JP4876225B2 - High-strength copper alloy sheet with excellent bending workability and manufacturing method thereof - 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, etc., and particularly to a copper alloy plate material excellent in bending workability while maintaining high strength and high conductivity. .

  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. In addition, since electric / electronic parts are generally formed by bending, excellent “bending workability” is also required.

  The requirement for “bending workability” is not only that cracks do not occur in the bent part, but also that it is important to ensure the shape and dimensional accuracy of the bent product. A troublesome problem that appears more or less in bending is springback. Springback is a phenomenon in which elastic deformation recovers when the material is removed from the mold after processing, and does not match the shape when processed in the mold.

  In recent years, electrical and electronic parts have been increasingly integrated, miniaturized and lightened, and accordingly, copper and copper alloys as materials have been required to be thin. For this reason, the strength level required for the material is more severe. Under such circumstances, it is extremely important to improve the shape and dimensional accuracy of the parts, and the problem of springback is likely to become obvious.

  In order to reduce the springback, it is generally effective to design and adjust the mold according to the type of material. However, it is disadvantageous in cost to prepare an appropriate mold for each kind of material.

  On the other hand, in recent years, in order to improve the shape and dimensional accuracy of bent products, a method of notching (notching) the part of the material to be bent, and then bending along the notch ( Hereinafter, the “bending method after notching”) is employed. This processing method is extremely effective for improving the positional accuracy of the bent portion and reducing the springback.

  In recent years, Cu—Ni—Si based alloys (so-called Corson alloys) have attracted attention as copper alloy materials suitable for electric and electronic parts. In general, there is a trade-off relationship between “strength” and “conductivity” or particularly “strength” and “bending workability” in a copper alloy, and it is difficult to satisfy these simultaneously. Under such circumstances, the Cu—Ni—Si based alloy is relatively excellent in the characteristic balance between “strength” and “conductivity”. For example, the strength is remarkably improved while maintaining a relatively high conductivity (30 to 50% IACS) by a process based on solution treatment, cold rolling, aging treatment, finish cold rolling, and low temperature annealing. be able to. However, the bending workability of Cu—Ni—Si based alloys is not always good, and various methods for controlling precipitates and crystal grain forms have been proposed in order to improve this point. It has also been proposed to control the crystal orientation (texture) (Patent Documents 1 to 5).

JP 2000-80428 A JP 2006-9108 A JP 2006-9137 A JP 2006-16629 A JP 2006-152392 A

  As described above, adopting the “bending method after notching” in the copper alloy sheet material is effective in improving the positional accuracy during bending and improving the dimensional accuracy by reducing the spring back, which is effective for Cu—Ni. -It is also effective for Si-based copper alloys. However, the Cu—Ni—Si alloy has a drawback that cracking tends to occur in the bent portion by the “bending method after notching” particularly when trying to further increase the strength. Even in the case of Cu-Ni-Si based alloys that have improved the bending workability by controlling the texture as in Patent Documents 1-5, until the occurrence of cracking due to the "bending process after notching" is prevented. This is not considered, and the bending workability after notching is not sufficiently improved. For example, Patent Document 5 discloses a process in which cold rolling is performed at a rolling rate of 95% or more, solution treatment is performed, and then cold rolling and aging treatment are performed, whereby a tensile strength of 700 MPa or more is disclosed. Bending workability is improved in those having a thickness. However, even if such a process is simply adopted, it is difficult to improve the bending workability after notching in addition to the normal bending workability improvement (see Table 2 and Comparative Example 23 described later).

In this way, in the Cu-Ni-Si based copper alloy, which has a relatively good balance between strength and conductivity, the "bending method after notching" is used to improve the shape and dimensional accuracy of parts while further increasing the strength. A technique for preventing the occurrence of cracks when applied has not been established yet.
An object of the present invention is to provide a copper alloy sheet material in which the strength and the bending workability after notching are compatible at a high level in this alloy system.

  As a result of detailed examinations, the inventors have generally developed a rolling texture having a {220} crystal plane as a main orientation component by cold rolling, but the {420} crystal plane is preliminarily formed in the Cu-Ni-Si alloy. If a recrystallized texture with one orientation component is obtained, a crystal grain with {420} as the main orientation component is identified when a texture with {220} as the main orientation component is developed by cold rolling. It has been found that a rolled texture that remains at a ratio of 5% can be obtained, whereby high strength and remarkable bending workability after notching can be achieved simultaneously.

That is, in the present invention, by mass, Ni: 0.7 to 2.5%, Si: 0.2 to 0.7%, Sn: 0.1 to 1.2% are contained, and if necessary, further There is provided a copper alloy sheet material containing Zn: 2.0% or less, or further Mg: 0.3% or less, the balance being substantially Cu, and having a crystal orientation satisfying the following formula (1). In the above composition, one or more of Co, Cr, B, P, Fe, Zr, Ti, and Mn can be further contained within a total range of 3% or less.
0.1 ≦ I {420} / I {220} ≦ 0.5 (1)
Here, I {420} and I {220} are the X-ray diffraction intensities of the {420} crystal plane and the {220} crystal plane on the plate surface of the plate material, respectively. The “plate surface” is a surface (rolled surface) perpendicular to the thickness direction of the plate.

  “Remainder substantially Cu” means that mixing of elements other than the above is allowed within a range that does not impair the effects of the present invention, and includes the case where “remainder is Cu and inevitable impurities”.

  For example, when the copper alloy sheet is called LD as the direction parallel to the rolling direction and TD as the direction perpendicular to the rolling direction on the sheet surface, the copper alloy sheet is shown on one side of a strip-shaped sample taken so that the longitudinal direction becomes LD from the sheet material. A notched bending test piece in which a notch having a depth of 1/8 to 1/2 and a direction of TD is formed to fill the sample width using the notch forming jig having the cross-sectional shape shown in FIG. When a bending test is carried out, it has a bending workability in which no cracks are observed on the surface of the test piece.

[Notch bending test]
In the 90 ° W bending test specified in JIS H3110, a jig was prepared in which the R at the tip of the central projection of the lower die was 0 mm. The notched bending test piece was placed with the notch forming surface facing downward. A 90 ° W bend test is performed by setting the tip of the central protrusion of the core to match the notch.

In addition, when the above-mentioned notch bending test was performed using a strip-shaped sample collected so that the longitudinal direction was TD as a copper alloy sheet material with small anisotropy, cracks were observed on the surface of the test piece. Those having no bending workability are particularly preferred.
These have a structure that has undergone an aging treatment and exhibit a tensile strength of 650 MPa or more, or even 700 MPa or more.

FIG. 2 schematically shows the notching method.
FIG. 3 schematically shows a cross-sectional shape perpendicular to the longitudinal direction of the notch forming portion of the notched bending specimen (before the bending test). When the plate thickness is t (mm) and the notch depth is δ (mm), the notch is such that δ / t is 1/8 (ie, 0.125) or more and 1/2 (ie, 0.5) or less. Is formed. When subjected to a 90 ° bending test using a notched bending test piece in which this range of notches is formed, if the test piece does not crack, it is excellent when the “bending method after notching” is applied to the part processing. The crack prevention effect is obtained.

As a manufacturing method of this copper alloy sheet, cold rolling with a rolling rate of 85% or more, solution treatment with a heating temperature of less than 700 to 800 ° C., rolling rate of 0 to 50 with respect to the copper alloy material whose composition is adjusted as described above. % Intermediate cold rolling, an aging treatment at a material temperature of 400 to 500 ° C., and a finish cold rolling at a rolling rate satisfying the following formula (2) are sequentially provided. It is preferable to employ a step of performing a heat treatment at 150 to 550 ° C. after the finish cold rolling.
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (2)
Here, ε ₁ is the intermediate cold rolling rate (%), and ε ₂ is the finish cold rolling rate (%).
The rolling rate ε (%) is expressed by the following equation (3), where t _{0 is} the thickness before rolling and t ₁ is the thickness after rolling.
ε = (t ₀ −t ₁ ) / t ₀ × 100 (3)
In addition, said "rolling rate 0%" means the case where the said intermediate cold rolling is not performed.

  According to the present invention, in a Cu-Ni-Si based copper alloy plate having basic characteristics required for electrical / electronic components such as connectors, lead frames, relays, switches, etc., the tensile strength is 650 MPa or more, or even 700 MPa or more. A material having high strength and excellent bending workability capable of remarkably preventing the occurrence of cracking when the “notched bending method” is applied has been provided. It has been difficult for the conventional Cu—Ni—Si based copper alloy manufacturing technology to stably and significantly improve the tensile strength and the bending workability at such a high strength level. 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.

  In the case of a Cu—Ni—Si based copper alloy, the X-ray diffraction pattern from the plate surface (rolled surface) is generally composed of diffraction peaks of four crystal planes {111}, {200}, {220}, and {311}. Is done. As the cold rolling rate increases, the X-ray diffraction intensity of the {220} plane increases relatively, and the diffraction intensity of the {200} plane and {311} plane decreases. The diffraction intensity of the {111} plane usually tends to increase slightly. X-ray diffraction intensities from other crystal planes are much smaller than those from these crystal planes. In particular, when a Cu-Ni-Si-based copper alloy having a normal composition is subjected to a normal manufacturing process to obtain a plate material, the {420} plane X-ray diffraction intensity of the plate material becomes weak enough to be ignored.

  In the present invention, a rolling texture having the {420} plane as one of the main orientation components so as to satisfy the above formula (1) is realized, thereby significantly improving the bending workability after notching. The mechanism for improving the bending workability is not necessarily clear, but the following can be considered. That is, when a crack occurs in the bending process of the plate material, the surface layer part on the outside of the bent part is particularly hardened, and the surface crack is almost always along the direction of about 45 ° from the plate surface outside the bent part. appear. If the slip surface {111} of the copper alloy of the fcc type is oriented in the direction of about 45 ° (or 135 °) with respect to the plate surface, it is considered that the above cracks are greatly reduced. In a crystal grain having a {420} plane parallel to the plate surface, two of the four {111} planes are present at an angle of about 39 ° from the plate surface. That is, the crystal grains have a plurality of slip planes existing at an angle close to 45 ° with respect to the plate surface. The rolling texture satisfying the expression (1) is a texture in which crystal grains having {420} faces parallel to the plate surface exist. Therefore, by obtaining a rolling texture satisfying the expression (1), it is considered that slip in the 45 ° direction from the plate surface is likely to occur in bending after notching, and cracking can be remarkably suppressed.

In order to obtain such a rolled texture, first, a recrystallized texture with {420} as one of the main orientations is obtained in the recrystallization stage. For that purpose, it is important to perform a solution treatment after cold rolling at a large rolling rate of 85% or more using an alloy adjusted to a specific composition range. Thereafter, when cold rolling is performed, a rolling texture having {220} as a main orientation component gradually develops. At this time, the above formula (1) is satisfied by controlling the intermediate crystal orientation between the two types of textures, and high bending strength and excellent bending workability after notching are achieved at once. The crystal orientation can be controlled by adjusting the composition and finish cold rolling that satisfies the above-mentioned formula (2).
Hereinafter, matters for specifying the present invention will be described.

[Alloy composition]
In the present invention, a Cu—Ni—Si based copper alloy is employed. A copper alloy in which Sn, Zn, Mg, and other alloy elements are added to a Cu—Ni—Si ternary basic component is also collectively referred to as a Cu—Ni—Si copper alloy in this specification.

  Ni and Si form precipitates and contribute to an increase in strength and an improvement in conductivity and thermal conductivity. When the Ni content is less than 0.7% by mass or the Si content is less than 0.2% by mass, it is difficult to effectively bring out the above effects. The Ni content is more preferably 1.2% by mass or more, and even more preferably 1.5% by mass or more. The Si content is more preferably 0.3% by mass or more, and still more preferably 0.35% by mass or more. On the other hand, if the Ni content is too high or the Si content is too high, coarse precipitates are likely to be formed, and work hardening at notching increases, so the bending workability after notching decreases for both LD and TD. It's easy to do. Further, it becomes difficult to develop a recrystallized texture having {420}, which will be described later, as a main orientation component in the solution treatment, and finally it is difficult to obtain a plate material excellent in bending workability. For this reason, the upper limit of the Ni content is limited to 2.5% by mass, and a regulation of 2.2% by mass or less, or even less than 2.0% by mass may be provided. The upper limit of Si content is limited to 0.7% by mass, more preferably 0.6% by mass or less, and still more preferably less than 0.5% by mass.

The Ni—Si based precipitate formed by Ni and Si is considered to be an intermetallic compound mainly composed of Ni ₂ Si. However, Ni and Si in the alloy are not necessarily all precipitated by the aging treatment, and to some extent, exist in a solid solution state in the Cu matrix. Although Ni and Si in a solid solution state cause a slight increase in strength, the effect thereof is small as compared with a precipitated state, and it causes a decrease in conductivity. For this reason, it is desirable that the ratio of the Ni and Si contents be as close as possible to the composition ratio of the precipitate Ni ₂ Si. Therefore, in the present invention, it is desirable to adjust the Ni / Si ratio expressed in mass% to the range of 3.5 to 6.0, and more preferably 3.5 to 5.0.

  Sn has a solid solution strengthening action. In the present invention, this solid solution strengthening action is utilized by combining it with precipitation strengthening and work hardening. In order to fully exhibit the effect | action, it is necessary to ensure Sn content of 0.1 mass% or more. However, when Sn content exceeds 1.2 mass%, electrical conductivity will fall remarkably. For this reason, Sn content shall be 0.1-1.2 mass%. In particular, it is more preferable to adjust to the range of 0.2-0.7 mass%.

  Zn improves solderability and strength, and also has an effect of improving castability. Further, the addition of Zn has an advantage that inexpensive brass scrap can be used. However, if it exceeds 2.0 mass%, a decrease in conductivity and stress corrosion cracking resistance tends to be a problem. For this reason, when adding Zn, it carries out in the range of 2.0 mass% or less. In order to sufficiently obtain the above effects, it is desirable to ensure a Zn content of 0.1% by mass or more, and it is particularly preferable to adjust the content to a range of 0.3 to 1.0% by mass.

  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, if the Mg content exceeds 0.3% by mass, the castability and hot workability are remarkably lowered, which tends to cause a problem. For this reason, when adding Mg, it carries out in the range of 0.3 mass% or less.

  As other elements, Co, Cr, B, P, Fe, Zr, Ti, Mn and the like can be contained as necessary. For example, Co, Cr, B, P, Fe, Zr, Ti, and Mn have the effect of further increasing the alloy strength and reducing the stress relaxation. Co, Cr, Zr, Ti, and Mn easily form a high melting point compound with S, Pb, etc. present as inevitable impurities, and B, P, Zr, and Ti have a refinement effect on the cast structure, It can contribute to the improvement of inter-workability.

  In the case where one or more of Co, Cr, B, P, Fe, Zr, Ti, and Mn are contained, the total amount of these elements becomes 0.01% by mass or more in order to sufficiently obtain the action of each element. It is desirable to contain. However, if the total amount exceeds 3% by mass, if it is contained in a large amount, the hot or cold workability is adversely affected, and the cost is 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. .

(Crystal orientation)
A Cu-Ni-Si-based copper alloy has better bending workability as the texture having {420} as a main orientation component as obtained by a solution treatment described later is stronger. However, finish cold rolling is indispensable for achieving high strength. As the cold rolling rate increases, a rolling texture with {220} as the main orientation component develops. Then, it is possible to realize an intermediate structure state between the two, thereby maintaining “strength” and “bending workability after notching” at a high level. In addition, the bendability after notching is significantly improved at the same time in both directions of the bending axis TD and LD. That is, a thing with small anisotropy is obtained. This is an effect caused by the fact that the crystal grains {420} are parallel to the plate surface have a plurality of sliding surfaces existing at an angle close to 45 ° with respect to the plate surface (described above). Inferred.

As a result of various studies, the inventors have found that the intermediate tissue state can be expressed by the following equation (1).
0.1 ≦ I {420} / I {220} ≦ 0.5 (1)
Here, I {420} and I {220} are the X-ray diffraction intensities of the {420} crystal plane and the {220} crystal plane on the plate surface of the plate material, respectively.
When I {420} / I {220} is too large, the recrystallized texture having {420} as the main orientation component is relatively dominant, and it is difficult to obtain sufficient strength due to insufficient work hardening. When I {420} / I {220} is too small, the properties of the rolled crystal texture having {220} as the main orientation component are relatively dominant, and the strength is high as in the conventional material, and the bending workability is high. In particular, the bending workability after notching deteriorates.

It is more preferable to satisfy the following expression (1) ′ instead of the above expression (1).
0.2 ≦ I {420} / I {220} ≦ 0.4 (1) ′

〔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 650 MPa or more, and more preferably 700 MPa or more. In order to increase the strength by using age hardening, this material has an age-treated metal structure. The normal bending workability without notching is preferably such that the ratio R / t of the minimum bending radius R to the sheet thickness t in the 90 ° W bending test is 1.0 or less in both LD and TD. More preferably, it is 5 or less. Bending workability after notching requires at least a bending radius R = 0 mm and no cracking in a 90 ° W bending test in which the bending axis becomes TD. However, according to the manufacturing process described later, the bending axis becomes LD. Even in the 90 ° W bending test, a small anisotropy with no cracks is obtained.

〔Manufacturing process〕
The copper alloy sheet material of the present invention as described above can be produced by, for example, the following general production process without requiring a special production process that brings about an increase in cost.
“Melting / Casting → Hot Rolling → Cold Rolling → Solution Treatment → Intermediate Cold Rolling → Aging Treatment → Finish Cold Rolling → Heat Treatment”
However, it is necessary to control the manufacturing conditions as described later. Although not described in the above process, 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 temperature range below 650 ° C., hot cracking is likely to occur due to the formation of a coarse compound of Ni and Si. Therefore, it is preferable to perform hot rolling in the range of 950 to 650 ° C. and water-cool after the final pass. The hot rolling rate may be approximately 65 to 90%. After hot working, chamfering or pickling can be performed as necessary.

(Cold rolling)
In the cold rolling performed before the solution treatment, it is important that the rolling rate is 85% or more, and more preferably 90% or more. A recrystallized texture having {420} as the main orientation component can be obtained by subjecting the material processed at such a high rolling rate to a solution treatment in the next step. If this cold rolling rate is too low, the formation of the recrystallized texture becomes insufficient, making it difficult to achieve the object of the present invention. That is, the recrystallization texture depends on the cold rolling rate before recrystallization. Specifically, the crystal orientation having the orientation relationship of {420} is hardly generated in the region where the cold rolling rate is 60% or less, and with the increase in the cold rolling rate in the region of about 60 to 80%. It gradually increases, and when the cold rolling rate exceeds about 80%, it starts to increase rapidly. In order to obtain a crystal orientation in which the orientation relationship 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, so it is not necessary to define it in particular, but good results are likely to be obtained at approximately 98% or less.
When performing cold rolling multiple times after the intermediate annealing before the solution treatment after the hot rolling, the cold rolling in the cold rolling performed after the last intermediate annealing performed before the solution treatment. The rolling ratio is adjusted as described above.

[Solution treatment]
The solution treatment here is a heat treatment that serves the two purposes of “re-solution of solute elements in the matrix” and “recrystallization”. By targeting materials processed at a high rolling rate of 85% or more, a recrystallized texture with {420} as the preferred orientation is obtained after solution treatment, and at the same time, the generation of {220} orientation is suppressed. Is done. This solution treatment is preferably performed by adjusting the temperature and time so that the recrystallized grain size is 15 to 60 μm, and more preferably 20 to 40 μm. If the recrystallized grain size becomes too fine, the recrystallized texture becomes weak, so that the rolled texture tends to become dominant at the time of finish rolling, and it becomes difficult to improve the bending workability. However, it is important not to increase the solution treatment temperature excessively. Specifically, heating conditions of 10 sec to 10 min can be employed at a furnace temperature of 700 to less than 800 ° C., preferably 700 to 780 ° C. If the solution treatment temperature is too high, the {200} orientation is dominant, and it may be difficult to obtain a recrystallized texture having {420} as the preferred orientation. Further, the crystal grain size is likely to be coarsened, and bending workability is liable to be lowered. On the other hand, if the temperature is too low, recrystallization is incomplete and solute elements are not sufficiently dissolved, and it becomes difficult to finally obtain a high-strength material excellent in bending workability. In the present invention, the upper limit of the Ni and Si contents is strictly regulated as described above, so that the Ni ₂ Si phase can be sufficiently lost at a lower solution treatment temperature of less than 800 ° C. or 780 ° C. or less.

(Intermediate cold rolling)
Subsequently, cold rolling is performed at a rolling rate of 0 to 50%. Cold rolling at this stage has the effect of promoting precipitation during the aging treatment in the next step, and the aging time for extracting necessary properties (conductivity and hardness) can be shortened. By this cold rolling, a texture having {220} as the main orientation component develops. However, in the range of the cold rolling rate of 50% or less, the {420} plane is still sufficiently parallel to the plate surface. Crystal grains also remain. In particular, the rolling ratio in this cold rolling contributes to the final increase in strength and the improvement in bending workability after notching by combining well with the rolling ratio at the finishing cold pressure described later after the aging treatment. . Cold rolling at this stage needs to be performed at a rolling rate of 50% or less, and more preferably 0 to 35%. If the rolling rate is too high, precipitation will occur non-uniformly in the subsequent aging treatment, and overaging will tend to occur, and it will be difficult to obtain an ideal crystal orientation that satisfies the formula (1).
When the rolling rate is zero, it means that the intermediate cold rolling is not performed after the solution treatment and the aging treatment is directly performed. In order to improve productivity, the copper alloy sheet of the present invention may omit the cold rolling process at this stage.

[Aging treatment]
Subsequently, an aging treatment is performed. In the aging treatment, the temperature is not excessively raised under conditions effective for improving the conductivity and strength of the alloy. If the aging temperature is too high, the crystal orientation with {420} as the preferred orientation developed by the solution treatment is weakened, and as a result, sufficient bending workability improvement effect may not be obtained. Specifically, it is desirable to carry out at a temperature at which the material temperature is 400 to 500 ° C, and a range of 420 to 480 ° C is more preferable. An aging treatment time is about 1 to 10 hours, and good results are obtained.

(Finish cold rolling)
In this finish cold rolling, the strength level is improved and a rolling texture having {220} as the main orientation component is developed. If the rolling rate of finish cold rolling is too low, the effect of increasing the strength cannot be obtained sufficiently. On the other hand, if the rolling rate is too high, the rolling texture in the {220} orientation becomes relatively dominant, and an intermediate crystal orientation in which strength and bending workability after notching are compatible at a high level cannot be realized.

The finish rolling ratio needs to be 10% or more. However, for the upper limit of the finish cold rolling rate, the contribution of the intermediate cold rolling performed before the aging treatment must be taken into account. As a result of detailed studies by the inventors, the upper limit must be set so that the reduction rate of the sheet thickness does not exceed 65% from the solution treatment to the final step in total with the above-mentioned intermediate cold rolling rate. I understood. That is, finish cold rolling is performed so as to satisfy the following expression (2).
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (2)
Here, ε ₁ is the intermediate cold rolling rate (%), and ε ₂ is the finish cold rolling rate (%).
As the final plate thickness, approximately 0.05 to 1.0 mm is applied, and 0.08 to 0.5 mm is more preferable.

[Heat treatment (low temperature annealing)]
After the finish cold rolling, low-temperature annealing can be performed for the purpose of reducing the residual stress of the strip material and improving the spring limit value and stress relaxation resistance. The heating temperature is desirably set to 150 to 550 ° C. As a result, the residual stress inside the plate material is reduced, and bending workability and elongation at break can be increased 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. It is desirable to secure a heating time of 5 sec or more, and good results are usually obtained within a range of 1 h.

  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 various rolling rates, it was subjected to a solution treatment. In the solution treatment, the holding temperature was adjusted in the range of 700 to 780 ° C. according to the alloy composition so that the average crystal grain size (line segment method of JIS H0501) on the rolled sheet surface exceeded 25 μm to 40 μm. The holding time was in the range of 10 sec to 10 mim. Subsequently, the plate material after the solution treatment was subjected to intermediate cold rolling except for a part, and then subjected to an aging treatment. The aging treatment temperature was adjusted to a material temperature of 450 ° C., and the aging time was adjusted to a time when the hardness peaked at 450 ° C. according to the alloy composition. The optimum solution treatment conditions and aging treatment time according to such an alloy composition have been grasped by preliminary experiments. Next, finish cold rolling was performed at various rolling rates, and then a test material was obtained by performing heat treatment (low-temperature annealing) for 5 minutes in a 400 ° C. furnace. If necessary, chamfering was performed in the middle, and the thickness of the specimen was adjusted to 0.2 mm.

  Samples were collected from each test material and examined for X-ray diffraction strength, electrical conductivity, tensile strength, elongation at break, bending workability, and bending workability after notching by the following methods.

[X-ray diffraction intensity]
Prepare a sample with the surface (rolled surface) of the test material # 1500 water-resistant paper polished, using an X-ray diffractometer (XRD), under the conditions of Mo-Kα rays, tube voltage 20 kV, tube current 2 mA, With respect to the plate surface (rolled surface) of the sample, the reflection diffraction surface intensities of the {220} plane and the {420} plane were measured, and the X-ray diffraction intensity ratio shown in the equation (1) was determined.

〔conductivity〕
The electrical conductivity of each test material was measured according to JIS H0505.
[Tensile strength, elongation at break]
An LD tensile test piece (JIS No. 5) was collected from each test material, and subjected to a tensile test in accordance with JIS Z2241 in each direction n = 3, and the tensile strength and elongation at break were determined by the average value of n = 3.

[Normal bending workability]
Bending test pieces (width 10 mm) having a longitudinal direction of LD and TD were sampled from each test material, and a 90 ° W bending test based on 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.

[Bendability after notching]
A strip-shaped sample (width 10 mm) whose longitudinal direction is LD and TD is taken from each test material, and a notch forming jig having a cross-sectional shape shown in FIG. 1 (width of flat surface of convex tip 0.1 mm, angle on both sides) 45 °), a notch was formed to the full width of the sample by applying a load of 15 kN (see FIG. 2). 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, it was about 1/4 of the plate thickness.

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 LD and TD were carried out with n = 3, and the results of the test piece with the worst result among n = 3 were adopted to evaluate “○”, “×”, and “Break”. It was.
The production conditions and the results are shown in Table 2. In Table 2, in the columns of normal bending workability and bending workability after notching, LD and TD mean the longitudinal direction of the bending test piece.

  As can be seen from Table 2, all of the examples of the present invention have a crystal orientation in which the X-ray diffraction intensity ratio satisfies the formula (1), a high tensile strength of 700 MPa or more, and an R / t value. However, both LD and TD have excellent bending workability of 0.5 or less. Furthermore, with respect to the bending workability after notching, no cracking occurred even though severe bending was performed at 90 ° W bending test R / t = 0.

  On the other hand, Comparative Example No. 21 had a low Ni and Si content, resulting in less generation of precipitates and a low strength level. In No. 22, the contents of Ni and Si were too high, but even if the production conditions were appropriate, the relative amount of crystal grains having {420} as the main orientation component was insufficient, and the tensile strength was high. The normal bendability and the bendability after notching were very poor. No. 23 is an example in which finish cold rolling is omitted for the same composition as No. 22 in order to improve bending workability. In this case, the normal bending workability was improved as compared with No. 22, but the crystal orientation satisfying the formula (1) was not obtained because the relative amount of crystal grains having {420} as the main orientation component became insufficient. The bending workability after notching was not improved.

  In Comparative Examples No. 24 and No. 25, the cold rolling rate before the solution treatment was too low, so that the recrystallization texture having {420} as the main orientation component did not sufficiently develop in the solution treatment. A crystal orientation satisfying the formula (1) was not obtained. This is an example in which even if the finish rolling ratio is adjusted, the tensile strength and the bending workability after notching cannot be achieved. Comparative Example No. 26 had a low strength level because the finish rolling rate was too low. In Comparative Example No. 27, although the finish rolling ratio exceeded the upper limit of the formula (2), the crystal orientation satisfying the formula (1) was not obtained and the tensile strength was high, but after normal bending workability and notching Inferior in bending workability. In No. 28, since the intermediate cold rolling rate between the solution treatment and the aging treatment was too high, a crystal orientation satisfying the formula (1) could not be obtained even if the finish rolling rate was lowered. As a result, the precipitates became coarse, and the tensile strength, normal bending workability, and bending workability after notching were inferior.

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 (10)

In mass%, Ni: 0.7-2.5%, Si: 0.2-0.7%, Sn: 0.1-1.2%, the balance has the composition of Cu and inevitable impurities , A copper alloy sheet having a tensile strength of 700 MPa or more and a crystal orientation satisfying the following formula (1).
0.1 ≦ I {420} / I {220} ≦ 0.5 (1)
Here, I {420} and I {220} are the X-ray diffraction intensities of the {420} crystal plane and the {220} crystal plane on the plate surface of the plate material, respectively. When the parallel direction to the rolling direction on the plate surface is called LD and the perpendicular direction is called TD, a notch having a cross-sectional shape shown in FIG. 1 is formed on one side of a strip sample taken from the plate material so that the longitudinal direction becomes LD. When the following notch bending test was performed on a notched bending test piece in which a notch having a depth of 1/8 to 1/2 of the plate thickness and a direction of TD was formed using the jig to fill the sample width, The copper alloy sheet according to claim 1, which has a bending workability in which no cracks are observed on the surface of the test piece.
[Notch bending test]
In a 90 ° W bending test specified in JISH3110, a jig was prepared in which the R at the tip of the central projection of the lower die was 0 mm. The notched bending test piece was placed with the notch forming surface facing downward. A 90 ° W bend test is performed by setting the tip of the central protrusion so that it matches the notch.   Using a notch forming jig having a cross-sectional shape shown in FIG. 1 on one side of a strip sample collected so that the longitudinal direction is TD from the plate material, the depth is 1/8 to 1/2 of the plate thickness, 3. The bending test piece according to claim 2, wherein when the notch bending test is performed on a notched bending test piece in which a notch whose direction is LD is formed to the full width of the sample, no crack is observed on the surface of the test piece. Copper alloy sheet.   Furthermore, the copper alloy board | plate material in any one of Claims 1-3 which has a composition containing Zn: 2.0% or less.   Furthermore, Mg: The copper alloy plate | plate material in any one of Claims 1-4 which has a composition containing 0.3% or less.   Furthermore, the copper alloy board | plate material in any one of Claims 1-5 which has a composition which contains 1 or more types of Co, Cr, B, P, Fe, Zr, Ti, and Mn in the range of 3% or less in total. The copper alloy sheet material according to any one of claims 1 to 6, which has a structure subjected to an aging treatment. Cold-rolling with a rolling rate of 85% or more, solution treatment at less than 700-800 ° C. for adjusting the recrystallized grain size to 15-60 μm , intermediate cooling with a rolling rate of 0-50% The manufacturing method of the copper alloy sheet | seat material in any one of Claims 1-7 which has the process of performing a finish cold rolling with the rolling rate which satisfies the following (2) Formula and a cold rolling, an aging treatment of 400-500 degreeC.
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (2)
Here, ε ₁ is the intermediate cold rolling rate (%), and ε ₂ is the finish cold rolling rate (%). Cold-rolling with a rolling rate of 85% or more, solution treatment at less than 700 to 800 ° C. for adjusting the recrystallized grain size to 20 to 40 μm, intermediate cooling with a rolling rate of 0 to 50% for the copper alloy material whose composition is adjusted The manufacturing method of the copper alloy sheet | seat material in any one of Claims 1-7 which has the process of performing a finish cold rolling with the rolling rate which satisfies the following (2) Formula and a cold rolling, an aging treatment of 400-500 degreeC.
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (2)
Here, ε ₁ is the intermediate cold rolling rate (%), and ε ₂ is the finish cold rolling rate (%). The method for producing a copper alloy sheet according to claim 8 or 9, further comprising a step of performing heat treatment at 150 to 550 ° C after finish cold rolling.

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