JP6045635B2 - Method for producing copper alloy sheet - Google Patents

Description

  The present invention is a copper alloy plate material suitable for electrical and electronic parts such as connectors, lead frames, relays, switches, etc., and has excellent bending workability and response force relaxation characteristics while maintaining high strength and good conductivity. The present invention relates to a method for producing a copper alloy sheet having

  Materials used for electrical and electronic parts as current-carrying parts such as connectors, lead frames, relays, and switches are required to have good conductivity in order to suppress the generation of Joule heat due to current conduction. High strength is required to withstand the stress applied during assembly and operation. In addition, since electrical / electronic parts such as connectors are generally formed by bending after press punching, excellent bending workability is required.

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

  In particular, in recent years, electrical and electronic parts such as connectors have tended to be reduced in size and weight, and accordingly, a copper alloy plate material, for example, has a plate thickness of 0.15 mm or less, or more preferably 0.00. There is an increasing demand for thinning such as 10 mm or less. For this reason, the strength level required for the material is becoming stricter. Specifically, a strength level of 0.2% proof stress of 850 MPa or more, preferably 900 MPa or more, more preferably 950 MPa or more is desired.

  In addition, electrical and electronic parts such as connectors tend to be highly integrated, densely packed, and have a large current. Accordingly, copper and copper alloy plate materials are required to have high electrical conductivity. It is growing. Specifically, a conductivity level of 30% IACS or more, preferably 35% IACS or more is desired while maintaining 0.2% proof stress of 900 MPa or more.

  Conventionally, as a high-strength copper alloy, a Cu-Be-based alloy (for example, C17200 (Cu-2 mass% Be)), a Cu-Ti-based copper alloy (for example, C19900 (Cu-3.2 mass% Ti)), Cu-Ni-Sn based copper alloy (for example, C72700 (Cu-9 mass% Ni-6 mass% Sn)) can be mentioned.

  However, from the viewpoint of cost and environmental burden, there is a tendency to avoid Cu-Be alloys in recent years. Further, the Cu—Ti based copper alloy and the Cu—Ni—Sn based copper alloy have a modulation structure (spinodal structure) in which the solid solution element has a periodic concentration fluctuation in the matrix phase, and the strength is high, but the conductivity However, there is a low feature of about 10 to 15% IACS.

  Cu-Ni-Si-based alloys have attracted attention as materials that are relatively excellent in the property balance between strength and conductivity. For example, a Cu-Ni-Si-based copper alloy sheet has a relatively high conductivity of about 30 to 50% IACS through processes based on solution treatment, cold rolling, aging treatment, finish cold rolling and low temperature annealing. While maintaining the above, the 0.2% proof stress can be made 700 MPa or more. However, it is generally known that it is difficult for a Cu—Ni—Si based alloy sheet to achieve further improvement in strength, for example, 0.2% proof stress is 900 MPa or more.

  In the Cu—Ni—Si based copper alloy sheet material, as a means for increasing the strength, general methods such as addition of a large amount of Ni and Si and an increase in the finish rolling (tempering treatment) rate after aging treatment are known.

  However, the strength increases with increasing amounts of Ni and Si. However, when the amount of Ni becomes 3% by mass or more, for example, Si becomes about 0.7% by mass or more, the increase in strength tends to be saturated. It is difficult to achieve a 0.2% proof stress of 900 MPa or more. Further, addition of excessive amounts of Ni and Si is accompanied by a decrease in conductivity, and Ni—Si based precipitates are likely to be coarsened and bending workability is likely to be decreased. Although the strength can be improved by increasing the finish rolling rate after the aging treatment, the bending workability of the copper alloy sheet, particularly the bending workability (so-called BadWay bending) with the rolling direction as the bending axis, is significantly reduced. Accompany.

  For this reason, even if the strength level is high enough to achieve, for example, a 0.2% proof stress of 900 MPa or more, there are cases where the electrical / electronic component cannot be processed.

  In recent years, in order to increase the strength of Cu-Ni-Si-based copper alloy sheets, a copper alloy sheet in which Co is added in a relatively large amount (for example, 0.5 to 2.0 mass% Co or more), so-called Cu-Ni- Co-Si based copper alloys have been proposed in Patent Documents 1 to 3, for example. Further, for example, Patent Documents 4 and 5 propose copper alloys that control the abundance of twins (the number of twin boundaries included in crystal grains) in order to improve bending workability.

JP 2007-169765 A JP 2008-248333 A JP 2009-007666 A JP 2008-106356 A International Publication Number 2009-123140

  As is well known, Cu—Ni—Si based copper alloys and Cu—Co—Si based copper alloys have advantages and disadvantages, respectively. In the case of a Cu-Ni-Si based copper alloy, in order to improve the strength, if rolling is performed in addition to precipitation of the Ni-Si based compound, the strength is easily improved by work hardening, and the stress relaxation resistance is improved. Excellent. However, since strengthening by work hardening tends to cause a decrease in bending workability, it is common to reduce the rolling rate as much as possible. On the other hand, in the case of a Cu—Co—Si based copper alloy, the strength is relatively high due to the precipitation of the Co—Si based compound after aging at an equivalent alloy element amount as compared with the Cu—Ni—Si based copper alloy. However, further rolling has the disadvantages that the workability is low and the strength is difficult to further improve, although the decrease in bending workability is small. Moreover, there exists a tendency for a stress relaxation resistance to be inferior to a Cu-Ni-Si type copper alloy.

  Therefore, in Cu-Ni-Co-Si-based copper alloys, strength, bending workability, and stress relaxation resistance can be improved at the same time if the precipitation of Ni-Si-based compounds and the precipitation of Co-Si-based compounds can be controlled appropriately. There is sex.

  However, since the optimum aging temperature of the Ni—Si compound and the optimum precipitation temperature of the Co—Si compound are different, it is difficult to simultaneously achieve the optimum conditions for precipitating these two types.

  The optimum aging temperature of Ni—Si compounds is around 450 ° C. (generally, 425 to 475 ° C.). If the aging temperature is too high, so-called overaging occurs and the peak hardness is low. Si-based precipitates are easily coarsened. If the aging temperature is too low, the precipitation rate is slow and the precipitate does not coarsen, but the formation of the precipitate may be slow or not generated.

  On the other hand, the optimum precipitation temperature of the Co—Si based compound is higher than that of the Ni—Si based compound and is around 520 ° C. (generally 500 to 550 ° C.). Therefore, in Cu—Ni—Co—Si based copper alloy, when aging is performed at a temperature of about 450 ° C., the precipitation amount of Co—Si based compound is small, and when aging is performed at a temperature of about 520 ° C., Ni—Si The system precipitate becomes coarse. In any case, two types of precipitates cannot be used simultaneously. Moreover, even if an aging treatment is performed at an intermediate temperature, for example, 480 ° C., it is difficult to achieve the optimum state of the two types of precipitates at the same time. That is, for example, if it is divided into three stages of sub-aging, peak aging and overaging, when the aging time is short, Ni-Si based precipitates are peak aging and Co-Si based precipitates are still few. If the Co—Si based precipitates reach peak aging for a longer time, the Ni—Si based precipitates become coarse and do not contribute to the strength.

  Patent Document 1 discloses a Cu—Ni—Co—Si based copper alloy whose characteristics are improved by controlling the density of the second phase by suppressing coarse precipitates. This copper alloy has a conductivity level higher than 41% IACS and is excellent in bending workability, but has a 0.2% proof stress at a strength level of 600 to 770 MPa.

  In Patent Document 2, in addition to controlling the second phase density by suppressing coarse precipitates as in Patent Document 1, the strength is further improved by combining work hardening, and the 0.2% proof stress is 810 to 920 MPa. A Cu—Ni—Co—Si based copper alloy is disclosed. However, in order to suppress coarse precipitates, the end temperature of the hot rolling needs to be 850 ° C. or more, and it is difficult to realize the cost with a general industrial hot rolling facility. In addition, it is difficult to obtain a stress relaxation characteristic at a level that can be used for a vehicle-mounted connector or the like.

  Patent Document 3 discloses a Cu—Ni—Co—Si based copper alloy whose properties are improved by controlling the average crystal grains and texture, but the strength level is 0.2% proof stress of 652 to 862 MPa. , 900 MPa or more has not been reached.

  On the other hand, recent research clearly shows that the larger the amount of polycrystalline metal twins (the number of twin boundaries contained in a crystal grain), the more advantageous in bending workability and stress relaxation resistance. However, at present, the control method of the abundance of twins is hardly understood both theoretically and experimentally.

  Patent Documents 4 and 5 differ in the method of measuring the abundance of twins, but in any case, the average number of twin boundaries per crystal grain is about 1 to 3 at most, and the strength level is 600 to 830 MPa in tensile strength. Yes, the effect of improving the characteristics is limited. Patent Document 5 describes that in order to increase the twin boundary density, it is necessary to perform a heat treatment for annealing at a high temperature. As a result, the crystal grains become coarse and bending workability deteriorates. .

  Therefore, two types of precipitations are known in the known manufacturing method because the optimal precipitation temperature and time of Ni—Si compound and Co—Si compound do not match (displace) and the twinning mechanism is unknown. The material could not be fully utilized at the same time, and could not be controlled to a structure having a high density twin and an appropriate crystal grain size. Therefore, it has been difficult to simultaneously achieve high strength, excellent bending workability and stress relaxation resistance.

  In view of such conventional problems, the present invention has an electrical conductivity of 30% IACS or higher, 0.2% proof stress of 900 MPa or higher, excellent bending workability, and in a severe use environment such as an in-vehicle connector. It aims at providing the manufacturing method of the copper alloy board | plate material which comprises the stress relaxation characteristic which bears reliability simultaneously.

  In the Cu—Ni—Co—Si based copper alloy, the present inventors mainly composed of two kinds of compounds of Ni—Si and Co—Si, and a small amount of Ni—Co—Si. As a result, it was confirmed that two types of precipitates, Ni-Si and Co-Si, can be controlled. It was also found that stress relaxation characteristics and bending workability can be improved at the same time by increasing the density of twin boundaries inside the crystal grains. Furthermore, by increasing the proportion of crystal grains having a {100} orientation (Cube orientation) with little anisotropy, the bending workability can be improved and the anisotropy of the bending workability can be remarkably improved. As a result, the inventors have found that the strength is high while maintaining high conductivity, and that significant improvement in stress relaxation characteristics, bending workability and anisotropy can be achieved at the same time, and the present invention has been completed.

That is, the method for producing a copper alloy sheet according to the present invention includes 1.0 to 3.5% by mass of Ni, 0.5 to 2.0% by mass of Co, and 0.5 to 1.2% by mass of Si. And a raw material of a copper alloy having a composition in which the Co / Ni mass ratio is 0.15 to 1.5, the (Ni + Co) / Si mass ratio is 4 to 7, and the balance is Cu and inevitable impurities. A melting / casting step for casting, a hot rolling step for performing hot rolling after the melting and casting step, and a first cold rolling for performing cold rolling at a rolling rate of 70% or more after the hot rolling step. An intermediate annealing step in which heat treatment is performed at a heating temperature of 500 to 650 ° C. after the first cold rolling step, and a second cold in which cold rolling is performed at a rolling rate of 70% or more after the intermediate annealing step. A solution treatment step for performing a solution treatment after the rolling step and the second cold rolling step; Consists of a aging treatment step of performing an aging treatment at 400 to 500 ° C. after the solution treatment step, the solution treatment step, the heating step at 800 to 1020 ° C., 10 ° C. / s or higher until further 500 to 800 ° C. A first quenching step of rapidly cooling at a cooling rate of 500 ° C., a heat retaining step of holding at 500 to 800 ° C. for 10 to 600 seconds, and a second quenching step of rapidly cooling to 300 ° C. or less at a cooling rate of 10 ° C./s or more It is characterized by.

In the intermediate annealing step, heat treatment is performed at 500 to 650 ° C. for 0.1 to 20 hours so that the electrical conductivity after the intermediate annealing step is 40% IACS or more and the Vickers hardness is HV150 or less. Furthermore, after the solution treatment step, the average crystal grain size measured without using the twin boundary using the cutting method of JIS H0501 is set to 3 to 60 μm. Further, on the rolled surface, the observation results of the grain boundary character and crystal orientation by EBSP measurement are set such that the twin boundary density in all the grain boundaries is 40% or more and the area ratio of Cube orientation crystal grains is 20% or more.

  Furthermore, after the aging treatment step, there is a finish cold rolling step in which cold rolling is performed at a rolling rate of 10 to 80%, and low temperature annealing in which heat treatment is performed at 150 to 550 ° C. after the finishing cold rolling step. Process.

In the method for producing a copper alloy sheet, the copper alloy further includes at least one of Fe, Cr, Mg, Mn, Ti, V, Zr, Sn, Zn, AL, B, P, Ag, Be, and Misch metal. You may contain a seed | species or more in the range of 0.5 mass% or less in total.

  According to the present invention, it is possible to realize a copper alloy sheet having high strength of 0.2% proof stress 900 MPa or more and excellent bending workability and stress relaxation resistance at the same time while maintaining an electrical conductivity of 30% IACS or higher.

2 is an optical microscopic photograph of the copper alloy plate material of Example 1. FIG. 3 is an optical micrograph of the copper alloy sheet material of Example 2. 3 is an optical micrograph of a copper alloy sheet of Comparative Example 1. 4 is an optical micrograph of a copper alloy sheet material of Comparative Example 2.

  The copper alloy sheet produced according to the present invention contains 1.0 to 3.5 mass% Ni, 0.5 to 2.0 mass% Co, 0.3 to 1.5 mass% Si, and The Co / Ni mass ratio is 0.15 to 1.5, the (Ni + Co) / Si mass ratio is 4 to 7, and the balance is made of Cu and inevitable impurities. In addition, on the rolled surface of this copper alloy sheet, as a result of observing the grain boundary character and crystal orientation by EBSP measurement, the density of twin boundaries (Σ3-corresponding crystal boundary) in all the grain boundaries is 40% or more, the cubic orientation ( (Cube orientation) The crystal grain area ratio is 20% or more.

  This copper alloy sheet is made of at least one of Fe, Cr, Mg, Mn, Ti, V, Zr, Sn, Zn, AL, B, P, Ag, Be, and Misch metal as necessary. It is further included in the range of 2% by mass or less in total.

  Hereinafter, this copper alloy sheet and its manufacturing method will be described in detail.

  First, the alloy composition will be described. The copper alloy produced according to the present invention is a Cu—Ni—Co—Si based copper alloy. In this specification, a copper alloy in which Sn, Zn, Mg, Fe, Cr, Mn, Ti, V, Zr and other alloy elements are added to the basic component of Cu—Ni—Co—Si is also comprehensively included. It is called Cu-Ni-Co-Si based copper alloy.

  Ni has the effect of forming Ni—Si based precipitates and improving the strength and conductivity of the copper alloy sheet. When the Ni content is less than 1.0% by mass, it is difficult to sufficiently exhibit this effect. Therefore, the Ni content is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2.0% by mass or more. On the other hand, when there is too much Ni content, the strength improvement effect will be saturated and conductivity will fall. In addition, coarse precipitates are easily generated and cause cracks during bending. Therefore, the Ni content is preferably 3.5% by mass or less, and more preferably 3.0% by mass or less.

  Co has the effect of forming a Co—Si based precipitate and improving the strength and conductivity of the copper alloy sheet. In particular, there is an effect of dispersing Ni—Si based precipitates, and if two kinds of precipitates coexist, there is a synergistic effect of improving the strength. In order to fully exhibit these effects, it is desirable to secure a Co content of 0.5 mass% or more. However, since the melting point of Co is higher than that of Ni, when the content is 2.0 mass% or more, complete solid solution is difficult, and the undissolved portion does not contribute to the strength. Moreover, in order to exhibit the synergistic effect of strength improvement by the coexistence of two kinds of precipitates, the mass ratio Co / Ni of Co and Ni is preferably 0.15 to 1.5, and 0.2 to 1. More preferably, it is zero. For this reason, it is more preferable to adjust Co content to the range of 0.5-1.5 mass%.

Si produces Ni—Si based precipitates and Co—Si based precipitates. The Ni—Si based precipitate is a compound mainly composed of Ni ₂ Si, and the Co—Si based precipitate is considered to be in the form of Co ₂ Si. However, Ni, Co, and Si in the alloy are not necessarily all precipitated by the aging treatment, and exist to some extent in a solid solution state in the Cu matrix. Ni, Co, and Si in the solid solution state slightly improve the strength of the copper alloy sheet, but the effect is smaller than that in the precipitated state, and causes a decrease in conductivity. Therefore, in general, the Si content is preferably as close to the composition ratio of the precipitates Ni ₂ Si and Co ₂ Si as possible. That is, the (Ni + Co) / Si mass ratio is generally adjusted to 3 to 5 with about 4.2 as the center.

  However, as a result of detailed investigation of the influence of the (Ni + Co) / Si mass ratio on the characteristics of the Cu—Ni—Co—Si based copper alloy, the present inventors have found that the (Ni + Co) / Si mass ratio is 3 Within the range of ˜7, it was found that the final strength and conductivity did not change much, but the twin density and texture changed greatly. In addition, it was found that the twin density and the area ratio of the Cube-oriented grains are reduced by excessive Si. That is, the Si content needs to be adjusted so that the (Ni + Co) / Si mass ratio is 4 to 7, preferably 4.0 to 6.5, and more preferably 4.2 to 5.5. It is desirable to adjust so that Therefore, the Si content is preferably in the range of 0.3 to 1.5% by mass, and more preferably in the range of 0.5 to 1.2% by mass.

  The copper alloy sheet produced according to the present invention includes elements such as Fe, Cr, Mg, Mn, Ti, V, Zr, Sn, Zn, AL, B, P, Ag, Be, and misch metal as necessary. Etc. may be added. For example, Sn and Mg have the effect of improving the stress relaxation resistance, Zn has the effect of improving the solderability and castability of the copper alloy sheet, and Fe, Cr, Mn, Ti, V, Zr, etc. have the strength. Has the effect of improving. In addition, Ag has the effect of strengthening the solid solution without greatly reducing the electrical conductivity. P has a deoxidizing effect, B has an effect of refining the cast structure, and has an effect of improving hot workability. Furthermore, misch metal is a mixture of rare earth elements including Ce, La, Dy, Nd, Y, etc., and has the effect of refining crystal grains and the effect of dispersing precipitates.

  In addition, when the copper alloy plate material contains one or more of Fe, Cr, Mg, Mn, Ti, V, Zr, Sn, Zn, AL, B, P, Ag, Be and misch metal, each element In order to sufficiently obtain the effect of adding, it is preferable that the total amount thereof is 0.01% by mass or more. However, if the total amount exceeds 2% by mass, the electrical conductivity is lowered, the hot workability or the cold workability is lowered, and the cost is disadvantageous. Therefore, the total amount of these elements is 2% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less.

  Next, twin boundaries will be described. A twin crystal is a pair of crystal grains in which the crystal lattice of two adjacent crystal grains is in a mirror-symmetric relationship with respect to a certain plane (called a twin boundary, which is generally the {111} plane). . The most common twins in copper and copper alloys are the so-called twin zones sandwiched between two parallel twin boundaries in the crystal grains.

  The character of the crystal grain boundary is measured by the atomic orientation of adjacent crystal grains by an EBSP (Electron Back Scattering Pattern) method. A general grain boundary has no corresponding relationship between crystal lattice points of crystal grains on both sides, and is also called a random grain boundary. On the other hand, among the crystal lattice points of the two crystal grains sandwiching the grain boundary, a grain boundary having an orientation relationship in which a certain percentage of lattice points (appearing as Σ values) is common to both crystal grains is the corresponding grain boundary. Among them, the grain boundary corresponding to Σ3 is a twin boundary.

  The twin boundary is the grain boundary with the lowest grain boundary energy, and it may play a role in improving the bending workability as a grain boundary. On the other hand, the disorder of the atomic arrangement along the boundary compared to the general grain boundary. The structure is dense and structurally dense, and is difficult to diffuse atoms, segregate impurities, and form precipitates, and is difficult to break along boundaries. That is, the more twin boundaries, the more advantageous for improving stress relaxation characteristics and bending workability.

The density (frequency) of twin boundaries is
(Sum total of Σ3-compatible grain boundaries) / (Sum of grain boundary lengths) x 100%
It can be calculated with The density of twin boundaries is preferably 40% or more, more preferably more than 50%, and still more preferably 60% or more.

  The mechanism of twin boundary formation has not been elucidated at present. However, according to the investigation by the present inventors, (Ni + Co) / Si mass ratio, the presence state of alloy elements before solution treatment (recrystallization) (solid solution or precipitation) It has been found that it depends on the solution treatment conditions, the finish rolling rate, and the like.

  The density of twin boundaries of a copper alloy manufactured by a general manufacturing method is about 10 to 20% (in the optical microscope structure, the number of average twin bands per crystal grain is equivalent to about 0.5). On the other hand, in the present invention, 60% or more (corresponding to the number of average twin bands per crystal grain of 3 or more) can be obtained depending on the alloy composition and production conditions described later.

  Next, the crystal orientation will be described. The cube orientation ({100} <001> orientation) exhibits similar characteristics in three directions, ie, a thickness direction ND of the rolling surface, a rolling direction LD, and a direction TD perpendicular to the rolling direction, and is generally called a Cube orientation. Also, there are 8 combinations of slip planes and slip directions that can contribute to the slip in both LD: <001> and TD: <010>, and all of the Schmitt factors are 0.41. Furthermore, the slip line on the {100} crystal plane can have good symmetry at 45 ° and 135 ° with respect to the bending axis, so that bending deformation is possible without forming a shear band. all right. In other words, the Cube orientation is characterized in that both GoodWay and BadWay have good bending workability and no anisotropy.

  Therefore, on the surface of the copper alloy sheet material, the area of crystal grains having an orientation in which the orientation difference from the {100} orientation is within 10 ° in the grain orientation distribution map OIM (Orientation Imaging Microscopy) image measured by the EBSP method. The rate is preferably 20% or more, and more preferably 30% or more.

  Although it is well known that the Cube orientation is the main orientation of a pure copper-type recrystallized texture, it is difficult to develop the Cube orientation for copper alloys under general manufacturing conditions. However, in the present invention, as shown in the following manufacturing process, by combining an intermediate annealing process under specific conditions and appropriate solution treatment conditions, a crystal-oriented copper alloy sheet having a high Cube orientation is obtained. I was able to.

  The smaller the average crystal grain size is, the more advantageous the bending workability is. However, when the average crystal grain size is too small, the area fraction of the Cube orientation and the stress relaxation resistance are liable to be lowered. The final average crystal grain size is almost determined by the crystal grain size in the stage after the solution treatment. Therefore, if the average crystal grain size is too small, there is a high possibility that the solute elements are not sufficiently dissolved after the solution treatment and the final strength is lowered. As a result of various studies, the average grain size of the usual meaning measured without using the twin boundary is finally 3 μm or more, preferably 5 μm or more, more preferably more than 8 μm, using the cutting method of JIS H0501. Then, it has been found that it is easy to ensure a stress relaxation resistance at a level that can be satisfied even in the use of an in-vehicle connector, and is suitable. However, if the average crystal grain size becomes too large, the surface of the bent portion is likely to be rough, which may lead to a decrease in bending workability. It is more preferable to adjust to a range of 8 to 20 μm. The final average crystal grain size is almost determined by the crystal grain size in the stage after the solution treatment. Therefore, the average crystal grain size can be controlled by the solution treatment conditions described later.

  Next, the characteristics of the copper alloy sheet will be described.

  In order to reduce the size and thickness of electrical and electronic parts such as connectors, the 0.2% proof stress of the copper alloy sheet material is preferably 900 MPa or more, and more preferably 930 MPa or more. As for the bending workability, the ratio R / t between the minimum bending radius R and the sheet thickness t in the 90 ° W bending test is preferably 2.0 or less, and is 1.5 or less in both GoodWay and BadWay. Further preferred.

  In addition, electrical and electronic parts such as connectors tend to be highly integrated, densely packed, and increase in current. With this trend, the demand for high conductivity is increasing for copper and copper alloy plate materials. ing. Specifically, a conductivity level of 30% IACS or more is preferable, and a conductivity level of 35% IACS or more is more desirable.

  Since the value of TD is particularly important for applications such as in-vehicle connectors, it is desirable to evaluate the stress relaxation resistance with the stress relaxation rate using a test piece whose longitudinal direction is TD. When the maximum load stress on the surface of the plate material is 80% of 0.2% proof stress and kept at 150 ° C. for 1000 hours, the stress relaxation rate is preferably 7% or less, and preferably 5% or less. Is more preferable.

  Next, the manufacturing method of the copper alloy sheet | seat material concerning this invention is demonstrated.

  The copper alloy sheet having the above-described characteristics is produced by the method for producing a copper alloy sheet of the present invention. The method for producing a copper alloy sheet according to the present invention includes a melting / casting step of melting and casting a copper alloy raw material having the above composition, a hot rolling step performed after the melting / casting step, and this hot rolling. A first cold rolling process in which cold rolling is performed at a rolling rate of 70% or more after the process, an intermediate annealing process in which heat treatment is performed at a heating temperature of 500 to 650 ° C. after the first cold rolling process, and the intermediate A second cold rolling step for performing cold rolling at a rolling rate of 70% or more after the annealing step, a solution treatment step for performing solution treatment after the second cold rolling step, and the solution treatment step Is followed by an aging treatment step of aging treatment at 400 to 500 ° C.

  In addition, the solution treatment step includes a heating step of heating at 800 to 1020 ° C, a first quenching step of rapidly cooling to 500 to 800 ° C, a heat retaining step of holding at 500 to 800 ° C for 10 to 600 seconds, and then 300 ° C or less. A second quenching step of quenching to

  In the intermediate annealing step, heat treatment is performed at 500 to 650 ° C. for 0.1 to 20 hours so that the electrical conductivity of the copper alloy sheet after the intermediate annealing satisfies 40% IACS or more and the Vickers hardness satisfies HV150 or less. It is preferable to implement.

  Furthermore, it is preferable to have a finish cold rolling process with a rolling rate of 10 to 80% after the aging treatment process, and to have a low temperature annealing process in which heat treatment is performed at 150 to 550 ° C. after the finish cold rolling process. preferable. Further, after hot rolling, chamfering may be performed as necessary, and after the solution treatment step, pickling, polishing, degreasing, and the like may be performed as necessary. Below, each process is demonstrated in detail.

Melting / Casting Process After a copper alloy raw material is melted by the same method as a general copper alloy melting method, a slab is manufactured by continuous casting or semi-continuous casting. This step is preferably performed in an inert gas atmosphere or in a vacuum melting furnace in order to prevent oxidation of Si and Co.

Hot rolling step The slab is hot rolled in several passes while the temperature is lowered from 1000 ° C to 500 ° C. The total rolling ratio may be approximately 80 to 95%. After the hot rolling is completed, it is preferable to quench by water cooling or the like. Further, after hot rolling, chamfering or pickling may be performed as necessary.

First cold rolling step In the first cold rolling step, the rolling rate needs to be 70% or more, and more preferably 80% or more. By subjecting the material processed at such a rolling rate to an intermediate annealing step in the next step, the amount of precipitates can be increased.

Intermediate annealing step Next, an intermediate annealing step is performed for the purpose of precipitation. In the conventional manufacturing process of a copper alloy sheet, this intermediate annealing process is not performed, or high-temperature heat treatment is performed to soften or recrystallize the sheet in order to reduce the rolling load in the next process. However, in any of these cases, after the solution treatment step, the density of twin boundaries in the recrystallized grains and the formation of the recrystallized texture with the Cube orientation as the main orientation component were insufficient.

  As a result of detailed investigations and studies by the present inventors, it has been found that the formation of twins and Cube orientation during the recrystallization process is affected by the stacking fault energy of the parent phase immediately before the recrystallization. Annealing twins are more easily formed when the stacking fault energy is lower. Conversely, the higher the stacking fault energy, the easier it is for the Cube orientation to be formed. For example, the stacking fault energy is low in the order of brass, pure copper, and pure aluminum. Brass has a high density of annealing twins, but it is difficult to form the Cube orientation. On the other hand, although pure aluminum tends to form a Cube orientation, the density of annealing twins is low. In contrast, pure copper has a relatively high Cube orientation and annealing twin density. Therefore, in a precipitation-type copper alloy whose stacking fault energy is close to that of pure copper, there is a possibility that both the annealing twins and the density of the Cube orientation can be generated high.

  In order to generate both the annealing twin and the Cube orientation with a high density, Ni, Co, Si and the like are precipitated in the intermediate annealing step to reduce the amount of solid solution elements. Thereby, stacking fault energy can be made high. When the intermediate annealing step is performed at a temperature of 500 to 650 ° C. and the heat treatment time is aging precipitated within a range of 0.1 to 20 hours, good results are obtained.

  If the annealing temperature is too low, or if the annealing time is too short, sufficient precipitation cannot be achieved, the amount of solid solution elements becomes high, the electrical conductivity is not sufficiently recovered, and the stacking fault energy is little improved. If the annealing temperature is too high, the solid solubility limit of the solid solution element becomes high, and even if the annealing time is extended, sufficient precipitation cannot be achieved. In any case, both the annealing twins and the Cube orientation density cannot be generated high. Specifically, it is preferable that the electrical conductivity after the intermediate annealing step satisfies 40% IACS or higher and the Vickers hardness satisfies HV150 or lower during the intermediate annealing step.

2nd cold rolling process Then, the 2nd cold rolling process which is the second cold rolling is performed. In the second cold rolling step, the rolling rate is preferably 70% or more. In the second cold rolling step, strain energy can be efficiently introduced due to the presence of precipitates from the previous step. If the strain energy is insufficient, the recrystallized grain size generated during the solution treatment may become non-uniform, and the density of twin boundaries and the formation of recrystallized texture with the Cube orientation as the main orientation component are insufficient. Become.

Solution Treatment Process Conventional solution treatments were mainly aimed at re-solution and recrystallization of solute elements in the matrix. However, in the present invention, the formation of high-density twins and the Cube orientation are mainly used. The formation of a recrystallized texture as an orientation component is also an important purpose.

  In this solution treatment process, it is preferable to heat-process at 800-1020 degreeC for 10 to 600 second according to a component. If the temperature is too low, recrystallization is incomplete and solute elements are not sufficiently dissolved. In addition, components having an annealing twin density and a Cube orientation as the main orientation tend to be low, and it is finally difficult to obtain a copper alloy sheet material having excellent bending workability and high strength. On the other hand, if the temperature is too high, the crystal grains are coarsened, which tends to cause a decrease in bending workability.

  Specifically, in the heating step in the solution treatment step, the holding time in the range of 800 to 1020 ° C. so that the average crystal grain size of recrystallized grains (not considering twin boundaries as crystal grain boundaries) is 3 to 60 μm. In addition, it is desirable to perform the heat treatment at the ultimate temperature, and it is more preferable to adjust the average crystal grain size to 8 to 20 μm. If the recrystallized grain size becomes too fine, the density of the annealing twins becomes low. It is also disadvantageous in improving the stress relaxation resistance. If the recrystallized grain size becomes too large, the surface roughness of the bent portion is likely to occur. The recrystallized grain size varies depending on the cold rolling rate and chemical composition before the solution treatment, but by previously obtaining the relationship between the solution treatment heat pattern and the average crystal grain size for each alloy by experiment, The holding time and ultimate temperature in the 800 to 1020 ° C. region can be set. Specifically, in the copper alloy having the chemical composition of the present invention, a heating condition that is maintained at a temperature of 800 to 980 ° C. for 10 to 600 seconds can be set as an appropriate condition.

  In the solution treatment step, the cooling after the heating step is generally rapidly cooled to a temperature at which precipitation does not occur in order to avoid precipitation of the compound during cooling as much as possible. However, as described above, the optimal precipitation temperature and time of the Ni—Si compound and the Co—Si compound do not match (deviate), so conventionally two types of precipitates cannot be fully utilized at the same time. This was the reason why high yield strength of 900 MPa or more while maintaining electrical conductivity, and good bending workability and stress relaxation resistance could not be realized at the same time. Therefore, in the present invention, a cooling pattern is used in which the sample is held for a certain time in a specific temperature range in the rapid cooling process and then rapidly cooled. That is, in the present invention, cooling is performed in advance so that the Co—Si compound is finely precipitated in a temperature range where the Ni—Si compound is hardly precipitated.

  Specifically, the cooling pattern after the heating step in which the heat treatment is performed at a heating temperature of 800 to 1020 ° C. is 10 ° C./s or more, preferably 50 ° C./s or more, more preferably up to a temperature range of 500 to 800 ° C. A first quenching step of quenching at a cooling rate of 100 ° C./s or higher, a heat retaining step of holding for 10 to 600 seconds in a temperature range of 500 to 800 ° C., and then 10 ° C./s or higher again to 300 ° C. or lower, preferably It comprises a second quenching step of quenching at a cooling rate of 50 ° C./s or more, more preferably 100 ° C./s or more. The cooling rate of the first quenching step is an average cooling rate from 800 to 1020 ° C. to the holding temperature of the heat retaining step of 500 to 800 ° C., and the cooling rate of the second quenching step is the holding temperature of the heat retaining step. The average cooling rate from 500 to 800 ° C. to 300 ° C. or less. The heat retention step performed at 500 to 800 ° C. for 10 to 600 seconds is for finely depositing the Co—Si based compound in a temperature range in which the Ni—Si based compound hardly precipitates. If the holding temperature in the heat-holding step is too high, the driving force for precipitation of the Co—Si compound is reduced, and the precipitates are reduced while being easily coarsened. On the other hand, if the holding temperature is too low, it takes a long time for the Co—Si compound to precipitate, so that substantially no precipitation occurs, and two types of precipitates cannot be fully utilized simultaneously as in the conventional manufacturing method. . That is, finally, it becomes impossible to satisfy all of the high yield strength of 900 MPa or more, the good bending workability, and the excellent stress relaxation resistance while maintaining the good electrical conductivity. Further, if the holding time is too long, the Co—Si based precipitates are likely to be coarsened, and if the holding time is too short, the Co—Si based precipitates are reduced.

  Specifically, in the copper alloy having the composition of the present invention, it can be set as an appropriate condition that the heat retention step is held at a temperature of 500 to 800 ° C. for 10 to 600 seconds. It is further preferable to hold at a temperature of 550 ° C. to 750 ° C. (or a temperature exceeding 550 ° C. and not higher than 750 ° C.) for 20 to 300 seconds, and more preferably holding for 50 to 300 seconds.

  In the first quenching step, if the temperature is kept cool by quenching to a temperature higher than 800 ° C, Co-Si compounds are likely to precipitate and coarsen. If the temperature is kept cool by quenching to a temperature lower than 500 ° C, Co -There is little precipitation amount of Si type compound. In any case, finally, it becomes impossible to satisfy all of the high yield strength, the good bending workability and the excellent stress relaxation characteristics.

  Although it is desirable in terms of cost to perform the solution treatment step in a series of flows in a continuous furnace, due to restrictions on equipment and the like, a heating step of heating to 800 to 1020 ° C and then rapidly cooling to 300 ° C or less and The process can be divided into a first rapid cooling process, a heat retaining process that is heated again and held at 500 to 800 ° C. for 10 to 600 seconds, and a second rapid cooling process that is rapidly cooled to 300 ° C. or lower. Furthermore, in the case of carrying out two steps, a cold rolling process of 50% or less may be sandwiched between them in order to further promote the precipitation of the Co—Si based compound. However, since the structure can be controlled by performing the heat treatment in a series of flows, it is desirable to perform in a continuous furnace from the viewpoint of cost.

  Further, in order to promote the subsequent precipitation of the Ni—Si compound, a cold rolling process of 50% or less may be performed after the second quenching step. However, after heat treatment and before rolling, a process for improving surface properties such as acid cleaning and buffing is required, which complicates the process and is disadvantageous in terms of cost. In the production method of the present invention, this cold rolling process can be omitted in combination with the aging treatment conditions described later.

  The solution treatment process consisting of the above heating process, the first quenching process, the heat retaining process, and the second quenching process is performed by modifying a solution treatment furnace constituted by, for example, a normal heating zone and a cooling zone, It can be implemented in a solution treatment furnace composed of four zones, a cooling zone, a heat retention zone, and a cooling zone. The residence time between the heating zone and the heat insulation zone of the plate can be controlled by adjusting the length of the zone and the plate passing speed. The cooling rate in the cooling zone can be controlled by the rotation speed of the cooling fan. The cooling method is not limited to the above, and it is sufficient that the cooling rate can be controlled, such as water cooling, oil cooling, gas rapid cooling, or cooling with a salt bath.

Aging treatment step The subsequent aging treatment is performed mainly for precipitation of Ni-Si compounds. When the aging treatment temperature is too high, the Ni—Si based precipitates are likely to be coarsened, and at the same time, the Co—Si based precipitates generated in the rapid cooling step of the solution treatment step are also easily coarsened. On the other hand, if the aging temperature is too low, the Ni—Si compound is not sufficiently precipitated, and it is necessary to increase the aging time, which is disadvantageous in terms of productivity. Therefore, it is preferable to determine the conditions by adjusting in advance the temperature and time at which the hardness reaches a peak by aging treatment according to the alloy composition. Specifically, it is preferably performed at 400 to 500 ° C., more preferably at a temperature of 425 to 475 ° C. The aging treatment time is about 1 to 10 hours, and good results are obtained.

Finish cold rolling process This finish cold rolling is important for improving the strength level, particularly for improving 0.2% proof stress. 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, when the rolling ratio of finish cold rolling is too high, the bending workability in the TD direction may be deteriorated.

  The rolling rate of this finish cold rolling needs to be 10% or more, preferably 15% or more. However, it is more desirable to set the upper limit of the rolling rate to 80% and not to exceed 60%. The final plate thickness is preferably about 0.05 to 1.0 mm, more preferably 0.08 to 0.5 mm, although it depends on the use of the plate material.

Low-temperature annealing step After the finish cold rolling step, it is preferable to perform low-temperature annealing for the purpose of improving the strength by low-temperature annealing hardening, reducing the residual stress of the strip material, and improving the spring limit value and the stress relaxation resistance. The heating temperature is preferably set to 150 to 550 ° C. Thereby, the residual stress inside the plate material is reduced, and there is an effect of improving the electrical 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. On the other hand, if the heating temperature is too low, the above-described effect of improving the characteristics cannot be obtained sufficiently. The heating time is preferably 5 seconds or longer, and good results are usually obtained within 1 hour.

  Hereinafter, the Example of the manufacturing method of the copper alloy board | plate material by this invention is described.

  Each raw material having the composition shown in Table 1 was melted and cast using a vertical semi-continuous casting machine to obtain a slab.

  Each slab is heated to 980 ° C., hot rolled while lowering the temperature from 980 ° C. to 500 ° C. to form a plate having a thickness of 10 mm, and then rapidly cooled by water cooling (cooling rate of 10 ° C./s or more). Thereafter, the surface oxide layer was removed (faced) by mechanical polishing.

  Next, after performing the first cold rolling at a rolling rate of 86%, Examples 1 to 13 to which the present invention was applied were subjected to intermediate annealing heat treatment at 500 to 640 ° C. for 3 to 8 hours. The electric conductivity after the intermediate annealing of Examples 1 to 13 was 40 to 57% IACS, and the hardness was HV 96 to 148. Thereafter, second cold rolling was performed at a rolling rate of 80 to 90%.

  Next, at a temperature adjusted within the range of 860 to 1000 ° C. according to the composition of the alloy so that the average crystal grain size (by the cutting method of JIS H0501) on the surface of the rolled plate is greater than 5 μm and 30 μm or less. The solution was held for a minute and heat-treated in the solution treatment step. The temperature and time in this heat treatment were determined by determining the optimum temperature and time by preliminary experiments according to the composition of the alloy of each example.

  Next, after the heat treatment, it is rapidly cooled to a temperature of 700 ° C. at a cooling rate of 15 ° C./s or more by immersion in a salt bath, and then held at a temperature of 700 ° C. for 52 seconds, and then cooled to 50 ° C./s or more. Rapid cooling (water cooling) to room temperature at a speed. Thereafter, an aging treatment was performed at 450 ° C. for 2 to 4 hours. The aging treatment time was adjusted to a time when the hardness peaked at 450 ° C. according to the alloy composition.

  Subsequently, finish cold rolling was performed at a rolling rate of 15 to 55%, and finally low temperature annealing was performed at 425 ° C. for 1 minute to obtain copper alloy sheet materials of Examples 1 to 13. In addition, it chamfered in the middle as needed, or the rolling rate was adjusted to 80 to 90% by the 2nd cold rolling process, and the plate | board thickness of the copper alloy board | plate material was arrange | equalized with 0.15 mm. The manufacturing conditions are shown in Table 2.

  Next, a sample is taken from each of the obtained copper alloy sheet materials, twin boundary density, area ratio of Cube orientation grains, average crystal grain size, conductivity, strength (0.2% proof stress), bending workability, The stress relaxation characteristics were examined as follows.

After polishing the surface of the rolled plate with # 1500 water-resistant paper, the surface is finish-polished by vibration polishing to prevent polishing distortion on the surface, and the surface is FESEM (field emission scanning electron microscope: A distribution map of CSL (coincidence site lattice boundary) and a grain orientation map (OIM image) were measured by an EBSP method using a Field Emission Scanning Electron Microscope). The density (ratio) of Σ3-compatible grain boundaries (corresponding to twin boundaries) is
(Total sum of Σ3-compatible grain boundaries) / (Total sum of grain boundary lengths) x 100 (%)
Calculated with Further, from the crystal grain orientation distribution map (OIM image), crystal grains having an orientation whose orientation difference from the {100} orientation is within 10 ° were extracted, and the area ratio was obtained as the area ratio of the Cube orientation.

  The average crystal grain size was determined by polishing the surface of the rolled plate, etching it, observing the surface with an optical microscope, and cutting with JIS H0501 (not including twin boundaries). The conductivity of the copper alloy sheet was measured according to the conductivity measurement method of JIS H0505.

  As 0.2% proof stress, specimens for tensile test of LD (rolling direction) of copper alloy sheet material (No. 5 test piece of JIS Z2241) were sampled three by 3 and a tensile test based on JIS Z2241 was conducted. The average value was obtained.

  In addition, in order to evaluate the bending workability, a bending test of a bending test piece (width 10 mm) whose longitudinal direction is LD (rolling direction) and TD (a direction perpendicular to the rolling direction and the plate thickness direction) from a copper alloy plate material. Three pieces (10 mm in width) were each collected, and each test piece was subjected to a 90 ° W bending test according to JIS H3110. For the test piece after this test, the surface and cross section of the bent portion were observed with an optical microscope at a magnification of 50 times to determine the minimum bending radius R at which no cracks occurred, and this minimum bending radius R was determined from the copper alloy sheet. By dividing by the thickness t, each R / t value of LD and TD was determined. Of the three test pieces of LD and TD, the result of the worst test piece was adopted.

Further, a bending test piece (width 10 mm) having a longitudinal direction of TD is taken from each specimen, and the arch is formed so that the surface stress of the central portion in the longitudinal direction of the test piece is 80% of 0.2% proof stress. Fixed in a bent state. The surface stress (MPa) is obtained as ₆ Etδ / L ₀ ² . Where E is the elastic modulus (MPa), t is the thickness (mm) of the sample, and δ is the deflection height (mm) of the sample. The stress relaxation rate (%) is (L ₁ -L ₂ ) / (L ₁ -L ₀ ) × 100 (%) from the bending habit after holding the test piece in this state at a temperature of 150 ° C. in the atmosphere for 1000 hours.
Calculated as However, L ₀ is the length of the jig, that is, the horizontal distance (mm) between the sample ends fixed during the test, L ₁ is the sample length (mm) at the start of the test, and L ₂ is the sample after the test. Horizontal distance (mm) between ends.

  Table 3 shows the results of the twin boundary density, the area ratio of the Cube-oriented crystal grains, the average crystal grain size, the electrical conductivity, the strength (0.2% proof stress), the bending workability, and the stress relaxation resistance investigated as described above. Shown in

  As shown in Table 3, in Examples 1 to 13 to which the present invention is applied, 0.2% proof stress of 900 MPa or more, conductivity of 35% IACS or more, stress relaxation rate of 5% or less, minimum bending radius R The sheet thickness t had a ratio R / t of 1.5 or less. In addition, as can be seen from the optical micrographs shown in FIG. 1 and FIG. 2, very many twins were observed. As a result of measuring twin boundaries, the twin boundary densities of Examples 1 and 2 were 73% and 78%, respectively.

  Moreover, as shown to Tables 1-3, the board | plate material of Comparative Examples 1-8 which remove | deviated from the range of this invention was manufactured, and the property of each board | plate material was investigated similarly to Examples 1-13.

  Comparative Example 1 has substantially the same amounts of Ni and Co as in Example 1, has a composition in which the amount of Si is excessive and (Ni + Co) /Si=3.8, and under the same production conditions as in Example 1. Manufactured. The obtained copper alloy sheet had a low conductivity after intermediate annealing and a high hardness value. As a result, as shown in FIG. 3, there were few twins, and both the final twin boundary density and the area ratio of the Cube-oriented grains were low. Further, due to the excessive amount of Si, there were few precipitates during the aging treatment, and as a result, the conductivity, 0.2% proof stress, bending workability, and stress relaxation resistance were slightly low.

  Comparative Examples 2 to 5 have the same composition as in Example 2 and do not perform intermediate annealing (Comparative Example 2), or do not perform a heat retention process at 700 ° C. during cooling of the solution treatment process (Comparative Example) 3-5), which is a copper alloy sheet produced by a conventional production method.

  In Comparative Example 2, the manufacturing conditions except that the intermediate annealing step is not performed are the same as in Example 2, and there are few twins as shown in FIG. 4, and both the final twin boundary density and the area ratio of the Cube orientation grains are both It became low. Moreover, the performance of bending workability and stress relaxation resistance was lowered.

  In Comparative Example 3, the manufacturing conditions were the same as in Example 2 except that the temperature during the intermediate annealing process was low, and the heat retention process at 700 ° C. was not performed during the cooling of the solution treatment process. It became low with the crystal boundary density and the area ratio of the Cube-oriented grains. Since the heat retention process at 700 ° C. in the solution treatment process is omitted, the Co—Si compound is not sufficiently precipitated, and the performance is low in terms of conductivity, 0.2% proof stress, bending workability, and stress relaxation resistance. It was.

  Comparative Example 4 was produced under the same production conditions as Comparative Example 3, except that the aging treatment was performed at 500 ° C., which is considered to be the optimum aging temperature of the Co—Si-based compound, for 6 hours. Since the Ni-Si based precipitates of the obtained copper alloy sheet were already coarsened, as a result, the conductivity and 0.2% proof stress were higher than those of Comparative Example 3, but in the example to which the present invention was applied, Compared with the copper alloy, the characteristics were significantly inferior.

  Comparative Example 5 is the same production conditions as Comparative Example 3 except that aging treatment was performed at 475 ° C. for 8 hours, which is considered to be an intermediate position between the optimum aging temperatures of the Co—Si based precipitate and the Ni—Si based compound as aging conditions. Manufactured with. Although the obtained copper alloy sheet material has an improved balance between conductivity and 0.2% proof stress as compared with Comparative Examples 3 and 4, the properties other than the conductivity are significantly inferior to those of Example 2 having the same composition. It was.

  Comparative Example 6 is a composition composed of 1.46% by mass of Ni, 2.46% by mass of Co, 0.82% by mass of Si, and the balance of Cu and inevitable impurities. A slab was obtained by casting using a semi-continuous casting machine. Because the amount of Co added is over 2.0% by mass, the coarse crystallized material formed during the casting process did not dissolve during heating before hot rolling and cracked violently during hot rolling. The subsequent process was interrupted.

  The comparative example 7 was the same composition as Example 2, and manufactured the copper alloy board | plate material on the manufacturing conditions similar to Example 2 except the intermediate annealing conditions differing. Although the electrical conductivity and the 0.2% proof stress were good, the temperature condition of the intermediate annealing was too high (the condition of the above-mentioned Patent Document 5), and as a result, the twin boundary density and the area ratio of the Cube orientation grains were Both became low, and both BW bending workability and stress relaxation resistance deteriorated.

  The comparative example 8 is a case where the heat treatment process at 700 ° C. is not performed during the intermediate annealing and cooling in the solution treatment process, and is a copper alloy sheet manufactured by a conventional manufacturing method. In Comparative Example 8, in order to suppress the coarsening of precipitates during the hot rolling process, the hot end temperature was kept at 850 ° C. (holding the sample in a 900 ° C. furnace for 5 min for each rolling pass). After that, it was rapidly cooled at 15 ° C./s or more. Further, in order to suppress a decrease in bending workability, finish rolling after aging treatment was not performed, and cold rolling with a rolling rate of 50% was performed instead before aging treatment (after solution treatment). It manufactured on the manufacturing conditions similar to Example 1 except the manufacturing conditions shown in Table 2. As a result, the conductivity, 0.2% proof stress and bending workability were good, but the twin boundary density was low and the stress relaxation resistance was poor.

  As described above, Comparative Examples 1 to 8 cannot have the performance of the copper alloy sheet of the present invention because the composition or manufacturing conditions are out of the scope of the present invention. As compared with Examples 1 to 13 to which the invention was applied, it was found that the characteristics were greatly inferior.

  The present invention can be applied as a method for producing a copper alloy sheet having high conductivity, high strength, and excellent bending workability and stress relaxation resistance at the same time.

Claims (2)

1.0-3.5 mass% Ni, 0.5-2.0 mass% Co, 0.5-1.2 mass% Si are included, and Co / Ni mass ratio is 0.15- 1.5, (Ni + Co) / Si mass ratio of 4-7, melting / casting step of melting and casting a raw material of a copper alloy having a composition in which the balance is Cu and inevitable impurities;
A hot rolling step of performing hot rolling after the melting and casting steps;
A first cold rolling step of performing cold rolling at a rolling rate of 70% or more after the hot rolling step;
An intermediate annealing step in which heat treatment is performed at a heating temperature of 500 to 650 ° C. after the first cold rolling step;
A second cold rolling step of performing cold rolling at a rolling rate of 70% or more after the intermediate annealing step;
A solution treatment step of performing a solution treatment after the second cold rolling step;
An aging treatment step of performing an aging treatment at 400 to 500 ° C. after the solution treatment step;
After the aging treatment step, a finish cold rolling step for cold rolling at a rolling rate of 10 to 80%,
After the finish cold rolling step, it comprises a low temperature annealing step in which heat treatment is performed at 150 to 550 ° C.,
In the intermediate annealing step, heat treatment is performed at 500 to 650 ° C. for 0.1 to 20 hours so that the electrical conductivity after the intermediate annealing step is 40% IACS or more and the Vickers hardness satisfies HV150 or less,
The solution treatment step is a heating step at 800 to 1020 ° C., a first rapid cooling step in which the solution is rapidly cooled to a temperature of 500 to 800 ° C. at a cooling rate of 10 ° C./s or more, and held at 500 to 800 ° C. for 10 to 600 seconds. It has a second quenching step of quenching at a cooling rate of 10 ° C./s or higher to a temperature of 300 ° C. or less, and does not include twin boundaries using the cutting method of JIS H0501 after the solution treatment step. The average crystal grain size measured in 3 to 60 μm,
On the rolling surface, the observation results of the grain boundary character and crystal orientation by EBSP measurement are such that the twin boundary density in all the grain boundaries is 40% or more, and the area ratio of the Cube orientation crystal grains is 20% or more,
A method for producing a copper alloy sheet, characterized in that a 0.2% proof stress is 900 MPa or more and a conductivity is 30% IACS or more. The copper alloy further includes at least one of Fe, Cr, Mg, Mn, Ti, V, Zr, Sn, Zn, Al, B, P, Ag, Be, and Misch metal in a total amount of 0.5 % by mass. The method for producing a copper alloy sheet according to claim 1, comprising the following range.