JP5156317B2 - Copper alloy sheet and manufacturing method thereof - Google Patents

Description

  The present invention is a Cu-Ni-Si based copper alloy sheet suitable for electrical and electronic parts such as connectors, lead frames, relays, switches, etc., and has particularly high strength and high conductivity, stress relaxation characteristics and bending. The present invention relates to a copper alloy sheet material excellent in workability.

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

  In particular, in recent years, electrical and electronic components have been increasingly integrated, miniaturized, and lightened, and accordingly, copper and copper alloys, which are materials, have been demanded to be thin. For this reason, the “strength” level required for the material has become more severe. In addition, in order to cope with the downsizing of electrical and electronic parts and the complexity of their shapes, it is increasingly important to improve the “bending workability” of the parts. Furthermore, the demand for “stress relaxation characteristics” becomes severe as electrical and electronic parts are used in harsh environments. For example, when used in an environment exposed to a high temperature such as an automobile connector, the “stress relaxation property” is particularly important.

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

  In recent years, a Cu—Ni—Si based alloy (so-called Corson alloy) has attracted attention as a copper alloy having an excellent balance between strength and conductivity. This type of copper alloy can remarkably improve the strength while maintaining a relatively high conductivity (30 to 45% IACS). However, it is generally known that Cu—Ni—Si based alloys are alloy systems that are difficult to achieve both high strength and bending workability.

  As means for increasing the strength, there are general methods such as adding a large amount of solute elements such as Ni and Si and increasing the finish rolling (tempering treatment) rate after aging treatment. However, the former tends to deteriorate the bending workability as the amount of the Ni—Si based precipitate increases. In the latter, work hardening increases, so that bending workability (particularly bending workability in a direction perpendicular to the rolling direction) is significantly deteriorated. For this reason, even if the strength level and the conductivity level are high, it may not be usable for electric / electronic parts.

  Patent Documents 1 and 2 describe that Mg addition is effective for improving stress relaxation characteristics in Cu—Ni—Si based alloys. Patent Document 3 describes that refinement of crystal grains is effective for improving the Cu-Ni-Si alloy bending workability.

Japanese Patent No. 2503793 JP 2001-181759 A JP 2006-152393 A

  Stress relaxation is said to decrease with time in a relatively high temperature (for example, 100 to 200 ° C.) environment even if the contact pressure of the spring portion of the material constituting the electrical / electronic component is maintained at a constant state at room temperature. It is a kind of creep phenomenon. In other words, in the state where stress is applied to the metal material, dislocations move due to self-diffusion of atoms constituting the matrix or diffusion of solute atoms, and plastic deformation occurs, thereby relaxing the applied stress. It is a phenomenon.

  The means for adding Mg disclosed in Patent Documents 1 and 2 is effective for simultaneous improvement of strength and stress relaxation characteristics, and has a small adverse effect on the decrease in conductivity. However, the addition of Mg becomes a factor that deteriorates the bending workability. Moreover, since Mg is an element which is very easily oxidized, it causes deterioration of castability.

  The means for refining crystal grains disclosed in Patent Document 3 is effective in improving bending workability. However, as the crystal grains become finer, the area of the crystal grain boundary existing per unit volume of the metal material increases, so that atomic diffusion due to grain boundary diffusion is likely to occur. For this reason, stress relaxation, which is a kind of creep phenomenon, tends to occur.

As described above, it is difficult to simultaneously improve the stress relaxation characteristic and the bending workability while further increasing the strength in the Cu—Ni—Si based copper alloy having a relatively excellent balance of various characteristics. In order to cope with the recent severe usage environment of electric / electronic parts, it is desired that excellent stress relaxation characteristics can be obtained more stably and excellent bending workability can be obtained.
An object of the present invention is to provide a copper alloy sheet material in which, in this alloy system, stress relaxation characteristics and bending workability are compatible at a high level.

  One of the major factors that make it difficult to achieve both stress relaxation resistance and bending workability is that it is extremely difficult to set the crystal grain size of the material within a range where both characteristics are good. For example, the smaller the crystal grain size, the larger the area of the crystal grain boundary that exists per unit volume of the metal material. In this case, it is convenient for improving the bending workability. The grain boundary functions as an interface that enables grain boundary sliding and crystal grain rotation on both sides of the grain boundary during bending, so the larger the area of the interface, the more local stress concentration is avoided and the bending workability is It tends to improve. However, an increase in the area of the crystal grain boundary is a factor that promotes stress relaxation, which is a kind of creep phenomenon as described above. In particular, in applications that are used in a high temperature environment such as an in-vehicle connector, the diffusion rate along the grain boundaries of atoms is remarkably faster than in the grains, so that the deterioration of stress relaxation characteristics due to crystal grain refinement becomes a serious problem.

  If it is possible to realize a grain structure where there are many grain boundary parts that have a large resistance to the grain boundary diffusion while ensuring sufficient grain boundary area per unit volume, it is It will be an effective means to achieve simultaneous improvement of workability and stress relaxation properties at once. As a result of detailed studies, the inventors focused on the existence of a “twin zone”. And, it was found that the boundary of the twin band functions as an interface contributing to deformation during bending and corresponds to the above-mentioned “grain boundary portion having a high resistance to the grain boundary diffusion of atoms”. . Based on this knowledge, the present invention provides a copper alloy sheet material controlled to have a metal structure in which the existence ratio of twin bands is more than a certain level.

In other words, the present invention contains, by mass%, Ni: 0.6 to 4.2%, Si: 0.2 to 1.0%, Sn: 0.1 to 1.3%, and if necessary, Zn : 2.0% or less, or further contains one or more of Co, Cr, Mg, B, P, Fe, Zr, Ti, Mn in a total range of 3% or less, with the balance being Cu and inevitable impurities having the composition, have a bi-crystal zone density N _G satisfying the following formula (1), having a crystal orientation satisfying the following formula (2), copper with an average crystal grain size D satisfying the following formula (a) An alloy sheet is provided.
N _G = (D−D _T ) / D _T ≧ 0.3 (1)
0.1 ≦ I {420} / I {220} ≦ 0.5 (2)
10 μm ≦ D ≦ 60 μm (A)
Here, D _T is an average crystal grain size according to the cutting method of JIS H0501, which is measured by regarding a twin zone as a grain boundary. In this case, the center position of the twin band width is the grain boundary position. I {420} and I {220} are the X-ray diffraction intensities of the {420} crystal face and {220} crystal face 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. D is the same average grain size measured without considering the twin band as a grain boundary. When a twin boundary that does not form a twin zone exists, the twin boundary is not regarded as a grain boundary when either D _T or D is measured.

As a method for producing such a copper alloy sheet, hot rolling with a rolling rate of 40% or higher in a temperature range of 700 ° C. or lower, and a rolling rate of 85% or higher with respect to the copper alloy material whose composition is adjusted as described above. Cold-rolling, heating temperature 700 to 850 ° C., solution treatment in which the heating time from 100 ° C. to 700 ° C. is preferably 20 sec or less, intermediate cold rolling with a rolling rate of 0 to 50%, material temperature 400 to 500 aging treatment ° C., under Symbol (3) manufacturing process with sequential subjected steps of finish cold rolling for the rolling rate satisfying the equation is 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 (3)
Here, ε ₁ is the intermediate cold rolling rate (%), and ε ₂ is the finish cold rolling rate (%).
The “rolling rate 0%” means a case where the intermediate cold rolling is not performed.

The rolling rate ε (%) is expressed by the following equation (4), where the thickness before rolling is t ₀ and the thickness after rolling is t ₁ .
ε = (t ₀ −t ₁ ) / t ₀ × 100 (4)
In hot rolling, “the rolling ratio in a temperature range of 700 ° C. or lower is set to 40% or more” means that the plate thickness at the time of being subjected to the first rolling pass at a temperature of 700 ° C. or lower is t ₀ , and the plate after the final pass It means that the value of ε is 40% or more when the above equation (4) is applied with the thickness as t ₁ .

  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 having excellent stress relaxation properties and bending workability at the same time was provided. It has been difficult for the conventional Cu—Ni—Si based copper alloy manufacturing technology to stably and significantly improve the tensile strength, stress relaxation characteristics and 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.

《Metallic structure》
[Twinned zone density]
A twin crystal refers to a pair of crystals in which two adjacent crystal lattices are mirror-symmetrically related to a certain plane (called a twin boundary, which is generally a {111} plane in a copper alloy). The most common twin morphology of copper and copper alloys is the type that forms what is also called a “twin zone” sandwiched between two parallel twin boundaries. The twin boundary is a kind of “crystal grain boundary” with a crystal orientation difference of 15 ° or more on both sides of the boundary. However, since both crystal lattices are basically in contact with each other while maintaining consistency, they are “crystal grain boundaries” having a special interface property.

  According to the inventors' detailed study, for example, when a strong mechanical stress is applied to the copper alloy material, the twin boundaries on both sides of the twin band are the same as other general grain boundaries. It acts as a boundary responsible for “slip” and “displacement” between adjacent crystal lattices, and has an effect of helping deformation of the material. For this reason, if the twin zone which exists per unit volume of a metal material increases, the bending workability of the material tends to be improved. In other words, the twin band has a positive effect on the bending workability, like other general grain boundaries.

  On the other hand, twin boundaries are structurally dense with little disorder of atomic arrangement, and therefore, diffusion of atoms along the boundaries is less likely to occur compared to other general grain boundaries. The formation of is difficult to occur. For this reason, the twin zone has almost no function as a grain boundary against deformation such as a creep phenomenon accompanied by atomic grain boundary diffusion. That is, unlike other general crystal grain boundaries, twin bands hardly act negatively on stress relaxation, which is a kind of creep phenomenon.

For this reason, the more twin zones, the more advantageous for simultaneous improvement of stress relaxation characteristics and bending workability. Specifically, SoAkiratai density N _G adopts metallographic satisfying the following equation (1). It is more preferable that the expression (1) ′ is satisfied instead of the expression (1).
N _G = (D−D _T ) / D _T ≧ 0.3 (1)
N _G = (D−D _T ) / D _T ≧ 0.35 (1) ′
Here, D _T is an average crystal grain size according to the cutting method of JIS H0501, measured by regarding the twin band as a grain boundary. In this case, the center position of the twin band width is the grain boundary position. D is the same average grain size measured without considering the twin band as a grain boundary. In copper alloys, the presence of twin boundaries that bisect crystals without forming twin bands is rare. Therefore, when there is a twin boundary that does not form a twin band, the above-described _DT and D may be measured ignoring the twin boundary.
For example, when N _G = 1, there is an average of one twin zone in each crystal grain specified only by a general grain boundary excluding the twin zone. is there. At this time, D = 2D _T and N _G = 1. When _NG is smaller than 0.3, bending workability is insufficient.

  The crystal grain size is measured with respect to the surface obtained by polishing and etching the plate surface (that is, the rolled surface) of the copper alloy sheet, for example, using an optical microscope. The metal structure satisfying the above expression (1) can be realized by controlling hot rolling conditions, cold rolling conditions, solution treatment conditions, and the like as described later. In particular, imparting high deformation strain before the solution treatment and rapid heating during the solution treatment are effective for increasing the twin zone density.

[Average crystal grain size]
In addition to the twin band density being adjusted as described above, the average crystal grain size D (generally referred to as the average crystal grain size) by a cutting method measured without considering the twin band as a grain boundary. Is preferably 10 to 60 μm, and more preferably 15 to 40 μm. If the average crystal grain size D is too small, the stress relaxation property tends to be poor, and if it is too large, the bending workability tends to be lowered.

[Group organization]
In order to achieve both “strength” and “bending workability” of the Cu—Ni—Si based copper alloy at a high level, it is effective to control the texture. As a result of detailed studies by the inventors, bending workability is improved as the texture having {420} as a main orientation component, which is obtained by a solution treatment described later, is more strongly developed. Although the mechanism is not necessarily clear at present, 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. Occur. 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. For this reason, when having a texture with {420} as the main orientation component, it is considered that slip in the 45 ° direction from the plate surface is likely to occur during bending, and cracking can be remarkably suppressed.

  However, finish cold rolling is indispensable for achieving high strength. Even if it has a texture with {420} as the main orientation component after solution treatment, a rolling texture with {220} as the main orientation component develops as the cold rolling rate increases. As a result of detailed studies, the inventors have finally made it possible to achieve both high levels of strength and bending workability when the copper alloy sheet is finally finished to an intermediate structure between the two. I found.

Specifically, it is desirable to adjust the crystal orientation to satisfy the following formula (2), and it is more preferable to satisfy the formula (2) ′.
0.1 ≦ I {420} / I {220} ≦ 0.5 (2)
0.2 ≦ I {420} / I {220} ≦ 0.4 (2) ′
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. Becomes worse.

"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. When the rolling direction is called LD and the direction perpendicular to the rolling direction and the plate thickness direction is called TD, the bending workability is the ratio R / t of the minimum bending radius R and the plate thickness t in the 90 ° W bending test in both LD and TD. Is preferably 1.0 or less, and more preferably 0.5 or less. Since the value of TD is particularly important for applications such as automobile connectors, it is desirable to evaluate the stress relaxation characteristic with the stress relaxation rate using a test piece whose longitudinal direction is TD. The stress relaxation rate is preferably 5% or less and preferably 3% or less when the maximum load stress on the surface of the plate is 0.2% and 80% of the proof stress and held at 150 ° C. for 1000 hours. Is more preferable.

<Alloy composition>
In the present invention, a Cu—Ni—Si based copper alloy is employed. A copper alloy obtained by adding Sn, Zn, and other alloy elements 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 0.6% by mass or the Si content is less than 0.2% by mass, it is difficult to effectively bring out the above effects. On the other hand, when the Ni content is excessive or the Si content is excessive, coarse precipitates are likely to be generated, and both the bending workability and the stress relaxation characteristics are likely to decrease. Further, it becomes difficult to develop a recrystallized texture having {420} as the main orientation component in the solution treatment, and it becomes difficult to finally obtain a plate material excellent in bending workability. For this reason, Ni content needs to be 4.2 mass% or less, it is more preferable to set it as 3.5 mass% or less, and it is still more preferable to set it as 3.0 mass% or less. The Si content must be 1.0% by mass or less, and more preferably 0.7% by mass or less.
The Ni content is defined as 0.6 to 4.2% by mass, more preferably 0.7 to 4.2% by mass, and more preferably 1.0 to 3.5% by mass. preferable. You may manage in the range of 1.2-2.5 mass%.
Although Si content is prescribed | regulated to 0.2-1.0 mass%, it is more preferable to set it as the range of 0.3-0.6 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 content of Ni and Si is 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 the effect of reducing the stacking fault energy of the Cu matrix and promoting the formation of twins. It also has a solid solution strengthening action. In order to fully exhibit these actions, it is necessary to secure an Sn content of 0.1% by mass or more. However, a large amount of Sn will cause a decrease in conductivity. In addition, surface cracks and edge cracks are likely to occur during hot working, leading to a decrease in yield. As a result of various studies, the Sn content is limited to a range of 1.3% by mass or less.
Although Sn content is prescribed | regulated to 0.1-1.3 mass%, it is more preferable to set it as the range of 0.1-1.2 mass%, and the range of 0.2-0.7 mass% is one layer. preferable.

  Zn has the effect of reducing the stacking fault energy of the Cu matrix and promoting the formation of twins. In addition to improving solderability and strength, it also has the effect of improving castability. Furthermore, the addition of Zn has an advantage that inexpensive brass scrap can be used. However, if Zn content exceeds 2.0% by mass, the conductivity, stress relaxation resistance and stress corrosion cracking resistance are likely to be reduced. 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.

  As other elements, Co, Cr, Mg, B, P, Fe, Zr, Ti, Mn, and the like can be contained as necessary. For example, Co, Cr, Mg, 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.

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

<Production method>
The copper alloy sheet material of the present invention as described above can be produced by, for example, the following general manufacturing process.
“Melting / Casting → Hot Rolling → Cold Rolling → Solution Treatment → Intermediate Cold Rolling → Aging Treatment → Finish Cold Rolling → Low Temperature Annealing”
However, as described later, it is important to strictly control manufacturing conditions in several steps. 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)
When the slab is hot-rolled, a rolling rate in a temperature range of 700 ° C. or lower where rolling distortion is likely to occur is secured by 40% or more. Thereby, it is possible to increase the twin band density in the solution treatment in the subsequent step, and it is easy to form a recrystallized texture having {420} as the main orientation component. Moreover, it is desirable that the rolling rate in a temperature range higher than 700 ° C. at which recrystallization is likely to occur be 60% or more. Thereby, a cast structure can be destroyed and a component and a structure can be made uniform. If the rolling rate in this temperature range is insufficient, complete recrystallization may not occur. For example, when the thickness of the slab to be subjected to hot rolling is 100 mm, assuming that the slab is rolled up to 20 mm in a high temperature range from 700 ° C., the rolling rate in the high temperature range from 700 ° C. is 80% from the above formula (4). . Then, if rolling is performed from 20 mm to 10 mm in a temperature range of 700 ° C. or less, the rolling rate in the temperature range of 700 ° C. or less is 50% from the above equation (4). As described above, when a rolling rate of 60% or higher in the temperature range higher than 700 ° C. and 40% or higher in the temperature range of 700 ° C. or lower are secured, destruction of the cast structure and introduction of rolling strain are appropriately achieved. The total rolling rate may be approximately 80 to 95%. It is desirable to cool rapidly after completion of hot rolling by water cooling or the like. 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. By applying a solution treatment to the material processed at such a high rolling rate in the next step, it is possible to increase the twin band density and to form a recrystallized texture with {420} as the main orientation component. become. In particular, the recrystallization texture greatly depends on the cold rolling rate before recrystallization. Specifically, the crystal orientation having {420} as the main orientation component hardly generates when the cold rolling rate is 60% or less, and gradually increases with the increase of the cold rolling rate in the region of about 60 to 80%. However, when the cold rolling rate exceeds about 80%, it suddenly increases. In order to obtain a crystal orientation in which the 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]
In the solution treatment here, in addition to “re-solution of solute elements in the matrix” and “recrystallization”, particularly in the present invention, “increase of twin zone density” and “{420} This is an important process aiming at the formation of a recrystallized texture as a component. This solution treatment is desirably performed at a furnace temperature of 700 to 850 ° C. If the temperature is too low, recrystallization is incomplete and solute elements are not sufficiently dissolved. If the temperature is too high, the crystal grains become coarse. In any of these cases, it is difficult to finally obtain a high-strength material excellent in bending workability. Further, it has been found that it is extremely effective to rapidly raise the temperature to 700 ° C. in order to increase the twin band density. If the rate of temperature rise is too slow, recovery and precipitation occur during the temperature rise, and the recrystallization progress rate becomes slow, which is disadvantageous for twin formation. Specifically, the temperature raising time from 100 ° C. to 700 ° C. is preferably 20 sec or less, and more preferably 15 sec or less.

  Further, this solution treatment is preferably performed by adjusting the temperature and time so that the recrystallized grain size (a twinning zone and other twin boundaries are not regarded as grain boundaries) is 15 to 60 μm. It is more preferable to adjust so that it may become 15-40 micrometers. If the recrystallized grain size becomes too fine, the twin band density tends to be low, and the recrystallized texture having {420} as the main orientation component becomes weak. Specifically, heating conditions for holding for 10 sec to 10 min at a temperature of 700 to 850 ° C. can be employed.

(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 of the next process, and this can shorten the aging time for extracting necessary characteristics (conductivity and hardness). This cold rolling develops a texture with {220} as the main orientation component, but in the range of the cold rolling rate of 50% or less, the crystal still has {420} plane parallel to the plate surface. Grains also remain. In particular, the rolling rate in this cold rolling contributes to the final increase in strength and the improvement of bending workability by combining well with the rolling rate at the finish 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 during 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 (2). 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 are compatible at a high level cannot be realized.

The finish rolling rate is desired 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 is preferably 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-described intermediate cold rolling rate. That is, finish cold rolling is performed so as to satisfy the following expression (3).
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (3)
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.

[Low temperature annealing]
After the finish cold rolling, low temperature annealing can be performed for the purpose of improving the bending workability by reducing the residual stress of the strip material and improving the stress relaxation resistance by reducing the dislocations on the pores and the sliding surface. The heating temperature is preferably set so that the material temperature is 150 to 550 ° C. Thereby, bending workability and stress relaxation resistance can be improved with almost no decrease in strength. It also has the effect of increasing the conductivity. If this heating temperature is too high, it softens in a short time, and variations in characteristics are likely to occur in both batch and continuous systems. Conversely, if the heating temperature is too low, the effect of improving the above characteristics cannot be obtained sufficiently. It is desirable to secure the holding time at the above temperature for 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., hot rolling was started from about 950 ° C., and a pass schedule was set so as to perform rolling even in a temperature range of 700 ° C. or lower. The total hot rolling rate from the slab is about 90%. Rapid cooling (water cooling) was performed after the final pass. 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. The temperature change during the solution treatment was monitored by a thermocouple attached to the sample surface, and the temperature raising time from 100 ° C. to 700 ° C. in the temperature raising process was determined. Except for some comparative examples, the holding temperature is alloyed so that the average grain size after solution treatment (a twin band and other twin boundaries are not regarded as grain boundaries) exceeds 15 μm to ˜40 μm. It adjusted within the range of 700-850 degreeC according to the composition. 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 low temperature annealing in a furnace at 400 ° C. for 5 min. 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 the crystal grain structure, X-ray diffraction intensity, conductivity, tensile strength, stress relaxation characteristics, and bending workability were examined by the following methods.

[Grain structure]
The plate surface (rolled surface) was polished and then etched, the surface was observed with an optical microscope, and the average crystal grain size was measured by the cutting method of JIS H0501. At that time, the average crystal grain size D _T when the twin zone is regarded as a grain boundary and the average crystal grain size D when the twin zone is not regarded as a grain boundary are measured, Based on this, the twin band density _NG was determined. The average crystal grain size D was in the range of 15 to 30 μm except for some test materials.

[X-ray diffraction intensity]
A sample whose surface (rolled surface) was polished with # 1500 water-resistant paper was prepared, and using an X-ray diffractometer (XRD), Mo-Kα ray, tube voltage 20 kV, tube current 2 mA. Then, the reflection diffraction integrated intensity of the {220} plane and the {420} plane was measured for the polished finished surface, and the X-ray diffraction intensity ratio shown in the equation (2) was determined.

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

[Stress relaxation characteristics]
Bending test pieces (width: 10 mm) with a TD longitudinal direction are taken from each test material and fixed in an arch-bent state so that the stress at the center of the test piece is 80% of the 0.2% proof stress. The stress relaxation rate was calculated using the following equation from the bending habit after holding at a temperature of 150 ° C. in the atmosphere for 1000 hours.
Stress relaxation rate (%) = (L ₁ −L ₂ ) / (L ₁ −L ₀ ) × 100
L ₀ : Jig length (mm)
L ₁ : Sample length at the start of the test (mm)
L ₂ : Horizontal distance between the sample ends after the test (mm)

[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.
The main production conditions and the results are shown in Tables 2 and 3. In Tables 2 and 3, in the column of bending workability, LD and TD mean the longitudinal direction of the bending test piece.

As can be seen from Tables 2 and 3, each of the examples of the present invention has a twin band density _NG satisfying the formula (1) and an X-ray diffraction intensity ratio having a crystal orientation satisfying the formula (2). In addition, the tensile strength is as high as 700 MPa or more, and the R / t value is excellent in bending workability such that both LD and TD are 0.5 or less. Furthermore, the outstanding result that the stress relaxation rate of TD direction was 5% or less was obtained.

  On the other hand, Comparative Examples No. 21 to 23 are examples in which good characteristics were not obtained because the content of Ni or Si was outside the specified range. In No. 21, since the contents of Ni and Si were too low, the generation of precipitates was small and the strength level was low. In No. 22, since the contents of Ni and Si were too high, even if the production conditions were appropriate, the twin band density was small, and the crystal orientation with {420} as the main orientation component was weakened, resulting in tension. Although its strength was high, it was inferior in bending workability. No. 23 is an example having the same composition as No. 22 and adjusting the holding temperature at the time of solution treatment so as to improve the bending workability, so that the average crystal grain size D is as fine as about 6 μm. In this case, although the bending workability was improved as compared with No. 22, the stress relaxation characteristics were deteriorated because the crystal grains became finer.

  In Comparative Examples No. 24, 25, 29, and 30, the hot rolling rate in the temperature range of 700 ° C. or lower is too low, and the cold rolling rate before the solution treatment is too low. In this example, the recrystallization texture having {420} as the main orientation component is not sufficiently developed. In this case, even if the finish cold rolling rate is adjusted, simultaneous improvement in tensile strength and bending workability cannot be achieved.

  Comparative Examples Nos. 26 to 28 and 32 are examples in which good characteristics were not obtained because the solution treatment conditions were outside the specified range. In No. 26, since the solution retention temperature was too high, the crystal grains became coarse, and good bending workability was not obtained. On the other hand, No. 27 had a solution retention temperature that was too low, so that the recrystallization itself did not proceed sufficiently to form a mixed grain structure, and all the tensile strength, bending workability, and stress relaxation characteristics were poor. No. 28 and No. 32 were the same as Comparative Example No. 24 in which some deformation strain was released by recovery because the temperature rising rate during solution treatment was too slow, and eventually the rolling rate before solution treatment was small. The result was as follows.

  In No. 31, since the intermediate cold rolling rate was too large, the rolling texture developed and the crystal orientation with {420} as the main orientation became weak, and the target bending workability could not be obtained. Since No. 33 had too much Sn content, cracks occurred during hot rolling, making it impossible to manufacture. No. 34 was inferior in stress relaxation resistance because the Zn content was too high.

Claims (6)

In mass%, Ni has a composition of 0.6 to 4.2%, Si: 0.2 to 1.0%, Sn: 0.1 to 1.3%, and the balance being Cu and inevitable impurities A copper alloy sheet having a twin band density _NG satisfying the following formula (1) , a crystal orientation satisfying the following formula (2), and an average grain size D satisfying the following formula (A).
N _G = (D−D _T ) / D _T ≧ 0.3 (1)
0.1 ≦ I {420} / I {220} ≦ 0.5 (2)
10 μm ≦ D ≦ 60 μm (A)
Here, D _T is an average crystal grain size measured by the cutting method of JIS H0501 measured with a twin zone as one crystal grain boundary, and I {420} and I {220} are { 420} crystal planes and X-ray diffraction intensities of {220} crystal planes, D is the same average grain size measured without considering twin bands as grain boundaries.   Furthermore, the copper alloy plate material of Claim 1 which has a composition containing Zn: 2.0% or less.   The copper alloy sheet according to claim 1 or 2, further comprising a composition containing one or more of Co, Cr, Mg, B, P, Fe, Zr, Ti, and Mn in a total range of 3% or less. For the copper alloy material whose composition is adjusted, hot rolling with a rolling rate of 40% or higher in a temperature range of 700 ° C. or lower, cold rolling with a rolling rate of 85% or higher, solution treatment at 700 to 850 ° C., rolling ratio 0-50% of the intermediate cold rolling, aging treatment 400 to 500 ° C., to any one of claims 1 to 3 having a sequentially subjected steps of finish cold rolling reduction ratios that satisfy the following expression (3) The manufacturing method of the copper alloy board | plate material of description.
10 ≦ ε ₂ ≦ (65−ε ₁ ) / (100−ε ₁ ) × 100 (3)
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 4 , wherein the temperature rise time from 100 ° C to 700 ° C in the solution treatment is 20 sec or less. The method for producing a copper alloy sheet according to claim 4, further comprising a step of performing a heat treatment at 150 to 550 ° C. after the finish cold rolling.