KR20050007139A - High strength and electric conductivity copper alloy excellent in ductility - Google Patents

Abstract

PURPOSE: To provide a high strength high electric conductivity copper alloy that is excellent in strength and formability, easy in production management and suitably used as a conductive spring material for terminals, connectors, relays and switches. CONSTITUTION: The high strength high electric conductivity copper alloy comprises 0.05 to 1.0 mass% of Cr, 0.05 to 0.25 mass% of Zr, and the balance being Cu and inevitable impurities, wherein a ratio of coincidence site lattice Σ3 at the grain boundary is 10% or more in case that a space between each crystals is regarded as a grain boundary when misorientation of adjacent grains is 5 degrees or more of an angle, wherein the copper alloy further comprises 0.01 to 1.0 mass% of one or more elements selected from the group consisting of Zn, P, Fe, Mg, Mn, Al, Co and Ni, wherein the cooper alloy comprises 0.6 mass% or less of Cr and has an elongation of 8% or more, and wherein the cooper alloy comprises 0.2 mass% or less of Cr and has an elongation of 10% or more.

Description

High Strength High Conductivity Copper Alloy with High Ductility {HIGH STRENGTH AND ELECTRIC CONDUCTIVITY COPPER ALLOY EXCELLENT IN DUCTILITY}

The present invention relates to a high-strength highly conductive copper alloy suitable for conductive spring materials used for terminals, connectors, relays or switches, and excellent in strength and conductivity.

Conventionally, phosphor bronze is used as a conductive spring material used in various terminals, connectors, relays, switches, and the like.

In recent years, high-strength highly conductive copper alloys such as Cu-Cr or Cu-Cr-Zr are attracting attention due to the demand for miniaturization and thinning of components (see, for example, Patent Documents 1 and 2). Since Cu-Cr type copper alloy and Cu-Cr-Zr type copper alloy improve material strength by precipitation of Cr or Cu-Zr, electroconductivity can be improved compared with a solid solution type alloy. However, the strength improvement by precipitation of Cr and Zr is not so large, and the said alloy is cold-rolled, and high strength is achieved by performing precipitation hardening and work hardening together.

In general, however, work hardening of a metal material deteriorates ductility and deteriorates workability and stress relaxation resistance such as bendability. In this regard, attention has been paid to modifying the material by the recent processing heat treatment method. For example, Patent Document 3 describes a technique of forming fine crystal grains in a Cu—Cr—Zr based copper alloy by (dynamic) recrystallization after cold rolling to improve ductility.

[Patent Document 1] Japanese Patent Application Laid-Open No. 9-87814

[Patent Document 2] Japanese Patent Application Laid-Open No. 7-258804

[Patent Document 3] Japanese Unexamined Patent Publication No. 2002-356728

However, in the case of the technique described in Patent Document 3, since it is necessary to manage the shape and particle size of the grain boundary, there is a problem that separation production and quality control in actual production are difficult. Moreover, even if this technique was used, ductility improvement was inadequate.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a high-strength highly conductive copper alloy having excellent strength and workability and easy production management.

As a result of various studies, the inventors have found that when the ratio of the corresponding grain boundaries 3 described later in the grain boundaries increases, the workability does not decrease even when the material is hardened, and the ductility is remarkably improved. That is, in order to achieve the above object, the high-strength highly conductive copper alloy of the present invention is made of mass% of Cr: 0.05 to 1.0%, Zr: 0.05 to 0.25%, residual Cu and inevitable impurities, and the orientation of adjacent crystals. In the case where the difference is regarded as a grain boundary when the difference is 5 degrees or more, the ratio of the corresponding grain boundary 3 at the grain boundary is 10% or more.

Moreover, it is preferable to contain 0.01-1.0% by mass of 1 or more types chosen from the group of Zn, P, Fe, Mg, Mn, Al, Co, and Ni in total.

It is preferable to make Cr content into 0.6% or less and to show 8% or more of elongation, and it is more preferable to make Cr content into 0.2% or less and to show 10% or more of elongation.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the high strength highly conductive copper alloy which concerns on this invention is described.

First, the reason which prescribed | regulated content of each component element in this invention is demonstrated. In this invention,% shall represent the mass% unless there is particular notice.

[Cr, Zr]

The present invention targets a Cu—Cr—Zr based copper alloy to secure conductivity and strength. Here, Cr and Zr are elements which precipitate in the Cu mother phase by aging after the solution treatment and contribute to the strength improvement. The Cr content is 0.05 to 1.0% and the Zr content is 0.05 to 0.25%. It is because intensity | strength will not fully improve that Cr content is less than 0.05%, and an effect will be saturated even if it exceeds 1.0%. The reason for specifying the upper limit and the lower limit of the Zr content is also the same as in the case of Cr. Moreover, when Cr content is made into 0.6% or less, 8% or more elongation is obtained, More preferably, when it is 0.2% or less, high elongation 10% or more is obtained.

Next, the addition element added as needed is demonstrated.

[Zn, P, Fe, Mg, Mn, Al, Co, Ni]

These elements improve the strength by solid solution or precipitation in the copper matrix without significantly lowering the conductivity, and are contained in an amount of 0.01 to 1.0% in total. If the content is less than 0.01%, the effect of improving strength is small, and if it exceeds 1.0%, the electrical conductivity is lowered.

Next, the structure of the high strength highly conductive copper alloy which concerns on this invention is demonstrated. As a method of improving the ductility of Cu-Cr-Zr-based copper alloys, the present invention defines a corresponding grain boundary 3 in view of the grain boundary structure. Here, the corresponding grain boundary refers to a grain boundary in which a lattice point (corresponding lattice) overlapping with each other occurs periodically when the lattice point of one crystal constituting the grain boundary is extended to see the state overlapping with the lattice point of another crystal. . At this time, the inverse of the density of the corresponding lattice point is defined as? Value. 3 means that the corresponding lattice points have a density of 1/3, that is, one corresponding lattice point appears for three original lattice points, which means that the lattice spacing at which the corresponding lattice appears periodically is three lattice points. Smaller values indicate shorter periods and higher regularity of grain boundaries. Also, ∑3 is the smallest value. Corresponding grain boundaries are described in, for example, "Atomic Theory of Lectures on Modern Metallurgical Materials, Vol.

In the present invention, when the orientation difference between adjacent crystals is 5 DEG or more, when each crystal is regarded as a grain boundary, the ratio of the corresponding grain boundary 3 at the grain boundary is 10% or more. Generally, when the orientation difference between crystal grains is 15 degrees or more, it becomes a diagonal grain boundary, and when it is less than 15 degrees, it becomes an incineration grain boundary. In the present invention, the azimuth difference of less than 5 ° is regarded as a sub-grain tissue and a cell structure, which are lower tissues of grains, and a 5 ° or more is regarded as a grain boundary.

The reason why the ratio of the corresponding grain boundary 3 at the grain boundary is 10% or more is because when the ratio of 3 is less than 10%, ductility and workability improvement cannot be expected. It is not clear why the ductility improves when the ratio of Σ3 is 10% or more. However, it is conceivable that the grain boundary segregation of Cr or Zr, which causes embrittlement, is worsened by increasing the ratio of ∑3.

As a method of calculating the ratio of the corresponding grain boundary 3, there is, for example, an Electron Backscatter Diffraction Pattern (EBSP) method using a Field Emission Scanning Electron Microscope (FESEM). This method is a method of analyzing the crystal orientation based on the backscattered electron diffraction pattern (Kikuchi pattern) generated when an electron beam is projected obliquely on the sample surface. In this method, it is interpreted as the following procedure. First, the measurement area of the material to be measured is usually divided into areas such as hexagons, and the Kikuchi pattern obtained for each partitioned area is compared with data of known crystal structures to determine the crystal orientation at the measurement point. Similarly, the crystal orientation of the measurement point adjacent to the measurement point is determined, and if the orientation difference between the two crystals is 5 ° or more, the boundary (between the sides of both hexagons, etc.) is placed between them, and if the angle is less than 5 °, both are the same crystal. do. In this way, the distribution of grain boundaries on the sample surface is obtained. Next, it is determined whether or not each crystal grain is the corresponding grain boundary ∑3 by a predetermined method, and the ratio of the corresponding grain boundary ∑3 is multiplied by 100 by multiplying (the sum of the corresponding grain boundaries ∑3) / (the sum of the lengths of the grain boundaries). Obtain In addition, since a commercially available FESEM / EBSP apparatus has a mode for identifying the corresponding grain boundary? 3, this may be used. In addition, there is also a method of using a Kikuchi pattern by a TEM (transmission electron microscope), but the FESEM / EBSP method is advantageous from the simplicity of measurement.

As a method for making the ratio of the corresponding grain boundary 3 to 10% or more, for example, recrystallization after annealing can be used (static recrystallization). In this case, it becomes the process of strain removal annealing after rolling, and the strength raised once by rolling may fall, or sufficient ductility may not be obtained. Therefore, it is more preferable to use the dynamic recrystallization which does not have such a problem and produces the material excellent in both strength and ductility. In general, when the rolling workability is increased, the strength is increased by work hardening. If the workability is too high, further work hardening does not occur, and the ductility decreases as the strength is increased. However, when the workability is further increased, a behavior called dynamic recrystallization in which recrystallization proceeds by processing occurs, whereby the structure is improved and ductility is restored. Therefore, in the present invention, the strength and ductility (processability) can be simultaneously improved to a high level by preferably managing the ratio of the corresponding grain boundary 3 to 10% or more and using the dynamic recrystallization method.

Specifically, by increasing the cold workability of the cold rolling of the material, for example, making the overall workability in the final cold rolling be 95% or more, the dynamic recrystallization can be generated to produce the corresponding grain boundary? 3. In this case, preferably, when the average workability of each pass (the calculated value of workability per one pass is calculated by averaging the workability of each pass) in the final cold rolling, the generation of the corresponding grain boundary? 3 Is promoted. More preferably, the difference in average workability of each pass is ± 10% or less, and most preferably, the difference is ± 5% or less. Also, when setting the difference between the degree of workability and the degree of workability of each of the above-mentioned paths, a pass with a low processing rate (for example, a pass less than 0.5% of a work rate and a skin pass) of a degree that does not affect the rolling workability so much as It may be performed one or more times after the initial, intermediate, or final pass, and such a pass setting is also included in the present invention.

In addition, as a method of increasing the ratio of 3, recrystallization may be generated by heat treatment (for example, strain removal annealing) in addition to generating recrystallization dynamically by the above processing.

The copper alloy of this invention can be manufactured as follows, for example. First, an element of the above composition is blended with copper or oxygen-free copper, an ingot is cast in an inert atmosphere or vacuum, and appropriately heat treated, followed by hot rolling, solution treatment, cold rolling, and aging treatment to obtain a desired thickness. Manufacture alloy foils or plates. And these thin ribbons and board | plate materials are processed suitably, and it becomes products, such as a spring material.

Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example

1. Preparation of Sample

The alloy of the composition shown in Table 1 was mix | blended with the predetermined | prescribed element with respect to copper, and the ingot was cast in an inert atmosphere or vacuum in a vacuum induction melting furnace (VIM). The obtained ingot was homogenized and annealed at a temperature of 900 ° C. or higher for at least 300 minutes, followed by hot rolling, followed by solution treatment, and finally cold rolling to prepare a material having a thickness of 0.15 mm. Thereafter, a predetermined aging treatment was performed to generate recrystallization, and then the sample was cut out. Cold rolling conditions are as shown in Table 1.

Here, the total workability is a value expressed by {(plate thickness before cold rolling)-(plate thickness after full pass rolling)} × 100 / (plate thickness before cold rolling). In addition, the average workability of each pass is first determined by the value expressed by {(plate thickness before rolling of the pass)-(plate thickness after rolling of the pass)} / (plate thickness before rolling of the pass). The workability was calculated | required and this value was averaged over the whole pass | pass.

2. Measurement of the ratio of ∑3

About each Example and the comparative example, the crystal orientation was measured by the EBSP method using Schottky-type FESEM (JSM6500F by Nippon Electronics Co., Ltd.), and the ratio of the corresponding grain boundary 3 in a grain boundary was calculated | required. The measurement was performed with a region of at least 0.01 mm 2 or more as a hexagonal measuring point and 50 nm or less in the beam feeding interval. And when the orientation difference of adjacent measuring points is 5 degrees or more, (the side which each hexagon contact | connects) between the measuring points was considered as a grain boundary. In addition, identification of the corresponding grain boundary 3 was performed by setting the mode of the FESEM to the "EBSP System Technology Laboratories OIM System". And the ratio of the corresponding grain boundary 3 was calculated | required by calculating | requiring the value represented by {(sum of the corresponding grain boundary 3 length) / (sum of the grain boundary length)} x100 from the measurement data.

3. Evaluation

(1) elongation

The elongation at break when the No. 5 test piece was produced from each sample and the tensile test was measured in accordance with the tensile test method prescribed | regulated to JIS-Z 2241.

(2) processability

The sample was bent by a W bending tester, and the outside of the bend was observed at 50 times magnification with an optical microscope, and the presence of cracks was visually evaluated.

○: no cracking

△: no cracking but high surface roughness

×: cracks are remarkable

(3) tensile strength

Tensile strength was measured in the tensile test.

(4) conductivity

The conductivity of the sample was measured by the four-terminal method.

The obtained results are shown in Table 1.

As is clear from Table 1, in each of the examples, the ratio of Σ3 is 10% or more, shows an elongation of 8% or more, and is excellent in both workability and tensile strength. Moreover, the conductivity is high and the conductivity is excellent. In particular, in the case of Examples 1, 3, 5-7 which made Cr content less than 0.6%, all showed the high elongation exceeding 10%.

On the other hand, in the case of Comparative Examples 1-7 in which the ratio of 3 was less than 10%, the elongation was less than 8% in all cases, and it fell compared with each Example. In particular, in Comparative Examples 2 and 4 to 7, the workability was deteriorated in addition to the elongation. In addition, in the case of Comparative Examples 1-3 and 5-7, although the total workability was 95% or more, the average workability of each path | pass was less than 20%. On the other hand, in the case of Comparative Example 4, the average workability of each pass was 20% or more, but the overall workability was less than 95%. In this regard, in order to make the ratio of 3 to 10% or more, it is understood that the overall workability is 95% or more and the average workability of each pass is preferably 20% or more.

According to the high-strength highly conductive copper alloy of the present invention, a copper alloy excellent in both strength and workability is obtained. In addition, since the measurement of the corresponding grain boundary 3 is simple, production management becomes easy.

Claims (4)

The grain boundary is composed of Cr: 0.05 to 1.0%, Zr: 0.05 to 0.25%, residual Cu, and unavoidable impurities, and when the orientation difference between adjacent crystals is 5 ° or more, the grain boundaries are regarded as the grain boundaries. A high-strength highly conductive copper alloy, wherein the ratio of the corresponding grain boundary Σ3 at 10% or more. The high-strength altitude according to claim 1, further comprising 0.01 to 1.0% by mass of one or more selected from the group consisting of Zn, P, Fe, Mg, Mn, Al, Co, and Ni. Malleable copper alloy. The high-strength highly conductive copper alloy according to claim 1 or 2, wherein the Cr content is 0.6% or less and an elongation of 8% or more is shown. The high-strength highly conductive copper alloy according to claim 1 or 2, wherein the Cr content is 0.2% or less and an elongation of 10% or more is shown.