JP2011012321A - Copper alloy material and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy material superior in fatigue resistance without changing a composition and precipitates of the alloy.SOLUTION: The copper alloy material superior in fatigue resistance has a texture in which an area rate of Cube orientation {001}<100> measured with an EBSD method is 5-50%, and an average crystal grain size is 15-200 μm.

Description

  The present invention relates to a copper alloy material applied to electrical / electronic devices such as lead frames, terminals, connectors, wire harnesses, terminals, relays, switches, and spring materials.

Conventionally, as materials for electric / electronic devices, copper-based materials such as phosphor bronze, red brass, brass, etc., which are excellent in electrical conductivity and thermal conductivity, have been widely used as materials for electric / electronic devices.
In recent years, there has been an increasing demand for smaller and lighter electrical and electronic devices and higher density mounting of components, and copper-based materials applied to these devices are required to have higher levels of various characteristics. Yes. Among the required properties, the main properties include conductivity, stress relaxation resistance, bending workability, springiness, and fatigue resistance. In order to satisfy these requirements, Corson alloys (Cu-Ni-Si series), titanium copper, and beryllium copper with high mechanical strength, excellent bending workability, and high conductivity have been developed for use in electrical and electronic equipment. ing.
For example, a titanium-copper alloy with improved mechanical strength without reducing bending workability and a method for producing the same have been proposed (see Patent Document 1). A method for improving fatigue properties by controlling the composition and precipitates of the alloy has also been proposed (see Patent Documents 2 to 4). However, there is a limit to increase in mechanical strength due to alloy composition and precipitates. In addition, there is a limit in terms of improving mechanical strength and fatigue characteristics while balancing with bending workability and conductivity, and an improvement has been desired.

JP 2002-356726 A JP 2002-3963 A Japanese Patent Laid-Open No. 2005-187885 JP 2004-225112 A

  An object of the present invention is to provide a copper alloy material having excellent fatigue resistance without changing the composition and precipitates of the alloy.

As a result of intensive studies to solve these problems, the present inventors have a texture in which the ratio of the Cube orientation {001} <100> measured by the EBSD method is 5 to 50%, and It has been found that a copper alloy material having a crystal grain size of 15 μm or more and 200 μm or less is excellent in fatigue resistance. The present invention has been made based on this finding.
That is, the present invention
(1) It has a texture where the area ratio of Cube orientation {001} <100> measured by EBSD method is 5 to 50%, and the crystal grain size is 15 μm or more and 200 μm or less Copper alloy material,
(2) The copper alloy material according to (1), which has a texture in which the area ratio of ND Rotated Cube orientation {100} <011> measured by EBSD method is 2 to 30%,
(3) The content of Ni is 2.0 to 5.0 mass%, Si is 0.40 to 1.70 mass%, and the balance is made of Cu and inevitable impurities, as described in (1) or (2) Copper alloy material,
(4) The copper alloy is at least selected from the group consisting of B, Al, As, Hf, Zr, Cr, Ti, C, Co, Fe, P, In, Sb, Mn, Ta, V, Sn, Zn, and Mg. The copper alloy material according to any one of (1) to (3), wherein 0.001 to 1.5 mass% in total is contained, and
(5) A method for producing the copper alloy material according to any one of (1) to (4), wherein the [100] axis of the columnar crystal of the copper alloy is ± 15 ° from a plane perpendicular to the casting direction. A method for producing a copper alloy material by continuous casting or semi-continuous casting,
Is to provide.

  According to the present invention, a copper alloy material excellent in fatigue resistance can be obtained without impairing any of strength, bending workability, and conductivity. Therefore, it is possible to provide a copper alloy material suitable for electrical / electronic devices such as lead frames, terminals, connectors, wire harnesses, terminals, relays, switches, and spring materials.

  Preferred embodiments of the copper alloy material and the method for producing the same of the present invention will be described in detail below. The copper alloy material of the present invention is a copper alloy material having a specific shape, for example, a plate material, a strip material, a wire material, a rod material, a foil, and the like, and can be used for any electric / electronic component. Although it is not particularly limited, for example, it is suitably used for components that require high fatigue characteristics such as lead frames, terminals, connectors, wire harnesses, terminals, relays, switches, and spring materials.

First, the EBSD method and information obtained from the method will be described.
(1) EBSD Method The crystal orientation of the copper alloy material of the present invention is measured by an EBSD (Electron Backscatter Diffraction) method (hereinafter simply referred to as “EBSD method”). In the EBSD method, an electron beam is made incident on one point on the surface of a sample in a scanning electron microscope (SEM), and a crystal orientation and a crystal structure at that point can be obtained from a generated reflected electron diffraction pattern. Then, by scanning the surface of the sample with an electron beam at regular intervals, the crystal orientation and crystal structure of the scanned portion can be obtained. In the present invention, a 500 μm square sample area containing 200 or more crystal grains was scanned in 0.5 μm steps, and the orientation was analyzed. The deviation angle is calculated for all measurement points, the first decimal place is an effective number, and the area of crystal grains having an orientation within 10 ° from the Cube orientation is divided by the total measurement area to obtain the area ratio. .
The information obtained in the azimuth analysis by EBSD includes azimuth information up to a depth of several tens of nanometers at which the electron beam penetrates into the sample. It was described as an area ratio. In addition, since the azimuth distribution may differ in the plate thickness direction, the azimuth analysis by EBSD took three points in the plate thickness direction and took an average.
As described above, the area ratios of the Cube orientation {001} <100> and the ND Rotated Cube orientation {100} <011> of the copper alloy material are measured.

(2) Cube orientation In the copper alloy material of the present invention and the manufacturing method thereof, the Cube orientation {001} <100> measured by the EBSD method has a texture with an area ratio of 5 to 50%. . Specifically, 5 to 50% of the area of the part measured by the EBSD method may be the Cube orientation {001} <100>.
Bending stress within elastic stress is repeatedly applied to metal parts of electrical / electronic devices such as terminals, connectors, and wire harnesses when the parts are operated or detached. Macroscopically, even a stress in the elastic range causes a behavior of inelastic behavior that does not return to the place where only a part of the atoms originated microscopically, which accumulates and introduces and breaks a crack. On the other hand, by increasing the area ratio of the Cube orientation {001} <100> to 5 to 50%, the frequency of occurrence of inelastic behavior of microscopic atoms is reduced, so that the generation of cracks is suppressed. The effect that the fatigue life is increased is obtained. If the area ratio is less than 5%, the effect is small. If the area ratio is more than 50%, the elongation characteristics deteriorate, so the area ratio is set to 5 to 50%.
Furthermore, the area ratio of the ND Rotated Cube orientation {100} <011> measured by the EBSD method is preferably set to 2 to 30%. In that case, the effect of reducing the frequency of occurrence of inelastic behavior of microscopic atoms can be obtained. When the area ratio is less than 2%, the effect is small. When the area ratio is more than 30%, the elongation characteristics deteriorate. Therefore, the area ratio is set to 2 to 30%.

(3) Crystal grain size In the present invention, by setting the crystal grain size measured by the EBSD method to 15 μm or more and 200 μm or less, the number of microscopically disordered atomic arrangements such as grain boundaries is reduced. The frequency of occurrence of inelastic behavior of microscopic atoms is reduced, the generation of cracks is suppressed, and the fatigue strength is increased. When the crystal grain size is less than 15 μm, the effect of improving the fatigue strength is small. When the crystal grain size is larger than 200 μm, the bending workability characteristics deteriorate, so the crystal grain size is set to 15 μm to 200 μm. In order to set the crystal grain size to 15 μm or more, for example, the temperature and time of solution heat treatment and the amount of strain during pre-processing can be adjusted.
The crystal grain size measured by the EBSD method was determined by a cutting method in accordance with JIS H 0501.

  Next, preferred materials used for the alloy of the present invention will be described. In the present invention, a copper alloy material containing 1.5 to 5.0% (mass%, hereinafter the same) of Ni, 0.40 to 1.70% of Si, and the balance of Cu and inevitable impurities is preferably used. can do. By using this alloy, it is possible to obtain a precipitation-strengthened alloy in which Ni and Si are added to Cu and the Ni—Si compound is finely precipitated. The following two important heat treatments are incorporated into the process for producing the precipitation strengthened alloy. First, a so-called aging precipitation treatment in which Ni and Si are dissolved in a Cu matrix at a high temperature (usually 700 ° C. or more) called a solution treatment and a heat treatment at a temperature lower than the solution treatment temperature. is there. By this aging precipitation treatment, Ni and Si dissolved at a high temperature can be precipitated. In this way, the alloy of the present invention can be produced using the difference in the amount of atoms in which Ni and Si are dissolved in Cu at high and low temperatures.

  For Ni and Si, the strength of the copper alloy material can be improved by precipitation strengthening of the Ni—Si compound by controlling the addition ratio of Ni and Si. The content of Ni is 1.5 to 5.0 mass%, preferably 2.0 to 4.5 mass%. The content of Si is 0.40 to 1.70 mass%, preferably 0.45 to 1.2 mass%.

The copper alloy material of the present invention further includes a group consisting of B, Al, As, Hf, Zr, Cr, Ti, C, Co, Fe, P, In, Sb, Mn, Ta, V, Sn, Zn, and Mg. 0.005 to 1.5 mass% in total can be contained.
If the total content of these elements in the copper alloy material exceeds 1.5 mass%, there may be a negative effect of lowering the conductivity.
By adding Mg, Sn, and Zn, the stress relaxation resistance can be improved. The stress relaxation resistance is further improved by the synergistic effect when added together than when each is added. In addition, the solder embrittlement is remarkably improved. When Mn is added, the strength can be improved. Cr, Fe, Ti, Zr, and Hf are finely precipitated as a compound or simple substance with Ni or Si and contribute to precipitation hardening. B and P improve the hot workability and improve the strength.
In addition, Al, As, C, Co, In, Sb, Ta, and V are dissolved in the parent phase to improve the strength.

A manufacturing method will be described.
The manufacturing method of copper alloy material (for example, Corson alloy) applied to the conventional electric and electronic equipment is casting-homogenization-hot rolling-cold rolling-solution heat treatment-aging precipitation heat treatment-finish rolling-tempering Annealing. Usually, the area ratio of the Cube orientation in this method is less than 3% at most.
As a result of intensive studies, it has been found that in order to increase the area ratio of the Cube orientation, it is significant that a large number of crystal grains of the Cube orientation exist in the ingot stage. In the conventional method, the area ratio of the Cube orientation in the ingot is small, and the copper after a series of steps of casting-homogenization-hot rolling-cold rolling-solution heat treatment-aging precipitation heat treatment-finish rolling-temper annealing The Cube orientation of the alloy material did not grow sufficiently.
In the present invention, it is preferable to cast the [100] axis of the columnar crystal of the copper alloy material within ± 15 ° from the plane orthogonal to the casting direction. Thus, the Cube orientation of the ingot can be increased, and the copper alloy material after a series of steps of casting-homogenization-hot rolling-cold rolling-solution heat treatment-aging precipitation heat treatment-finish rolling-temper annealing The area ratio of the Cube orientation can be increased. In order to adjust the direction of the [100] axis of the columnar crystals of the ingot structure, the cooling capacity of the secondary cooling after the lower end of the mold is set to be small, or borax and boric acid are used as mold fluxes to increase the primary cooling. , And a melt flux composed mainly of cryolite, or both may be performed simultaneously. In the processes after casting, after the homogenization treatment, hot rolling with a total processing rate of 20 to 97% is performed at a temperature of 500 to 1000 ° C., and then cold rolling with 50 to 99.9% is performed. Good. Then, in the solution heat treatment where recrystallization occurs, the crystal grain size is controlled to 15 microns or more by holding it for 5 seconds to 5 minutes within the temperature range where the solute element is completely dissolved and within the range of 20 ° C. from that temperature. it can.
The copper alloy material of the present invention can be produced by either continuous casting or semi-continuous casting.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Production of test materials)
The copper alloy used for the Example and comparative example of this invention is an alloy (Examples 1-3, Comparative Examples 1-4) which contains the component shown in Table 1, and remainder consists of Cu and an unavoidable impurity. Each of these alloys is melted in the atmosphere under charcoal coating in a coreless furnace (high frequency induction melting furnace), cast into a mold surrounded by a copper mold on four sides, and an ingot having a thickness of 250 mm, a width of 620 mm, and a length of 2500 mm Was made.
Next, a SUS rod having a diameter of 3 mm was inserted in the vertical direction from the molten metal surface at the upper end of the mold at the intersection of the position of the width 155 mm and the thickness 125 mm of the mold, and the depth of the unsolidified portion was measured. A value obtained by subtracting the mold length (copper mold length) from the depth of the obtained unsolidified portion was defined as the distance from the mold lower end depth to the solidification end depth. The casting speed was adjusted in the range of 50 to 200 mm / min so that this distance was 250 mm or more, and casting was performed to obtain an ingot.
A 250 × 620 × 300 mm block of a stationary part was cut out from the obtained ingot, and a slice (250 × 15 × 300 mm) having a cross section parallel to the casting direction was collected from a central part of 620 mm width. This was immersed in nitric acid for 0.5 to 1 hour, and the direction of the [100] axis of the columnar crystal was obtained from the macrostructure obtained by etching. The angle at which the direction perpendicular to the casting direction and the direction of the [100] axis of the columnar crystal intersect was measured, and the average value is shown in Table 1.
Further, after the ingot is homogenized, the temperature is adjusted to 500 to 1000 ° C., rolling is performed at a total processing rate of 60 to 96%, and then the obtained rolled material is directly cooled with water to form a coil having a thickness of about 10 mm. . The surface of the rolled material was milled to remove oxide scale. At this time, the ratio of the Cube orientation of the rolled material was set to 5 to 95%. Then, cold rolling at a working rate of 85 to 99.8%, solution heat treatment at 700 to 1020 ° C. for 5 seconds to 1 hour, finish cold rolling at a working rate of 1 to 60%, and 200 to 600 ° C. for 5 seconds to The temper annealing for 10 hours was performed in the order of description, and a specimen having a thickness of 0.15 mm was obtained.

(Characteristic evaluation of copper alloy materials)
The following characteristics evaluation was performed on the copper alloy material, and the results are shown in Table 1.
a. Evaluation by EBSD method A sample area of 500 μm square containing 200 or more crystal grains was scanned in steps of 0.5 μm, and the orientation was analyzed. First, the crystal orientation of the measurement portion was identified, and the area ratios occupied by the Cube orientation {001} <100> and the ND Rotated Cube orientation {100} <011> were respectively determined. At the same time, the crystal grain size was measured.

b. Tensile test Three test pieces of JIS Z2201-13B cut out in parallel with the rolling direction from the test material were measured according to JIS Z2241 under the conditions of a tensile speed of 50 mm / min and a gauge length of 50 mm, and 0.2% proof stress. The average values for the applied stress were also shown.

c. Fatigue test A test piece having a width of 10 mm cut out from the test material in parallel with the rolling direction was subjected to a double-bending plane bending fatigue test in accordance with JIS Z 2273. Test conditions are set so that the maximum stress (σ), amplitude (f), distance between fulcrum and action point (L), and sample thickness (t: 0.15 mm) applied to the test piece are as follows: did.
L = √ (3tEf / (2σ))
E: Young's modulus (= 120 GPa)
The number of times (Nf) when the sample broke was measured five times, and the average value was defined as the fatigue life repetition number.

The copper alloy materials of Examples 1 to 3 of the present invention have no problem in 0.2% proof stress and applied stress, and the fatigue life repetition number is as good as 1.2 × 10 ^{7 to} 1.6 × 10 ^7. Show.
On the other hand, in Comparative Example 4, the area ratio (%) of the Cube orientation {001} <100> is less than 5% and the crystal grain size is less than 15 μm. It has become. In Comparative Example 3, the crystal grain size is 15 μm or more, but the area ratio (%) of the Cube orientation {001} <100> is less than 5%. It has become.
In Comparative Examples 1 and 2, the area ratio (%) of the Cube orientation {001} <100> is in the range of 5 to 50%, but the crystal grain size is less than 15 μm. The result is inferior.

Claims (5)

  A copper alloy having a texture in which the area ratio of Cube orientation {001} <100> measured by EBSD method is 5 to 50%, and having an average crystal grain size of 15 μm or more and 200 μm or less Wood.   2. The copper alloy material according to claim 1, wherein the copper alloy material has a texture in which an area ratio of ND Rotated Cube orientation {100} <011> measured by EBSD method is 2 to 30%.   The copper alloy material according to claim 1 or 2, wherein Ni is contained in an amount of 1.5 to 5.0 mass%, Si is contained in an amount of 0.40 to 1.70 mass%, and the balance is made of Cu and inevitable impurities.   The copper alloy is at least one selected from the group consisting of B, Al, As, Hf, Zr, Cr, Ti, C, Co, Fe, P, In, Sb, Mn, Ta, V, Sn, Zn, and Mg. It contains 0.005-1.5mass% in total, The copper alloy material of any one of Claims 1-3 characterized by the above-mentioned.   It is a method of manufacturing the copper alloy material according to any one of claims 1 to 4, wherein the [100] axis of the columnar crystal of the copper alloy is within ± 15 ° from the plane orthogonal to the casting direction. A method for producing a copper alloy material by continuous casting or semi-continuous casting.