JP2015183262A - Cu-Ni-Si-BASED COPPER ALLOY SHEET MATERIAL, MANUFACTURING METHOD THEREOF AND ELECTRIFICATION COMPONENT - Google Patents

Abstract

PROBLEM TO BE SOLVED: To markedly improve fatigue resistance of a Cu-Ni-Si-based copper alloy sheet material having good balance of strength and conductivity at a high level and good in bendability and stress relaxation resistance.SOLUTION: There is provided a copper alloy sheet material having a composition containing, by mass%, Ni:2.5 to 5.0%, Si:0.6 to 1.5%, Sn:0 to 1.2%, Zn:0 to 2.0%, Mg:0 to 1.0%, Co:0 to 2.0%, Fe:0 to 0.5%, Cr:0 to 0.5%, B:0 to 0.05%, P:0 to 0.1%, Zr:0 to 1.0%, Al:0 to 1.0%, Ti:0 to 1.0%, Mn:0 to 1.0%, V:0 to 1.0% and the balance Cu with inevitable impurities with the total content of Fe, Cr, B, P, Zr, Al, Ti, Mn and V of 0 to 3.0 mass%, with a maximum width of a grain boundary reaction type deposition product of 500 nm or less and the number density of a granular deposition product having a diameter of 100 nm or more of 10/mmor less.

Description

  The present invention is a Cu-Ni-Si-based copper alloy sheet material with excellent strength and bending workability suitable for electrical and electronic parts such as connectors, lead frames, relays, switches, and the like, and particularly significantly improves fatigue resistance. The present invention relates to a copper alloy sheet and a manufacturing method thereof. Moreover, it is related with the electricity supply components using the copper alloy board | plate material.

  Materials used for energized parts constituting electric / electronic parts are required to be excellent in “strength”, “conductivity”, “bending workability”, and “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 level of “strength” required for materials has become even stricter. Specifically, a tensile strength of 850 MPa or more, preferably 900 MPa or more, more preferably 950 MPa or more is desired. In addition, since the thinning of parts leads to an increase in electrical resistance, it is necessary to maintain high “conductivity” as well as high strength. Specifically, a conductivity level of 35% IACS or more, preferably 38% IACS or more, more preferably 40% IACS or more is desired.

  As a copper alloy having a relatively excellent balance between strength and conductivity, there is a Cu—Ni—Si based copper alloy (so-called Corson alloy). This alloy system can be adjusted to a tensile strength of 800 MPa or higher while maintaining a relatively high electrical conductivity (30-50% IACS), and recently developed a technology for increasing strength such as 850 MPa or higher, or even 900 MPa or higher. Has been.

  On the other hand, “fatigue resistance” that can withstand repeated stress loads is also important for energized parts having movable parts such as connectors, relays, and switches. However, it is not easy to improve fatigue resistance while maintaining high strength and good conductivity with a Cu—Ni—Si based copper alloy. The reason is that a grain boundary reaction type precipitate is likely to be generated. Cu-Ni-Si-based copper alloys achieve high strength by generating fine Ni-Si-based precipitates by aging treatment. During this aging treatment, usually, a grain boundary reaction type precipitate is also generated. Grain boundary reaction type precipitates act as a starting point and a propagation path of fracture cracks, so if a large amount of grain boundary reaction type precipitates are formed, the fatigue resistance is significantly lowered. In addition, the strength, bending workability, and stress relaxation resistance may be reduced. In a Cu—Be-based copper alloy or the like, by adding a third element such as Ni or Co, these elements segregate at the grain boundary, and the generation of grain boundary reaction type precipitates is suppressed. However, in the Cu—Ni—Si based copper alloy, since Si is a very active element, most of the additive elements and compounds are generated, and the effect of suppressing grain boundary reaction type precipitation is unlikely to occur. The present condition is that the effective method which suppresses a grain boundary reaction type precipitation in a Cu-Ni-Si type copper alloy is not established.

JP 2007-169664 A JP 2008-75172 A

The precipitate form of the Cu—Ni—Si based copper alloy is roughly classified into two types: a granular precipitate and a grain boundary reaction type precipitate. Both are second phases mainly composed of Ni ₂ Si. Of the granular precipitates, fine ones impede dislocation movement and contribute to high strength, but coarse ones with a particle diameter of 100 nm or more cause a reduction in ductility. On the other hand, the grain boundary reaction type precipitate is a lamellar nodule generated from the grain boundary. The grain boundary portion where this is generated is very fragile and acts as a starting point of fatigue fracture or bending crack and a crack propagation path, and deteriorates strength, bending workability, fatigue resistance characteristics and stress relaxation resistance.

  FIG. 1 illustrates a SEM photograph of a metal structure obtained by polishing and etching a plate surface (rolled surface) of a conventional general Cu—Ni—Si based copper alloy sheet material that has undergone finish cold rolling after aging treatment. The granular precipitates (reference numeral 1) are dispersed in the crystal grains, and the grain boundary reaction precipitates (reference numeral 2) are generated in layers from the crystal grain boundaries.

  If the Cu-Ni-Si-based copper alloy merely prevents the formation of grain boundary reaction type precipitates, the Ni content is 2.5 mass% or less, or the Si content is 0.6 mass% or less. I know what to do. Further, since the grain boundary reaction type precipitation is likely to occur in the temperature range of 430 to 530 ° C., the production of a large amount of grain boundary reaction type precipitates can be avoided if the production conditions are such that the residence time in that temperature range is as short as possible. However, when Ni or Si is reduced as described above, a high strength such as a tensile strength of 850 MPa or more cannot be obtained. In addition, the temperature range in which age hardening is most easily obtained in the alloy system is usually about 430 to 470 ° C., and the temperature range is included in the temperature range of 430 to 530 ° C. at which grain boundary reaction type precipitates are easily generated. Therefore, the aging conditions that completely avoid the temperature range of 430 to 530 ° C. at which grain boundary reaction type precipitates are easily generated cannot be easily adopted in order to increase the strength.

  Patent Documents 1 and 2 describe Cu—Ni—Si based copper alloys in which grain boundary reaction precipitation is suppressed. However, these copper alloys are desired to be further improved in the balance between strength and conductivity in consideration of the strict needs for thinning which are imposed on the current-carrying parts.

  The present invention provides a technique for remarkably improving fatigue resistance in a Cu-Ni-Si based copper alloy sheet having good bending workability and stress relaxation resistance, which balances strength and conductivity at a high level. Is.

As a result of detailed studies, the inventors have determined that in a Cu-Ni-Si based copper alloy having a predetermined composition,
(I) Ensure that the total extension of the grain boundary is sufficiently secured in consideration of the crystal grain size not being coarsened by the solution treatment.
(Ii) generating a small amount of fine granular precipitates in advance in a high temperature range where no grain boundary reaction type precipitates are generated before aging treatment;
(Iii) Fine grain precipitation effective for strength improvement by applying aging treatment in a temperature range in which grain boundary reaction type precipitates shifted to a lower temperature side are less likely to be formed and combined with the fine grain precipitates produced in the high temperature range. Ensure a sufficient number of items,
It has been found that the above purpose can be realized.

That is, in the present invention, by mass%, Ni: 2.5 to 5.0%, Si: 0.5 to 1.5%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg : 0 to 1.0%, Co: 0 to 2.0%, Fe: 0 to 0.5%, Cr: 0 to 0.5%, B: 0 to 0.05%, P: 0 to 0.0. 1%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Ti: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%, balance Cu And a granular precipitate having a composition in which the total content of Fe, Cr, B, P, Zr, Al, Ti, Mn and V is 0 to 3.0% by mass and having a diameter of 100 nm or more A copper alloy sheet having a number density of 10 ⁶ pieces / mm ² or less, and preferably having an average crystal grain size of 5 to 25 μm is provided. The maximum width of the grain boundary reaction type precipitate is preferably 1000 nm or less.

[Measurement method of maximum width of grain boundary reaction type precipitate]
In the SEM observation of the surface polished and etched on the plate surface (rolled surface), a total observation region of 5000 to 7000 μm ² is set, and all the grain boundary reaction type precipitates existing in the region are grains in which a reaction occurs. The distance from the boundary to the tip of the reaction phase is examined, and the maximum value of this distance is defined as “the maximum width of the grain boundary reaction type precipitate”.
[Method for measuring number density of granular precipitates]
In the same manner as described above, an observation region having a total of 5000 to 7000 μm ² is set, and among all the granular precipitate particles in which the entire particle is present within the area of the region, the diameter of the particle having the smallest circle surrounding the particle is 100 nm or more The number is counted, and the value obtained by dividing the number by the area of the observation region is converted into a number density per 1 mm ² , and the value is defined as “number density of granular precipitates having a diameter of 100 nm or more (pieces / mm ² )”. .
[Measurement method of average crystal grain size]
An average crystal is obtained by counting the number of crystal grains that are completely cut by a line segment of a known length perpendicular to the rolling direction according to JIS H0501 by observing the etched surface of the plate surface (rolled surface) using an optical microscope. Obtain the particle size. However, the total number of crystal grains to be measured is 100 or more. Twin boundaries are not considered grain boundaries.

The above-mentioned copper alloy sheet material is fatigue resistant in a fatigue test according to JIS Z2273 with a fatigue life at the maximum applied stress of 700 MPa on the surface of the test piece (the number of repeated vibrations until the test piece is broken) of 100,000 times or more. Has characteristics. The tensile strength TS in the rolling direction of the plate is 850 MPa or more, and the A value of the following formula (1) represented by the product of the conductivity R (% IACS) and the tensile strength TS (MPa) is 35,000 or more. What has a characteristic becomes a more preferable object. The conductivity is, for example, 35% IACS or more.
A value = R (% IACS) × TS (MPa) (1)
Further, when the rolling direction of the plate is LD, and the direction perpendicular to the rolling direction and the plate thickness direction is TD, the minimum bending radius MBR and the plate thickness t that cause no crack in the 90 ° W bending test according to JIS H3110 A material having a bending workability in which the value of the ratio MBR / t is 2.0 or less for both LD and TD is provided.

As a manufacturing method of the above copper alloy sheet, when manufacturing in a process including hot rolling, cold rolling, solution treatment, aging treatment,
In the solution treatment, the plate surface (rolling surface) is perpendicular to the rolling direction as a heat pattern that is heated and held at 780 to 1000 ° C. and then held for 10 to 120 seconds in the temperature range of 530 to 730 ° C. in the cooling process. Performed under the condition that the average crystal grain size by the measured cutting method is 5 to 25 μm,
The aging treatment is performed at 350 to 420 ° C.
A method for producing a copper alloy sheet is provided. In this manufacturing method, cold rolling with a rolling rate of 1 to 35% can be performed after the solution treatment and before the aging treatment. Moreover, finish cold rolling with a rolling rate of 1 to 50% can be performed after the aging treatment. It is preferable to perform low temperature annealing at 150 to 430 ° C. after finish cold rolling.

  Moreover, in this invention, the electricity supply component using the said copper alloy board | plate material as a material is provided.

  According to the present invention, it is possible to remarkably improve fatigue resistance in a Cu-Ni-Si-based copper alloy plate material having a balance between strength and conductivity at a high level and excellent in bending workability and stress relaxation resistance. It has become possible. The present invention is useful as an electrical / electronic component such as a connector, a lead frame, a relay, or a switch that is expected to be further reduced in size and thickness.

The SEM photograph which illustrated the metal structure of the conventional general Cu-Ni-Si system copper alloy sheet material. The SEM photograph which illustrated the metal structure of the Cu-Ni-Si system copper alloy sheet material according to the present invention.

<Alloy composition>
The present invention is directed to a Cu—Ni—Si based copper alloy having a Ni content in the range of 2.5 to 5.0 mass%. Hereinafter, “%” regarding alloy components means “% by mass” unless otherwise specified.

  Ni and Si form precipitates and contribute to an increase in strength and an improvement in conductivity and thermal conductivity. If Ni is less than 2.5% or Si is less than 0.5%, it is difficult to stably obtain a tensile strength of 850 MPa or more in the final plate product. On the other hand, when Ni or Si is excessive, coarse precipitates are likely to be generated and easily cracked during hot rolling. The Ni content must be 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less. The Si content needs to be 1.5% or less, more preferably 1.2% or less. A particularly preferable Ni content range is 2.5 to 4.0%, and a particularly preferable Si content range is 0.6 to 1.1%.

Ni and Si form precipitates 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 content of Ni and Si is as close as possible to the composition ratio of the precipitate Ni ₂ Si. In the present invention, it is desirable to adjust the Ni / Si ratio expressed in mass% to a range of 3.0 to 6.0, and more preferably 3.5 to 5.0. However, when an element capable of forming a precipitate with Si, such as Co and Cr shown below, is added, it is desirable to adjust the Ni / Si ratio in the range of 3.0 to 4.2.

  Sn has a solid solution strengthening action and a stress relaxation resistance improving action, and therefore Sn is contained as necessary. It is more effective to ensure the Sn content of 0.1% or more, and it is more effective to set the content to 0.2% or more. However, a large amount of Sn will cause a decrease in conductivity. The Sn content is limited to a range of 1.2% or less. You may manage to 0.7% or less.

  Zn not only improves solderability and strength, but also has an effect of improving castability, so it is contained as necessary. Inexpensive brass scrap can be used as the Zn source. It is more effective to secure a Zn content of 0.1% or more, and it is more effective to set it to 0.3% or more. However, a large amount of Zn is likely to cause a decrease in conductivity and stress corrosion cracking resistance. The Zn content is limited to a range of 2.0% or less. It is more preferable to adjust within the range of 1.0% or less.

  Mg has an action of improving stress relaxation resistance and an action of removing S, and is thus contained as necessary. It is more effective to secure a Mg content of 0.01% or more, and it is more effective to set it to 0.1%. However, Mg is an element that is easily oxidized, and a large amount of addition causes a decrease in castability. The Mg content is limited to a range of 1.0% or less. You may manage to 0.5% or less.

  Co is effective in improving both strength and conductivity, and is added as necessary. The added Co reacts with solute Si in the Cu matrix to form precipitates, while excess Co precipitates even in a simple substance. It is more effective to secure a Co content of 0.1% or more, and it is more effective to make it 0.5%. However, Co is an expensive element, and excessive addition causes an increase in cost, so Co addition is performed in a content range of 2.0% or less. It is more preferable to adjust within the range of 1.5% or less.

  As other elements, Fe, Cr, B, P, Zr, Al, Ti, Mn, V, and the like can be contained as necessary. For example, Cr, B, P, Zr, Al, Ti, Mn, and V have the effect of further increasing the alloy strength and reducing the stress relaxation. Fe, Cr, Zr, Ti, Mn, and V easily form a high melting point compound with S, Pb, etc. present as inevitable impurities, and B, P, Zr, and Ti have an effect of refining the cast structure. It can contribute to improvement of hot workability. When one or more of Fe, Cr, B, P, Zr, Al, Ti, Mn, and V are contained, it is more effective to set the total content to 0.01% or more. . However, if it is contained in a large amount, it adversely affects hot or cold workability and is disadvantageous in terms of cost. The total amount of these elements is limited to a range of 3.0% or less, and it is more preferable to adjust within a range of 2.0% or less, or 1.0% or less. May be.

《Metallic structure》
(Granular precipitate)
The granular precipitates are scattered within the crystal grains and at the grain boundaries. When the particle diameter is small (several nm to several tens of nm), the curing action is remarkable and the loss of ductility is small. On the other hand, coarse granular precipitates (100 nm or more) have a large loss of ductility despite their small curing action. In addition, large-scale formation of coarse granular precipitates inevitably leads to a decrease in the density of fine granular precipitates, which hinders strength improvement. As a result of various studies, in the present invention, the number density of granular precipitates having a diameter of 100 nm or more is limited to 10 ⁶ pieces / mm ² or less, and more preferably 5.0 × 10 ⁵ pieces / mm ² or less.

(Grain boundary reaction type precipitate)
The grain boundary reaction type precipitate is a very weak part and causes a decrease in strength. Furthermore, it becomes a starting point of fatigue fracture or bending crack and a crack propagation path, and deteriorates fatigue resistance, bending workability, and stress relaxation resistance. Conventionally, by reducing the area ratio of grain boundary reaction type precipitates (nodules), an example in which strength reduction is suppressed (Patent Document 1) and grain boundary reaction type precipitation (discontinuous precipitation) are caused. There is an example (Patent Document 2) in which a decrease in tensile strength and bending workability is suppressed by limiting the width of a precipitation-free zone generated in the vicinity of the boundary. However, it has been found that in order to significantly improve the fatigue resistance, it is necessary to strictly control the width of the grain boundary reaction type precipitate itself that becomes the crack initiation point and propagation path. As a result of detailed investigations by the inventors, when the width of the grain boundary reaction type precipitate becomes 1000 nm or more, the strength and the bending workability are remarkably lowered. On the other hand, if the maximum width of the grain boundary reaction type precipitates is suppressed to 500 nm or less, it is possible to improve fatigue resistance characteristics in addition to strength and bending workability. The maximum width of the grain boundary reaction type precipitate is preferably 1000 nm, and more preferably 500 nm or less. More preferably, it is 300 nm or less. Furthermore, it is more preferable that the grain boundary reaction precipitates have a width of less than 100 nm, and the grain boundary reaction precipitation is suppressed to such a degree that the accurate width is difficult to measure.

[Average crystal grain size]
The smaller the average crystal grain size, the better the bending workability, but the Cu—Ni—Si based copper alloy has a problem that coarse granular precipitates tend to remain as the crystal grains become finer. On the other hand, if the average crystal grain size is too small, the stress relaxation resistance tends to deteriorate. As a result of various studies, the average crystal grain size is preferably a value of 5 μm or more, and more preferably 7 μm or more. In particular, a value exceeding 8 μm is preferable because it is easy to ensure a sufficient level of stress relaxation resistance even in the use of an in-vehicle connector. However, if the crystal grain size becomes too large, the surface of the bent portion is likely to be rough, and the bending workability may be lowered. Therefore, the average crystal grain size according to the above measurement method is limited to a range of 25 μm or less. . It is more preferable to adjust to a range of 20 μm or less or 15 μm or less. The final average crystal grain size is almost determined by the crystal grain size in the stage after the solution treatment. The crystal grains in the stage after the solution treatment are substantially equiaxed. The final crystal grain shape is slightly flattened by rolling and extends in the rolling direction, but is almost unchanged in a direction perpendicular to the rolling direction and the plate thickness direction (hereinafter referred to as “T direction”). If the average crystal grain size is measured by cutting along the T direction on the plate surface (rolled surface), the final average crystal grain size is almost the same as the crystal grain size in the stage after solution treatment, and the difference is ignored. it can.

"Characteristic"
[Strength / Conductivity]
In order to cope with further downsizing and thinning of electric / electronic parts using a Cu—Ni—Si based copper alloy, a strength level of 850 MPa or more in the rolling direction (LD) is desired. More preferably, it is 900 MPa or more, and more preferably 950 MPa or more. On the other hand, in order to reduce the thickness of the current-carrying parts, it is an important requirement even though the conductivity is good. Specifically, the electrical conductivity is desirably 35% IACS or more, more preferably 38% IACS or more, and even more preferably 40% IACS or more. It is important that both strength and conductivity are high values, that is, excellent in strength-conductivity balance. As a result of various studies, the A value in the following formula (1) represented by the product of conductivity R (% IACS) and LD tensile strength TS (MPa) is preferably 35000 or more, and 37000 or more. Is more preferable, and it is still more preferable that it is 37500 or more.
A value = R (% IACS) × TS (MPa) (1)

[Bending workability]
Regarding bending workability, the minimum bending radius at which cracks do not occur in the 90 ° W bending test in accordance with JIS H3110 in both the rolling direction (LD) of the plate and the direction perpendicular to the rolling direction and the thickness direction (TD). The ratio MBR / t of the MBR and the plate thickness t is desirably 2.0 or less. The MBR / t is more preferably 1.5 or less for both LD and TD. More preferably, it is 1.0 or less. Here, “MBR / t of LD” is MBR / t when the bending axis is TD (so-called GW), which is evaluated by a bending test piece cut out so that the LD is in the longitudinal direction. “TD MBR / t” is MBR / t when the bending axis is LD (so-called BW), which is evaluated by a bending test piece cut so that TD is in the longitudinal direction.

[Fatigue resistance]
Regarding fatigue resistance, it is preferable that the fatigue life at the maximum applied stress of 700 MPa on the surface of the test piece (the number of repeated vibrations until the test piece breaks) is 100,000 times or more in the fatigue test according to JIS Z2273. More preferable is 200,000 times or more.

[Stress relaxation resistance]
As for stress relaxation resistance, the value of TD is particularly important for applications such as in-vehicle connectors. Therefore, here, using a test piece having a longitudinal direction of TD, the stress relaxation rate is evaluated by the following method. .
Bending test piece (width: 10 mm) having a longitudinal direction of TD was taken from a copper alloy sheet, and arch-bending was performed so that the surface stress at the center in the longitudinal direction of the test piece was 0.2% of the proof stress of 80%. Secure with. 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 is 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 are evaluated as having high durability as in-vehicle connectors.

"Production method"
The copper alloy sheet material described above can be produced by, for example, the following general manufacturing process.
“Melting / Casting → Hot Rolling → Cold Rolling → Solution Treatment → (Cold Rolling Before Aging) → Aging Treatment → (Finish Cold Rolling → Low Temperature Annealing)”
However, it is important to devise manufacturing conditions in several steps as described later. 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. Here, “cold rolling before aging”, “finish cold rolling” and “low temperature annealing” may be omitted. Hereinafter, each step will be described.

[Melting / Casting]
The slab may be manufactured by continuous casting, semi-continuous casting, or the like. In order to prevent oxidation of Si, it is preferable to carry out in an inert gas atmosphere or a vacuum melting furnace.

(Hot rolling)
When the slab is hot-rolled, it is advantageous to carry out the first rolling pass in a high temperature range of 700 ° C. or more where recrystallization is likely to occur, in order to destroy the cast structure and make the components and structure uniform. . However, if the temperature exceeds 1000 ° C., cracks may occur at a location where the melting point is lowered, such as a segregation location of the alloy component. In order to promote the occurrence of complete recrystallization during the hot rolling process, it is effective to perform rolling at a rolling rate of 60% or more in a temperature range of 1000 ° C to 700 ° C. In order to prevent the formation and coarsening of precipitates, it is effective to set the final pass temperature of hot rolling to 500 ° C. or higher. Water cooling is desirable after hot rolling.
In addition, the rolling rate from a certain plate thickness t ₀ (mm) to a certain plate thickness t ₁ (mm) is obtained by the following equation (2). The same applies to the rolling rate in each step described later.
Rolling ratio (%) = (t ₀ −t ₁ ) / t ₀ × 100 (2)

(Cold rolling)
In the cold rolling performed before the solution treatment, it is more effective to set the rolling rate to 90% or more, and it is more effective to set it to 95% or more. By applying a solution treatment to the material processed at such a high rolling rate in the next step, the strain introduced at the rolling rate functions as a nucleus of recrystallization, and a structure having a uniform crystal grain size is formed. can get. 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 99% or less from the viewpoint of preventing edge cracks and the like.

[Solution treatment]
The conventional solution treatment is mainly aimed at “re-solution of solute elements in the matrix” and “recrystallization”, but in the present invention, the “structure in which grain boundary reaction precipitation is suppressed in the subsequent aging process” “To state” is also an important purpose. The heating temperature of the solution treatment is set within a range of 780 to 1000 ° C. What is necessary is just to set the time hold | maintained in the said temperature range in the range of 30 sec-10min. The average crystal grain size after the solution treatment can be controlled by this heating condition. In the plate material after the solution treatment, the heating temperature and the heating time are adjusted so that the average crystal grain size obtained by the above-mentioned method is 5 to 25 μm, more preferably 7 to 20 μm, and still more preferably 8 to 17 μm. Optimal solution conditions for ensuring re-solution and recrystallization and adjusting the average crystal grain size to the above range vary depending on the composition and cold rolling rate before solution treatment, but preliminary experiments By grasping the optimum solution treatment heat pattern condition according to the composition and the cold rolling rate, it becomes easy to set the appropriate condition range.

  The cooling after the solution treatment is generally “quenching” in order to prevent the precipitation of the second phase during the cooling as much as possible. However, under such normal solution treatment conditions, grain boundary reaction precipitation is likely to occur during subsequent aging. In the present invention, during the cooling of the solution treatment, the grain boundary reaction type precipitation hardly occurs at 530 to 730 ° C., more preferably 580 to 725 ° C. for 10 to 120 sec, more preferably 20 to 100 sec. Thus, fine granular precipitates are generated at the crystal grain boundaries (and within the crystal grains). When the solution treatment material in such a state that there is no coarsening of crystal grains and fine granular precipitates are already formed is subjected to an aging treatment under conditions shifted to a relatively low temperature side, It was found that the formation of boundary reaction type precipitates can be remarkably suppressed. Moreover, the fine granular precipitate formed here also contributes to strength improvement. If the holding temperature during the cooling is too high, the crystal grains become coarse and the production amount of fine granular precipitates is insufficient. If the holding temperature is too low and the holding is in a temperature range of less than 530 ° C. and 430 ° C. or more, grain boundary reaction type precipitation occurs, and if the temperature is lower, fine granular precipitates are not generated, and a solution by normal rapid cooling The result is the same as the conversion process. On the other hand, if the holding time is too long, fine granular precipitates are coarsened and the strength is lowered. If the holding time is too short, the amount of fine granular precipitates is reduced, resulting in the same result as a solution treatment by normal rapid cooling. The average cooling rate from 530 ° C. to 300 ° C. is preferably 100 ° C./sec or more.

  In the case of a continuous plate line, the cooling conditions after the solution treatment described above can be realized by controlling the temperature and length of each cooling zone and the plate passing speed. When there is an equipment limitation, after a normal solution treatment (rapid cooling), a heat treatment is performed in a heating furnace at 530 to 730 ° C., more preferably 580 to 725 ° C. for a holding time of 10 to 120 seconds, more preferably 20 to 100 seconds. May be.

[Cold rolling before aging]
Subsequently, cold rolling can be performed before the aging treatment. Cold rolling at this stage has the effect of accelerating precipitation during the subsequent aging treatment, thereby lowering the aging temperature for extracting necessary properties (conductivity and hardness) or shortening the aging time. This is advantageous.
Although this cold rolling may be omitted, when it is performed, the rolling rate is preferably in the range of 1 to 50%, more preferably 1 to 40%, and even more preferably 1 to 35%. . When the rolling rate is too high, the bending workability of the final product in the TD direction is deteriorated.

[Aging treatment]
The aging treatment of the Cu—Ni—Si based copper alloy is conventionally performed in a temperature range of about 430 to 500 ° C. in general. However, grain boundary reaction precipitation is extremely likely to occur in this temperature range. In the solution treatment described above, since a small amount of fine granular precipitates have already been generated after the solution treatment, the aging treatment temperature at which the maximum strength after aging is obtained is shifted to a lower temperature side. For this reason, it is possible to increase the strength by low temperature aging. Specifically, an aging treatment is performed at 350 to 420 ° C. In this temperature range, grain boundary reaction type precipitation is remarkably suppressed. 380-410 degreeC is more preferable. The aging treatment time may be set in the range of 60 to 600 min, and may be managed in the range of 120 to 540 min. In order to suppress the surface oxidation during the aging treatment as much as possible, a hydrogen, nitrogen or argon atmosphere can be used.

[Finish cold rolling]
Finish cold rolling is extremely effective in improving the strength level (particularly 0.2% yield strength). However, when the finish cold rolling rate increases, the TD bending workability tends to deteriorate. It is effective to perform the finish cold rolling within a range of a rolling rate of 1 to 35%, and a range of 5 to 20% is more preferable. This finish cold rolling may be omitted.

[Low temperature annealing]
After finish cold rolling, low-temperature annealing can be performed for the purpose of reducing the residual stress of the strip material, improving the bending workability, and improving the stress relaxation resistance by reducing the dislocations on the pores and the sliding surface. The heating temperature is preferably 150 to 430 ° C, more preferably 200 to 420 ° C. Thereby, strength, electrical conductivity, bending workability and stress relaxation resistance can be improved at the same time. If this heating temperature is too high, grain boundary reaction precipitation tends to occur. 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 5 seconds or longer, and good results are usually obtained within a range of 1 h.
The final thickness of the copper alloy sheet may be, for example, 0.05 to 1.0 mm. More preferably, the thickness is 0.08 to 0.5 mm.

  A copper alloy having the composition shown in Table 1 was melted and cast using a vertical semi-continuous casting machine. The obtained slab was heated to 950 ° C. and extracted, and hot rolling was started. The final pass temperature of hot rolling is between 600 ° C and 500 ° C. After the hot rolling was finished, it was cooled with water. The total hot rolling rate from the slab is about 90%. Among these, the rolling rate at 950 to 750 ° C. was about 70%. After hot rolling, the surface oxide layer was removed (faced) by mechanical polishing to obtain a rolled plate having a thickness of 10 mm. Subsequently, after performing cold rolling in the range of a rolling rate of 97 to 99%, it was subjected to a solution treatment.

The solution treatment was performed in the air under the conditions shown in Table 2. Except for some comparative examples, using the cooling process of the solution treatment, the temperature was maintained at an intermediate temperature for a predetermined time, and then cooled with water. The average cooling rate from 530 ° C. to 300 ° C. by water cooling was 100 ° C./sec or more. In an example in which this holding was not performed, water cooling was performed after heating and holding the solution, as in the conventional general solution treatment. A sample was taken from the plate material after the solution treatment, and the average crystal grain size was measured by the method described above. The results are shown in Table 2. After the solution treatment, cold rolling before aging at the rolling rates shown in Table 2 was performed in some examples. Next, an aging treatment was performed in a nitrogen atmosphere under the conditions shown in Table 2, and then finish cold rolling at a rolling rate shown in Table 2 was performed in some examples. In the example where the finish cold rolling was performed, a low temperature treatment of 420 ° C. and 1 minute was then performed in the air. A copper alloy plate material having a thickness of 0.15 mm was produced by the above steps, and used as a test material.
In addition, No. 32 and No. 33 obtain commercially available Cu—Ni—Si based copper alloys (saved by DOWA Aurin Metal Co., Ltd., C7025-TM03 and TM04 produced by DOWA Metanics Co., Ltd., thickness 0.15 mm). Thus, it is a sample material.

For each sample material, the surface of the plate surface (rolled surface) polished and etched is observed, and according to the measurement method described above, the average crystal grain size, the maximum width of the grain boundary reaction type precipitate, and the grain size of 100 nm or more The number density of precipitates was determined. The surface of the plate was polished by a method of electrolytic polishing after polishing to 1500 with water resistant paper. The electropolishing liquid was a mixed solution of distilled water: 10, phosphoric acid: 5, ethanol: 5, 2-propanol: 1 by volume ratio. Electropolishing was performed by using ElectroMet4 (manufactured by BUEHLER) and performing electropolishing for 20 seconds at a voltage of 15 V at a room temperature of φ10 mm at room temperature. The average crystal grain size, the width of the grain boundary reaction type precipitate, and the diameter were also measured using the same plate surface sample. At that time, in observation with an optical microscope for measuring the average crystal grain size, the observation area was a rectangular area of 300 μm × 300 μm. Further, in SEM observation of grain boundary reaction type precipitates and granular precipitates, an observation area of 42 μm × 29 μm was set in each of five randomly selected visual fields, and the total area of the observation areas was set to 6090 μm ² . From this total area, the number density (particles / mm ² ) of granular precipitates per unit area was calculated. These results are shown in Table 3.

In addition, the following characteristics of the test material were examined.
〔conductivity〕
The electrical conductivity of each test material was measured according to JIS H0505.
[Tensile strength and 0.2% yield strength]
An LD tensile test piece (JIS No. 5) was sampled from each specimen, and a tensile test according to JIS Z2241 was performed with the number of tests n = 3, and the tensile strength and 0.2% proof stress were measured. Tensile strength and 0.2% yield strength were determined by the average value of n = 3.
[Bending workability]
A bending test piece having a LD in the longitudinal direction and a bending test piece having a TD (both 10 mm in width) were sampled from the test material and subjected to a 90 ° W bending test in accordance with JIS H3110. 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 MBR at which no crack occurs is obtained, and this is divided by the thickness t of the specimen. As a result, the MBR / t values of LD and TD were obtained. Both the LD and TD of each test material were tested with the number of tests n = 3, and the result of the test piece with the worst result among n = 3 was adopted to display the MBR / t value.
[Fatigue life]
A fatigue test was performed according to JIS Z2273 using a test piece of LD. One end of a strip-shaped test piece having a width of 10 mm was fixed to a fixture, and the other end was subjected to sinusoidal vibration through a knife edge to measure the fatigue life. The fatigue life at the maximum applied stress of 700 MPa on the surface of the test piece (the number of repeated vibrations until the test piece was broken) was measured. The measurement was performed four times under the same conditions, and the average value of the four measurements was adopted as the performance of the plate material.
[Stress relaxation rate]
The stress relaxation rate was measured according to the method described above.
These results are shown in Table 3. LD and TD described in Table 3 mean the longitudinal direction of the test piece.

As can be seen from Table 3, all of the copper alloy sheets of the examples of the present invention have an average crystal grain size of 5 to 25 μm, a grain boundary reaction type precipitate width of 500 nm or less, and a number density of granular precipitates having a diameter of 100 nm or more. Excellent fatigue resistance of ⁶ pieces / mm ² or less, tensile strength of 850 MPa or more, MBR / t value of 2.0 or less for both LD and TD, and fatigue life of 200,000 cycles or more at an applied stress of 700 MPa Have. Furthermore, it has excellent stress relaxation resistance with a TD stress relaxation rate of 5% or less, which is important in applications such as in-vehicle connectors.

  On the other hand, Comparative Examples Nos. 21 to 25 are manufactured in a normal process (although rapidly cooled after the solution treatment) for alloys having the same composition as the inventive examples Nos. 1 to 5. Since none of these has suppressed the formation of grain boundary reaction precipitates, the characteristics such as conductivity, strength, bending workability, fatigue resistance, and stress relaxation resistance are generally compared to the inventive examples of the same composition. Inferior.

  Comparative Examples Nos. 26 to 28 are examples in which good characteristics were not obtained because the chemical composition was outside the specified range. No. 26 has a low strength level due to too low contents of Ni and Si, and accordingly, fatigue resistance is inferior. In No. 27, since the contents of Ni and Si were too high, cracking occurred during hot rolling, and a plate material that could be evaluated could not be made. In No. 28, a large amount of Cr and Fe was added to suppress the intergranular reaction precipitation, so that almost no intergranular reaction precipitation occurred, but Cr, Fe and Si were coarse intermetallic compounds (granular precipitates). ) Deteriorated in strength, bending workability, fatigue resistance, and stress relaxation resistance.

  Comparative Examples Nos. 29 to 31 are solutions in which the solution treatment process was performed under inappropriate conditions for an alloy having the same composition as that of Invention Example No. 3. In No. 29, since the solution heating temperature was too high, the crystal grains became coarse, and despite the holding at 650 ° C. for 50 sec during the cooling process, grain boundary reaction precipitation could not be suppressed during the aging treatment. As a result, bending workability was inferior to fatigue resistance. In contrast, No. 30 had a solution treatment temperature of 750 ° C. which was too low, so that a large amount of granular precipitates having a diameter of 100 nm or more remained (not solid solution), and the grain boundary reaction precipitation could be suppressed during the aging treatment. The results were poor in strength, bending workability, fatigue resistance, and stress relaxation resistance. No. 31 had too long a holding time in the cooling process after solution treatment, so that granular precipitates were generated excessively, and grain boundary reaction precipitation could be suppressed during the aging treatment, but the strength and bending work The fatigue and fatigue resistance properties deteriorated.

  Comparative Examples No. 32 and 33 are commercially available products (both plate thicknesses of 0.15 mm) of C70250-TM03 and C70250-TM04 that represent Cu—Ni—Si based copper alloys. In all of these, grain boundary reaction precipitates having a width of more than 500 nm are generated, and compared with Example No. 1 of the present invention having almost the same composition, conductivity, strength, bending workability, fatigue resistance, stress relaxation Inferior to sex.

  In FIG. 2, the metal structure SEM photograph which grind | polished and etched the plate | board surface (rolling surface) about this invention example No. 1 test material is illustrated.

1 granular precipitate 2 grain boundary reaction type precipitate

Claims (12)

In mass%, Ni: 2.5 to 5.0%, Si: 0.5 to 1.5%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1. 0%, Co: 0 to 2.0%, Fe: 0 to 0.5%, Cr: 0 to 0.5%, B: 0 to 0.05%, P: 0 to 0.1%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Ti: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%, remaining Cu and inevitable impurities The total content of Fe, Cr, B, P, Zr, Al, Ti, Mn and V is 0 to 3.0% by mass, and the maximum width of the grain boundary reaction type precipitate is 500 nm or less. A copper alloy sheet material in which the number density of granular precipitates having a diameter of 100 nm or more is 10 ⁶ pieces / mm ² or less. In mass%, Ni: 2.5 to 5.0%, Si: 0.5 to 1.5%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1. 0%, Co: 0 to 2.0%, Fe: 0 to 0.5%, Cr: 0 to 0.5%, B: 0 to 0.05%, P: 0 to 0.1%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Ti: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%, remaining Cu and inevitable impurities The total content of Fe, Cr, B, P, Zr, Al, Ti, Mn and V is 0 to 3.0% by mass, and the number density of granular precipitates having a diameter of 100 nm or more is 10 ⁶ pieces / mm ² or less, the fatigue test according to JIS Z2273, fatigue life of up to additional stress 700MPa surface of the test piece (repetition number of oscillations up to the test piece to fracture) is more than 100,000 times Has fatigue resistance Copper alloy sheet that. The tensile strength TS in the rolling direction of the plate is 850 MPa or more, and the A value of the following formula (1) represented by the product of the conductivity R (% IACS) and the tensile strength TS (MPa) is 35,000 or more. The copper alloy sheet material according to claim 1 or 2.
A value = R (% IACS) × TS (MPa) (1)   The copper alloy sheet according to any one of claims 1 to 3, wherein an average crystal grain size by a cutting method measured in a direction perpendicular to the rolling direction with respect to the sheet surface (rolled surface) is 5 to 25 µm.   The copper alloy sheet according to any one of claims 1 to 4, wherein the conductivity is 35% IACS or more.   When the rolling direction of the plate is LD, and the direction perpendicular to the rolling direction and the plate thickness direction is TD, the ratio MBR of the minimum bending radius MBR and the plate thickness t in which cracking does not occur in the 90 ° W bending test according to JIS H3110. The copper alloy sheet material according to any one of claims 1 to 5, wherein the copper alloy sheet has bending workability in which the value of / t is 2.0 or less for both LD and TD.   The copper alloy sheet according to any one of claims 2 to 6, wherein the maximum width of the grain boundary reaction type precipitate is 1000 nm or less. In mass%, Ni: 2.5 to 5.0%, Si: 0.5 to 1.5%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1. 0%, Co: 0 to 2.0%, Fe: 0 to 0.5%, Cr: 0 to 0.5%, B: 0 to 0.05%, P: 0 to 0.1%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Ti: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%, remaining Cu and inevitable impurities A copper alloy sheet having a composition in which the total content of Fe, Cr, B, P, Zr, Al, Ti, Mn and V is 0 to 3.0% by mass, hot rolling, cold rolling, solution When manufacturing in processes including aging treatment and aging treatment,
In the solution treatment, the plate surface (rolling surface) is perpendicular to the rolling direction as a heat pattern that is heated and held at 780 to 1000 ° C. and then held for 10 to 120 seconds in the temperature range of 530 to 730 ° C. in the cooling process. Performed under the condition that the average crystal grain size by the measured cutting method is 5 to 25 μm,
The aging treatment is performed at 350 to 420 ° C.
A method for producing a copper alloy sheet.   The method for producing a copper alloy sheet according to claim 8, wherein cold rolling is performed at a rolling rate of 1 to 50% after the solution treatment and before the aging treatment.   The manufacturing method of the copper alloy sheet material of Claim 8 or 9 which performs finish cold rolling with a rolling rate of 1-35% after an aging treatment.   The manufacturing method of the copper alloy sheet | seat material of Claim 10 which performs low temperature annealing at 150-430 degreeC after finish cold rolling.   The electricity supply component which used the copper alloy board | plate material of any one of Claims 1-7 for the material.