JP2020158817A - Cu-Ni-Si BASED ALLOY STRIP EXCELLENT IN STRENGTH AND BENDABILITY IN ROLLING PARALLEL DIRECTION AND ROLLING RECTANGULAR DIRECTION - Google Patents

Abstract

To provide a Cu-Ni-Si based alloy strip excellent in bendability in the rolling rectangular direction even when subjected to severe processing, such as notching, etc., while maintaining bendability in the rolling parallel direction.SOLUTION: The Cu-Ni-Si based alloy strip excellent in strength and bendability includes Ni of 1.0-4.5 mass%, Si of 0.25-1.5 mass% and the remainder consisting of copper and inevitable impurities, and has a texture that the maximum value of an X ray random intensity ratio in the range of the following (1)-(2) is 10.0 or more and 20.0 or less in a {111} positive pole figure and the maximum value of an X ray random intensity ratio in the range of the following (3) is 0 or more and 2 or less in a {200} positive pole figure. (1) α=65±10° and β=0 ±15°, (2) α=65±10°and β=180 ±15°, (3) α=80-90° (where, α: an axis perpendicular to the axis of rotation of a diffraction goniometer specified by the Shultz method and β: an axis parallel to the axis of rotation).SELECTED DRAWING: Figure 1

Description

The present invention relates to copper alloys, and more particularly to copper alloy strips preferably used for conductive spring materials such as connectors, terminals, relays and switches.

With the recent miniaturization of electronic devices, terminals, connectors, etc. have become smaller and thinner, and the copper alloys for electronic materials used for these are required to have higher strength and bendability than before. ing. In response to this demand, precipitation-reinforced copper alloys such as Cu-Ni-Si-based Corson alloys and titanium copper are being used in place of conventional solid-melt reinforced copper alloys such as phosphor bronze and brass, and the demand for them is increasing. .. Among the precipitation-strengthened copper alloys, Cu-Ni-Si alloys are alloys that have both high strength and relatively high conductivity, and the strengthening mechanism is that Ni-Si intermetallic compound particles are contained in the Cu matrix. The strength is improved by precipitating.

In general, strength and bending workability are contradictory properties, and it has been conventionally desired to improve bending workability while maintaining high strength even in Cu—Ni—Si based alloys, but high strength and excellent bending workability have been conventionally desired. At present, it is difficult to combine bending workability. In particular, since ultra-miniaturized terminals are subjected to severe bending such as bending after notching (box bending), copper alloy strips having both high bendability and high strength after notching are required.

As a method for improving bending workability, Patent Document 1 discloses a method for controlling the crystal orientation of a Cu—Ni—Si alloy system. In the present invention, the X-ray diffraction intensities of the (200) plane, (220) plane, and (311) plane are I (200), I (220), and I (311), and the following equation: I (200) + I (311) ) / I (220) ≥ 0.5, it is said that the bendability is improved when the texture is formed.
However, considering that I (200) and I (311) increase due to the coarsening of the particle size at the time of recrystallization, and I (220) increases due to the increase in the workability of cold rolling, the above equation is satisfied. It is necessary to coarsen the crystal grain size and reduce the workability of cold rolling, which causes a decrease in strength. Therefore, there has been a demand for a method capable of improving bending workability without requiring adjustment of a manufacturing process such as coarsening of crystal grain size causing a decrease in strength and reduction of workability in cold rolling.

Therefore, Patent Documents 2 and 3 disclose Cu—Ni—Si alloys having good bending workability while maintaining high strength by adjusting the manufacturing process and controlling the texture. However, although the alloys obtained in the manufacturing processes of these documents improve the bendability in the rolling parallel direction (“Bad way” in which the bending axis is parallel to the rolling direction), the bendability in the rolling orthogonal direction (rolling direction). “Good way”) whose bending axis is orthogonal to the above is not considered.
Further, Patent Document 4 discloses a Cu—Ni—Si based alloy having good bending workability in the perpendicular direction. In general, when bending is performed after notching, cracks occur in the bent portion, and especially when the notching depth is long, large cracks occur. However, this technique examines the improvement of bendability after deep notching. It has not been.

Japanese Unexamined Patent Publication No. 2000-80428 JP-A-2007-921135 Japanese Unexamined Patent Publication No. 2012-193408 Japanese Unexamined Patent Publication No. 2013-204079

Here, the Corson alloy is generally characterized by having good bendability in the Bad way direction but low bendability in the Good way direction. Then, when the Corson alloy strip is press-processed, bendability in the Good way direction may be required.
Therefore, an object of the present invention is to provide a Cu—Ni—Si alloy strip having good bendability in the direction perpendicular to rolling even if severe processing such as notching is performed while maintaining bendability in the parallel direction of rolling. To do.

As a result of diligently investigating the relationship between the crystal orientation and bending workability of the Cu—Ni—Si based copper alloy, the present inventor found that the {111} positive angle diagram was in two regions including the {123} <412> orientation. By controlling the maximum value of the X-ray intensity within a specific range and controlling the maximum value of the X-ray random intensity ratio in the region including the {001} <100> orientation on the {200} positive point diagram, the right angle It has been found that the directional (Good way) bending workability is improved, and in particular, the bending workability after notching processing is improved.

In order to achieve the above object, the Cu—Ni—Si based copper alloy strip of the present invention contains 1.0 to 4.5% by mass of Ni and 0.25 to 1.5% by mass of Si. However, the balance is composed of copper and unavoidable impurities, and in the {111} positive point diagram, the maximum value of the X-ray random intensity ratio in the range of (1) to (2) below is 10.0 or more and 20.0 or less. {200} In the positive point diagram, Cu having excellent strength and bendability, characterized by having an texture in which the maximum value of the X-ray random intensity ratio in the range of (3) below is 0 or more and 2 or less. -Ni-Si based alloy strip.
(1) α = 65 ± 10 °, β = 0 ± 15 °
(2) α = 65 ± 10 °, β = 180 ± 15 °
(3) α = 80 to 90 °
(However, α: the axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schultz method, β: the axis parallel to the rotation axis)

The 0.2% proof stress is preferably 600 MPa or more.
It is preferable that one or more of Zn, Sn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn and Ag are contained in a total amount of 0.005 to 2.0% by mass.

According to the present invention, a Cu—Ni—Si copper alloy strip having excellent bending workability in the right angle direction (Good way) even if severe processing such as notching is performed while maintaining bendability in the parallel rolling direction. can get.

{111} It is a figure which shows the two regions (1) and (2) defined on the positive electrode point diagram. {200} It is a figure which shows the region (3) defined on the positive electrode point diagram. It is a figure which shows the method of performing the notching processing. It is a figure which shows the method of performing the W bending process.

Hereinafter, Cu—Ni—Si based copper alloy strips according to the embodiment of the present invention will be described. In the present invention,% means mass% unless otherwise specified.

(composition)
[Ni and Si concentration]
Ni and Si are precipitated as intermetallic compounds such as Ni ₂ Si by performing an aging treatment. This compound improves the strength, and by precipitating, Ni and Si dissolved in the Cu matrix are reduced, so that the conductivity is improved. However, if the Ni concentration is less than 1.0% or the Si concentration is less than 0.25%, the desired strength cannot be obtained, and conversely, if the Ni concentration exceeds 4.5% or the Si concentration is 1.5%. If it exceeds, the hot workability deteriorates.
Therefore, Ni: 1.0 to 4.5% and Si: 0.25 to 1.5%.

[Other additive elements]
Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn and Ag contribute to the increase in the strength of the alloy. Further, Zn is effective in improving the heat-resistant peeling property of Sn plating, Mg is effective in improving stress relaxation characteristics, and Zr, Cr, and Mn are effective in improving hot workability.
If the total content of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn and Ag is less than 0.005%, the above effect cannot be obtained, and the total amount is 2.5%. If it exceeds, the conductivity may decrease.

[Aggregate organization]
In general, the texture is a statistical bias of the crystal orientation formed by processing and heat treatment, and is largely dependent on the processing conditions and heat treatment conditions.
The present inventors measured the texture of Cu—Ni—Si alloys with different manufacturing processes using an X-ray diffractometer (RINT2500 manufactured by Rigaku Co., Ltd.) and perpendicular to the texture of Cu—Ni—Si alloy strips. The relationship between the bending workability (bending crack resistance and bending wrinkle) of the direction (Good way) was investigated.

As a result, there is a correlation between the two, and the bendability of the Bad way is improved when the maximum value of the X-ray random intensity ratio in the region including the {123} <412> orientation is within a certain range. , {001} <100> It was found that the bendability of Goodway is improved when the maximum value of the X-ray random intensity ratio in the region including the orientation is within a certain range.
The {123} <412> azimuth is {111 when expressed by the angle α around the axis perpendicular to the rotation axis of the diffraction goniometer defined by the Schultz method and the angle β around the axis parallel to the rotation axis. } On the positive point diagram, α = 68 °, β = 0 ° and α = 68 °, β = 180 °, and the {001} <100> orientation is α = on the {200} positive point diagram. It corresponds to 80 to 90 ° and β = 0 to 360 °.

By controlling the strength in the above two directions, it is possible to obtain an alloy having excellent bending workability in both the parallel direction and the perpendicular direction. This is because the {123} <412> orientation is the stable orientation of the rolling deformation of the Cu—Ni—Si based alloy, and the slip deformation is prevented as compared with the case of having other crystal orientations. Further, in the {001} <100> orientation, the introduction of the shear band at the time of plastic deformation is suppressed more than in other orientations, but the optimum ratio of each crystal orientation to the bending workability is different.
Even if one of the above two directions is extremely large, it is difficult to achieve both parallel and right-angle bending workability, and it is necessary to satisfy both the α and β ranges of the two directions.
The range of α and β is widened as in the claims (1) to (3) (that is, for example (1), α = 68 ° in the above description, but α = 65 ±. The reason (having a width of 10 °) is that the peak position of the X-ray intensity ratio corresponding to each direction fluctuates due to processing, heat treatment conditions, measurement error, and the like.

The 0.2% proof stress of the Cu—Ni—Si based alloy strip of the present invention is preferably 600 to 950 MPa, more preferably 700 to 950 MPa. If the 0.2% proof stress is less than 600 MPa, the strength is lowered, and if it exceeds 950 MPa, there is a high possibility that cracks will occur when bent.
The conductivity of the Cu—Ni—Si based alloy strips of the present invention is preferably 30% IACS or higher, more preferably 35% IACS or higher.

An example of the manufacturing process of the Cu—Ni—Si based alloy strip of the present invention will be described. First, using an atmospheric melting furnace, raw materials such as electrolytic copper, Ni, and Si are melted under charcoal coating to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. After that, hot rolling is performed, cold rolling, solution treatment (700 to 1,000 ° C for 10 to 300 seconds), aging treatment (350 to 550 ° C for 2 to 20 hours), and final cold rolling (workability). 5-40%).

Strain removal annealing may be performed after the final cold rolling. The strain-removing annealing is usually carried out at 250 to 600 ° C. for 5 to 300 seconds in an inert atmosphere such as Ar. Cold rolling may be performed between the solution treatment and the aging treatment in order to further increase the strength. Further, after the solution heat treatment, the final cold rolling and the aging treatment may be performed in this order, and the order of these steps may be changed.

If it is adopted in the manufacturing process of Cu-Ni-Si alloy strips and is within the conditions of the usual solution heat treatment, aging treatment and final cold rolling exemplified above, hot rolling and subsequent cold rolling are performed. In the material that has undergone rolling, the crystal grains in the target orientation are recrystallized in both the surface layer and the central portion by the solution treatment, and the structure of the crystal orientation does not essentially change even after the aging treatment and the final cold rolling.
The production conditions of the essential steps in the method for producing alloy strips of the present invention will be described in detail below.

Solution treatment: The solution treatment temperature is 700 to 1,000 ° C. for 10 to 300 seconds. By adjusting the cooling rate during the solution treatment in two steps, the crystal orientation that develops can be controlled. That is, the cooling rate is divided into two stages with 600 ° C as a boundary, the cooling rate is in the range of 40 to 60 ° C / sec at 600 ° C or higher in the first stage, and 80 to 100 ° C at less than 600 ° C in the second stage. Cool in the range of / sec.
When the cooling rate of the first stage exceeds 60 ° C./sec, the maximum value of the X-ray intensity ratio of the (111) plane in the ranges (1) and (2) becomes smaller than 10, and when it falls below 40 ° C./sec. , The maximum value of the X-ray intensity ratio of the (111) plane in the ranges (1) and (2) increases by more than 20.
When the cooling rate of the second stage exceeds 60 ° C./sec or falls below 40 ° C./sec, the maximum value of the X-ray intensity ratio of the (200) plane in the range (3) becomes larger than 3.

Examples of the present invention are shown below together with comparative examples, but these examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.
2.50 kg of electrolytic copper was dissolved in an alumina or magnesia crucible having an inner diameter of 110 mm and a depth of 230 mm in an argon atmosphere in a high-frequency melting furnace. After adding elements other than copper according to the composition in Table 1 and adjusting the molten metal temperature to 1,300 ° C., the molten metal was cast into a 30 × 60 × 120 mm ingot using a mold (material: cast iron), and the following In the process, copper alloy strips were made.

(Step 1) After heating at 950 ° C. for 3 hours, hot rolling was performed to a thickness of 10 mm.
(Step 2) The oxide scale on the plate surface after hot rolling was ground and removed with a grinder.
(Step 3) Cold rolling was performed to a plate thickness of 0.180 mm at a rolling reduction of 70%. The strain rate was determined from the rolling speed / roll contact arc length.
(Step 4) As the solution treatment, the first stage cooling rate until the material temperature drops to 600 ° C. and the second stage until the material temperature drops from 600 ° C. to 300 ° C. by heating in the air at 800 ° C. for 10 seconds. The cooling rate of the eyes was changed as shown in Table 1.
(Step 5) As an aging treatment, the mixture was heated at 450 ° C. for 5 hours in an Ar atmosphere using an electric furnace.
(Step 6) Final cold rolling was performed to a plate thickness of 0.18 mm.
(Step 7) For strain removing annealing, the mixture was heated at 400 ° C. for 10 seconds in an Ar atmosphere.
The following characteristics of the sample prepared in this manner were evaluated.

Maximum value of X-ray random intensity ratio Using a Co tube with an X-ray differential meter (Rigaku Co., Ltd., RINT2500), measure the {111} positive electrode point of each sample with a tube voltage of 30 kV and a tube current of 100 mA. This was done to create a {111} positive electrode point diagram. Copper powder (manufactured by Kanto Chemical Co., Inc., trade name: copper (powder) 2N5, 325 mesh (JIS Z8801, purity 99.)) measured in the range (1) and (2) described above and similarly measured as a standard sample. The ratio with the X-ray intensity of 5%) was calculated and the maximum value was obtained. The maximum value of the X-ray random intensity ratio was measured on the rolled surface. In the measurement of the rolled surface, the surface of the rolled surface was phosphoric acid. The structure was exposed by electrolytic polishing in a solution of 67% + 10% copper + water at 15 V for 60 seconds, washed with water and dried.
The X-ray intensity within the above-mentioned range (3) was also measured for the {200} positive electrode point diagram.

0.2% proof stress and conductivity 0.2% proof stress was measured according to JIS Z 2241 using a tensile tester. Specifically, a JIS13B test piece was prepared using a press machine so that the tensile direction of the sample was parallel to the rolling direction. A tensile test of this test piece was performed according to JIS-Z2241. The conditions of the tensile test were a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, and a gauge length of L = 50 mm, and a tensile test was performed in the rolling direction of the copper foil.
The conductivity was measured at 25 ° C. (% IACS) by the 4-terminal method in accordance with JIS H 0505.

Flexibility As an evaluation of bendability, as shown in FIG. 3, notching with depths of 50, 75, and 100 μm was performed, respectively. The extending direction of the notch was the direction along the bending axis (rolling perpendicular direction).
Then, according to JIS H 3130, 90 ° W bending was performed in the Good Way direction with a bending radius of 0 mm (see FIG. 4). The sample notched in FIG. 3 is used upside down in FIG.
The cross section of the bent portion parallel to the rolling direction and parallel to the plate thickness direction was finished to a mirror surface by mechanical polishing and buffing, and the presence or absence of cracks was visually observed with an optical microscope (magnification 50 times). The case where no crack was observed by the optical microscope observation was evaluated as ◯, and the case where crack was observed was evaluated as ×.
In the present invention, "excellent in bending workability" means that when the above evaluation is performed on a sample having a plate thickness of 0.18 mm, no cracks are observed even in a notching process having a depth of 75 μm.

The results are shown in Table 1. In each of the examples in which the X-ray random intensity ratios in the ranges (1) to (3) are within the predetermined range, cracks are observed even if the Goodway is bent after the notching while maintaining the bending workability of the Badway. However, it showed good Goodway bending workability.
In the case of Comparative Example 1 in which both the Ni and Si concentrations were less than the specified range, the 0.2% proof stress was reduced to less than 600 MPa. In the case of Comparative Example 2 in which both the Ni and Si concentrations exceeded the specified range, cracks occurred during hot rolling, and alloy strips could not be produced.

In the cases of Comparative Examples 3 and 4, where the cooling rate of the first-stage solution treatment is too slow or too fast, the maximum value of the X-ray random intensity ratio of the {111} plane is out of the range of 10.0 to 20.0. , Bad Way was inferior in bending workability.
In the cases of Comparative Examples 5 and 6, where the cooling rate of the second-stage solution treatment is too slow or too fast, the maximum value of the X-ray random intensity ratio of the {200} plane exceeds 2.0, and the bending workability of Goodway Was inferior.
In the case of Comparative Example 7 in which the cooling rates of the first-stage and second-stage solution treatments were the same, the cooling rate of the first stage was too fast, so that the maximum value of the X-ray random intensity ratio on the {111} plane was the maximum. It was less than 10.0, and the bending workability of Bad Way was inferior.

Rolling direction of RD sample Lateral direction of TD sample α Axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schultz method β Axis parallel to the rotation axis of the diffraction goniometer specified in the Schultz method

Claims (3)

It contains 1.0-4.5% by weight Ni and 0.25-1.5% by weight Si, with the balance consisting of copper and unavoidable impurities.
{111} In the positive electrode point diagram, the maximum value of the X-ray random intensity ratio in the range of (1) to (2) below is 10.0 or more and 20.0 or less.
{200} In the positive electrode point diagram, Cu having excellent strength and bendability, characterized by having an texture in which the maximum value of the X-ray random intensity ratio in the range of (3) below is 0 or more and 2 or less. -Ni-Si based alloy strip.
(1) α = 65 ± 10 °, β = 0 ± 15 °
(2) α = 65 ± 10 °, β = 180 ± 15 °
(3) α = 80 to 90 °
(However, α: the axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schultz method, β: the axis parallel to the rotation axis) The Cu—Ni—Si based alloy strip according to claim 1, wherein the 0.2% proof stress is 600 MPa or more. The Cu- according to claim 1 or 2, which contains 0.005 to 2.0% by mass of one or more of Zn, Sn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, and Ag in a total amount. Ni—Si based alloy strip.