JP5002766B2 - High strength copper alloy sheet with excellent bending workability and manufacturing method - Google Patents

Description

  The present invention relates to a copper alloy material suitable for electrical and electronic parts such as connectors, lead frames, relays, switches, and the like, and more particularly to a copper alloy sheet material having improved bending workability while maintaining high strength and high conductivity. It is.

  Electrical components such as connectors, lead frames, relays, and switches that make up electrical and electronic components are required to have good “conductivity” in order to suppress the generation of Joule heat due to energization. Therefore, “strength” that can withstand the stress applied during assembly and operation is required. In addition, electric / electronic parts are generally formed by bending, and the “bendability” of the material is required. However, there is a trade-off relationship between “strength” and “conductivity” or particularly “strength” and “bending workability”. Conventionally, materials having good “conductivity”, “strength” or “bending workability” are appropriately selected and used for such energized parts depending on the application.

  In recent years, with the trend toward higher integration, miniaturization, and weight reduction of electrical and electronic components such as connectors, lead frames, relays, and switches, there is an increasing demand for thinning of these materials such as copper and copper alloys. . Accordingly, the strength level required for the material is becoming stricter. Further, in order to cope with the miniaturization of electric / electronic parts, it is necessary to expand the degree of freedom in designing the parts. For this purpose, it is essential to improve the “bending workability” of the material.

  However, as described above, there is a trade-off relationship between “strength” and “conductivity”, or in particular, “strength” and “bending workability”. “Strength”, “conductivity”, “bending workability” It is not easy to increase "" at the same time.

  Examples of the strengthening mechanism of the copper alloy include work hardening, solid solution strengthening, and precipitation strengthening. Among these, solid solution strengthening tends to cause a decrease in conductivity. In order to achieve high strength while maintaining the conductivity of the copper alloy at a high level, it is advantageous to use precipitation strengthening. On the other hand, work hardening is a traditional strengthening method, but a high strengthening action can be obtained particularly in combination with precipitation strengthening. Moreover, the decrease in conductivity due to work hardening is small. Therefore, in order to increase the strength without reducing the electrical conductivity as much as possible, it is effective and general to combine work hardening and precipitation strengthening, specifically to employ a process combining cold working and aging treatment. It is a simple method.

  However, when the final cold rolling is performed in order to obtain an increase in strength due to work hardening, the bending workability of the plate material (especially when the bending axis is parallel to the rolling direction (BW)) is significantly reduced. Even if both “strength” and “conductivity” are high, if “bending workability” decreases, it may become unusable as a material for electric / electronic parts.

  As precipitation strengthening type copper alloys, alloys such as Cu—Cr (—Zr), Cu—Fe—P, Cu—Mg—P, and Cu—Ni—Si have been put to practical use. Among these, Cu—Ni—Si based alloys (so-called Corson alloys) have recently attracted attention as an alloy having an excellent balance between strength and electrical conductivity.

  In the case of a Cu-Ni-Si alloy, when the conventional solution treatment, cold rolling, and aging treatment are used, the strength increases as the aging time elapses, and after a certain peak point, it is monotonous. (I.e., an over-aged state of coarse precipitates). If an attempt is made to obtain a high tensile strength of about 700 MPa, the conductivity falls to a level of 30-40% IACS, and conversely, if an attempt is made to raise the conductivity to 50% IACS or more, the tensile strength falls to 650 MPa or less. . That is, it is difficult to achieve high strength (for example, tensile strength of 700 MPa or more) while maintaining high conductivity (for example, 45% IACS or more) simply by using precipitation strengthening (aging treatment). If cold rolling and low-temperature annealing are further performed after the aging treatment, the strength can be greatly improved, but the bending workability is generally significantly reduced accordingly.

  Patent Document 1 discloses a multiple aging treatment method as a method for simultaneously improving the conductivity and strength of a Cu—Ni—Si based alloy. Patent Document 2 discloses a method of repeating cold rolling and aging treatment. However, no consideration is given to improving the workability at the same time. In addition, these methods are not advantageous in terms of cost due to an increase in the number of processes.

  Patent Document 3 discloses a technique for refining the crystal grain size of a copper alloy to 1 μm or less by strong processing of 95% or more. In this method, in the case of a Cu-Ni-Si alloy, a tensile strength of 800 MPa or more is obtained. However, the refined grain structure produced by cold cold working has low ductility (for example, Non-Patent Document 1), and is difficult to apply to applications that require little bending and excellent bending workability.

  In order to improve the bending workability, means for reducing the final cold work rate or performing annealing after the final cold rolling is effective. However, the former is accompanied by a decrease in strength level. In the latter case, when the annealing temperature is low, the bending workability is not sufficiently improved, and when the annealing temperature is high, softening tends to occur. For this reason, it is not easy to achieve both strength and bending workability.

  Control of impurities such as S, H, and O, and control of precipitate size are also effective for improving bending workability (Patent Document 4). However, in order to control these, the heat treatment process becomes complicated, resulting in an increase in manufacturing cost. Further, the improvement effect of the bending workability itself is not necessarily a satisfactory level, and further improvement is desired.

  Patent Document 5 discloses that the bending workability of a Cu—Ni—Si alloy is improved by controlling the crystal orientation. However, the crystal orientation control method, that is, the relationship between crystal orientation, composition, and manufacturing conditions is not necessarily clear. And the tensile strength in the case of showing the outstanding bending workability is not so high, and has stopped at about 650 MPa (maximum 730 MPa).

JP-A-10-152737 JP 7-41887 A JP 2002-356728 A Japanese Patent No. 3049137 JP 2000-80428 A “Plasticity and processing”, Japan Society for Technology of Plasticity, February 2003, Vol. 44, No. 505, p.

As described above, even if a conventionally known method is used, it is difficult to improve the conductivity, strength, and bending workability of the copper alloy material in a balanced manner at the same time.
The present invention has been made in view of the above problems of conventional materials, and an object of the present invention is to provide a copper alloy sheet having excellent bending workability while maintaining high strength and conductivity.

As a result of various studies, the inventors have found that the above object can be achieved by providing a difference in the amount of precipitates in both the surface layer portion and the center portion in the plate thickness direction in the plate material of precipitation strengthened copper alloy. It has been confirmed that such a plate material can be manufactured by applying an aging treatment after passing through a device such as a tension leveler that applies continuous repeated bending deformation.
That is, in the present invention, by mass, Ni: 0.4 to 4.8%, Si: 0.1 to 1.2%, and if necessary, Mg: 0.3% or less is included, and further if necessary Sn, Zn, Co, Cr, P, B, Al, Fe, Zr, Ti, Mn in a total range of 3% or less, with the balance being substantially Cu, and at least the plate thickness Precipitates having a particle diameter of 0.1 μm or more exist in the 1/2 position in the direction ± 5 μm region, and the density Ms (particles / μm) of precipitates having a particle diameter of 0.1 μm or more in the 1/8 position in the plate thickness direction ± 5 μm region ² ) and both the surface layer part and the center part so that the density Mc (particles / μm ² ) of precipitates having a particle diameter of 0.1 μm or more in the ½ position in the plate thickness direction ± 5 μm region satisfies the following formula (1): A copper alloy sheet having a difference in the amount of precipitates is provided. The Mc is, for example, about 0.1 to 1.5 pieces / μm ² .
Ms / Mc ≦ 0.8 (1)

  Here, the 1/8 position in the plate thickness direction is a position that advances from the plate surface (the surface that becomes the wide surface of the plate) by 1/8 of the plate thickness toward the center of the plate thickness. This means both the position advanced by / 8 and the position advanced by 1/8 of the plate thickness from the other plate surface. The 1/2 position in the thickness direction is the center position in the thickness direction. The plate thickness direction 1/8 position ± 5 μm region is a region ± 5 μm from the position in the plate thickness direction centering on the 1/8 position in the plate thickness direction. Similarly, the plate thickness direction 1/2 position ± 5 μm region is a region ± 5 μm from the position in the plate thickness direction centered on the plate thickness direction 1/2 position.

The density Ms and Mc (number / μm ² ) of the precipitates is a cross section (longitudinal cross section) parallel to the rolling direction and the plate thickness direction, and the precipitate particles in the above region at a substantially central portion with respect to the plate width. This can be determined by examining the particle size and number of particles. Specifically, it can be determined by observing a polished and etched sample cross section using, for example, an SEM (scanning electron microscope). As the particle diameter, the diameter of the longest part appearing on the observation surface is adopted for each precipitate particle. In the thickness direction 1/8 position of both surface layer portions ± 5 μm, at least 90 μm ² or more measurement areas are observed in 3 or more fields each, and a total of 6 or more fields are observed, and the particle diameter present in each measurement area is 0.1 μm or more. An average value obtained by dividing the number of particles by the area of the measurement region can be defined as Ms (number / μm ² ). Similarly, at least 90 μm ² of the measurement region in the thickness direction 1/2 position ± 5 μm region is observed over 3 fields of view, and the number of particles having a particle diameter of 0.1 μm or more present in each measurement region is measured. The average value of the values divided by the area can be Mc (pieces / μm ² ). The surface layer portion refers to a region from the plate surface to approximately 1/4 depth in the plate thickness direction, and the central portion refers to a region excluding both surface layer portions.

  The balance substantially Cu means that the remainder can be mixed with elements other than the above as long as the object of the present invention is not impaired in addition to Cu, and the case of “remainder Cu and unavoidable impurities”. included.

  The unique precipitate distribution as described above can be realized by applying an aging treatment to a material that has been subjected to continuous repeated bending after cold rolling. Specifically, as a method for producing the copper alloy sheet material, a material corresponding to 15 to 50% cold rolling is subjected to a tension corresponding to 5 to 20% of 0.2% proof stress (MPa) of the material. There is provided a method for producing a copper alloy sheet having a step of performing continuous repeated bending with an elongation of 0.1 to 1.5% while applying, followed by an aging treatment at 420 to 520 ° C, for example. After the aging treatment, it is preferable to employ a production method including a step of performing a final cold rolling of 30% or less and a heat treatment at 250 to 550 ° C.

  The continuous repetitive bending process is one in which a strain is alternately applied to each surface layer part while passing a plate material in the state of a strip, and can be realized by, for example, passing it through a tension leveler. Tension levelers are equipment used to correct the shape of metal strips or reduce residual stress, and apply repeated bending deformation with rolls arranged alternately on both sides of the plate surface while applying tension to the strips. is there.

  According to the present invention, the bending workability is remarkably improved while maintaining the strength of the conventional precipitation strengthened copper alloy at a high level. Therefore, the present invention can meet the needs for miniaturization and thinning of electric / electronic parts, which are expected to be further developed in the future, by providing materials for energizing parts such as connectors, lead frames, relays and switches.

  In the present invention, a “precipitation strengthened copper alloy” is used as a material, which exhibits a remarkable work hardening effect. Examples of such alloys include Cu—Cr (—Zr), Cu—Fe—P, Cu—Mg—P, and Cu—Ni—Si, among which Cu—Ni—Si is preferably used. it can.

  In these copper alloy sheet materials, it is necessary to secure a sufficient amount of precipitates to achieve high strength. On the other hand, however, if the precipitation is sufficiently advanced, there are many relatively coarse precipitates having a particle diameter of 0.1 μm or more. Such coarse precipitate particles have almost no contribution to strength, but they become the starting point of cracking during bending, so it is better to suppress the formation of coarse precipitates as much as possible in order to improve bending workability. It is advantageous. Therefore, in the present invention, a metal structure having a small amount of precipitates in both surface layer portions in the plate thickness direction and a large amount of precipitates in the center portion of the plate thickness, that is, a peculiarity in which there is a difference in the amount of precipitates between both surface layer portions and the center portion By realizing a stable metal structure, we have succeeded in satisfying the above conflicting requirements at the same time.

  As a result of the inventors conducting bending tests on many precipitation-strengthened alloys, most of the cracks generated during these tests originated from precipitate particles of 0.1 μm or more near the surface of the plate. I found out. Therefore, the bending workability can be remarkably improved by eliminating precipitates of 0.1 μm or more. However, in the case of a precipitation strengthened alloy, precipitated particles are continuously generated during the aging treatment process, so in order to maintain a certain level of strength and conductivity (for example, a tensile strength of 700 MPa or more and a conductivity of 35% IACS or more) Formation of coarse precipitates of 0.1 μm or more is inevitable.

  According to this finding, high strength and high electrical conductivity can be maintained if the formation of coarse precipitates can be suppressed only at the surface layer portion without preventing the formation of coarse precipitates of 0.1 μm or more for the entire material. However, it is considered that bending workability can be improved. Therefore, the inventors have conducted detailed research and found that it is possible to reduce coarse precipitates in the surface layer portion from the central portion by performing continuous repeated bending before aging treatment as described later. It came. It has also been found that continuous repeated bending process makes it difficult to over-age during aging treatment by changing the internal stress state of the plate. When the amount of coarse precipitates is differentiated between the surface layer portion and the central portion so as to satisfy the formula (1), high strength and high conductivity are improved at the same time, and bending workability is remarkably improved. It became clear.

In the case of a Cu—Ni—Si based copper alloy, in order to obtain the high strength required for the current-carrying parts, precipitates having a particle diameter of 0.1 μm or more are present at least in the plate thickness direction 1/2 position ± 5 μm region. Must be aged under various conditions. In particular, the density Mc of the precipitates having a particle diameter of 0.1 μm or more in the ½ position in the plate thickness direction ± 5 μm region is preferably in the range of 0.1 to 1.5 particles / μm ² . If the Mc is lower than this, it becomes difficult to stably realize a high strength such as a tensile strength of 700 MPa or more. On the other hand, even if the precipitation proceeds too excessively, the strength is lowered. Density Mc is more preferably 0.1 to 1.0 pieces / [mu] m ^2, and still more preferably 0.3 to 1.0 pieces / [mu] m ^2.

Also, the density Ms (particles / μm ² ) of precipitates having a particle diameter of 0.1 μm or more in the plate thickness direction 1/8 position ± 5 μm region and the particle diameter 0.1 μm or more in the plate thickness direction 1/2 position ± 5 μm region. What realized the structure | tissue state which provided the difference in the amount of precipitates of both surface layer parts and a center part so that the density Mc (piece / micrometer < ² >) of a precipitate may satisfy | fill following (1) Formula is the structure state after that. Unless a thermal history that breaks the surface is applied or excessive processing is performed, the bending workability is remarkably improved. It is more preferable to satisfy the following formula (1) ′.
Ms / Mc ≦ 0.8 (1)
Ms / Mc ≦ 0.75 (1) ′

Such a copper alloy sheet material with a “difference” in the amount of precipitates in the surface layer portion and the central portion can be produced by the following manufacturing process, for example.
Melting / Casting → Hot Rolling → Cold Rolling → Solution Treatment → Cold Rolling → Continuous Repeat Bending → Aging Treatment → Final Cold Rolling → Heating Process Here, processes other than continuous repeated bending are common copper Alloy manufacturing methods can be followed. 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 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)
By hot working the slab, the crystallization phase generated in the casting process disappears, and at the same time, the cast structure is destroyed by recrystallization to make the recrystallized grain structure uniform. This hot rolling is desirably performed in the solid solution temperature range of the precipitate. It is desirable to quench immediately after the hot rolling by water cooling or the like. In the case of Cu-Ni-Si system, hot cracking is likely to occur due to the formation of coarse compounds of Ni and Si in the temperature range below 650 ° C, so hot rolling is performed in the range of 950 to 650 ° C, and the final pass is completed It is preferable to cool with water later. The hot rolling rate may be about 75 to 90%. After hot working, chamfering or pickling can be performed as necessary.

(Cold rolling)
In the cold rolling at this stage, the rolling rate is desirably 80% or more. If the rolling rate is lower than that, recrystallized grains become large in the next solution treatment and a mixed grain structure is easily formed, which is disadvantageous in obtaining good bending workability.

[Solution treatment]
It is desirable to adjust the temperature conditions so that the crystal grain size is 5 to 15 μm. In the case of Cu—Ni—Si, heating conditions of 700 to 850 ° C. × 10 sec to 10 min can be employed.

(Cold rolling)
Subsequently, cold rolling is performed at a rolling rate of 15 to 50%. As the rolling rate increases, the subsequent aging promotes precipitation. When the rolling rate exceeds 50%, precipitation occurs unevenly, tends to be over-aged, and it is difficult to control actual operating conditions. When the rolling rate is less than 15%, it takes a long time to increase the strength and the electrical conductivity by aging treatment, and the productivity is lowered. In particular, if the rolling rate is small, the plate material will be subjected to continuous repeated bending while remaining soft in the solution state, and both surface layers of the plate are more likely to work harden than the center (there are many strains introduced). In the subsequent aging treatment, the amount of precipitates generated in both surface layers tends to be larger than that in the central portion. Such a hard state of the surface layer is desirable for another purpose (for example, when wear resistance is required), but is not good in the present invention. In that sense, the cold rolling rate is preferably 15 to 50%. A more preferable cold rolling rate is 25 to 40%.

[Continuous repeated bending]
The plate material after cold rolling is subjected to continuous repeated bending. “Continuous” as used herein refers to processing while passing in the state of strips. Repeated bending is to repeatedly apply a bending process in which the bending axis is a direction substantially perpendicular to the longitudinal direction of the strip (through plate direction) and the plate thickness direction so that the bending directions are alternately opposite to each other. Unlike the case where a large deformation is locally applied as in the bending process at the time of molding the part, repeated deformation such as bending, stretching, bending, stretching, is continuously applied in the longitudinal direction of the strip, The bending rate at each stage is small enough to finally return to a flat plate shape. Although the number of times of bending is required at least twice, good results are usually obtained in the range of several times to 20 times.

  Such a continuous repeated bending process can be provided by rolls alternately arranged on both surface sides of the strip. The strip is subjected to an arc-shaped bending deformation along the surface of the roll. At that time, tensile strain is applied to the surface layer outside the radius of curvature. Next, bending deformation in the reverse direction is applied by a roll disposed on the opposite side of the roll with the strip interposed therebetween, and tensile strain is applied to the surface layer portion on the opposite side to the previous time. By such alternate bending deformation, both surface layer portions are repeatedly subjected to stress loading and unloading, and both surface layer portions are softened as compared with the central portion due to the Bauschinger effect.

When the aging treatment is performed on the plate material that has been subjected to continuous repeated bending in this manner, the generation of precipitated particles is delayed in the soft surface layer portion as compared with the central portion of the plate material. As a result, the “cracking origin” that becomes a problem during bending is less likely to occur, and the bending workability is significantly improved. Further, by changing the internal stress state at the center of the plate material by continuous repeated bending, overaging is less likely to occur during the aging treatment. That is, the aging temperature range in which the highest strength can be obtained can be shifted in the direction in which higher conductivity can be obtained.
Therefore, strength, electrical conductivity, and bending workability can be improved at the same time.

  It is efficient to apply the continuous repeated bending process with a tension leveler. The tension leveler is an apparatus originally used for correcting the shape of a metal strip and removing residual stress, and is configured by alternately arranging rolls on both surface sides of a strip to be passed. Tension is applied to the strip material to be passed through from the entrance side and the exit side of the tension leveler, so that loading and unloading of the tensile stress to the surface layer portion can be performed more efficiently. Moreover, the shape correction effect which is the original purpose of the tension leveler can also be obtained.

  However, it is difficult to soften the surface layer so that the precipitate distribution of the formula (1) can be obtained stably even if the plate is passed under general conditions for the purpose of shape correction and residual stress removal. In other words, it is necessary to secure a certain degree of elongation in order to correct the shape and remove residual stress, but in the case of shape correction, the higher the tension, the more advantageous. The lower the value, the more advantageous. However, if the tension leveler is passed with the former high elongation rate, the surface layer portion and the central portion both extend to substantially the same extent. On the other hand, if the latter tension is set low, it is difficult to apply sufficient bending deformation to both surface layers. As a result, the difference between the surface layer and the center becomes insufficient, and a remarkable improvement in bending workability can be expected. Absent.

  As a result of detailed studies by the inventors, when continuous bending is performed with a tension leveler, it corresponds to 5 to 20% of the 0.2% proof stress (MPa) of the material before passing through the tension leveler (after cold rolling). It was found that it is desirable to adopt a condition in which the elongation rate of the entire strip material is 0.1 to 1.5% while applying tension (tensile stress; MPa). It is more preferable that the tension (tensile stress) is 10% to 15% of the 0.2% proof stress and the elongation is 0.1% to 0.5%. If the tension or elongation rate is too large, the work hardening imparted to the surface layer part exceeds the contribution of the Bauschinger effect, so the surface layer part hardens more than the center part, and the bending workability becomes worse. If the tension or elongation is too small, the amount of bending deformation of both surface layers is insufficient, and the effect of improving the bending workability is not sufficiently exhibited.

  As the tension leveler, a type used for straightening the shape of a general copper alloy strip can be used. A total of about 15 to 30 work rolls and a roll diameter of about 10 to 20 mm can be preferably used.

[Aging treatment]
The aging treatment employs general conditions effective for improving conductivity and strength depending on the alloy system. In the case of a Cu—Ni—Si system, a range of 420 to 520 ° C. is desirable. When it is lower than 420 ° C., the aging time becomes long, which is disadvantageous for productivity. If the temperature exceeds 520 ° C., element re-dissolution starts, and a sufficient amount of precipitation cannot be secured, leading to a decrease in conductivity and strength.

[Final cold rolling]
If necessary, the strength of the product can be further improved by performing final cold rolling. The copper alloy sheet of the present invention preferably has a final cold rolling reduction of 10 to 30%. If the rolling rate is less than 10%, the increase in strength (work hardening) is small. Conversely, if the rolling rate exceeds 30%, the strength is significantly increased, but the effect of improving the bending workability is small.
The final plate thickness is generally about 0.1 to 1.0 mm, and more preferably 0.1 to 0.5 mm.

[Heat treatment (low temperature annealing)]
When the final cold rolling is performed, low temperature annealing can be performed mainly for the purpose of reducing the residual stress of the strip. The Cu—Ni—Si alloy is preferably heat-treated at a temperature range of 250 ° C. to 550 ° C. As a result, the residual stress inside the strip is further reduced, and the bending workability and elongation at break can be significantly increased with almost no decrease in strength. In addition, the 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 change in the characteristics is small and not efficient. It is desirable to secure a heating time of 5 seconds or longer, and the bending workability and the electrical conductivity can be sufficiently improved within a range usually within 1 h. A more preferable temperature range is 350 to 500 ° C.

Hereinafter, the composition of a Cu—Ni—Si based copper alloy will be described as an example of a copper alloy suitable for the present invention.
[Chemical composition]
When Ni and Si are added together in a copper alloy, the amount of Ni and Si dissolved decreases with the precipitation of a precipitate mainly composed of a compound of Ni and Si (hereinafter referred to as "Ni-Si-based precipitate"), This is advantageous in improving strength while maintaining high conductivity.

  When the Ni content is less than 0.4% by mass or the Si content is less than 0.1% by mass, it is difficult to effectively bring out the above effects. On the other hand, when the Ni content exceeds 4.8% by mass or the Si content exceeds 1.2% by mass, the conductivity is lowered and the precipitates are easily coarsened, so that the strength is also easily lowered. For this reason, it is desirable that the Ni content is 0.4 to 4.8 mass% and the Si content is 0.1 to 1.2 mass%. A more preferable Ni content is 2.0 to 3.5% by mass, and a more preferable Si content is 0.4 to 0.8% by mass.

  The mass ratio of Ni and Si (Ni / Si) is preferably in the range of 3.5 to 6.0. Outside this range, the amount of Ni or Si not dissolved in the formation of Ni—Si-based precipitates increases, and the conductivity may decrease.

  Mg has an effect of preventing the coarsening of Ni—Si based precipitates. It also has an effect of improving stress relaxation resistance. In order to fully exhibit these actions, it is desirable to secure an Mg content of 0.01% by mass or more. However, when the Mg content exceeds 0.3% by mass, the castability and hot workability are remarkably lowered, and the cost is disadvantageous. For this reason, when adding Mg, it should carry out in the range of 0.3 mass% or less.

  The remainder other than Ni and Si, or the remainder other than Ni, Si and Mg may be composed of Cu and inevitable impurities. However, other alloy elements may be added as necessary. For example, Sn, Co, Cr, P, B, Al, Fe, Zr, Ti, and Mn have an effect of further increasing the alloy strength and reducing stress relaxation. Co, Cr, Zr, Ti, and Mn are easy to form a high melting point compound with S, Pb, etc. present as inevitable impurities, and B, Zr, and Ti have the effect of refining the cast structure, It can contribute to improvement of sex. Sn and Zn have the effect of improving cold workability.

  When one or more of Sn, Zn, Co, Cr, P, B, Al, Fe, Zr, Ti, and Mn are contained, the total amount is 0.01 mass in order to sufficiently obtain the action of each element. It is desirable to make it contain so that it may become more than%. However, when the total amount exceeds 3% by mass, hot workability or cold workability may be deteriorated. It is also economically disadvantageous. Accordingly, the total amount 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 still more preferably in the range of 0.5% by mass or less. .

Examples of the alloy composition include the following.
[1] By mass%, Ni: 0.4 to 4.8%, Si: 0.1 to 1.2%, remaining Cu and inevitable impurities.
[2] By mass%, Ni: 0.4 to 4.8%, Si: 0.1 to 1.2%, Mg: 0.3% or less, preferably 0.01 to 0.3%, balance Cu and Inevitable impurities.
[3] By mass%, Ni: 0.4 to 4.8%, Si: 0.1 to 1.2%, Mg: 0.3% or less, preferably 0.01 to 0.3%, Sn, Zn , Co, Cr, P, B, Al, Fe, Zr, Ti, Mn: Total 3% or less, preferably 0.01 to 3%, more preferably 0.01 to 0.5%, balance Cu and Inevitable impurities.

  The copper alloys shown in Table 1 were melted and cast using a vertical continuous casting machine. The obtained slab was heated to 950 ° C., and hot-rolled in a temperature range of 950 to 650 ° C. to obtain a plate having a thickness of 10 mm, and then rapidly cooled (water cooled). After hot rolling, the surface oxide layer was removed (faced) by mechanical polishing.

Next, after cold rolling at a reduction rate of 80% or more, solution treatment was performed. In the solution treatment, the temperature conditions were adjusted within a temperature range of 650 to 900 ° C. depending on the alloy composition so that the crystal grain size was 5 to 15 μm. The plate after the solution treatment was further cold-rolled at a processing rate of 10 to 30%. Thereafter, continuous bending was performed using a tension leveler. Subsequently, an aging treatment was performed. The aging treatment temperature was set to 450 ° C., and the aging time was adjusted to a time at which the center of the plate material had a peak according to the alloy composition at an aging time of 450 ° C. Such an optimal aging treatment time is known in advance by a preliminary test. Finally, cold rolling with a rolling rate of 10 to 30% and heat treatment (low temperature annealing) at 400 ° C. for 5 minutes were performed. For comparison, some materials were not subjected to continuous repeated bending.
From the final process finished material thus obtained, a structure observation sample, a tensile test piece, a bending workability test piece, and a conductivity measurement sample were collected.

Structure observation was performed using an optical microscope and SEM for a cross section (longitudinal cross section) parallel to the rolling direction and the plate thickness direction. The density (preceding Ms and Mc) of precipitates having a particle diameter of 0.1 μm or more in the surface layer portion and the central portion was determined by SEM observation. Ms is an average of the measured values of a total of 6 visual fields: 3 visual fields in the plate thickness direction 1/8 position ± 5 μm region on one plate surface side, and 3 visual fields in the 1/8 position ± 5 μm region on the other plate surface side. Value was adopted. For Mc, the average value of the measured values of 6 fields of view in the plate thickness direction 1/2 position ± 5 μm region was adopted. In order to obtain Ms and Mc, the measurement region was a rectangular region (measurement area 100 μm ² ) of 10 μm in the plate thickness direction and 10 μm in the rolling direction for each visual field.

  The tensile test was performed according to JIS Z2241 using a test piece parallel to the rolling direction, and the tensile strength and elongation at break were determined.

  For bending workability, a 90 ° W bending test (conforming to JIS H3110, width W = 10 mm) in which the bending axis is perpendicular to the rolling direction (GW) and parallel (BW) is performed. By observing the surface and cross section of the bent part with an optical microscope at a magnification of 100 times, the minimum R / t at which no cracks occurred was determined and evaluated. Here, R is the inner bending radius, and t is the plate thickness. The smaller the minimum R / t, the better the bending workability. It is judged that a material having R / t of 1.0 or less for both GW and BW has good bending workability for an energized part.

The conductivity was measured according to JIS H0505.
Table 2 shows the manufacturing conditions and test results.

As can be seen from Tables 1 and 2, all of Nos. 1 to 11 of the examples of the present invention have a precipitate density Mc with a particle size of 0.1 μm or more in the central portion of 0.1 to 1.0 / μm ^2. In addition, the density of precipitates having a particle diameter of 0.1 μm or more was smaller in the surface layer portion than in the central portion so as to satisfy the formula (1). These had high electrical conductivity of 45% IACS or higher, high tensile strength of 750 MPa or more, breaking elongation of 7% or more, and bending workability cleared the minimum bending radius R / t ≦ 1.0 or less. That is, a copper alloy sheet material having improved conductivity, strength and bending workability at a high level in a well-balanced manner was obtained.

  On the other hand, Comparative Examples Nos. 21 to 24 having the same composition as No. 1 of the present invention example are those manufactured without performing continuous repeated bending (conventional process materials). It can be seen that the strength and bending workability are in a trade-off relationship depending on the final cold rolling rate. That is, in these, bending workability could not be improved while maintaining the strength at a high level.

Comparative Examples Nos. 25 to 27 are examples in which the strength and bending workability could not be improved with good balance when the composition defined in the present invention was not appropriate.
In No. 25, the Ni and Si contents are too low and the amount of precipitates is small, so that the electrical conductivity and bending workability are good, but the strength is low and the effect of continuous repeated bending work is not clear. In No. 26, the Ni and Si contents were too high, but the strength was high but the bending workability was remarkably deteriorated, and the bending workability could not be improved even when continuous repeated bending was performed. In No. 27, since the Ni and Si contents were too high, severe cracks occurred during hot rolling, and the final characteristics could not be evaluated.

Comparative examples Nos. 28 to 31 are examples in which strength and bending workability could not be improved in a well-balanced manner when the production conditions defined in the present invention were not appropriate.
No. 28 was not subjected to cold rolling before continuous repeated bending, and in the final product, the surface layer portion had more coarse precipitated particles than the center portion. In No. 29, the cold rolling rate before continuous repeated bending was too high, and the coarsely precipitated particles in the surface layer portion and the central portion were almost the same amount, both of which were satisfactory because they did not satisfy the formula (1). Strength and bending workability could not be realized.

Comparative examples Nos. 30 to 31 are examples in which the strength and bending workability could not be improved in a well-balanced manner when the conditions of continuous repeated bending were not appropriate.
Since No. 30 had a small amount of processing (elongation) in continuous repeated bending, the effect of improving the characteristics was hardly seen as compared with No. 23 in which continuous repeated bending was not performed. In No. 31, the tension at the time of repeated bending was increased too much, so there was almost no difference in the density of coarse precipitate particles between the surface layer and the center, and the bending workability was also reduced by not satisfying the formula (1). It was not improved.

  Reference Example No. 32 exhibits a precipitate distribution that satisfies the formula (1) by performing continuous repeated bending under appropriate conditions, but the final cold rolling rate is too high, and is due to continuous repeated bending. Bending workability improvement effect was offset.

Claims (9)

It has a composition of Ni: 0.4 to 4.8%, Si: 0.1 to 1.2%, the balance Cu and unavoidable impurities in mass%, and particles at least in the plate thickness direction 1/2 position ± 5 μm region Precipitates with a diameter of 0.1 μm or more exist, and density Ms (particles / μm ² ) of precipitates with a particle diameter of 0.1 μm or more in the plate thickness direction 1/8 position ± 5 μm region and plate thickness direction 1/2 position Copper alloy provided with a difference in the amount of precipitates in both the surface layer portion and the central portion so that the density Mc (pieces / μm ² ) of precipitates having a particle diameter of 0.1 μm or more in the ± 5 μm region satisfies the following formula (1) Board material.
Ms / Mc ≦ 0.8 (1)   Furthermore, the copper alloy board | plate material of Claim 1 which has a composition containing Mg: 0.3% or less.   The copper alloy sheet according to claim 1 or 2, further comprising a composition containing one or more of Sn, Zn, Co, Cr, P, B, Al, Fe, Zr, Ti, and Mn in a total range of 3% or less. The copper alloy according to any one of claims 1 to 3, wherein a density Mc of a precipitate having a particle diameter of 0.1 µm or more in a plate thickness direction 1/2 position ± 5 µm region is 0.1 to 1.5 pieces / µm ^2. Board material.   The copper alloy according to any one of claims 1 to 4, wherein a difference is provided in the amount of precipitates in both the surface layer portion and the central portion by performing an aging treatment on a material subjected to continuous repeated bending after cold rolling. Board material. A material having a composition of Ni: 0.4 to 4.8% by mass, Si: 0.1 to 1.2%, the balance Cu and unavoidable impurities, and subjected to 15 to 50% cold rolling. Then, continuous tension bending is performed using a tension leveler to give an elongation of 0.1 to 1.5% while applying a tension corresponding to 5 to 20% of 0.2% proof stress (MPa) of the material, then the preparation of the copper alloy sheet that have a step of applying an aging treatment at 420-520 ° C.. The method for producing a copper alloy sheet according to claim 6, further comprising a step of performing a final cold rolling of 30% or less and a heat treatment at 250 to 550 ° C. after the aging treatment. The method for producing a copper alloy sheet according to claim 6 or 7, wherein the material further has a composition containing Mg: 0.3% or less . 9. The composition according to claim 6, wherein the material further has a composition containing one or more of Sn, Zn, Co, Cr, P, B, Al, Fe, Zr, Ti, and Mn in a total range of 3% or less. The manufacturing method of the copper alloy board | plate material of description .