JP5578827B2 - High-strength copper alloy sheet and manufacturing method thereof - Google Patents

Description

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

  Materials used for electrical and electronic parts as current-carrying parts such as connectors, sockets, lead frames, relays, and switches are required to have good “conductivity” in order 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 electronic equipment. In addition, since electrical / electronic components such as connectors are generally formed by bending after press punching, excellent bending workability is also required.

  Furthermore, the demand for “stress relaxation resistance” has become stricter as the use of electrical and electronic parts in harsh environments increases. For example, “stress relaxation resistance” is particularly important when used in an environment exposed to high temperatures, such as an automobile connector. 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.

Particularly, in recent years, electrical and electronic parts such as connectors tend to be reduced in size and weight, and accordingly, a copper alloy plate material is required to be thin (for example, a plate thickness of 0.15 mm). Hereinafter, 0.10 mm or less) is increasing. For this reason, the strength level required for the material is becoming stricter. Specifically, a 0.2% yield strength of 800 MPa or more, preferably 850 MPa or more, more preferably 900 MPa or more is desired.
In addition, electrical and electronic parts such as connectors and lead frames tend to be highly integrated, densely packed, and have a high current. Accordingly, copper and copper alloy plates, which are materials, have high conductivity. The demand is growing. Specifically, a conductivity level of 30% IACS or higher, preferably 35% IACS or higher, more preferably 40% IACS or higher is desired.

High-strength copper alloys include Cu-Be based alloys such as C17200 (Cu-2 wt% Be), Cu-Ti based copper alloys such as C19900 (Cu-3.2 wt% Ti), Cu-Ni-Sn based copper. An alloy, for example, C72700 (Cu-9 wt% Ni-6 wt% Sn) may be mentioned.
However, in recent years, there is a tendency to avoid Cu-Be alloys (so-called de-verification orientation) from the viewpoint of cost and environmental load. Cu-Ti copper alloys and Cu-Ni-Sn copper alloys have a modulation structure (spinodal structure) in which the concentration of solid solution elements periodically varies in the matrix phase, so that the strength is high. The electrical conductivity is low (about 10 to 15% IACS).

  Cu-Ni-Si-based alloys (so-called Corson alloys) are attracting attention as materials having a relatively excellent balance of properties between strength and conductivity. For example, Cu—Ni—Si based copper alloy sheet material has a relatively high conductivity (30 to 50% IACS) by processes based on solution treatment, cold rolling, aging treatment, finish cold rolling and low temperature annealing. While maintaining the above, it can have a 0.2% proof stress of 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, achieving 0.2% proof stress of 800 MPa or more).

In the Cu—Ni—Si based copper alloy sheet material, as means for increasing the strength, techniques 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 widely known.
However, the strength increases as the addition amount of Ni and Si increases, but if the amount exceeds a certain amount (for example, about 3 mass% Ni, about 0.7 mass% Si), the increase in strength tends to be saturated. Therefore, it is difficult to achieve a 0.2% proof stress of 800 MPa or more. Further, excessive addition of Ni and Si is accompanied by a decrease in electrical conductivity, and Ni—Si based precipitates are likely to be coarsened, and bending workability is likely to be reduced.
Further, although the strength can be improved by increasing the finish rolling ratio after the aging treatment, the bending workability of the copper alloy sheet, particularly the bending (so-called Bad Way bending) workability with the rolling direction as the bending axis is remarkably deteriorated.
For this reason, even if the strength level is high (for example, 0.2% proof stress of 850 MPa or more can be achieved), it may be impossible to process the electrical / electronic component.

  In recent years, in order to increase the strength of a Cu—Ni—Si based copper alloy sheet, a copper alloy sheet in which Co is added in a relatively large amount (for example, 0.5 to 2.0 wt% Co or more), so-called Cu—Ni. -Co-Si based copper alloys have been proposed (for example, Patent Documents 1 to 3).

As is well known, in the case of a Cu—Ni—Si based copper alloy, the strengthening of the alloy is mainly due to precipitation of Ni—Si based compounds and work hardening accompanying rolling. Among them, strengthening by work hardening tends to cause a decrease in bending workability, so it is necessary to reduce the rolling rate as much as possible.
Therefore, in order to improve the strength of the Cu—Ni—Si based copper alloy, it is most important to control the amount of precipitation of the Ni—Si based compound and the size of the precipitate. The optimum aging temperature for Ni-Si compounds is around 450 ° C (generally 425 to 475 ° C). If the aging temperature is too high, Ni-Si-based precipitates are likely to become coarse (so-called overaging), and peak. Hardness decreases. On the other hand, if the aging temperature is too low, the precipitate is not coarsened because the precipitation rate is slow, but the formation of the precipitate is slow or may not be generated.

  On the other hand, when Co is added, that is, there are mainly two types of precipitates of Cu—Ni—Co—Si based copper alloys, Ni—Si based compounds and Co—Si based compounds. Therefore, in the Cu—Ni—Co—Si based copper alloy, it is very important to control both the Ni—Si based precipitate and the Co—Si based precipitate. However, when optimizing the precipitation of Ni-Si compounds and Co-Si compounds, conventional solution treatment, depending on the case, cold rolling, aging, cold rolling, and processing represented by low temperature annealing In the heat treatment process, the 0.2% proof stress could not exceed 900 MPa, no matter how the process conditions were optimized.

[Optimization of Co-Si compounds]
The deposition temperature of the Co—Si-based compound is higher than that of the Ni—Si-based compound, specifically, around 520 ° C. (generally 500 to 550 ° C.).
Therefore, when Cu-Ni-Co-Si-based copper alloy is aged at around 450 ° C, which is the optimum aging temperature for Ni-Si-based compounds, the amount of precipitation of Co-Si-based compounds is small. In the case of aging at a temperature around 520 ° C. which is the optimum aging temperature of the compound, the Ni—Si based precipitate is coarsened. None of the aging conditions can utilize the two types of precipitates at the same time. Further, even when aging is performed at an intermediate temperature between the respective optimum aging temperatures (for example, 480 ° C.), it is difficult to simultaneously achieve the optimum state of the two types of precipitates. (For example, if the precipitation state 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 sub-aged. If the aging is longer and the Co-Si-based precipitates become peak aging, the Ni-Si-based precipitates become coarse due to overaging and do not contribute to the strength.

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

  Patent Document 2 proposes a Cu—Ni—Co—Si based copper alloy whose characteristics are improved by controlling average crystal grains and texture. As for the strength level, the 0.2% proof stress is 652 to 862 MPa and does not reach 900 MPa or more.

  Patent Document 3 proposes a Cu—Ni—Co—Si based copper alloy (strength 810 to 920 MPa) with improved strength by controlling the cooling rate of the solution treatment to 10 ° C./s or more. The 2% proof stress has not reached 900 MPa or more.

Therefore, the conventional method cannot obtain a high 0.2% proof stress exceeding 880 MPa, and more than 900 MPa, and further has a conductivity of 35% IACS or more required as an electronic material such as a connector material, and good bending. There is no disclosure about satisfying all processability.
As yet another problem, the reason for the Cu-Ni-Co-Si based copper alloy containing Co has not been elucidated, but compared with the Cu-Ni-Si based copper alloy not containing Co, the stress relaxation resistance However, in this respect, Patent Documents 1 to 3 do not provide any improvement measures.
That is, as described above, in order to produce a copper alloy sheet material having an electrical conductivity of 35% IACS or higher, a 0.2% proof stress of 900 MPa or higher, good bending workability, and excellent stress relaxation resistance, A technical breakthrough is required.

JP 2007-169765 A JP 2008-248333 A International Publication Number WO 2006/101172 A1

  In view of such a conventional problem, the present invention has a conductivity of 30% IACS or more, preferably 35% IACS or more, more preferably 40% IACS or more, and 0.2% proof stress exceeding 880 MPa, preferably 900 MPa. It has the above characteristics, more preferably less anisotropy, excellent bending workability, and simultaneously has "stress relaxation resistance" that bears reliability in harsh usage environments such as in-vehicle connectors. It aims at providing a copper alloy plate material and its manufacturing method.

As a result of intensive studies on the possibility of further improving the 0.2% proof stress in Cu-Ni-Co-Si based copper alloys, the present inventors have found that both precipitates of Ni-Si based compounds and Co-Si based compounds are present. By maximizing the effect, it was found that 0.2% proof stress of 900 MPa or more, good bending workability and stress relaxation resistance can be obtained while maintaining the conductivity, and the present invention was completed. It was.
In other words, in Cu-Ni-Co-Si-based copper alloys, the optimum aging temperature (precipitation temperature) and aging time (precipitation time) of Ni-Si compounds and Co-Si compounds are different, which can be controlled sufficiently in the past. By adopting the production method described later for the precipitates that did not exist, the ratio of the number of Ni-Si-based and Co-Si-based compounds in the total precipitates, the particle size of the precipitates can be optimized, 0.2 It has been found that the% yield strength exceeds 880 MPa and can be set to 900 MPa or more, and good bending workability and stress relaxation resistance can be obtained.
Furthermore, Fe, Cr, Mn, Ti, V, Zr, which have different optimum aging temperatures and aging times from Ni-Si compounds and have optimum aging temperatures and aging times similar to Co-Si compounds, are the same as Co It was found that the precipitation can be controlled and that it has the same effect as Co. In the present application, in addition to Co or Co, an element (group) of Fe, Cr, Mn, Ti, V, and Zr is sometimes referred to as X for convenience, and the alloy of the present invention may be expressed as a Cu—Ni—X—Si alloy.
Further, increasing the proportion of crystal grains having {200} orientation (Cube orientation) with little anisotropy can improve bending workability and at the same time remarkably improve anisotropy of bending workability. Therefore, it is preferable. Furthermore, it has been found that stress relaxation characteristics and bending workability can be significantly improved simultaneously by increasing the twin density inside the crystal grains. Therefore, it is preferable to increase the twin density.
It has been found that with these configurations, the strength and 0.2% proof stress can be improved while maintaining the conductivity of the copper alloy sheet, and more preferably, the stress relaxation resistance, bending workability and its anisotropy can be improved simultaneously and significantly. .

That is, the present invention includes 0.8 to 3.5 mass% Ni, 0.3 to 2.0 mass% Si, 0.5 to 2.0 mass% Co, with the balance being Cu and inevitable impurities. When X is Co, the ratio of the mass of X to the mass of Ni is in the range of 0.3 to 1.5, the sum of the mass of Ni and the mass of X and Si The mass ratio (Ni + X) / Si is in the range of 3-6, the number of precipitates per unit area is N, the number of Ni—Si based precipitates among the precipitates is N _N , the average particle size is d _N , X-Si based precipitates the number of N _X of the precipitates, the average particle diameter is taken as d _X, it possesses the precipitation the number satisfying the following Equation 1, the average particle size of the precipitates which satisfies the following Expression 2, the following has a crystal orientation satisfying Expression 3, 0.2% proof stress above 900 MPa, conductivity, characterized in der Rukoto least 30% IACS Is a copper alloy sheet to be.

  Here, by TEM-EDS (energy dispersive X-ray analysis) of the precipitate component, a precipitate containing 50 mass% or more of Ni is converted into a Ni-Si based precipitate, and a precipitate containing 50 mass% or more of X. Is an X-Si-based precipitate.

Further, the copper alloy sheet material contains one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr as required in a total range of 2.0% by mass or less, and the X In addition to Co, Fe, Cr, Mn, Ti, V, and Zr may be used.
That is, 0.8 to 3.5% by mass of Ni, 0.3 to 2.0% by mass of Si, 0.5 to 2.0% by mass of Co, and Fe, Cr, Mn, Ti, V, Zr When one or more elements selected from the group consisting of: in the range of 2.0% by mass or less and X is added to Co and Fe, Cr, Mn, Ti, V, Zr, The ratio of the total mass and the mass of Ni X / Ni is in the range of 0.3 to 1.5, the sum of the mass of Ni and the mass of the elements contained in X and the ratio of the mass of Si (Ni + X) / Si Is a copper alloy consisting of Cu and inevitable impurities, wherein the number of precipitates per unit area is N, the number of Ni-Si-based precipitates among the precipitates is N _N , and the average particle size the d _N, a X-Si based precipitates the number of the precipitates N _X, the mean particle size is taken as d _X, below And precipitation the number satisfying 1, a copper alloy sheet and having an average particle size of the precipitates satisfies the following equation (2).

  Furthermore, it is preferable that the copper alloy sheet has a crystal orientation satisfying Equation 3 when the integrated intensity of the {hkl} diffraction peak when X-ray diffraction is performed on the sheet surface (rolled surface) is I {hkl}.

Here, I {200} is the integrated intensity of the X-ray diffraction peak of the {200} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {200} is the X-ray diffraction peak of the {200} crystal plane of the pure copper standard powder. Is the integrated intensity of.

  Moreover, it is preferable that the said copper alloy board | plate material has a crystal grain twin density which satisfy | fills number four.

Here, _NG is the average twin density per crystal grain. D and D _T are the average crystal grain size measured without using the twin boundary and the average crystal grain size measured by regarding the twin boundary as a grain boundary using the cutting method of JIS H0501.
Moreover, it is preferable that the average crystal grain diameter D is 5-30 micrometers.

Moreover, the said copper alloy board | plate material is further in the range of 1 mass% or less in total of 1 or more types of elements chosen from the group which consists of Sn, Zn, Mg, Al, B, P, Ag, Be, and Misch metal as needed. You may have the composition which contains.
The copper alloy sheet preferably has a 0.2% proof stress exceeding 880 MPa, preferably 900 MPa or more, and a conductivity of 30% IACS or more, and more preferably 35% IACS or more.

  Moreover, the manufacturing method of the copper alloy plate material by this invention contains 0.8-3.5 mass% Ni, 0.3-2.0 mass% Si, 0.5-2.0 mass% Co. A melting and casting step for melting and casting a copper alloy raw material having a composition in which the balance is Cu and inevitable impurities, a hot rolling step for performing hot rolling after the melting and casting step, and this hot rolling A first cold rolling process in which cold rolling is performed after the process, an intermediate annealing process in which heat treatment is performed at a heating temperature of 450 to 600 ° C. after the first cold rolling process, and a rolling rate after the intermediate annealing process. A second cold rolling process for performing cold rolling at 70% or more, a solution treatment process for performing a solution treatment after the second cold rolling process, and 350 to 520 ° C. after the solution treatment process. An aging treatment step in which the aging treatment is performed in the solution treatment step. Then, the solution temperature is set to 800 to 1020 ° C., then rapidly cooled to 500 to 800 ° C., held at 500 to 800 ° C. for 10 to 600 seconds, and then rapidly cooled to 300 ° C. or lower. It is characterized by that.

  In the method of manufacturing the copper alloy sheet, in the intermediate annealing step, Eb / Ea and Vickers hardness before and after the intermediate annealing are Eb / Ea, Hb and Ha, respectively, and Ea / Eb ≧ 1.5 and Ha / Hb ≦ 0. It is preferable to perform the heat treatment at 450 to 600 ° C. for 1 to 20 hours so as to satisfy 8.

  Moreover, it is preferable to control the conditions of the solution treatment step so that the average crystal grain size D after the solution treatment is 5 to 30 μm.

The copper alloy sheet manufacturing method preferably includes a finish cold rolling step in which cold rolling is performed at a rolling rate of 50% or less after the aging treatment step, and is 150 to 550 ° C. after the finish cold rolling step. It is preferable to provide a low-temperature annealing step for performing heat treatment.

  In the method for producing a copper alloy sheet, the copper alloy sheet further contains one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr, if necessary, in total 2.0 mass. %, And may contain a composition containing at least one element selected from the group consisting of Sn, Zn, Mg, Al, B, P, Ag, Be, and Misch metal as required. You may have the composition further included in the range of the mass% or less.

  Furthermore, an electrical / electronic component according to the present invention is characterized by using the above-described copper alloy sheet as a material. This electrical / electronic component is preferably a connector, socket, lead frame, relay or switch.

  According to the present invention, the electrical conductivity is 30% IACS or higher, preferably 35% IACS or higher, more preferably 40% IACS or higher, and 0.2% proof stress is higher than 880 MPa, preferably 900 MPa or higher. It has both the above-mentioned conductivity and 0.2% proof stress while having excellent bending workability and stress relaxation resistance at the same time, and also has little anisotropy in characteristics, and either bending work of GoodWay or BadWay It is possible to provide a copper alloy sheet having excellent properties and a method for producing the same.

Embodiments of the copper alloy sheet according to the present invention include 0.8 to 3.5 mass% Ni, 0.3 to 2.0 mass% Si, 0.5 to 2.0 mass% Co, Further, it contains one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr as required in a total range of 2.0% by mass or less, and further contains Sn, Zn, Mg as required. A copper alloy containing one or more elements selected from the group consisting of Al, B, P, Ag, Be and Misch metal in a total amount of 1% by mass or less, with the balance being Cu and inevitable impurities, When Co is added to Co or X is added to Co, and Fe, Cr, Mn, Ti, V, and Zr, the ratio X / Ni of the total mass of the elements of X to the mass of Ni is 0.3 to 1.5; The ratio of the sum of the mass and the mass of the element X to the mass of Si (Ni + X) / Si is 3 to 3. , And the precipitation the number per unit area N, the Ni-Si based precipitate the number N _N of the precipitates, the average particle diameter d _N, NX the X-Si based precipitates the number of the precipitates, the average particle When the diameter is d _X , the number of precipitates satisfying the following formula 1 and the average particle diameter of the precipitates satisfying the following formula 2 are included.

  Here, by TEM-EDS (energy dispersive X-ray analysis) of the precipitate component, a precipitate containing 50 mass% or more of Ni is converted into a Ni-Si based precipitate, and a precipitate containing 50 mass% or more of X. Was X-Si based precipitate.

  The copper alloy plate preferably has a crystal orientation satisfying Equation 3 when the integrated intensity of the {hkl} diffraction peak when X-ray diffraction is performed on the plate surface is I {hkl}.

Here, I {200} is the integrated intensity of the X-ray diffraction peak of the {200} crystal plane on the plate surface of the copper alloy sheet, and I ₀ {200} is the X-ray diffraction peak of the {200} crystal plane of the pure copper standard powder. Is the integrated intensity of.

  Moreover, it is preferable that the said copper alloy board | plate material has the twin density in a crystal grain which satisfy | fills number four.

Here, _NG is the average twin density per crystal grain. D and D _T are an average crystal grain size D measured by using the cutting method of JIS H0501 without including a twin boundary, and an average crystal grain size D _T measured by regarding the twin boundary as a grain boundary. . Moreover, it is preferable that the average crystal grain diameter D is 5-30 micrometers.

The copper alloy sheet preferably has a 0.2% proof stress exceeding 880 MPa and a conductivity of 30% IACS or more.
Hereinafter, the copper alloy sheet of the present invention and the manufacturing method thereof will be described in detail.

[Alloy composition]
In the present invention, a Cu—Ni—X—Si based copper alloy (X is composed of Fe, Cr, Mn, Ti, V, and Zr in addition to Co or Co) is employed. That is, the Cu—Ni—X—Si based copper alloy is a Cu—Ni—Co—Si based alloy and Cu—Ni—Co— (one kind selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr). The above element) refers to a Si-based alloy. Furthermore, a copper alloy in which Sn, Zn, Mg, and other alloy elements are added to the basic component of the Cu—Ni—X—Si based copper alloy is also comprehensively referred to in this specification as a Cu—Ni—X—Si based copper alloy. It is called.
As described above, for convenience, X is added to Co or Co and composed of Fe, Cr, Mn, Ti, V, and Zr elements. X-Si based precipitates are more than Ni-Si based precipitates. This is because the deposition temperature is high, the deposition temperature is close to that of the Co—Si-based compound related to Co, which is an essential component of the present invention, and the same effect on characteristics can be obtained.

  Ni has the effect of forming Ni—Si based precipitates and improving the strength, 0.2% proof stress and conductivity of the copper alloy sheet. When the Ni content is less than 0.8% by mass, it is difficult to sufficiently exhibit this effect. Therefore, the Ni content needs to be 0.8% by mass or more, preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and 2.0% by mass or more. Is most preferred. On the other hand, if the Ni content is too high, the effect of improving the strength is saturated, but the conductivity is reduced and coarse precipitates are easily generated, which causes 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 improving the strength, 0.2% yield strength, and conductivity of the copper alloy sheet by forming a Co—Si based precipitate, and also has the effect of dispersing the Ni—Si based precipitate. Yes, if two kinds of precipitates coexist, there is a synergistic effect of strength improvement. In order to fully exhibit these effects, it is desirable to secure a Co content of 0.5 mass% or more. However, when the content is 2.0% by 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 the mass of Co and the mass of Ni needs to be 0.3 to 1.5, It is preferable to make it 0.5-1.2. For this reason, the Co content is preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. More preferably, the Co content is adjusted to a range of 0.5 to 1.5 mass%.
When X is Co, the mass ratio X / Ni of the mass of Co and the mass of Ni is 0.3 to 1.5, and preferably 0.5 to 1.2.

  Furthermore, one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr may be added to the copper alloy sheet as necessary, and these elements are precipitated with Si. When formed, it has substantially the same effect as Co, and a part of expensive Co can be replaced. When these elements have a total content of 2.0% by mass or more, it is difficult to completely dissolve them. That is, the total of one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr is 2.0% by mass or less. When X is Co, Fe, Cr, Mn, Ti, V, Zr (consisting of elements of the group consisting of), the total mass of elements contained in X in the copper alloy and the mass of Ni The mass ratio X / Ni is 0.3 to 1.5, preferably 0.5 to 1.2.

Si produces Ni—Si based precipitates and X—Si based precipitates. The Ni—Si based precipitate is a compound mainly composed of Ni ₂ Si, and the X—Si based precipitate is in the form of X _m Si _n (when X is Co, Fe, Cr, Mn, Ti, V, Zr). It is considered that the compounds are mainly composed of Co ₂ Si, FeSi, Cr ₃ Si, Mn ₅ Si ₃ , Ti ₅ Si ₃ , V ₅ Si ₃ , Zr ₅ Si _{3, and the} like. However, Ni, X, 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, X, and Si in the solid solution state slightly improve the strength of the copper alloy sheet, but the effect is small compared to the precipitation state, and also causes a decrease in conductivity. Therefore, the Si content is preferably as close to the composition ratio of the precipitates Ni ₂ Si and X _m Si _n as possible. Therefore, the mass of Ni and the mass of X (when X is Co, the mass of Co, when X is Co, Fe, Cr, Mn, Ti, V, Zr, the total mass of all elements contained in X) ) And the mass ratio of the mass of Si (Ni + X) / Si 3-6, and preferably 3.5-5.0. Therefore, the Si content is in the range of 0.3 to 2.0% by mass, and preferably in the range of 0.5 to 1.2% by mass.

  If necessary, one or more elements selected from the group consisting of Sn, Zn, Mg, Al, B, P, Ag, Be, and Misch metal may be added to the copper alloy sheet. For example, Sn has an effect of improving stress relaxation resistance, and Zn has an effect of improving solderability and castability of a copper alloy sheet. Mg also has the effect of improving the stress relaxation resistance. In addition, Ag has the effect of developing solid solution strengthening without significantly reducing the electrical conductivity. P has a deoxidizing effect during melting and casting, and B has an effect of refining the cast structure and improving hot workability. Furthermore, misch metal, which is a mixture of rare earth elements such as Ce, La, Dy, Nd, and Y, has an effect of refining crystal grains and an effect of dispersing precipitates.

  In addition, when a copper alloy board | plate material contains 1 or more types chosen from the group which consists of Sn, Zn, Mg, Al, B, P, Ag, Be, and a misch metal, the effect which added each element is fully acquired. Therefore, the total amount of these is preferably 0.01% by mass or more. However, if the total amount exceeds 1% by mass, the electrical conductivity is lowered, hot workability or cold workability is adversely affected, and the cost is disadvantageous. Therefore, the total amount of these elements is preferably 1% by mass or less, and more preferably 0.5% by mass or less.

(Precipitate)
For Cu-Ni-X-Si based copper alloys (X is composed of one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V and Zr in addition to Co or Co), Ni-Si based precipitates, X-Si based precipitates, and Ni-X-Si based precipitates exist. In the conventional general manufacturing process, the ratio of Ni—X—Si based precipitates is large among them. In fact, when the precipitate confirmed by TEM observation is identified by TEM-EDS analysis, the Ni-Si-based precipitate is clearly coarser than the Ni-Si-based precipitate and X-Si-based precipitate. Many are observed within. Since such a coarse precipitate does not contribute to the strength improvement, it is necessary to reduce the abundance ratio.
Therefore, in the copper alloy sheet of the present invention, the number of precipitates observed per unit area is N, the number of Ni—Si based precipitates among the precipitates is N _N , and the number of X—Si based precipitates among the precipitates is N _X. In this case, the ratio of the number of Ni—Si based precipitates to the number of X—Si based precipitates satisfies Formula 1.

Here, by TEM-EDS (energy dispersive X-ray analysis) of the precipitate component, a precipitate containing 50 mass% or more of Ni is converted into a Ni-Si based precipitate, and a precipitate containing 50 mass% or more of X. Is an X-Si-based precipitate.
Further, a precipitate in which Ni is less than 50% by mass and X is less than 50% by mass is regarded as a Ni—X—Si based precipitate.

Furthermore, as described above, since the optimum precipitation temperature (for example, aging temperature) and optimum heat treatment time (aging time, precipitation time) of the Ni—Si based precipitate and the X—Si based precipitate are shifted, The particle size distribution of the two kinds of precipitates is greatly different, and the synergistic effect of improving the strength is lowered. In the copper alloy sheet of the present invention, any of the precipitates can be finely precipitated by the manufacturing method described later, and the difference in average particle diameter between the two precipitates can be reduced. Since X-Si based precipitates can be reduced, a copper alloy plate having a 0.2% proof stress exceeding 30% IACS and exceeding 880 MPa, which has not been obtained in the past, and further 35% IACS or more. It has a 0.2% proof stress of 900 MPa or more, has excellent bending workability and stress relaxation resistance at the same time while maintaining the conductivity and 0.2% proof stress, and has less anisotropy. Good Way and Bad Way Thus, it is possible to provide a copper alloy sheet having excellent bending workability.
Therefore, in the copper alloy sheet of the present invention, the average particle diameter of the Ni—Si-based precipitates observed per unit area is d _N , and the average particle diameter of the X-Si-based precipitates per unit area is d _X. Sometimes, as expressed by Equation 2, there is a small deviation between the precipitate particle sizes of the two.

  In the same manner as described above, these precipitates are identified by TEM-EDS (energy dispersive X-ray analysis) of a precipitate component. A precipitate containing 50% by mass or more of Ni is converted into a Ni-Si-based precipitate, A precipitate containing 50% by mass or more of X is defined as an X-Si based precipitate.

(Crystal orientation)
The {200} crystal plane ({100} <001> orientation) is called the Cube orientation, and has a plate thickness direction (direction perpendicular to the rolling surface) ND, a rolling direction LD, and a direction TD perpendicular to the rolling direction and the plate thickness direction. Similar characteristics are shown in the three directions. Also, both LD: <001> and TD: <010> can contribute to the slip. Furthermore, since the slip line on the {200} crystal plane has good symmetry with respect to the bending axis at 45 ° and 135 °, it can be bent without forming a shear band. That is, crystal grains having a Cube orientation are characterized by good GoodWay bending property and BadWay bending property and no anisotropy.
For this reason, it is preferable to have a crystal orientation satisfying Equation 3, and it is desirable to have a crystal orientation satisfying Equation 5.

Here, I {200} is the integrated intensity of the X-ray diffraction peak of the {200} crystal plane on the plate surface (rolled surface) of the copper alloy sheet, and I ₀ {200} is the {200} crystal plane of the pure copper standard powder. This is the integrated intensity of the X-ray diffraction peak.

  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 a Cube orientation under general process conditions in a copper alloy. However, in the present invention, as shown in the manufacturing process described later, by combining an intermediate annealing step under a specific condition and an appropriate solution treatment condition, a plate material having a crystal orientation satisfying the equations 3 and 5 is obtained. I was able to get it.

[Twin density]
The twin crystal refers to a pair of crystal grains in which the crystal lattice of two adjacent crystal grains is in a mirror-symmetrical relationship with respect to a certain plane (a twin boundary, which is generally a {111} plane). The most common twins in copper and copper alloys are the parts sandwiched between two parallel twin boundaries in the grains (called twin zones).
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, there is less disorder of atomic arrangement along the boundary than the grain boundary. It is dense and has properties such as diffusion of atoms, segregation of impurities, formation of precipitates, and failure to break along the boundary.
That is, the more twin boundaries, the more advantageous for improving stress relaxation characteristics and bending workability.

Therefore, it is preferable that the twin density _NG satisfies the equation (4), and it is even more preferable that the twin density satisfies the equation (6).

Here, _NG is the average twin density per crystal grain. D and D _T are an average crystal grain size D measured by using the cutting method of JIS H0501 without including a twin boundary, and an average crystal grain size D _T measured by regarding the twin boundary as a grain boundary. . For example, in the case of D = 2D _T and N _G = 1, it means that one twin per crystal grain on average.

  In face-centered cubic (fcc) copper alloys, twins are mostly formed during recrystallization, that is, annealed twins. The mechanism of the formation of annealing twins has not been elucidated at present, but the present inventors have investigated the state of alloying elements (solid solution or precipitation) before solution treatment (recrystallization) and solution treatment conditions. It turned out to be influenced. The final twin density is almost determined by the twin density in the stage after the solution treatment. Accordingly, the twin density can be controlled by the intermediate annealing conditions and the solution treatment conditions before the solution treatment described later.

[Average crystal grain size]
A smaller average crystal grain size is advantageous for improving the bending workability, but if it is too small, the stress relaxation resistance tends to deteriorate. 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 adjusted to be too small in the solution treatment step, the solute element is not sufficiently dissolved during the solution treatment, and the strength of the finally obtained copper alloy copper material is likely to be low. As a result of various studies, if the average grain size D finally measured using the cutting method of JIS H0501 without including the twin boundary is a value of 5 μm or more, preferably a value exceeding 8 μm, an in-vehicle connector or the like A stress relaxation resistance level that can be satisfied even in severe applications can be secured, which is preferable. However, if the average crystal grain size becomes too large, the surface of the bent portion is likely to be rough and may cause a decrease in bending workability. Therefore, the range is preferably 30 μm or less, and in the range of 8 to 20 μm. It is more preferable to adjust. The final average crystal grain size D 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.

[Characteristic]
In order to reduce the size and thickness of electrical / electronic components such as connectors, the 0.2% proof stress of the copper alloy sheet material is preferably 850 MPa or more, and more preferably 900 MPa or more. Moreover, in order to increase the strength by using age hardening, the copper alloy sheet has a metal structure that has been subjected to an aging treatment. Since connectors and the like have a bending process in their manufacturing process, the bending workability of the copper alloy sheet is such that the ratio R / t between the minimum bending radius R and the sheet thickness t in the 90 ° W bending test is good for both GoodWay and BadWay. It is preferably 1.0 or less, and more preferably 0.5 or less.
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, 30% IACS or more is necessary, 35% IACS or more is preferable, and conductivity of 40% IACS or more is more desirable.

  For stress relaxation resistance, since the value of TD is particularly important for applications such as in-vehicle connectors, stress relaxation using a test piece whose longitudinal direction is TD (direction perpendicular to the rolling direction LD and the plate thickness direction ND). It is desirable to evaluate the stress relaxation characteristics by the rate. It is preferable that the stress relaxation rate is 5% or less when the maximum load stress on the surface of the plate is 80% of 0.2% proof stress and held at 150 ° C. for 1000 hours.

[Production method]
The copper alloy sheet as described above can be produced by the embodiment of the method for producing a copper alloy sheet according to the present invention. An embodiment of a method for producing a copper alloy sheet according to the present invention includes a melting / casting process in which a raw material of a copper alloy having the above-described composition is melted and cast, and a hot rolling in which hot rolling is performed after the melting / casting process. A rolling process, a first cold rolling process in which cold rolling is performed after the hot rolling process, an intermediate annealing process in which heat treatment is performed at a heating temperature of 450 to 600 ° C. after the first cold rolling process, A second cold rolling step in which cold rolling is performed at a rolling rate of 70% or more after the intermediate annealing step, a solution treatment step in which solution treatment is performed after the second cold rolling step, and this solution treatment An aging treatment step of performing an aging treatment at 350 to 520 ° C. after the treatment step, and in the solution treatment step, a heating temperature is set to 800 to 1020 ° C., and then rapidly cooled to 500 to 800 ° C., 500 to 800 ° C. Hold for 10 to 600 seconds Process, comprising the step of quenching to then 300 ° C. or less.

  In the intermediate annealing step, the electrical conductivity before and after the intermediate annealing is Eb and Ea, the Vickers hardness is Hb and Ha, respectively, and Ea / Eb ≧ 1.5 and Ha / Hb ≦ 0.8 are satisfied. Thus, it is preferable to implement heat processing at 450-600 degreeC for 1 to 20 hours. Moreover, it is preferable to provide the finishing cold rolling process of 50% or less of rolling rate after the said aging process, and it is preferable to heat-process (low-temperature annealing) at 150-550 degreeC after a finishing cold rolling process. Further, after hot rolling, chamfering may be performed as necessary, and after heat treatment, pickling, polishing, and degreasing may be performed as necessary. Hereinafter, these steps will be described in detail.

(Melting and casting process)
A slab is produced by continuous casting or semi-continuous casting after the raw material of the copper alloy is melted by the same method as a general copper alloy melting method. Melting / casting is usually carried out in the atmosphere, but in order to prevent oxidation of the X element, it can also be carried out in an inert gas atmosphere or a vacuum melting furnace.

(Hot rolling process)
The hot-rolling of the slab is preferably performed in several to a dozen or more passes while the temperature is lowered from 900 ° C. or higher, desirably from 980 ° C. or higher 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. In addition, after hot working, chamfering or pickling may be performed as necessary.

(First cold rolling process)
In this cold rolling step, the rolling rate is preferably 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 process)
Next, an intermediate annealing process heat treatment is performed for the purpose of precipitation. In a normal manufacturing process, this intermediate annealing process is not performed, or is performed at a relatively high temperature at which the plate material is softened or recrystallized in order to reduce the rolling load in the next process. In either case, after the next solution treatment step, the formation of a recrystallized texture whose main orientation component is the density of annealing twins in the recrystallized grains and the {200} crystal plane (Cube orientation) becomes insufficient.

As a result of detailed investigations and studies by the present inventors, the formation of annealing twins and Cube orientation during the recrystallization process is affected by the stacking fault energy of the parent phase immediately before the recrystallization. The lower the stacking fault energy, the easier it is to form annealing twins. Conversely, when the stacking fault energy is high, the Cube orientation is likely to be formed. For example, the stacking fault energy decreases in the order of pure aluminum, pure copper, and brass, and the density of annealing twins increases, but the Cube orientation is difficult to form. That is, in a copper alloy whose stacking fault energy is close to that of pure copper, there is a high possibility that both the annealing twins and the density of the Cube orientation will be high.
In order to increase both the density of annealing twins and the Cube orientation, it can be achieved by reducing the amount of solid solution elements by precipitation of Ni, X, Si, etc. in the intermediate annealing process and increasing the stacking fault energy. The intermediate annealing step is performed in a temperature range of 450 to 600 ° C., and the heat treatment time is set in the range of 1 to 20 hours, and the heat treatment conditions are selected so as to obtain the intended annealing state.
When the annealing temperature is too low or the annealing time is too short, the amount of solid solution elements is high because of insufficient precipitation (insufficient recovery of conductivity), and the stacking fault energy is little increased. On the other hand, if the annealing temperature is too high, the solid solubility limit of the solid solution element also becomes high, and in this case, too much precipitation is insufficient.
Specifically, during the intermediate annealing step, the electrical conductivity before and after the intermediate annealing is Eb and Ea, the Vickers hardness is Hb and Ha, respectively, and Ea / Eb ≧ 1.5 and Ha / Hb ≦ 0.8. It is preferable to satisfy.
Moreover, since the Vickers hardness is softened to 80% or less by this intermediate annealing step, there is also an effect that the rolling load in the next step is reduced.

(Second cold rolling process)
Subsequently, the second cold rolling is performed. In this cold rolling, the rolling rate is preferably set to 70% or more. In this cold rolling process, strain energy can be efficiently introduced due to the presence of precipitates from the previous process. If the strain energy is insufficient, the recrystallized grain size generated during the solution treatment may be non-uniform, and the formation of the recrystallized texture having the {200} crystal plane as the main orientation component becomes insufficient. That is, the recrystallization texture depends on the dispersion state and amount of precipitates before recrystallization, and further on the rolling rate in cold rolling. The upper limit of the rolling rate in this cold rolling need not be specified, but since it has been softened by the previous process, it is possible to further perform strong rolling with a rolling rate of 80% or more.

(Solution treatment process)
The conventional solution treatment mainly aims at “re-solution dissolution of solute elements in a matrix” and “recrystallization”, but in the present invention, “formation of high density annealing twins” and “{200} Another important objective is the formation of a recrystallized texture having a main orientation component.
The solution treatment is preferably performed at 800 to 1020 ° C. for 10 seconds to 10 minutes depending on the components. If the temperature is too low, recrystallization will be incomplete and solute elements will not be sufficiently dissolved. Further, if the density of the annealing twins is low, the main orientation component of the {200} crystal plane tends to be low, and it becomes difficult to finally obtain a high-strength copper alloy sheet material excellent in bending workability. 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 this solution treatment, the ultimate temperature and the holding time in the range of 800 to 1020 ° C. are set so that the average crystal grain size of recrystallized grains (the twin boundary is not regarded as a grain boundary) is 5 to 30 μm. It is desirable to set and perform the heat treatment, and it is more preferable to adjust so as to be 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, 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 ultimate temperature and holding time in the range of 800 to 1020 ° C. can be set. Specifically, in an alloy having a chemical composition defined in the present invention, appropriate conditions can be set under heating conditions in which the alloy is held at a temperature of 800 to 980 ° C. for 10 seconds to 10 minutes.

(Cooling process after solution treatment)
In order to avoid the precipitation of the compound as much as possible during the cooling, the cooling after the solution treatment is generally rapidly cooled to a temperature at which no precipitation occurs. However, in the method described in this patent, a cooling pattern is used in which the sample is held for a certain time in a specific temperature range of the rapid cooling process and then rapidly cooled again. As described above, the optimal precipitation temperature and time of Ni-Si compound and X-Si compound do not match (displace), so that the two types of precipitates cannot be fully utilized at the same time. As a result, it is a cause that the high yield strength of 900 MPa or more, and further good bending workability and stress relaxation resistance cannot be realized at the same time. Therefore, in the temperature range in which the Ni—Si based compound hardly precipitates in advance, the X—Si based compound is used. In order to deposit finely, such a cooling pattern is used. Specifically, after performing the solution treatment at a heating temperature of 800 to 1020 ° C., the temperature range of 500 to 800 ° C. is 10 ° C./s or more, preferably 50 ° C./s or more, more preferably 100 ° C./s. It is rapidly cooled at the above cooling rate and held at a temperature range of 500 to 800 ° C. for 10 to 600 seconds, and then again to 300 ° C. or less, again 10 ° C./s or more, preferably 50 ° C./s or more, more preferably 100 ° C. / A cooling pattern that rapidly cools at a cooling rate of s or more is preferred. That is, the holding performed at 500 to 800 ° C. for 10 to 600 seconds is for finely depositing the X-Si compound in a temperature range where the Ni—Si compound is hardly precipitated. When the holding temperature is too high, the driving force for the precipitation of the X-Si compound is reduced, and the precipitates are reduced while being easily coarsened. On the other hand, if the holding temperature is too low, the X-Si compound takes a long time to precipitate, so substantially no precipitation occurs, and two types of precipitates are fully utilized at the same time as in the normal manufacturing method. Can not. Therefore, the above-mentioned number 1 cannot be satisfied, and finally it is impossible to satisfy all of the high proof stress of 900 MPa or more, the good bending workability and the excellent stress relaxation property while maintaining a good electrical conductivity. End up.

Further, if the holding time is too long, the X-Si based precipitates are likely to be coarsened, and if the heat treatment time is too short, the X-Si based precipitates are reduced.
Specifically, in an alloy having a chemical composition defined in the present invention, an appropriate condition can be set under the condition of holding at a temperature of 500 to 800 ° C. for 10 to 600 seconds. The condition of holding 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, more preferably 50 to 300 seconds is more preferable.
In addition, if the quenching is not performed in a temperature range higher and lower than 500 to 800 ° C., the former tends to cause the coarsening of crystal grains and the precipitation and coarsening of the X—Si compound, and the Ni—Si compound precipitates in the latter. -It will become coarse and will eventually fail to meet all of its high yield strength, good bending workability and excellent stress relaxation properties.

The above solution treatment and the subsequent cooling, holding, and cooling steps are carried out by modifying a solution treatment furnace composed of, for example, a normal heating zone and a cooling zone, so that a heating zone, a cooling zone, a heat retention zone, and a cooling zone can be used. It can be implemented in a solution treatment furnace composed of zones. The staying time of the heating zone and the heat insulation zone of the plate material can be controlled by adjusting the length of the zone and the plate passing speed. Further, 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 process)
Subsequently, an aging process is performed. In this aging treatment, precipitation of Ni—Si compounds is the main purpose. When the aging treatment temperature is too high, the Ni—Si based precipitates are likely to be coarsened, and at the same time, the X—Si based precipitates generated in the cooling step after the solution treatment are also easily coarsened. On the other hand, if the heating temperature is too low, the Ni—Si compound is not sufficiently precipitated, and the aging time becomes too long, 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 its peak due to aging according to the alloy composition. Specifically, the temperature is 350 to 520 ° C., preferably 400 to 500 ° C., more preferably 425 to 475 ° C. The aging treatment time is about 1 to 10 hours, and good results are obtained.

(Finish cold rolling process)
In this finish cold rolling, the strength level is improved and a rolling texture having a {220} crystal plane as a 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 ratio of finish cold rolling is too high, the rolling texture having the {220} crystal plane as the main orientation component becomes relatively dominant, and an intermediate crystal orientation that can achieve both strength and bending workability. Cannot be realized.

The rolling rate of this finish cold rolling is preferably 10% or more. However, the upper limit of the finish cold rolling ratio is preferably set so as not to exceed 50%, and more preferably 45% or less.
The final plate thickness is preferably about 0.05 to 1.0 mm, more preferably 0.06 to 0.5 mm.

(Low temperature annealing process)
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 usually good results are obtained within 1 hour.

  Hereinafter, examples of the copper alloy sheet material and the manufacturing method thereof according to the present invention will be described in detail.

  The raw materials having the compositions shown in Table 1 were melted and cast using a vertical semi-continuous casting machine to obtain slabs.

  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 100 ° 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%, an intermediate annealing heat treatment was performed at 520 to 570 ° C. for 6 to 8 hours, respectively.
The electrical conductivity before and after the intermediate annealing is Eb and Ea, the Vickers hardness is Hb and Ha, respectively, Ea / Eb is around 2.0 (1.8 to 2.5), and Ha / Hb is 0.5 Before and after (0.39 to 0.62). 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 treatment was performed by holding for a minute. The holding temperature and holding time in the solution 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 solution treatment, after quenching at a cooling rate of 15 ° C./s or more by immersion in a salt bath to a temperature of 700 ° C., holding at a temperature of 700 ° C. for 52 seconds, and then a cooling rate of 50 ° C./s or more. And cooled rapidly to room temperature (water cooling). Thereafter, an aging treatment was performed at 450 ° C. for 3 to 8 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 20 to 40%, respectively, and finally low temperature annealing was performed at 425 ° C. for 1 minute to obtain copper alloy sheet materials of Examples 1 to 11. In addition, chamfering was performed in the middle as needed, or the rolling rate was adjusted to 80 to 90% in the second cold rolling step, and the thickness of the copper alloy sheet was adjusted to 0.15 mm.

  Detailed process conditions are shown in Table 2.

  Next, a sample is taken from the obtained copper alloy sheet, and the TEM-EDS, crystal grain structure, X-ray diffraction intensity, conductivity, 0.2% proof stress, bending workability, and stress relaxation resistance are as follows. Examined.

Precipitates were observed at a magnification of 300,000 times using a transmission electron microscope (TEM) JEM-2010 manufactured by JEOL Ltd. Moreover, the component of the deposit was analyzed by EDS (energy dispersive X-ray analysis). A precipitate containing 50 mass% or more of Ni is a Ni-Si-based precipitate, a precipitate containing 50 mass% or more of X is an X-Si-based precipitate, and the number of all observed precipitates is N, Of the precipitates, the number of Ni—Si-based precipitates is N _N , the average particle size is d _N , and the number of X-Si-based precipitates of the precipitates is N _X , and the average particle size is d _X, and (N _N + N _X ) / N, and the ratio of the absolute value of the difference between the average particle diameters of the Ni—Si based precipitate and the X—Si based precipitate to the average particle diameter of the Ni—Si based precipitate | d _N −d _X | / d _N Asked.
X is Co when the raw material of the copper alloy sheet is Cu, Ni, Co, Si and inevitable impurities, and the raw material of the copper alloy sheet is Cu, Ni, Co, Si and further Fe, Cr, Mn, Ti, When it is one or more elements selected from the group consisting of V and Zr and inevitable impurities, X is Co, Fe, Cr, Mn, Ti, V, and Zr.

The surface of the rolled plate was polished and etched, the surface was observed with an optical microscope, and the average crystal grain size was determined by the cutting method of JIS H0501. N _G = (D−D _T ) / D _T is used from the average crystal grain size D measured without including the twin boundary and the average crystal grain size D _T measured by regarding the twin boundary as the grain boundary. Twin density was determined.

The X-ray diffraction intensity (X-ray diffraction integrated intensity) was measured using an X-ray diffractometer (XRD) under the conditions of Mo-Kα1 and Kα2 rays, tube voltage 40 kV, tube current 30 mA (rolling). Plane), the integrated intensity I {200} of the diffraction peak of the {200} plane was measured. Further, using the same X-ray diffractometer as described above, the X-ray diffraction intensity of the {200} plane of pure copper standard powder was measured under the same measurement conditions as described above. Using these measured values, the X-ray diffraction intensity ratio I {200} / I ₀ {200} shown in Equation 3 was determined.

  The conductivity of the copper alloy sheet was measured according to the conductivity measurement method of JIS H0505.

  As a 0.2% proof stress of the copper alloy sheet, three specimens for tensile test of LD (rolling direction) of the copper alloy sheet (sample No. 5 of JIS Z2241) were sampled and tensile according to JIS Z2241. The test was conducted, and the 0.2% yield strength was determined by the average value.

  In order to evaluate the bending workability of the copper alloy sheet material, a bending test piece (width 10 mm) whose longitudinal direction is LD (rolling direction) and TD (direction perpendicular to the rolling direction and sheet thickness direction) from the copper alloy sheet material Three bending test pieces (width 10 mm) were sampled, and a 90 ° W bending test based on JIS H3110 was performed on each test piece. 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. Among the three test pieces of LD and TD, the result of the worst test piece was adopted to obtain the R / t value.

A bending test piece (width: 10 mm) having a longitudinal direction of TD was taken from each test material, and arch-bending was performed so that the surface stress of the central portion in the longitudinal direction of the test piece was 80% of 0.2% proof stress. Fixed in state. The surface stress (MPa) is determined 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 (%) was calculated as (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.
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 evaluation results such as precipitates, average crystal grain size, X-ray diffraction intensity, electrical conductivity, strength (0.2% yield strength), bending workability, and stress relaxation resistance.

  As shown in Table 3, in Examples 1 to 11 of the present invention, 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 and plate Bending workability with a ratio R / t of thickness t of 1.0 or less.

[Comparative Example 1]
A copper alloy sheet produced under the same process conditions as in Example 2 except that a copper alloy having the same composition as in Example 2 was used, and the solution was rapidly cooled to room temperature at 15 ° C./s after the solution treatment.
| D _N −d _X | / d _N related to the number 2 of the obtained copper alloy sheet was as high as 76%, which was outside the scope of the present invention.
In the aging treatment at 450 ° C. for 6 hours, there were few Co—Si based precipitates, and as a result, both conductivity and 0.2% proof stress were low.

[Comparative Example 2]
A copper alloy sheet was produced in the same process as in Comparative Example 1 except that the aging temperature of Comparative Example 1 was aged for 6 hours at 500 ° C., which is considered to be the optimum aging temperature of the Co—Si compound.
| D _N −d _X | / d _N related to the number 2 of the obtained copper alloy sheet was 43%, which is outside the range of the present invention, and the Ni—Si based precipitates were already coarsened.
As a result, the conductivity and 0.2% proof stress were higher than those of Comparative Example 1. However, the 0.2% proof stress was 783 MPa, which was significantly inferior to the alloy of the present invention.

[Comparative Example 3]
A copper alloy sheet was produced in the same process as in Comparative Example 1 except that a copper alloy having the same composition as Comparative Example 1 was used and the aging temperature was aging at 475 ° C., which was about the middle of Comparative Examples 1 and 2.
It is estimated that (N _N + N _x ) / N related to the number 1 of the obtained copper alloy sheet is as low as 54%, and the proportion of Ni—Co—Si based precipitates that are likely to be coarsened is relatively high.
Although the 0.2% proof stress was improved to 839 MPa, it was lower than Example 2 by about 60 MPa. The cause is considered to be a high proportion of the Ni-Co-Si-based precipitates that are likely to be coarsened.

[Comparative Example 4]
In Comparative Example 4, a raw material having a composition of 1.46% by mass of Ni, 0.82% by mass of Si, 2.46% by mass of Co, the balance Cu and inevitable impurities was melted, and a vertical semi-continuous casting machine was prepared. The slab was obtained by casting.
Since Co exceeds 2.0 mass and the addition amount is too large, coarse crystals formed during the casting process are not dissolved during heating before hot rolling, so cracks violently during hot rolling The subsequent process was interrupted.

[Comparative Example 5]
In Comparative Example 5, a raw material having a composition comprising 1.56% by mass of Ni, 0.98% by mass of Si, 0.51% by mass of Co, 2.03% by mass of Cr, the balance Cu and unavoidable impurities is melted. The slab was obtained by casting using a vertical semi-continuous casting machine.
Since Cr exceeds 2.0 mass and the addition amount is too large, the coarse crystallized product formed during the casting process is not dissolved during heating before hot rolling. The subsequent process was interrupted.

[Comparative Example 6]
A copper alloy sheet having the same composition as in Example 2 was used, and a copper alloy sheet was produced by the same manufacturing method as in Example 2 except that the intermediate annealing conditions were different. As a result, the conductivity was 46.2% IACS and the 0.2% proof stress was 891 MPa. However, since the conditions for the intermediate annealing were not appropriate, both I {200} / I ₀ {200} and the intragranular twin density _NG decreased, resulting in BW bending workability and stress relaxation. Both characteristics deteriorated.

[Comparative Example 7]
In Comparative Example 7, 1.80% by mass of Ni, 0.75% by mass of Si, 1.45% by mass of Co, 0.2% by mass of Cr, 0.05% by mass of Mg, the balance Cu and inevitable impurities A copper alloy having a composition as described above was cast in the same manner as in Example 1, then heated to 1000 ° C. and hot-rolled while lowering the temperature to 900 ° C. to form a plate material having a thickness of 10 mm, and then water-cooled (100 ° C. / (cooling rate of s or more) and then the surface oxide layer was removed (faced) by mechanical polishing.
Subsequently, it was set as the board of thickness 0.3mm by cold rolling. Next, solution treatment was performed at 950 ° C. for 2 minutes, and the solution was cooled to 400 ° C. or lower at a cooling rate (gas cooling) of about 20 ° C./s, and then cooled to room temperature. Thereafter, it was cold-rolled to 0.15 mm and finally subjected to aging treatment at 500 ° C. for 3 hours. As a result, the conductivity was 46.2% IACS and the 0.2% yield strength was 897 MPa. However, there was no intermediate annealing, and there was no precipitation control of X-Si based precipitates at 500 to 800 ° C. in the cooling process after solutionization. As a result, the ratio of the precipitates was outside the scope of the present invention. Both I {200} / I ₀ {200} and intragranular twin density _NG were lowered, and both BW bending workability and stress relaxation resistance were deteriorated.

The compositions and production conditions of these examples and comparative examples are shown in Table 1 and Table 2, respectively. Table 3 shows the evaluation results for the structure and characteristics.
From the above, Comparative Examples 1 to 7 cannot be provided with the configuration of the copper alloy sheet of the present invention due to inappropriate composition, manufacturing process, or process conditions, and any of the comparative examples is an example. It turned out that the characteristic is greatly inferior compared with 1-11.

Claims (14)

A copper alloy containing 0.8 to 3.5% by mass of Ni, 0.3 to 2.0% by mass of Si, 0.5 to 2.0% by mass of Co, with the balance being Cu and inevitable impurities. When X is Co, the ratio of the mass of X to the mass of Ni, X / Ni is in the range of 0.3 to 1.5, the ratio of the mass of Ni, the mass of X, and the mass of Si (Ni + X ) / Si is in the range of 3 to 6, the number of precipitates per unit area is N, the number of Ni—Si based precipitates among the precipitates is N _N , the average particle size is d _N , and the number X− When the number of Si-based precipitates is N _X and the average particle size is d _X , the number of precipitates satisfying the following Equation 1 and the average particle size of precipitates satisfying the following Equation 2 and the crystal orientation satisfying the following Equation 3 A copper alloy sheet having a 0.2% proof stress of 900 MPa or more and an electrical conductivity of 30% IACS or more.

Here, by TEM-EDS (energy dispersive X-ray analysis) of the precipitate component, a precipitate containing 50 mass% or more of Ni is converted into a Ni-Si based precipitate, and a precipitate containing 50 mass% or more of X. Is an X-Si-based precipitate.

Here, I {200} is the integrated intensity of the X-ray diffraction peak of the {200} crystal plane on the surface of the copper alloy sheet, and I ₀ {200} is the X-ray diffraction peak of the {200} crystal plane of the pure copper standard powder. Is the integrated intensity of. One or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr are included in a total range of 2.0% by mass or less, and X is added to Co, Fe, Cr, Mn, Ti, V The copper alloy sheet according to claim 1, comprising Zr. 3. The copper alloy sheet according to claim 1, wherein an average crystal grain size D measured on the surface of the sheet without using twin boundaries is 5 to 30 μm using a cutting method of JIS H0501. The copper alloy sheet according to claim 1, 2 or 3, having an intragranular twin density that satisfies the following formula 4.

Here, _NG is the average twin density per crystal grain. D and D _T are an average crystal grain size D measured by using the cutting method of JIS H0501 without including a twin boundary, and an average crystal grain size D _T measured by regarding the twin boundary as a grain boundary. . The said copper alloy board | plate material has a composition which further contains 1 or more types of elements chosen from the group which consists of Sn, Zn, Mg, Al, B, P, Ag, Be, and a misch metal in the range of a total of 1 mass% or less. Item 5. A copper alloy sheet according to item 1, 2, 3 or 4. Copper having a composition containing 0.8 to 3.5 mass% Ni, 0.3 to 2.0 mass% Si, 0.5 to 2.0 mass% Co, the balance being Cu and inevitable impurities A melting and casting process for melting and casting an alloy raw material, a hot rolling process for performing hot rolling after the melting and casting process, and a first cold for performing cold rolling after the hot rolling process A rolling process, an intermediate annealing process in which heat treatment is performed at a heating temperature of 450 to 600 ° C. after the first cold rolling process, and a second cold in which cold rolling is performed at a rolling rate of 70% or more after the intermediate annealing process. An intermediate rolling step, a solution treatment step for performing a solution treatment after the second cold rolling step, and an aging treatment step for performing an aging treatment at 350 to 520 ° C. after the solution treatment step, In the solution treatment step, the heating temperature is set to 800 to 1020 ° C. In the step of rapid cooling to 500 to 800 ° C., the step of holding 10 to 600 seconds at 500 to 800 ° C., the manufacturing method of the copper alloy sheet, characterized in that it comprises a step of quenching thereafter until 300 ° C. or less. In the intermediate annealing step, the electrical conductivity before and after the intermediate annealing is Eb and Ea, and the Vickers hardness is Hb and Ha, respectively, so that Ea / Eb ≧ 1.5 and Ha / Hb ≦ 0.8 are satisfied. The method for producing a copper alloy sheet according to claim 6, wherein the heat treatment is performed at 450 to 600 ° C. for 1 to 20 hours. In the said solution treatment process, the average crystal grain diameter after solution treatment is 5-30 micrometers, The manufacturing method of the copper alloy board | plate material of Claim 6 or 7. The method for producing a copper alloy sheet according to claim 6, 7 or 8, further comprising a finish cold rolling step in which cold rolling is performed at a rolling rate of 50% or less after the aging treatment step. The method for producing a copper alloy sheet according to claim 9, further comprising a low-temperature annealing step in which heat treatment is performed at 150 to 550 ° C after the finish cold rolling step. The copper alloy sheet has a composition further including one or more elements selected from the group consisting of Fe, Cr, Mn, Ti, V, and Zr in a total range of 2.0% by mass or less. The method for producing a copper alloy sheet according to claim 6, 7, 8, 9 or 10. The copper alloy sheet has a composition further containing one or more elements selected from the group consisting of Sn, Zn, Mg, Al, B, P, Ag, Be, and Misch metal in a total range of 1% by mass or less. The method for producing a copper alloy sheet according to claim 6, 7, 8, 9, 10 or 11. An electrical / electronic component using the copper alloy sheet according to claim 1 as a material. The electrical / electronic component according to claim 13, wherein the electrical / electronic component is a connector, a socket, a lead frame, a relay, or a switch.