably 90% or more. By subjecting the material processed at such a high rolling rate to recrystallization annealing in the next step, it becomes possible to form a recrystallized texture having {420} as the main orientation component. 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 secure a cold rolling rate of 85% or more, and more preferably 90% or more. The upper limit of the cold rolling rate is inevitably restricted by the mill power or the like, and thus need not be specified. However, good results are likely to be obtained at approximately 98% or less from the viewpoint of preventing edge cracks and the like.

  In addition, in this invention, the process of implementing cold rolling of 1 time thru | or several times on both sides of intermediate annealing after hot rolling and before recrystallization annealing is not employ | adopted. If the intermediate annealing is performed after the hot rolling and before the recrystallization annealing, the recrystallization texture having {420} as the main orientation component formed by the recrystallization annealing is significantly weakened.

[Recrystallization annealing]
Conventional recrystallization annealing is mainly aimed at “recrystallization”, but in the present invention, “recrystallization texture formation having {420} as a main orientation component” is also an important purpose. This recrystallization annealing, intends line in the furnace temperature of 600~750 ℃. If the temperature is too low, recrystallization is incomplete or recrystallized grains are too small. If the temperature is too high, the crystal grains become coarse. In either case, it is disadvantageous for the generation of the {420} orientation, and it becomes difficult to finally obtain a high-strength material excellent in bending workability.

Further, the recrystallization annealing, (the twin boundaries not considered crystal boundaries) average grain size of recrystallized grains sets the holding time and ultimate temperature of 600 to 750 ° C. range such that 5～40Myu m It performs the heat treatment Te. It is more preferable to carry out so that it may become 10-40 micrometers. If the recrystallized grain size becomes too fine, the recrystallized texture with {420} as the main orientation component becomes weak. It is also disadvantageous in improving the stress relaxation resistance. If the recrystallized grain size becomes too large, surface roughness of the bent portion is likely to occur. The recrystallized grain size varies depending on the cold rolling rate and chemical composition before recrystallization annealing, but by obtaining the relationship between the recrystallized annealing heat pattern and the average crystal grain size for each alloy in advance by experiment, The holding time and ultimate temperature in the 600 to 750 ° C. region can be set. Specifically, in an alloy having a chemical composition defined in the present invention, appropriate conditions can be set under heating conditions in which the temperature is maintained at 600 to 750 ° C. for several seconds to several hours.

[Aging treatment]
Unlike Cu-Ni-Si-based alloys and Cu-Ti-based alloys, such as Cu-Ni-Sn-P-based copper alloys, Ni-P-based precipitates mainly have stress relaxation resistance. Used for improvement. Since this Ni-P-based precipitate is likely to precipitate finely, considerable fine precipitates are generated during the cooling of the recrystallization annealing. For this reason, it is not always necessary to perform the aging treatment, but it is effective to perform the aging treatment in order to further improve the strength level and the electrical conductivity. When the aging treatment is performed, the temperature should not be raised excessively under conditions effective for improving the conductivity and strength of the alloy. If the aging treatment temperature becomes too high, the crystal orientation with {420} as the preferred orientation developed by recrystallization annealing is weakened, and as a result, a sufficient bending workability improvement effect may not be obtained. Specifically, it is desirable to carry out the holding temperature of the material in the range of 375 to 500 ° C, and more preferably in the range of 400 to 460 ° C. Good results are obtained when the aging treatment time is in the range of about 1 to 10 hours.

(Finish cold rolling)
This finish cold rolling is a process necessary for improving the strength level. If the cold rolling rate is too low, it is difficult to obtain sufficient strength due to insufficient work hardening. However, as the cold rolling rate increases, a rolling texture having {220} as the main orientation component develops. If the rolling rate is too high, the rolling texture in the {220} orientation becomes relatively dominant, and crystal orientation in which strength and bending workability are compatible at a high level cannot be realized. As a result of detailed studies by the inventors, it is desirable that the finish cold rolling is performed in a range of 30 to 80%. Thereby, the crystal orientation satisfying the expressions (1) and (2) can be maintained.
As the final plate thickness, approximately 0.05 to 1.0 mm is applied, and 0.08 to 0.5 mm is more preferable.

[Low temperature annealing]
After the finish cold rolling, low temperature annealing can be performed for the purpose of improving the bending workability by reducing the residual stress of the strip material and improving the stress relaxation resistance by reducing the dislocations on the pores and the sliding surface. The heating temperature is desirably set so that the material temperature is 150 to 450 ° C. Thereby, bending workability and stress relaxation resistance can be improved with almost no decrease in strength. It also has the effect of increasing the conductivity. 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. Conversely, if the heating temperature is too low, the effect of improving the above characteristics cannot be obtained sufficiently. The holding time at the above temperature is desirably secured for 5 seconds or longer, and good results are usually obtained within a range of 1 hour.

The copper alloys shown in Table 1 were melted and cast using a vertical continuous casting machine. A sample with a thickness of 60 mm was cut out from the obtained slab (thickness 180 mm) except for some comparative examples, heated to 950 ° C., extracted, and hot rolling was started. At that time, except for some comparative examples, the pass schedule was set so that the rolling rate in the temperature range of 950 ° C. to 700 ° C. was 60% or more and the rolling was performed in the temperature range of less than 700 ° C. The final pass temperature of hot rolling is between 600 ° C. and 400 ° C. except for some comparative examples. The total hot rolling rate from the slab is about 80-90%. After hot rolling, the surface oxide layer was removed (faced) by mechanical polishing. Then, after cold rolling at various rolling rates, it was subjected to recrystallization annealing. Except for some comparative examples, the ultimate temperature is 600 to 750 ° C. depending on the alloy composition so that the average grain size after recrystallization annealing (the twin boundary is not regarded as a grain boundary) is 5 to 40 μm. The holding time in the temperature range of 600 to 750 ° C. was adjusted in the range of 10 seconds to 600 minutes. Subsequently, an aging treatment was applied to the plate material after the recrystallization annealing except for some examples. The aging treatment temperature was adjusted to a material temperature of 420 ° C., and the aging time was adjusted to a time at which the hardness peaked at 420 ° C. according to the alloy composition. The optimum recrystallization annealing conditions and aging treatment time according to such an alloy composition have been determined by preliminary experiments. Then, finish cold rolling was performed at various rolling rates. Thereafter, it was further subjected to low temperature annealing for 5 minutes in a 400 ° C. furnace. In this way, a test material was obtained. If necessary, chamfering was performed in the middle, and the thickness of the specimen was adjusted to 0.15 mm. The main production conditions are listed in Table 2.
Moreover, about a part of comparative examples (No. 21, 22, 24, 25), as a normal manufacturing method, after hot rolling, in cold rolling before recrystallization annealing, when the plate thickness is reduced by 50% Intermediate annealing was performed at 550 ° C. for 3 hours.

  Samples were collected from each test material, and crystal grain structure, X-ray diffraction strength, electrical conductivity, tensile strength, stress relaxation property, normal bending workability, and bending workability after notching were examined by the following methods.

[Grain structure]
The plate surface (rolled surface) of the test material was polished and etched, the surface was observed with an optical microscope, and the average crystal grain size was measured by the cutting method of JIS H0501.

[X-ray diffraction intensity]
A sample whose surface (rolled surface) was polished with # 1500 water-resistant paper was prepared, and using an X-ray diffractometer (XRD), Mo-Kα ray, tube voltage 20 kV, tube current 2 mA. The reflection diffraction surface intensity of the {420} plane and the {220} plane was measured for the polished surface. On the other hand, using the same X-ray diffractometer as described above, the X-ray diffraction intensities of the {420} plane and {220} plane of pure copper standard powder were measured under the same measurement conditions as described above. Using these measured values, the X-ray diffraction intensity ratio I {420} / I ₀ {420} shown in the formula (1) and the X-ray diffraction intensity ratio I {220} shown in the formula (2) are used. / I ₀ {220} was obtained.

〔conductivity〕
The electrical conductivity of each test material was measured according to JIS H0505.
〔Tensile strength〕
A tensile test piece (JIS No. 5) of TD was collected from each test material, a tensile test based on JIS Z2241 was performed with n = 3, and the tensile strength was determined by the average value of n = 3.

[Stress relaxation characteristics]
A bending test piece (width: 10 mm) having a longitudinal direction of TD was taken from each test material, and arch-bent was performed so that the surface stress at the center in the longitudinal direction of the test piece was 80% of the 0.2% proof stress. Fixed in state. The surface stress is determined by the following equation.
Surface stress (MPa) = 6 Etδ / L ₀ ²
However,
E: Elastic modulus (MPa)
t: sample thickness (mm)
δ: Deflection height of sample (mm)
The stress relaxation rate was calculated using the following equation from the bending habit after holding the test piece in this state at a temperature of 150 ° C. in the atmosphere for 1000 hours.
Stress relaxation rate (%) = (L ₁ −L ₂ ) / (L ₁ −L ₀ ) × 100
However,
L ₀ : Length of the jig, that is, horizontal distance (mm) between the sample ends fixed during the test
L ₁ : Sample length at the start of the test (mm)
L ₂ : Horizontal distance between the sample ends after the test (mm)
Those having a stress relaxation rate of 5% or less were evaluated as having high durability as in-vehicle connectors, and judged to be acceptable.

[Normal bending workability]
A bending test piece having a longitudinal direction of LD and a bending test piece of TD (both 10 mm in width) were sampled from each test material, and a 90 ° W bending test in accordance with JIS H3110 was performed. By observing the surface and cross section of the bent portion of the test piece after the test with an optical microscope at a magnification of 100 times, the minimum bending radius R at which no crack is generated is obtained, and this is divided by the thickness t of the specimen. Thus, R / t values of LD and TD were obtained. The LD and TD of each test material were carried out with n = 3, and the result of the test piece with the worst result among n = 3 was adopted to display the R / t value. Those having an R / t value of 0.5 or less for both LD and TD were determined to be acceptable.

[Bendability after notching]
A strip-shaped sample (width: 10 mm) whose longitudinal direction is LD is taken from each test material, and a notch forming jig having a cross-sectional shape shown in FIG. ), A notch was formed across the sample width by applying a load of 10 kN as shown in FIG. The direction of the notch (ie, the direction parallel to the groove) is a direction perpendicular to the longitudinal direction of the sample. When the notch depth of the notched bending test piece prepared in this way was measured, the notch depth δ schematically shown in FIG. 4 was about ¼ to の of the plate thickness t.

About these bending test pieces with a notch, the "notch bending test" was implemented by the 90 degree W bending test based on JISH3110. At this time, using a jig with R at the center protrusion tip of the lower die set to 0 mm, the notched bending test piece has the notch forming surface facing downward, and the tip of the center protrusion portion of the lower die matches the notch portion. 90 ° W bending test was performed.
By observing the surface and cross section of the bent part with a magnification of 100 times with an optical microscope, the presence or absence of cracks was judged on the test piece after the test. "X" was displayed. In addition, what fractured | ruptured in the bending process part was displayed as "break". Each test material was carried out with n = 3, and the test piece with the worst result among n = 3 was adopted to evaluate “○”, “×”, “Break”. Was judged as acceptable.

  These results are shown in Table 2. In Table 2, in the ordinary bending workability column, LD and TD mean the longitudinal direction of the bending test piece.

表２からわかるように、本発明例のものはいずれも（１）式と（２）式を満たす結晶配向を有し、導電率が３０％ＩＡＣＳ以上、引張強さが６００ＭＰａ以上という高強度を呈するとともに、Ｒ／ｔ値がＬＤ、ＴＤとも０.６以下という優れた曲げ加工性を有する。さらに、実用的に重要なＬＤ方向のノッチング後の曲げ加工性について、９０°Ｗ曲げ試験Ｒ／ｔ＝０での厳しい曲げを行ったにもかかわらず、割れが生じなかった。さらに、車載用コネクター等の用途において重要となるＴＤの応力緩和率が５％以下という優れた特性を兼ね備えている。

As can be seen from Table 2, all of the examples of the present invention have a crystal orientation satisfying the formulas (1) and (2), and have a high strength of 30% IACS or higher and tensile strength of 600 MPa or higher. In addition, it has excellent bendability with R / t values of 0.6 or less for both LD and TD. Furthermore, regarding bending workability after notching in the LD direction, which is practically important, cracks did not occur despite severe bending in the 90 ° W bending test R / t = 0. Furthermore, it has an excellent characteristic that the stress relaxation rate of TD, which is important in applications such as in-vehicle connectors, is 5% or less.

  On the other hand, Comparative Examples Nos. 21 to 25 were manufactured in a normal process for alloys having the same composition as Invention Examples Nos. 1 to 5 (those having a hot rolling final pass temperature of 700 ° C. or higher, After the hot rolling, the rolling ratio before recrystallization annealing is low or the intermediate annealing process is inserted. In all of these, the X-ray diffraction intensity of the {420} crystal plane was weak, and a trade-off relationship was observed between the strength and bending workability or between the bending workability and stress relaxation resistance. And it turns out that these have especially bad bending workability after notching.

  Comparative Examples Nos. 26 to 28 are examples in which good characteristics were not obtained because the content of Ni, Sn or P was outside the specified range. No. 26 had a low strength level because the contents of Ni and Sn were too low, and even when Mg was added, the stress relaxation resistance could not be improved. In addition, since almost no precipitate was generated at the stage after hot rolling, the crystal orientation with {420} as the main orientation component was weakened even if the subsequent cold rolling rate was increased to 90% or more, and the strength Even though the level was low, the bending workability after notching was not improved. In No. 27, since the P content was too high, cracks occurred during hot rolling, and a sample that could be finally evaluated could not be prepared. In No. 28, since the Sn content was too high, the tensile strength was high, but the electrical conductivity was low, and the bending workability and the stress relaxation resistance were inferior.

  Comparative Examples Nos. 29 to 31 are examples in which good characteristics were not obtained because the recrystallization annealing condition was outside the specified range. No. 29 has a recrystallization annealing temperature of 850 ° C. which is too high. In this case, the crystal grains became coarse and good bending workability could not be obtained. In contrast, No. 30 has a recrystallization annealing temperature as low as 500 ° C. In this case, the recrystallization itself did not proceed sufficiently, resulting in a mixed grain structure, resulting in poor bending workability and stress relaxation resistance. No. 31 is an example in which the holding temperature at the time of recrystallization annealing is adjusted to improve the bending workability so that the average crystal grain size is as fine as about 3 μm. In this case, although the bending workability was improved, the stress relaxation resistance was deteriorated because the crystal grains became fine.

  Comparative Examples No. 32 and 33 are examples in which good characteristics were not obtained because the finish cold rolling rate was outside the specified range. In No. 32, the finish cold rolling rate was too low, so the strength was low. In No. 33, the finish cold rolling rate was too high, so that the bending workability was remarkably deteriorated although the strength was high. Further, the crystal orientation with {420} as the main orientation component was weak, and good characteristics could not be obtained.

Standard reverse pole figure showing Schmid factor distribution of face-centered cubic crystal. The figure which showed the cross-sectional shape of the notch formation jig | tool. The figure which showed the method of notching typically. The figure which showed typically the cross-sectional shape of the notch formation part vicinity of a bending test piece with a notch.

Claims (8)

It has the composition of Ni: 0.1-5%, Sn: 0.1-5%, P: 0.01-0.5%, the balance Cu and unavoidable impurities , and the following formula (1) and (2) have a crystal orientation satisfying equation, the copper alloy sheet average crystal grain size of 5 to 40 m.
I {420} / I ₀ {420}> 1.0 (1)
1.5 ≦ I {220} / I ₀ {220} ≦ 3.5 (2)
Here, I {420} is the X-ray diffraction intensity of the {420} crystal plane on the plate surface of the copper alloy sheet, I ₀ {420} is the X-ray diffraction intensity of the {420} crystal plane of pure copper standard powder , I { 220} is the X-ray diffraction intensity of the {220} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {220} is the X-ray diffraction intensity of the {220} crystal plane of the pure copper standard powder . The copper alloy sheet according to claim 1 , further comprising a composition containing at least one of Fe: 3% or less, Zn: 5% or less, Mg: 1% or less, Si: 1% or less, and Co: 2% or less. . Furthermore, the copper alloy board | plate material of Claim 1 or 2 which has a composition which contains 1 or more types of Cr, B, Zr, Ti, Mn, and V in the range of 3% or less in total. The composition-adjusted copper alloy material is hot-rolled, cold-rolled, subjected to recrystallization annealing, and then subjected to finish cold rolling, with or without aging treatment, When a copper alloy sheet is produced by a technique that does not give a thermal history higher than the recrystallization temperature after the recrystallization annealing, the first rolling pass is performed in a temperature range of 950 ° C. to 700 ° C. in the hot rolling process, and 700 in a temperature range of ° C. below to 400 ° C. to perform a rolling or rolling of 40%, it is carried out in the rolling rate 30 to 80% of rolling specifications raised cold, and in the recrystallization annealing step, the temperature reached 600-750 The heat treatment is performed by setting a holding time and an ultimate temperature in a range of 600 to 750 ° C so that the average crystal grain size after recrystallization annealing is 5 to 40 µm in a range of ° C. copper according to any one of 1 to 3 Process for the preparation of gold plate. 5. The rolling according to claim 4 , wherein in the hot rolling step, rolling is performed at a rolling rate of 60% or more in a temperature range of 950 ° C. to 700 ° C., and rolling is performed at a rolling rate of 40% or more in a temperature range of less than 700 ° C. to 400 ° C. A method for producing copper alloy sheets. The method for producing a copper alloy sheet according to claim 4 or 5 , wherein a rolling rate of cold rolling before recrystallization annealing is 85% or more. The method for producing a copper alloy sheet according to any one of claims 4 to 6 , wherein when the aging treatment is performed, the holding temperature is 375 to 500 ° C. The method for producing a copper alloy sheet according to any one of claims 4 to 7 , wherein low-temperature annealing at 150 to 450 ° C is performed after finish cold rolling.

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