JP2012193408A - Cu-Ni-Si ALLOY HAVING EXCELLENT BENDABILITY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-Ni-Si alloy showing improved bendability, even when notched.SOLUTION: The alloy wire includes: 1.0-4.5% Ni, 0.2-1.0% Si, and copper and inevitable impurities as the balance, wherein at the surface layer and the center, the maximum value of the X-ray random intensity ratio on the {200} pole figure is 3.0-15.0 within a range where the turning angle α of the axis perpendicular to the turning axis of the goniometer for diffraction specified by the Shultz method is within a range of 0-10°; preferably the number of inclusions having a grain size of 1-2 μm is 50 to 200 inclusions/mm; and the alloy optionally may contain a total of 0.005-2.5% of one or more selected from Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Co, Cr and Ag. The alloy is produced by hot rolling, cooling to 600-300°C at a speed of 10 to 100°C/minute, then cold rolling at a strain rate of 1×10to 1×10/s, solution treatment, aging, and final cold rolling, and can then be annealed.

Description

  The present invention relates to a Cu—Ni—Si alloy strip suitable as a material for connectors, terminals, relays, switches, and the like.

In recent years, with the miniaturization of electronic devices, the miniaturization of electrical and electronic components has been progressing. And the copper alloy used for these components is required to have good strength and electrical conductivity.
With the miniaturization of in-vehicle terminals, the copper alloy used is required to have good strength and electrical conductivity. Furthermore, in-vehicle female terminals are often subjected to a notching process called notching on the inner surface of the bending before press bending. This is processing performed to improve the shape accuracy after press bending. With the miniaturization of products, notching processing tends to become deeper in order to further improve the shape accuracy of terminals. Therefore, a copper alloy used for a vehicle-mounted female terminal is required to have good bending workability in addition to good strength and electrical conductivity.
In response to this demand, instead of conventional solid solution strengthened copper alloys such as phosphor bronze and brass, precipitation strengthened copper alloys such as a Corson alloy having high strength and conductivity are used, and the demand is increasing. Among the Corson alloys, Cu—Ni—Si based alloys are alloy systems having both high strength and relatively high electrical conductivity, and the strengthening mechanism is that Ni—Si based intermetallic compound particles are precipitated in the Cu matrix. Thus, the strength and conductivity are improved.

In general, strength and bending workability are contradictory properties, and it is desired to improve bending workability while maintaining high strength even in Cu-Ni-Si alloys.
As a method for improving the bending workability of the Cu—Ni—Si based alloy, there is a method of controlling the crystal orientation as described in Patent Documents 1 to 3. In Patent Document 1, the area ratio of {001} <100> of the measurement result of EBSP analysis is set to 50% or more. In Patent Document 2, the area ratio of {001} <100> of the measurement result of EBSP analysis is 50%. With the above and no layered boundary, in Patent Document 3, the area ratio of {110} <112> in the measurement result of EBSP analysis is 20% or less, and the area ratio of {121} <111> is 20% or less. Bending workability is improved by setting the area ratio of {001} <100> to 5 to 60%.

JP 2006-283059 A JP 2006-152392 A JP 2011-017072 A

However, in these methods, if bending is performed after notching, cracks are generated in the bent part. Especially, if the depth of notching is large, large cracks are generated. These methods are not sufficient to improve bending workability. Met.
Therefore, the present invention has an object to improve the bending workability of the Cu—Ni—Si based alloy, and in particular to improve the bending workability when notching is performed.

As a result of intensive investigation on the relationship between the crystal orientation of the Cu—Ni—Si based copper alloy and the bending workability, the present inventor has found {001} <100 on the {200} positive electrode diagram in both the surface layer and the central portion. It has been found that bending workability is improved by controlling the maximum value of the X-ray random intensity ratio in the region including the azimuth, in particular, bending workability after notching is improved.
Furthermore, in order to control the X-ray random intensity ratio of both the surface layer and the center part, it is cooled at a specific speed after hot rolling to make a specific amount of inclusions having a particle diameter of 1 to 2 μm, and the cold after hot rolling. It was found that adjusting the strain rate of hot rolling is effective.

That is, the present invention relates to the following inventions.
(1) It contains 1.0 to 4.5% by mass of Ni and 0.2 to 1.0% by mass of Si, and the balance is made of copper and unavoidable impurities. 200} On the positive pole figure, the maximum value of the X-ray random intensity ratio in the range where the angle α around the axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schulz method is 0 to 10 ° is 3.0 to 15. A Cu—Ni—Si alloy strip excellent in bending workability, which is zero.
(2) The Cu—Ni—Si system described in (1), wherein the number of inclusions having a particle size of 1 to ² μm in a cross section parallel to the rolling direction and parallel to the plate thickness direction is 50 to 200 / mm ^2. Alloy strip.
(3) One or more of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Co, Cr, and Ag are contained in a total amount of 0.005 to 2.5 mass% (1) Or the Cu-Ni-Si-type alloy strip described in (2).

  Even if notching is performed on the inner surface of the bend before press bending, a crack does not occur and a Cu—Ni—Si based copper alloy having excellent bending workability is obtained.

FIG. 10 is a {200} positive dot diagram showing a range in which the angle α around the axis perpendicular to the rotation axis of the diffraction goniometer defined in the Schulz method is 0 to 10 ° in gray (in the center circle). It is the schematic of a notching process. The arrows in the figure indicate the pressure direction. It is the schematic of a 90 degreeW bending process.

(1) Ni and Si concentrations 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 precipitation, Ni and Si dissolved in the Cu matrix are reduced, so that the conductivity is improved. However, when the Ni concentration is less than 1.0% by mass (hereinafter referred to as “%”) or the Si concentration is less than 0.2%, the desired strength cannot be obtained. If the Si concentration exceeds 1.0%, the hot workability deteriorates.

(2) Other additive elements Addition of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Co, Cr, and Ag contributes to an increase in strength. Furthermore, Zn is effective in improving the heat-resistant peelability 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 concentration of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Co, Cr, and Ag is less than 0.005%, the above effect cannot be obtained. If it exceeds 5%, the electrical conductivity is remarkably lowered and it cannot be used as an electric / electronic component material.

(3) X-ray random intensity ratio In order to improve the bending workability, especially the bending workability after notching, the X-ray random intensity ratio of the region including the {001} <100> orientation on the {200} positive electrode diagram It is effective to increase the maximum value of. Furthermore, it is effective for improving the bending workability after notching to increase both the X-ray random intensity ratios in both the surface layer and the central part. In this specification, the “surface layer” represents a portion from the front and back surfaces of the strip to the 1/6 depth in the thickness direction, and the “central portion” represents a portion other than the surface layer. Note that the {001} <100> orientation on the {200} positive point diagram is the angle α around the axis perpendicular to the rotation axis of the diffraction goniometer specified by the Schulz method, and the axis around the axis parallel to the rotation axis. In terms of the angle β, α = 0 to 10 ° and β = 0 to 360 °.
In the present invention, the surface layer and the central portion are measured with an X-ray diffractometer (RINT2500 manufactured by Rigaku Corporation), and on the {200} positive pole figure, α is in the range of 0 to 10 ° (see FIG. 1). It has been found that bending workability is good when the maximum value of the random strength ratio is 3.0 or more. If the maximum value is less than 3.0, the bending workability deteriorates. On the other hand, it is difficult for the maximum value to actually exceed 15.0. Therefore, the upper limit of the maximum value is 15.0. Preferably, the maximum value is 5.0 or more in both the surface layer and the central portion.
The reason for achieving excellent bending cracking resistance by adjusting the X-ray random strength of the {001} <100> orientation is not clear, but the {001} <100> orientation is the introduction of shear bands during plastic deformation. It is considered that cracks are unlikely to occur during bending because the orientation is suppressed from other orientations. However, the present invention is not limited by the above theory. The ranges of α and β were determined in consideration of fluctuations in the peak position of the X-ray intensity ratio due to processing, heat treatment conditions, measurement errors, and the like.

The depth of cut by notching that is normally performed in the terminal manufacturing process reaches the center of the plate thickness if it is deep. Even if the maximum value of the X-ray random intensity ratio is increased only for the plate thickness surface layer, a microcrack is generated at the center of the plate thickness during notching, and this crack propagates to the surface layer by bending after notching. To do. Therefore, it is effective in improving the bending workability to adjust the crystal orientation by increasing the maximum value of the X-ray random intensity ratio in both the surface layer and the central portion.
On the other hand, Patent Documents 1 to 3 are all controlled by measuring the crystal orientation of the surface, and the crystal orientation of the central part is not controlled (claims 1 to 3 of Patent Documents 1 to 3). Therefore, in the bending process after the notching process, a micro crack is generated in the central part of the plate thickness, and the bending processability is inferior.

(4) Inclusions In the present invention, “inclusions” refers to generally coarse crystallized products that occur during the solidification process during casting, oxides, sulfides, and the like that are generated by reaction in the molten metal during melting, This is a concept that includes precipitates generated by precipitation reaction in the solid phase matrix after the solidification process during casting, that is, the cooling process after solidification, the hot rolling, the cooling process after solution treatment, and the aging treatment. The particles (so-called second phase particles) observed in the matrix by SEM observation of the copper alloy are included. “Inclusion particle size” refers to the diameter of the smallest circle including the inclusion, measured under SEM observation. “Number of inclusions” refers to a unit per square mm in which particles of components different from the parent phase are actually counted at a plurality of locations by SEM observation after etching in a cross section parallel to the rolling direction of the material and parallel to the plate thickness direction. Is the average number.

As described above, the inclusions of the present invention also include particles formed in the process after hot rolling, but it is the inclusion of a specific size that exists after hot rolling that mainly contributes to the intended function of the present invention. It is.
Specifically, the maximum X-ray random intensity ratio in both the surface layer and the central portion is present when inclusions having a particle diameter of 1 to 2 μm are present in the parallel rolling cross section after hot rolling at 50 to 200 pieces / mm ^2. The value becomes 3.0 or more. If it is outside the range of 50 to 200 pieces / mm ² , the maximum value of the X-ray intensity ratio becomes less than 3.0, and the bending workability deteriorates.
The number of inclusions having a particle size exceeding 1 μm after hot rolling is the number in the final product obtained through the manufacturing process of Cu—Ni—Si alloy including cold rolling, solution treatment, and aging treatment. Almost identical.
Specifically, after cold rolling, if cold rolling is performed on a material in which inclusions having a grain size of 1 to 2 μm are uniformly distributed in the thickness direction, the processing strain accumulates around the inclusions. Strain is uniformly distributed in the thickness direction. When solution treatment is performed on the material, crystal grains with {001} <100> orientation are recrystallized uniformly in the plate thickness direction, so that an X-ray intensity ratio within the above range can be obtained.

Conventionally, however, if there are coarse inclusions having a particle size of 1 to 2 μm after hot rolling of the precipitation-strengthened copper alloy, the desired strengthening will occur without the fine second-phase particles being sufficiently precipitated in the subsequent solution treatment step. There is a possibility that the effect cannot be achieved, and since it becomes a starting point of a crack at the time of bending, its bending workability was considered to deteriorate. Therefore, in the manufacturing process of the precipitation-strengthening-type copper alloy, it is sufficiently heated during hot rolling so that inclusions are not generated as much as possible after hot rolling, and is rapidly cooled by water cooling after hot rolling.
None of the above Patent Documents 1 to 3 pay attention to the conditions of the hot rolling process, and the crystal orientation of the rolling surface is adjusted by controlling only the degree of rolling processing or the solution treatment conditions. However, in cold rolling after hot rolling, if the strain rate is not controlled, the processing strains generated in the surface layer and the central portion are different, so the crystal orientations in the surface layer and the central portion are different. In the solution treatment, the amount of heat received by the surface layer and the central portion is different, and the target crystal orientation is usually not achieved in the central portion where the influence of the heat amount is small. Therefore, in the production methods of these patent documents, the crystal orientation in the central portion cannot be controlled, and the maximum value of the X-ray random intensity ratio in the region including the {001} <100> orientation has not increased in the central portion.

(5) Manufacturing process In the manufacturing process of the present invention, first, an atmospheric melting furnace is used, and raw materials such as electrolytic copper, Ni, and Si are melted under charcoal coating to obtain a molten metal having a desired composition. This molten metal is cast into an ingot. Then, hot rolling is performed, cold rolling, solution treatment (10 to 300 seconds at 700 to 1,000 ° C.), aging treatment (2 to 20 hours at 350 to 550 ° C.), final cold rolling (working degree) 5-40%). Strain relief annealing may be performed after the final cold rolling. The strain relief annealing is usually performed at 250 to 600 ° C. for 5 to 300 seconds in an inert atmosphere such as Ar. Further, in order to increase the strength, cold rolling may be performed between the solution treatment and the aging treatment. Further, after the solution treatment, the final cold rolling and the aging treatment may be performed in this order, and the order of these steps may be changed. As long as it is within the normal solution treatment, aging treatment, and final cold rolling conditions employed in the Cu—Ni—Si based alloy manufacturing process and exemplified above, The material that has undergone the cold rolling recrystallizes the crystal grains of the target orientation in both the surface layer and the central part by solution treatment, and the structure of the crystal orientation does not change essentially after the aging treatment and the final cold rolling.
Below, the manufacturing conditions of the process which becomes an important part in the manufacturing method of the alloy strip of this invention are explained in full detail.

(A) Hot rolling The ingot is heated at 800 to 1,000 ° C. for 1 to 20 hours and subjected to homogenization annealing, followed by rolling. The cooling rate while lowering the material temperature from 600 to 300 ° C. after rolling is preferably 10 to 100 ° C./min, more preferably 20 to 80 ° C./min. When the cooling rate is out of the above range, inclusions having a particle diameter of 1 to 2 μm tend to be out of the range of 50 to 200 / mm ² . That is, when the cooling rate is high, the number of inclusions having a particle size of 1 to 2 μm is less than 50 / mm ^2, and uniform strain cannot be generated in the thickness direction in the next cold rolling process, and when the cooling rate is low, the particle size is 1 to 2 μm. The number of inclusions exceeds 200 / mm ^2, and in the same way, uniform strain cannot be generated in the thickness direction in the next cold rolling step, and the bendability is lowered.

(B) Cold rolling after hot rolling The strain rate of cold rolling after hot rolling is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻⁴ / s, more preferably 5 × 10 ⁻⁵ to 8. 0.0 × 10 ⁻⁵ / s. In the present invention, “strain rate” is specified as rolling speed / roll contact arc length. When the strain rate is less than 1 × 10 ⁻⁶ / s, the maximum value of the X-ray intensity ratio of the obtained material is 3.0 or more at the surface layer, but less than 3.0 at the center. On the other hand, if it exceeds 1 × 10 ⁻⁴ / s, the maximum value of the X-ray intensity ratio of the obtained material is 3.0 or more at the center, but it is not preferable because it becomes less than 3.0 at the surface layer.

Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.
In a high frequency melting furnace, 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. After adding elements other than copper according to the composition of 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, a copper alloy strip was produced.
(Step 1) After heating at 950 ° C. for 3 hours, hot rolling to a thickness of 10 mm was performed, and the cooling rate until the material temperature decreased from 600 ° C. to 300 ° C. was changed as shown in Table 1.
(Step 2) The oxidized scale on the plate surface after hot rolling was ground and removed with a grinder.
(Step 3) Cold rolling was performed at a strain rate shown in Table 1 to a plate thickness of 0.180 mm. The strain rate was determined from rolling speed / roll contact arc length.
(Step 4) As a solution treatment, the solution was heated in the air at 800 ° C. for 10 seconds and rapidly cooled in water.
(Step 5) Using an electric furnace as an aging treatment, heating was performed in an Ar atmosphere at 450 ° C. for 5 hours.
(Step 6) The final cold rolling was performed to a plate thickness of 0.15 mm.
(Process 7) As strain relief annealing, it heated at 400 degreeC for 10 second in Ar atmosphere.
The samples thus produced were evaluated for the following characteristics.

(1) Inclusions In the sample after hot rolling, the structure of the cross section parallel to the rolling direction and parallel to the plate thickness direction is revealed by etching (water-ferric chloride), and FE-SEM (manufactured by FEI Japan) , XL30SFEG) was used to observe a secondary electron image in a 1 mm ² field at a magnification of 750 times. Thereafter, the particle size and number of inclusions in the observation field were determined using an image analyzer. Furthermore, although the inclusions of the product after the final process were measured, it was confirmed that the number of inclusions having a particle diameter of 1 to 2 μm after hot rolling did not change greatly after the final process.

(2) Maximum value of X-ray random intensity ratio Using an X-ray diffractometer (Rigaku Corporation, RINT2500), a Co tube is used, the tube voltage is 30 kV, the tube current is 100 mA, and the {200} positive electrode of each sample A point measurement was performed to create a {200} positive pole figure. The X-ray intensity within the above-mentioned range was measured, and the ratio with the X-ray intensity of copper powder (trade name copper (powder) 2N5, manufactured by Kanto Chemical Co., Ltd.) measured in the same manner as a standard sample was calculated. Asked. The maximum value of the X-ray random intensity ratio of the surface layer is the rolled surface, and the maximum value of the X-ray random intensity ratio of the central part is the central part of the plate thickness by spray etching of ferric chloride solution (1/2 of the plate thickness) Each of the exposed surfaces was measured. The measurement of the rolled surface was performed after the rolled surface was exposed to a solution of 67% phosphoric acid + 10% sulfuric acid + water by electrolytic polishing under conditions of 15 V 60 seconds, washed and dried.

(3) 0.2% yield strength and electrical conductivity 0.2% yield strength was measured according to JIS Z 2241 using a tensile tester. Good strength in the present invention means that 0.2% proof stress is in the range of 600 to 950 MPa, preferably 700 to 950 MPa.
The conductivity was measured according to JIS H 0505. In the present invention, good conductivity means 30% IACS or more, preferably 35% IACS or more.
(4) Bendability As an evaluation of bendability, notching was performed at depths of 25, 50, and 75 μm (see FIG. 2A). Thereafter, in accordance with JIS H 3130, a bending radius of 0 mm and 90 ° W bending in the Good Way direction were performed (see FIG. 2B). Note that the notched sample in FIG. 2A is used upside down in FIG. 2B. The cross section of the bent part 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 observed with an optical microscope (50 times magnification). The case where no crack was observed by optical microscope observation was evaluated as ◯, and the case where crack was observed was evaluated as x.
In the present invention, “excellent in bending workability” means that when the above evaluation is performed on a sample having a plate thickness of 0.15 mm, no cracking is observed even in a notching process having a depth of 50 μm.

Examples are shown in Table 1. Inventive Examples 1 to 23 were within the specified range, and even if bending was performed after notching, no cracks were observed, indicating good bending workability.
Comparative Example 1 had a low 0.2% proof stress because both the Ni and Si concentrations were low. In Comparative Example 2, cracks occurred during hot rolling because both Ni and Si concentrations were high. In Comparative Example 3, the concentration of additive elements other than Ni and Si was high, so the conductivity was low, and it was unsuitable as an electric / electronic component material.
Comparative Example 4 is an example in which the number of inclusions was large because the cooling rate of hot rolling was slow. The maximum value of the X-ray random intensity ratio was less than 3.0 in both the surface layer and the central portion, and the bending workability was poor. On the contrary, Comparative Examples 5 and 6 are examples of the prior art that are water-cooled after hot rolling. Since the cooling rate was high, the number of inclusions was small, and even when the strain rate of cold rolling was within an appropriate range, the maximum value of the X-ray random strength ratio was less than 3.0 in both the surface layer and the central portion, and the bending workability was It was bad.
Comparative Examples 7 and 8 are examples in which the strain rate of cold rolling after hot rolling was high. The maximum value of the X-ray random intensity ratio at the center is 3.0 or more, but the surface layer is less than 3.0 and the bending workability is poor even when the notching depth is 25 μm (1/6 of the plate thickness). It was. On the contrary, Comparative Examples 9 and 10 are examples in which the strain rate of cold rolling after hot rolling was slow. Although the maximum value of the X-ray random intensity ratio of the surface layer portion is 3.0 or more, the center portion is less than 3.0, and cracking did not occur at a notching depth of 25 μm, but 50 μm (1/1 of the plate thickness). 3) Cracks occurred and the bending workability was poor.
Comparative Example 11 is water-cooled after hot rolling in the same manner as in Patent Documents 1 to 3, and the maximum value of the X-ray random intensity ratio of the surface layer is increased to 3.0 or more by controlling the strain rate of the subsequent cold rolling. This is an adjusted example. Since the maximum value of the X-ray random intensity ratio in the center was less than 3.0, cracking occurred at a notching depth of 50 μm or more, and bending workability after notching was poor.

Claims (3)

  It contains 1.0 to 4.5% by mass of Ni and 0.2 to 1.0% by mass of Si, and the balance is made of copper and inevitable impurities, and the {200} positive electrode in both the surface layer and the central part On the dot diagram, the maximum value of the X-ray random intensity ratio in the range where the angle α around the axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schulz method is 0 to 10 ° is 3.0 to 15.0. Cu-Ni-Si alloy strip with excellent bending workability. ^{2. The} Cu—Ni—Si alloy strip according to claim 1, wherein the number of inclusions having a particle diameter of 1 to ² μm in a cross section parallel to the rolling direction and parallel to the plate thickness direction is 50 to 200 / mm ² .   Claim 1 or 2 containing at least 0.005 to 2.5 mass% in total of one or more of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Co, Cr and Ag. The Cu-Ni-Si-based alloy strip described.

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