KR101813372B1 - Copper alloy - Google Patents

Abstract

[PROBLEMS] A copper alloy exhibiting high strength, high electrical conductivity and excellent bending workability and exhibiting an excellent stress relaxation property even more than the prior art is realized.
[MEANS FOR SOLVING PROBLEMS] The steel sheet contains 0.005 to 0.15% in total of at least one element selected from the group consisting of Ti: 0.1 to 0.1%, Cr: 0.1 to 0.4%, Si: Copper and inevitable impurities, and the average particle diameter of the particle size distribution of the precipitate measured by the X-ray small angle scattering method is not less than 2.0 nm and not more than 7.0 nm, and the normalized dispersion of the particle size distribution is in the range of 30 to 40% Copper alloy.

Description

Copper alloy {COPPER ALLOY}

The present invention relates to a copper alloy. In particular, the present invention relates to a copper alloy exhibiting high strength, high electrical conductivity, excellent bending workability and excellent stress relaxation characteristics.

2. Description of the Related Art In recent years, along with the demand for downsizing and weight reduction of electronic devices, electric systems of electric and electronic parts have been complicated and highly integrated, and various kinds of materials for electric and electronic parts have been made thin and capable of enduring complicated shapes Is required. For example, in a material for electrical and electronic parts used in a current-carrying part such as a connector, a lead frame, a relay, and a switch that constitute an electric / electronic part, the sectional area of a material subjected to the same load is reduced , And the cross-sectional area of the material with respect to the amount of electricity is also reduced. Therefore, it is required to have a high strength capable of withstanding the stress imparted at the time of assembling or operating the electric / electronic equipment, a high conductivity for the purpose of suppressing the generation of joule heat due to energization, Excellent bending workability which does not cause fracture or the like even if it is processed is required.

A Cu-Cr-Ti-Si alloy and a production method thereof are proposed in, for example, Patent Documents 1 to 3 as a copper alloy having improved high strength, high electrical conductivity and bending workability.

Patent Document 1 proposes alloys of copper, chromium, titanium, and silicon in which the amount of chromium, the amount of titanium, and the amount of silicon are specified. In addition, as a manufacturing condition of the alloy, after alloying is performed at a temperature of 850 캜 to 950 캜 Rolled at one or more times under a temperature from 600 ° C to 830 ° C and cooled to room temperature at a cooling rate of from 10 ° C per minute to 2000 ° C per minute, Hot rolling, cold rolling, annealing, and tempering.

In Patent Document 2, the Cr amount, the Ti amount, the Si amount, the mass ratio of Cr and the Ti, the mass ratio of Cr and Si are specified, and the Cr, Ti and Si Of the copper alloy has a circle equivalent diameter of 300 nm or more as observed by a scanning electron microscope in a region of 25 占 퐉 in the thickness direction and 40 占 퐉 in the cross sectional direction from the copper alloy surface in the transverse cross section of the copper alloy in the cross- There is proposed a copper alloy in which the number of precipitates is 50 or less and the average circle equivalent diameter of precipitates having a circle equivalent diameter of less than 300 nm observed by a transmission electron microscope on the surface of the copper alloy is 15 nm or less. Also in Patent Document 3, the Cr amount, the amount of Ti, the amount of Si, the mass ratio of Cr and Ti, the mass ratio of Cr and Si are specified, and the surface of the copper alloy is observed with a transmission electron microscope There has been proposed a copper alloy having 200 or more precipitates having a circle-equivalent diameter of 5 nm or less in a region of 500 nm x 500 nm observed by the present invention.

As a copper alloy having a composition different from that of the Cu-Cr-Ti-Si alloy, for example, Patent Document 4 proposes a Cu-Cr-Zr-Si alloy. The Cu alloy contains Zr and Cr, the balance of Cu and inevitable impurities, and has a tensile strength of 600 N / mm ² or more, a conductivity of 75% IACS or more, and a longitudinal direction of the Cu alloy The ratio R / t of the minimum bending radius R and the thickness t of the copper alloy plate which does not cause cracking after the bending test of 90 占 bending test in accordance with JIS H3110 is less than 1.0. This Cu alloy also improves the high strength, high conductivity and bending workability.

Patent Document 5 proposes a precipitation hardening type copper alloy foil capable of improving both strength and ductility. This copper alloy foil is a Cu-Cr-Zr based copper alloy and has a structure in which the cross section perpendicular to the rolling direction is (1) the crystal grain size of the parent phase in the region of 600 nm 占 400nm is 50 占 퐉 or less, (2) Cr, or Zr, the arithmetic average value of the largest diameter of the crystal grain size is 15 nm or less; (3) the number of precipitates in the region of 900 nm ² 5 or more.

Japanese Patent No. 2515127 Japanese Patent Application Laid-Open No. 2013-173986 Japanese Patent Application Laid-Open No. 2014-114485 Japanese Patent Application Laid-Open No. 1262776 Japanese Patent Application Laid-Open No. H9-92368 Japanese Patent Application Laid-Open No. 2012-214882

However, when a copper alloy is used as a spring in a vehicle environment, there is a problem that exposure to a temperature higher than room temperature causes a stress relaxation phenomenon to occur and a spring holding force is lowered. However, in the above Patent Documents 1 to 3, the strength, the conductivity, and the bending workability of the copper alloy are considered, but the improvement of the stress relaxation resistance has not been studied. In addition, in the above Patent Documents 4 and 5, improvement of the internal stress relaxation property has not been studied.

Patent Document 6 discloses a copper alloy which is capable of improving the stress relaxation resistance in consideration of the use for electric parts and the like for automotive applications in addition to the above strength and the like. Patent Document 6 discloses a copper alloy having a Cr content, a Ti content, a Si content, And a copper alloy which does not have a recrystallized structure has been proposed. In recent years, however, it is required to exhibit higher stress relaxation resistance characteristics.

The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a copper alloy which exhibits high strength, high electrical conductivity and excellent bending workability and exhibits stress relaxation resistance superior to conventional ones.

The copper alloy according to the present invention capable of solving the above problems is characterized in that it comprises 0.15 to 0.4% of Cr, 0.01 to 0.1% of Si, and at least one kind of element selected from the group consisting of Ti and Zr, 0.005 to 0.15%, the balance of copper and inevitable impurities, and the average particle size of the particle size distribution of the precipitate measured by the X-ray small angle scattering method is 2.0 nm or more and 7.0 nm or less, And the standardized dispersion is in the range of 30 to 40%.

The copper alloy may further include at least one of the following (a) to (c) as another element.

(a) at least one element selected from the group consisting of Fe, Ni and Co, in mass%: more than 0% and not more than 0.3%

(b) In terms of% by mass, Zn: more than 0% and not more than 0.3%

(c) at least one element selected from the group consisting of Sn, Mg and Al, in mass%: more than 0% and not more than 0.3%

According to the present invention, it is possible to provide a copper alloy which exhibits high strength, high conductivity and excellent bending workability and exhibits excellent stress relaxation property by micronizing the precipitate and controlling the particle size distribution of the precipitate as compared with the prior art .

The present inventors have conducted intensive studies in order to solve the above problems. That is, in the techniques of Patent Documents 2 to 6 described above, the amount of the coarse compound and the average size of the precipitates are controlled, but in order to further improve the stress relaxation property in addition to the strength, the conductivity and the bending workability, It is necessary to study the form of the precipitate to be precipitated as a compound of Cr and Si, a compound of Ti and Si, a compound of Zr and Si, a compound of Ti and Zr and Si, And the like were examined from various aspects. As a result, on the basis of the particle size distribution of the precipitate when measured by the X-ray small angle scattering method, the average particle diameter of the particle size distribution is fine and within a certain range, and further, the normalized dispersion of the particle size distribution is within a certain range , The above characteristics can be achieved, and the present invention has been completed.

First, the form of this precipitate will be described.

The specification of the precipitate form in the present invention is based on the particle size distribution of the precipitate measured by the small angle scattering measurement method using X-ray as described above. For example, in the case of observing with a transmission electron microscope disclosed in the above Patent Document 3, the average size can be measured, but the size distribution can not be measured due to the contrast between the excessively fine and the dislocation. On the other hand, in the present invention, as described later, the X-ray small angle scattering method which can accurately measure the particle size distribution even if the precipitate is fine is used. Hereinafter, the X-ray small angle scattering method will be described.

The incineration scattering method itself using X-ray has been known for a long time as a representative method of investigating the structure information of a nanometer order. When the substance is irradiated with X-rays, the incident X-rays reflect the information of the electron density distribution inside the substance, and scattered X-rays are generated around the incident X-rays. For example, when a particle or a region having a non-uniform electron density exists in a material, X-rays interfere with each other regardless of crystal or amorphous state, and scattering as a density fluctuation occurs. If this is a metal such as a copper alloy, if minute particles of nanometer order are present in the copper alloy structure, scattering originating from the particles can be observed.

For example, in Japanese Patent Application Laid-Open No. 2014-62284, the X-ray small angle scattering method is used for measuring the average size and standardized dispersion of precipitates, which affects the strength of the Al-Zn-Mg based aluminum alloy.

However, the observed scattering is a combination of scattering due to precipitates and scattering due to dislocations. As described in Japanese Patent Application Laid-Open No. 2014-62284, when the addition Zn or Mg is large in several percent and the scattering as the precipitate is sufficiently large as compared with the scattering as the dislocation, the scattering from the dislocation can be neglected. However, even in the case of Cr, which is the essential component having the highest content such as the copper alloy of the present invention, when the content thereof is as small as 0.4% or less, that is, when the amount of precipitate is small and the scattering caused by the precipitate is small, I can not.

Thus, for the evaluation of the precipitates, small angle scattering measurement using the ideal dispersion was performed. The ideal incoherent scattering is a technique of obtaining only the scattering due to the precipitate by changing the energy of the X-ray in the energy near the absorption end (edge), for example, "radiation" vol. 19, No. 6, 419-427.

In order to measure the average particle diameter of the fine particle size distribution of the copper alloy structure and the normalized dispersion showing the expansion of the particle size distribution, the X-ray scattering intensity profile of the copper alloy plate measured by the X-ray small angle scattering method . The X-ray scattering intensity profile is obtained, for example, as a wavenumber vector q whose unit is nm ^-1 , where the vertical axis is the scattering intensity of the X-ray, that is, the scattering intensity of the scattered X-ray and the horizontal axis is the wavelength? At the measurement angle 2 ?. The scattering intensity of the X-ray used the difference in scattering intensity measured at 5720 eV, which is lower than the Cr absorption edge, from the scattering intensity measured at 5985 eV, which is higher than the Cr absorption edge.

The average particle diameter of the particle size distribution of the fine precipitates to be subjected in the present invention and the normalized dispersion indicating the expansion of the particle size distribution can be obtained from the scattering intensity profile of the X-ray. That is, fitting is performed by the nonlinear least squares method so that the scattering intensity of the measured X-ray and the X-ray scattering intensity calculated from the theoretical expression expressed by a function of the particle diameter and the size distribution become close to each other, whereby the particle diameter and the normalized dispersion value Can be obtained.

As an analysis method and analysis software for obtaining the particle size distribution of the fine precipitates by analyzing the scattering intensity profile of such X-rays, there may be mentioned, for example, a known analysis method by Schmidt et al., For example, I. S. Fedorova and P. Schmidt: J. Appl. Cryst. 11, 405, 1978 can be used.

The copper alloy of the present invention has an average particle diameter of the particle size distribution of the precipitate measured by the X-ray small angle scattering method within the range of 2.0 nm or more and 7.0 nm or less. The average particle diameter of the particle size distribution of this precipitate particularly affects strength and conductivity. In order to ensure high strength, the average particle diameter is set to 7.0 nm or less. The average particle diameter is preferably 6.5 nm or less, and more preferably 6.0 nm or less. On the other hand, if the average particle diameter is too small, precipitates are not sufficiently generated and the conductivity tends to be lowered. Therefore, the average particle diameter should be 2.0 nm or more. The average particle diameter is preferably 3.0 nm or more, and more preferably 3.5 nm or more.

In the copper alloy of the present invention, the normalized dispersion of the particle size distribution satisfies 30 to 40%. The normalized dispersion is a parameter obtained by normalizing the expansion of the particle size distribution by the average particle diameter as shown in the following equation (1). By using this normalized dispersion, the enlargement of the particle distribution can be compared regardless of the average particle diameter of each sample. In Equation (1),? Is a normalized dispersion, n is the number of particles, x _i is a particle diameter, and <x> is an additive average of the particle diameter.

The inventors of the present invention have found that by controlling the normalized dispersion value indicating the average particle diameter of the particle size distribution of the precipitate and the size distribution of the particle size of the precipitate to a predetermined range, the balance of strength, conductivity, stress relaxation resistance and bending workability . Since the precipitates are continuously produced and grown, if the precipitation occurs sufficiently, the value of normalized dispersion becomes large. In other words, when the value of the normalized dispersion is too small, precipitation does not occur sufficiently, and the strength, the conductivity, and the stress relaxation resistance tend to be lowered easily. On the other hand, when the value of the normalized dispersion is excessively large, it is presumed that precipitates are formed in processes other than the final aging, and that compounds of various sizes exist. Therefore, when the value of the normalized dispersion is too large, the strength and the bending workability tend to deteriorate easily.

As shown in Examples to be described later, it is necessary to set the value of the normalized dispersion to 30 to 40% in order to secure strength, conductivity, stress relaxation resistance and bending workability at a certain level or more. The value of the normalized dispersion is preferably 32 to 38%, more preferably 32 to 36%.

Next, the composition of the copper alloy of the present invention will be described below. On the other hand, in the composition of the components,% means% by mass.

(Cr: 0.15 to 0.4%)

Cr is an element that improves the strength of the copper alloy by precipitating as a compound of the metal Cr or a compound of Si, Ti, and Zr. If the Cr amount is less than 0.15%, it is difficult to secure the strength because the amount of precipitate is too small. If the amount of Cr is insufficient, the precipitated amount of Cr precipitated as a compound of Si, Ti, and Zr decreases, and as a result, the solid solution Ti, solid solution Zr and solid solution Si increase and the conductivity decreases. Therefore, the amount of Cr is 0.15% or more. The amount of Cr is preferably 0.20% or more, and more preferably 0.25% or more. On the other hand, when the amount of Cr exceeds 0.4%, the solid Cr is excessively adversely affected, and the bending workability is adversely affected. The conductivity is also reduced. Therefore, the amount of Cr should be 0.4% or less. The amount of Cr is preferably 0.35% or less.

(Si: 0.01 to 0.1%)

Si is an element contributing to the improvement of the strength of the copper alloy by precipitating a compound of Cr, Ti and Zr. If the amount of Si is less than 0.01%, the amount of precipitate becomes too small, and it becomes difficult to secure a desired strength. Therefore, the amount of Si should be 0.01% or more. The amount of Si is preferably 0.015% or more. On the other hand, when the amount of Si exceeds 0.1%, Si easily forms coarse creations with Cr, Ti and Zr. As a result, the strength tends to be lowered, and the bending workability is adversely affected. If the amount of Si is excessive, the amount of solute Si also increases and the conductivity is also reduced. Therefore, the amount of Si should be 0.1% or less. The amount of Si is preferably 0.08% or less, and more preferably 0.07% or less.

(At least one element selected from the group consisting of Ti and Zr: 0.005 to 0.15% in total)

Ti and Zr precipitate as a compound of Cr and Si, thereby improving the strength and stress relaxation resistance of the copper alloy. Ti and Zr are elements having an effect of lowering solubility of Cr and Si and promoting their precipitation. In order to sufficiently exhibit these effects, in the present invention, the total content of Ti and Zr is 0.005% or more. The total content of Ti and Zr is preferably 0.02% or more, and more preferably 0.030% or more. On the other hand, if the total content of Ti and Zr exceeds 0.15%, the amount of solid solution Ti and solid solution Zr becomes excessively large and the conductivity tends to be lowered. Also, the bending workability tends to deteriorate. Therefore, the total content of Ti and Zr should be 0.15% or less. The total content of Ti and Zr is preferably 0.09% or less, more preferably 0.080% or less. One kind of Ti and Zr may be used or may be used in combination. On the other hand, when the total content is Ti or Zr alone, the total content is the only content, and when the total content is two kinds, the total content.

The present invention meets the above composition and the balance is copper and inevitable impurities. Examples of the inevitable impurities include elements such as Mn, Ca, V, Nb, Mo and W. [ If the content of the inevitable impurities increases, the strength, the conductivity, the bending workability, and the like may decrease. Therefore, the total amount is preferably 0.1% or less, more preferably 0.05% or less.

The copper alloy of the present invention may further include the following elements.

(At least one element selected from the group consisting of Fe, Ni and Co: not less than 0% and not more than 0.3% in total)

Fe, Ni and Co precipitate a compound with Si to improve the strength and conductivity of the copper alloy. The same effect can be obtained even when Fe, Ni or Co is contained in any combination of Fe-Ni, Fe-Co and Ni-Co. do. That is, these elements may be used alone, or two or more kinds may be used. In order to effectively exhibit the above effect, the total content of the elements is preferably 0.01% or more, and more preferably 0.015% or more. On the other hand, when the total content of the above elements exceeds 0.3%, the amount of the excess amount is too large, and the conductivity is lowered. If the total content of the above elements is excessive, these elements are likely to form a coarse compound with Cr, Ti, and Zr, and the value of normalized dispersion becomes large, which adversely affects the strength and bending workability. Therefore, the total content of the above elements is preferably 0.3% or less, more preferably 0.2% or less. On the other hand, the total content of the above elements is the content of Fe, Ni and Co alone, and the total content of Fe, Ni and Co.

(Zn: more than 0% to 0.3% or less)

Zn is an element effective for improving heat peelability of Sn plating and solder used for joining electronic components and suppressing heat peeling. In order to effectively exhibit this effect, it is preferable that Zn is contained by 0.01% or more. On the other hand, when the amount of Zn is excessive, the conductivity is excessively low, so that the amount of Zn is preferably 0.3% or less. The amount of Zn is more preferably 0.1% or less.

(At least one element selected from the group consisting of Sn, Mg and Al: more than 0% and not more than 0.3% in total)

Sn, Al, and Mg are elements that increase strength by employment. These elements may be used alone, or two or more kinds may be used. In order to effectively exhibit the above effect, the total content of the elements is preferably 0.01% or more. On the other hand, if the total content of the above elements is excessive, the conductivity becomes too low or the bending workability decreases. Therefore, the total content of the above elements is preferably 0.3% or less, more preferably 0.1% or less. On the other hand, the total content of the above elements is the content by itself when Sn, Mg, and Al are contained alone, and the total content when containing a plurality of these elements.

Next, preferable manufacturing conditions of the copper alloy of the present invention will be described.

First, an ingot obtained by melting and casting a copper alloy whose composition has been adjusted is melted and then subjected to hot rolling (including a soaking treatment), followed by cold rolling, and then subjected to aging treatment , The final copper alloy of the present invention is produced.

Dissolution, casting and subsequent heat treatment of the copper alloy can be carried out by a conventional method. For example, after a copper alloy adjusted to a predetermined chemical composition is dissolved in an electric furnace, a copper alloy ingot is cast by continuous casting or the like. Thereafter, the heat treatment is carried out by heating the ingot to about 800 to 1000 占 폚 and holding it for a predetermined time, for example, for 10 to 120 minutes, if necessary.

In the present invention, the reduction rate of the hot rolling is not particularly limited, and it may be determined according to the relationship between the target plate thickness and the reduction rate of the cold rolling in the subsequent process. On the other hand, hot rolling can be carried out once or plural times.

In the present invention, for the purpose of obtaining a structure showing the above-described particle size distribution, in order to produce fine precipitates by the aging treatment as a later step, the amount of solid solution Cr, solid solution Ti, solid solution Zr in the copper alloy after hot rolling is increased It is important. Concretely, in order to increase the amount of solid solution Cr, the amount of solid solution Ti and the amount of solid solution Zr, (A) the end temperature of hot rolling is set to 800 ° C or higher, or (B) . In the case of (A) above, the end temperature of hot rolling is more preferably 830 캜 or higher. In the case of (B) above, the solution treatment temperature is more preferably 830 ° C or higher, more preferably 850 ° C or higher, and the upper limit is approximately 1000 ° C. The solution treatment time may be, for example, about 10 seconds to 30 minutes.

After the hot rolling of (A), it is preferable to quench to room temperature even after the solution treatment of (B). If the cooling rate after the hot rolling is low, coarse precipitates are formed in the cooling process, and even if the aging treatment is performed, fine precipitates are not sufficiently generated and a desired structure can not be obtained. In the present invention, quenching refers to cooling at an average cooling rate exceeding air cooling, preferably 20 ° C / second or more. The upper limit of the average cooling rate is not particularly limited, but is preferably about 500 DEG C / second or less in consideration of practical operation. The quenching means is not particularly limited, and various known cooling means such as water cooling may be employed.

The conditions of the cold rolling are not particularly limited, and general conditions can be employed. For example, it can be performed at a cold rolling rate of 80 to 99%. The number of times of rolling is not particularly limited.

After the cold rolling, the aging treatment is carried out. In the present invention, it is also important to make the holding time of the aging treatment prolonged in order to control the normalized dispersion of the particle size distribution of the precipitate within a prescribed range, in order to obtain a structure exhibiting the above-described particle size distribution. If the holding time is too short, the precipitate size and normalized dispersion become too small, and various properties are deteriorated. Concretely, the temperature at which the aging treatment is carried out is set at 300 to 550 캜, and the holding time at 300 to 550 캜 is set to 5 hours or more. The holding time is preferably 6 hours or more. On the other hand, considering productivity and the like, the upper limit of the holding time is about 24 hours. The holding at 300 to 550 占 폚 may be carried out at a single temperature, and if the temperature is within the range, the temperature may fluctuate, that is, the temperature may rise or fall. For example, the temperature may be changed continuously or stepwise as in continuous annealing.

The average temperature raising rate to the reaching temperature at which the aging treatment is performed is not limited. Also, the average cooling rate after the aging treatment is not limited. After the aging treatment, cooling to room temperature by, for example, water cooling or cooling is mentioned.

Example

The present invention will now be described in more detail with reference to the following examples. However, it should be understood that the present invention is not limited to the following examples, but may be practiced with modifications within the scope of the above and below All of which are included in the technical scope of the present invention.

The copper alloy was melted in kryptol in the atmosphere under a jacket coat and cast into a cast iron base mold to obtain a 45 mm thick ingot having the chemical composition shown in Table 1 below.

The surface of the ingot was subjected to a heat treatment, followed by heating to reach 1000 占 폚, followed by holding for 30 minutes to 2 hours. Thereafter, hot rolling was performed until the thickness became 20 mm, The hot rolling was terminated at a hot rolling end temperature of 700 to 850 캜 shown in Fig. 2, and water cooling was carried out at an average cooling rate of 20 캜 / sec. In this embodiment, in order to change the hot rolling end temperature, air cooling treatment for 5 to 2 minutes after the above cracking treatment is performed to change the start temperature of hot rolling. After hot rolling, some of the samples were subjected to a solution treatment at 900 ° C for 5 minutes and quenched in water, that is, to room temperature.

The surface of the hot-rolled plate was ground to remove the oxide scale to obtain a thickness of 18 mm, followed by cold rolling to obtain a copper alloy plate having a thickness of 0.5 mm. Thereafter, a two-stage aging treatment using a salt bath having an average heating rate of about 50 ° C / second, or a continuous aging treatment using a batch annealing furnace with an average heating rate of about 100 ° C / I did.

Table 2 below also shows the holding time at 300 to 550 캜. Table 2 below. 2, 6, 7, 10 and 11, the &quot; holding time at 300 to 550 占 폚 includes the time required for raising the temperature from 300 占 폚 to 450 占 폚: 1.5 hours.

Using the thus obtained copper alloy plate as a test piece, measurement was made by X-ray small angle scattering method, measurement of tensile strength and 0.2% proof stress, evaluation of conductivity, evaluation of bending workability and evaluation of stress relaxation resistance .

(Measurement by X-ray small angle scattering method)

X-ray small angle scattering measurement was performed by using X-ray of 5720 keV and 5985 keV energy using "BL08B2" of "Spring-8" in common to each example, and the X-ray scattering intensity profile was measured. In the test apparatus, X-rays are vertically incident on the surface of the test piece, and X-rays scattered backward from the test piece at a minute angle (incineration) of 5 degrees or less with respect to the incident X-ray are measured using a detector . As a sample to be measured, a copper alloy plate having a thickness of about 30 mu m made by mechanical polishing was used.

The scattering intensity profile of this X-ray was analyzed by a particle analysis / public analysis software &quot; NANO-Solver, Ver. &Quot;, available from Rigaku Co., 3.5 ", the fitting was performed by the nonlinear least squares method so as to be close to the values of the measured X-ray scattering intensity and the X-ray scattering intensity calculated by the analysis software, whereby the average particle diameter of the precipitate particle size distribution and the normalized dispersion Respectively. On the other hand, assuming that the average particle diameter is a perfect spherical shape, the scattering intensity was calculated using the theoretical formula, and the scattering intensity was obtained by fitting to the experimental value.

(Measurement of tensile strength and 0.2% proof stress)

The specimen was cut in parallel to the rolling direction of the copper alloy plate to prepare a test piece having a size of JIS No. 5, and the specimen was subjected to tensile test at a room temperature, a test speed of 10.0 mm / min and a GL of 50 mm by a 5882 type universal testing machine manufactured by Instron Strength and 0.2% proof stress were measured. In the present invention, when the 0.2% proof stress is 500 MPa or more, it is evaluated as high strength.

(Evaluation of conductivity)

The electrical conductivity was measured by milling a copper alloy plate into a test piece having a width of 10 mm and a length of 300 mm and measuring the electrical resistance of the test piece by means of a double- % Calculated the conductivity to IACS. In the present invention, it was evaluated that a conductivity of 80% IACS or more was high conductivity.

(Evaluation of bending workability)

The bending test was conducted according to the Nippon Shindong Association technical standard. A W bend test was conducted using a specimen cut out from a copper alloy plate in a width of 10 mm and a length of 30 mm. In the W bending test, the presence of cracks in the bent portion was observed with an optical microscope at 10 times while W bending was performed. Then, R / t, which is the ratio of the minimum bending radius R at which cracks do not occur and the plate thickness t of the copper alloy plate t: 0.5 mm, is obtained. A smaller value of R / t indicates excellent bending workability. In the present invention, those having a R / t value of 1.0 or less are evaluated as having good bending workability and indicated as "OK" in Table 3. On the other hand, when the ratio R / t is more than 1.0, the bending workability is evaluated as poor, and in Table 3, it is indicated as &quot; NG &quot;.

(Evaluation of stress relaxation resistance)

The stress relaxation resistance was evaluated by measuring the stress relaxation rate by the cantilever method. Details are as follows. First, as a plate material for measurement, a test piece having a width of 10 mm and a length of 60 mm was cut out such that the longitudinal direction thereof was parallel to the rolling direction of the copper alloy plate (L.D.) and vertical direction (T.D.). And one end thereof was fixed to a rigid body test stand. A 10 mm deflection was given to the test specimen at a predetermined distance from the fixed end (hereinafter sometimes referred to as span length), and 0.2% And subjected to a surface stress corresponding to 80% of the proof stress. The span length was calculated according to the "Test Method for Stress Relaxation by Bending of Copper and Copper Alloy Sheet Thin Film" prescribed in Nippon Shindong Association Technical Standard JCBA-T309: 2004. When the specimens were held in an oven at 180 DEG C for 24 hours and then taken out therefrom to remove the warping amount d of 10 mm in a state in which the specimen was fixed to the rigid body test stand and warped at a position spaced apart from the fixed end by a span length The permanent strain? Was measured, and the stress relaxation ratio RS was measured by the following equation (2). In the following formula (2), RS represents the stress relaxation rate (%), delta represents the permanent deformation (-) and d represents the deflection. In this experiment, the deflection amount d is 10 mm. In the present invention, it was evaluated that the stress relaxation ratio RS of 15.0% or less was acceptable.

The results are shown in Table 3.

The following can be seen from Tables 1 to 3. No. 1, 5, and 8 to 14 exhibit high strength, high conductivity, and excellent bending workability since the composition satisfies the composition specified in the present invention and is produced under the recommended conditions and the shape of the precipitate satisfies the requirements. And exhibits excellent stress relaxation resistance.

On the other hand, 2 to 4, 6, 7 and 15 to 18 do not satisfy at least one of the requirements specified in the present invention, at least one of strength, conductivity, bending workability and stress relaxation resistance is inferior. The details are as follows.

No. 2 is an example that is not manufactured under recommended conditions, the ending temperature of hot rolling is low and no solution treatment is carried out. Also, the holding time at 300 to 550 DEG C in the aging treatment is also short. Therefore, the value of the normalized dispersion of the particle size distribution of the precipitate became larger. As a result, the conductivity and the bending workability deteriorated. Further, in the case of No. 1, the strength was relatively lowered and the stress relaxation resistance was relatively poor.

No. 3 is an example not manufactured under the recommended conditions, and the holding time at 300-550 ° C in the aging treatment is short. Further, it is considered that the precipitate is not sufficiently generated because the temperature of the aging treatment is as low as 300 DEG C, which is the lowest recommended by the present invention, and that the average particle diameter and the normalized dispersion of the particle size distribution of the precipitate . As a result, all of the strength, conductivity, bending workability and stress relaxation resistance deteriorated.

No. 4 is an example not manufactured under the recommended conditions, and the holding time at 300-550 ° C in the aging treatment is short. As a result, the precipitate coarsened and the average particle diameter of the particle size distribution of the precipitate became large. As a result, the strength was lowered.

No. 6 is an example not manufactured under the recommended conditions, the ending temperature of hot rolling is low and no solution treatment is carried out. As a result, the average particle diameter and the normalized dispersion of the particle size distribution of the precipitate became larger. As a result, the strength and the stress relaxation resistance deteriorated.

No. 7 is an example not manufactured under the recommended conditions, and the holding time at 300-550 ° C in the aging treatment is short. As a result, the value of the normalized dispersion of the particle size distribution of the precipitate became smaller. As a result, strength, conductivity, and stress relaxation resistance deteriorated.

No. 15, the amount of Cr was excessive, so that the bending workability was deteriorated. In addition, the conductivity was also reduced.

No. Since the amount of Ti was excessive, the conductivity was remarkably lowered and the bending workability deteriorated.

No. 17 had a low content of Ti and Zr, so that the strength and the stress relaxation resistance deteriorated.

No. 18 had an excessive amount of Si, so that the strength was lowered, the conductivity was lowered, and the bending workability was lowered.

No. 19 and 20 are examples in which the amount of the arbitrarily added element is outside the range recommended in the present invention. Of these, 19 had an excessive amount of Fe, so that the strength was lowered, the conductivity was lowered, and the bending workability was lowered. No. 20 had an excessive amount of Sn, so that the conductivity was low and the bending workability also deteriorated.

Claims (5)

In terms of% by mass,
0.15 to 0.4% Cr,
Si: 0.01 to 0.1%
Zr: 0.018 to 0.077%, and
Ti and Zr: 0.02 to 0.15% in total,
The remainder being composed of copper and inevitable impurities, and
The average particle diameter of the particle size distribution of the precipitate measured by the X-ray small angle scattering method is 2.0 nm or more and 7.0 nm or less,
Wherein the normalized dispersion of the particle size distribution is in the range of 30 to 40%. The method according to claim 1,
As another element, in mass%
At least one element selected from the group consisting of Fe, Ni and Co: a total of not less than 0% and not more than 0.3%. The method according to claim 1,
As another element, in mass%
Zn: a copper alloy further comprising not less than 0% and not more than 0.3%. 3. The method of claim 2,
As another element, in mass%
Zn: a copper alloy further comprising not less than 0% and not more than 0.3%. 5. The method according to any one of claims 1 to 4,
As another element, in mass%
Sn, Mg and Al: not less than 0% and not more than 0.3% in total.