JP2019052343A - Cu-Ni-Si BASED COPPER ALLOY EXCELLENT IN DIE WEAR PROPERTIES - Google Patents

Abstract

To provide a Cu-Ni-Si based copper alloy excellent in die wear properties.SOLUTION: There is provided a Cu-Ni-Si based copper alloy which comprises, by mass%, 2.0 to 5.0% of Ni and 0.3 to 1.5% of Si and the balance Cu with inevitable impurities, wherein the Ni/Si ratio is 1.3 or more and 6.7 or less, the 0.2% proof stress YS is 700 MPa or more, the number of first Ni-Si particles having a diameter of 0.5 to 0.6 μm is 0.04×10to 1.4×10pieces/mmand the number of second Ni-Si particles having a diameter of less than 0.5 μm is less than 4.0×10pieces/mm, which is equal to or larger than the number of first N-Si particles.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a Cu—Ni—Si based copper alloy suitable for conductive spring materials such as connectors, terminals, relays, switches and the like.

  Conventionally, brass and phosphor bronze, which are solid solution strengthened alloys, have been used as materials for terminals and connectors. By the way, with the improvement in performance of electronic equipment, the copper alloy used is required to have a high current. Thus, precipitation-strengthened copper alloys that are superior in strength, electrical conductivity, and thermal conductivity have been used compared to conventional solid solution-strengthened copper alloys. Precipitation-strengthened copper alloys are obtained by aging the solution-treated supersaturated solid solution to disperse fine precipitates uniformly, increasing the strength of the alloy and reducing the amount of solid solution elements in copper. As a result, electrical conductivity is improved. For this reason, it is excellent in mechanical properties such as strength and springiness, and also has good electrical and thermal conductivity.

  A Cu—Ni—Si based copper alloy has been developed as a precipitation strengthening type copper alloy (Patent Document 1). However, in general, the Cu—Ni—Si based copper alloy has a large shearing surface of the press punching surface in continuous press working, and the area where a tool such as a punch in the mold comes into contact with the material is increased, so that wear is promoted. . For this reason, there is a problem that the maintenance frequency of the mold is increased and the productivity is lowered, and suppression thereof is desired.

Therefore, in recent years, a technique for controlling the number and distribution of precipitates has been proposed as a technique for improving the mold wear of Corson alloy. For example, in the invention of Patent Document 2, the process includes (1) hot rolling (2) cold rolling (3) solution treatment (4) aging treatment (5) final cold rolling (6) strain relief annealing in this order. Then, cooling after the end of the final pass of hot rolling is performed at a starting temperature of 300 to 450 ° C., and cold rolling before solution treatment is performed with an average rolling rate per pass of 15 to 30% and a total rolling rate of 70. The solution treatment is performed at 800 to 900 ° C. for 60 to 120 seconds, and the aging treatment is performed at 400 to 500 ° C. for 7 to 14 hours.
Accordingly, the number of Ni—Si precipitate particles having a surface particle diameter of 20 to 80 nm is 1.5 × 10 ^{6 to} 5.0 × 10 ⁶ particles / mm ² , and the Ni—Si precipitate exceeding the surface particle diameter of 100 nm is used. The number of particles is controlled to 0.5 × 10 ^{5 to} 4.0 × 10 ⁵ particles / mm ² , and Ni—Si having a particle size of 20 to 80 nm in the surface layer whose thickness from the surface is 20% of the total plate thickness When the number of precipitate particles is a / mm ² and the number of Ni—Si precipitate particles having a particle diameter of 20 to 80 nm in the inner portion of the surface layer is b / mm ² , a / b is 0.00. It is controlled so as to be 5 to 1.5, and the mold wear resistance is improved.

In the invention of Patent Document 3, (1) casting (casting at a cooling rate of 10 to 30 ° C./second) (2) reheat treatment (at 850 to 950 ° C. for 2 to 8 hours) (3) hot rolling (end temperature 680) ˜780 ° C., rolling time 180 to 450 seconds, cooling time 40 to 180 ° C./second) (4) face milling (5) cold rolling (6) solution treatment (950 ° C. for 20 seconds, then immediately water quenching) ( 7) Aging heat treatment (implemented at a temperature of 425 to 500 ° C. for 1 to 6 hours) (8) Implemented in a step including cold rolling (rolling rate 10%) in this order.
Thereby, (a) (three kinds of intermetallic compounds A (diameter: 0.3 μm or more and 2 μm or less) containing Ni and Si in total of 50 mass% or more), B (diameter: 0.05 μm or more and less than 0.3 μm), C (Diameter: more than 0.001 μm and less than 0.05 μm)), (b) (the relationship between the horizontal length x (μm) and the vertical length y (μm) of the crystal grain size in the cross section perpendicular to the rolling direction of the copper alloy sheet) Formula [x / y ≧ 2] is satisfied, and (c) (dispersion density a of compound A, dispersion density b of intermetallic compound B, and dispersion density c of intermetallic compound C are expressed by the relation [a / (B + c) ≦ 0.010] and [0.001 ≦ (b / c) ≦ 0.10]) are satisfied to improve mold wear resistance.

International Publication No. WO2011 / 068134 International Publication No. WO2013 / 094061 JP 2008-95185 A

However, the conventional Cu—Ni—Si based copper alloy improves the wear resistance of the mold, but has not been sufficiently studied in a higher strength region.
In view of these circumstances, the present invention has been made in order to solve the above-described problems, and an object thereof is to provide a Cu—Ni—Si based copper alloy having excellent mold wear.

Precipitation-strengthening Cu-Ni-Si based copper alloy deposits a large amount of Ni-Si particles having a particle size of nm level as precipitates by aging treatment, but does not contribute to improvement in strength, but has a fine particle size of μm level. There are also many Ni-Si particles.
When the Ni content is 2.0% or more, the Ni / Si ratio is 1.3 or more and 6.7 or less, and the 0.2% proof stress YS is high strength of 700 MPa or more, Cu— When a Ni-Si-based copper alloy material is pressed, if Ni-Si particles of a μm level existing on the surface and fracture surface of the material come into contact with the mold, scratches are generated starting from the particles. discovered. It was found that the number of Ni—Si particles having a diameter of 0.5 to 0.6 μm correlated with the number of scratches. Then, it discovered that metal mold | die abrasion could be improved by suppressing the Ni-Si deposit of 0.5-0.6 micrometers in diameter.
Furthermore, the yield ratio YS / TS, which is the ratio of the tensile strength TS (MPa) of the product to the 0.2% proof stress YS (MPa), is 0.9 or more, and the work hardening index n value (hereinafter n value) is 0. It has been found that the wear resistance of the mold is further improved when it is 0.05 or less.

Further, when the number of Ni—Si particles having a diameter of less than 0.5 μm is smaller than the number of Ni—Si particles having a diameter of 0.5 to 0.6 μm, adhesion wear is promoted, and Ni—Si particles having a diameter exceeding 0.6 μm are promoted. It has also been found that when the number of particles exceeds the number of Ni—Si particles having a diameter of 0.5 to 0.6 μm, scratch wear is promoted.
When the Ni content is less than 2.0% and the 0.2% proof stress YS is less than 700 MPa, the phenomenon in which the number of Ni—Si particles affects the mold wear is not noticeable. It was.

  Ni-Si particles with a particle size of nm level can be adjusted by controlling the conditions of solution treatment and aging treatment. However, when trying to control Ni-Si particles of μm level, overaging or the like must be performed. In other words, properties such as strength are impaired. Thus, it has been found that the diameter and number of Ni—Si particles immediately after hot rolling are controlled by controlling the hot rolling conditions.

In order to achieve the above object, the Cu-Ni-Si based copper alloy of the present invention contains, in mass%, Ni: 2.0 to 5.0%, Si: 0.3 to 1.5%, The Ni / Si ratio is 1.3 or more and 6.7 or less, the balance is Cu and inevitable impurities, the 0.2% proof stress YS is 700 MPa or more, and the first Ni having a diameter of 0.5 to 0.6 μm The number of second Ni—Si particles having a diameter of less than 0.5 μm is 0.04 × 10 ^{3 to} 1.4 × 10 ³ particles / mm ² or more than the number of the first Ni—Si particles. 0.0 × 10 ³ pieces / mm ^{2 or} less.

It is preferable that the yield ratio YS / TS is 0.9 or more and the work hardening coefficient n value is 0.05 or less.
The Cu—Ni—Si based copper alloy of the present invention preferably further contains at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr in a total amount of 0.005 to 1.0 mass%.

  According to the present invention, it is possible to obtain a Cu—Ni—Si based copper alloy excellent in mold wear.

It is a figure explaining the wear area of the punch for quantifying die wear.

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

(composition)
[Ni, Co and Si]
The copper alloy contains Ni: 2.0 to 5.0%, Si: 0.3 to 1.5%, and the Ni / Si ratio is 1.3 or more and 6.7 or less. Ni and Si form an intermetallic compound by performing an appropriate heat treatment, and improve the strength without deteriorating the electrical conductivity.
When the content of Ni and Si is less than the above range, the effect of improving the strength cannot be obtained.
In both cases where the Ni / Si ratio is less than 1.3 and the Ni / Si ratio exceeds 6.7, the conductivity is significantly reduced.

[Other additive elements]
The alloy may further contain 0.005 to 1.0% by mass in total of at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr.
Mg improves strength and stress relaxation resistance. Mn improves strength and hot workability. Sn improves the strength. Zn improves the heat resistance of the solder joint. Since Cr forms a compound with Si like Ni, it improves the strength without deteriorating conductivity by precipitation hardening.
In addition, when the total amount of each element described above is less than the above range, the above effect cannot be obtained, and when it exceeds the above range, the conductivity may be lowered.

[Ni-Si particles]
The first Ni—Si particles (precipitates) having a diameter of 0.5 to 0.6 μm contained in the Cu—Ni—Si based copper alloy are 0.04 × 10 ^{3 to} 1.4 × 10 ³ particles / mm ² . is there.
The first Ni—Si particles cause scratching of the mold as described above.
Therefore, it is better that the number of the first Ni—Si particles is smaller, but the number of the first Ni—Si particles is less than 0.04 × 10 ³ particles / mm ² per unit area of the Cu—Ni—Si based copper alloy. In this case, adhesion wear in which the Cu—Ni—Si based copper alloy adheres to the mold is promoted.

Here, since stress concentrates at the time of pressing Ni-Si particles and becomes a starting point of cracks, the larger the Ni-Si particles are distributed or the more the Ni-Si particles are distributed, the smaller the ratio of the material to the shear plane. This is because the greater the number of Ni—Si particles, the more the stress concentration portion and the earlier the cracks progress, so the ratio of the material to the shear plane becomes smaller. And since a shear surface is a surface which contacts the metal mold | die in press, when the area increases, the contact time of a metal mold | die and a material will become long, and it will become easy to adhere an adhesive substance from a material to a metal mold | die.
On the other hand, when the number of the first Ni—Si particles exceeds 1.4 × 10 ³ particles / mm ² , scratch abrasion of the mold is promoted.

The number of second Ni—Si particles having a diameter of less than 0.5 μm included in the Cu—Ni—Si based copper alloy is equal to or greater than the number of first Ni—Si particles and 4.0 × 10 ³ particles / mm ^2. Is less than.
Adhesive wear is promoted when the number of second Ni—Si particles is less than the number of first Ni—Si particles. On the other hand, when the number of the second Ni—Si particles is 4.0 × 10 ³ particles / mm ² or more, scratch wear is promoted.

Here, the influence on the mold wear by the number of the second Ni—Si particles is the same as the influence on the mold wear by the number of the first Ni—Si particles. When the number is small, adhesive wear is promoted, and when the number is large, scratch wear is promoted.
Note that the increase or decrease in the number of second Ni—Si particles tends to change as the number of first Ni—Si particles increases or decreases.

  The particle diameter and the number of the first and second Ni—Si particles are determined by polishing a rolled parallel section of a Cu—Ni—Si based copper alloy, and using an FE-SEM (electrolytic emission scanning electron microscope) after etching. Measurement is performed based on an image with a magnification of about 1500 to 5000 times. The components in the image are measured using particle analysis software and EDS (energy dispersive X-ray analysis), and particles composed of components different from the base material components are regarded as first to third Ni—Si particles. The particle size of each particle is measured, and the number is counted using image processing software (for example, ImageJ published by the National Institutes of Health). Here, the diameter of the circle circumscribing the precipitate is defined as the particle diameter of each Ni-Si particle.

The yield ratio YS / TS of the Cu—Ni—Si based copper alloy is preferably 0.9 or more and the work hardening coefficient (n value) is preferably 0.05 or less.
When the value of the yield ratio YS / TS is 0.9 or more, the difference between TS and YS is small, so that the fracture occurs as soon as the elongation starts. That is, when the yield ratio is high, the material breaks immediately during the pressing, so that the contact time between the mold and the material is shortened, and the wear resistance of the mold is improved.
The work hardening coefficient (n value) is a value correlated with the uniform elongation of the material. The smaller this value, the smaller the plastic deformation area required before punching when the material is pressed. That is, when the n value is 0.05 or less, the contact time between the mold and the material is shortened, so that the mold wear resistance is improved.

The work hardening coefficient (n value) is obtained as follows.
When a test piece is pulled and a load is applied in a tensile test, each part of the test piece is uniformly extended (uniform elongation) in the plastic deformation region exceeding the elastic limit and reaching the maximum load point. In the plastic deformation region where the uniform elongation occurs, there is an equation 1 between the true stress σ _t and the true strain ε _t.
σ _t = Kε _t ⁿ
This relationship is established, and this is called the n-th power hardening rule. “N” is defined as a work hardening coefficient (Kazuto Sudo: Material Testing Method, Uchida Otsukurakusha, (1976), p. 34). n takes a value of 0 ≦ n ≦ 1, and the larger the value of n, the greater the degree of work hardening. When a part that has undergone local deformation is work hardened, the deformation is transferred to other parts, and constriction is less likely to occur. . For this reason, a material with a large n value exhibits uniform elongation.

  The yield ratio and the n value have a correlation with the finish rolling work degree, respectively, and the yield ratio and the n value can be adjusted by controlling the rolling work degree of the finish rolling described later.

When the rolling degree of finish rolling is less than 10%, the yield ratio is smaller than 0.9 and the n value is larger than 0.05. When the rolling degree of finish rolling is 10% or more and less than 15%, it is preferable because the yield ratio becomes 0.9 or more by increasing the value of YS by work hardening. On the other hand, the n value remains greater than 0.05.
When the rolling degree of finish rolling is 15% or more and 30% or less, the yield ratio is 0.9 or more, and the n value becomes 0.05 or less because the uniform elongation decreases, which is the most suitable condition.

  When the rolling degree of finish rolling exceeds 30% and is 40% or less, the yield ratio becomes less than 0.9 because the strength of YS is saturated earlier than TS, and the n value is 0.05 or less. It becomes. Even if the rolling degree exceeds 40%, the same tendency is observed, but the die wear property is deteriorated as the yield ratio becomes smaller.

[0.2% yield strength]
The 0.2% yield strength of the Cu—Ni—Si based copper alloy in the rolling parallel direction is, for example, 700 MPa or more. When the 0.2% proof stress is 700 MPa or more, the strength is improved.
The tensile strength is obtained by a tensile test according to JIS-Z2241. The conditions of the tensile test were a test piece width of 12.7 mm, a room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, and a gauge length of 50 mm.

[Elongation]
The elongation in the rolling parallel direction of the Cu—Ni—Si based copper alloy is, for example, 13% or less. The lower limit of elongation is not particularly limited, but is, for example, 1%.
Elongation is elongation at break, and was measured simultaneously with the above-described tensile strength according to JIS-Z2241 using a tensile tester. And the difference of the length L (gauge length) between the gauge points when the test piece broke and the gauge distance L0 before the test was obtained in%.
The tensile test conditions were a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, a gauge length L = 50 mm, and a tensile test in the rolling direction of the copper foil.

[conductivity]
The conductivity (% IACS) of the Cu—Ni—Si based copper alloy is, for example, 30 or more.

<Manufacturing method>
The Cu—Ni—Si based copper alloy of the present invention can usually be produced by performing an ingot in the order of hot rolling, cold rolling, solution treatment, aging treatment, finish rolling, and strain relief annealing. Cold rolling and recrystallization annealing before solution treatment are not essential, and may be performed as necessary.

<Hot rolling>
Here, the third Ni—Si particles having a diameter of 1.0 μm to 3.5 μm in the material after hot rolling and before cold rolling are 3.5 × 10 ^{3 to} 8.5 × 10 ³ particles / mm. ^The hot rolling is set so as to be within the range of ² . This is because if the conditions of solution treatment and aging treatment are adjusted to control the Ni-Si particles at the μm level, overaging or the like must be performed, and properties such as strength are impaired.
Controlling the number of third Ni—Si particles having a diameter of 1.0 μm or more and 3.5 μm or less corresponds to controlling the number of first Ni—Si particles of the final product.
When the third Ni—Si particles are less than 3.5 × 10 ³ particles / mm ² , the first Ni—Si particles are less than 0.04 × 10 ³ particles / mm ² , and adhesion wear is promoted. . When the third Ni—Si particles exceed 8.5 × 10 ³ particles / mm ² , the first Ni—Si particles become 1.4 × 10 ³ particles / mm ² or more, and scratch abrasion is promoted.
The hot rolling conditions for regulating the diameter and number of the third Ni—Si particles can be adjusted, for example, in the range of a hot rolling temperature of 800 to 1000 ° C. and a holding time of 1 to 5 hours.

Electrolytic copper was melted in an air melting furnace, and a predetermined amount of additive elements shown in Table 1 was added as necessary, and the molten metal was stirred. Thereafter, the molten metal was poured into a mold at a casting temperature of 1200 ° C. to obtain a copper alloy ingot having the composition shown in Table 1. The ingot was hot-rolled to a plate thickness of 10 mm. Thereafter, chamfering, cold rolling, solution treatment, aging treatment, low-temperature heat treatment, and finish rolling were performed in this order to obtain a sample having a plate thickness of 0.05 to 0.4 mm. After finish cold rolling, strain relief annealing was performed in a temperature range of 200 ° C. to 500 ° C. for 1 second to 1000 seconds.
In addition, hot rolling was performed at 1000 degreeC for 3 hours, and the solution treatment was performed at 700-900 degreeC. The aging treatment was performed at 400 ° C. to 550 ° C. for 1 to 15 hours at a temperature and time at which the tensile strength after finish rolling was maximized, and the finish rolling was performed at a processing rate of 10 to 40%.

<Evaluation>
The following items were evaluated for the obtained samples.
[conductivity]
About the sample of the rolling parallel direction after strain relief annealing, based on JISH0505, electrical conductivity (% IACS) was computed from the volume resistivity calculated | required by the four-terminal method using a double bridge apparatus.
[Tensile strength]
About the sample after strain relief annealing, the JIS13B test piece was produced using the press so that the tension direction might become parallel to the rolling direction. The test piece was subjected to a tensile test according to JIS-Z2241, and the tensile strength TS was measured. The tensile test conditions were a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, a gauge length L = 50 mm, and a tensile test in the rolling direction of the copper foil.

[Elongation]
The elongation at break was determined by the tensile test. The difference between the length L between the gauge points when the test piece broke and the gauge distance L0 before the test was obtained in% and defined as elongation.

[Scratch wear evaluation]
Number of punch scratches: Scratches on the side surface of punches after punching 1 shot (10 shots in total) for each of 10 samples cut into 5 × 15 mm using a 5 mm square punch as the longitudinal direction of each sample. Were counted visually. When the number of punch scratches is 20 or less, there is little scratching of the mold, and the mold wear resistance is excellent.

[Adhesion wear evaluation]
Adhesion wear was determined using a ball-on-disk friction and wear tester. The test was performed with a load of 1 N and a sliding distance of 125 m, and the ball (mating material) was SUJ2.
When the profile of the cross section of the sliding part of the ball is measured with a laser microscope before and after the wear test, the height of the cross-sectional profile after the test is higher than before the test for the part with a length of 1 μm or more of the sliding part. It was determined that adhesive wear occurred.

[Evaluation of mold wear]
The mold wearability cannot be determined only by the above-described scratch wear evaluation and adhesion wear evaluation, and is also influenced by the mechanical properties of the material. In order to comprehensively judge these effects, use a turret punch press to measure the wear amount of the punch blade after punching out 100,000 shots of each sample on 5 samples cut out by 200 x 300 mm. The mold wear was evaluated. The amount of wear of the punch blade was measured on the basis of before the press.
A cylindrical punch was used, the clearance was 5% of the plate thickness, the press speed was 290 shots / min, and the indentation depth of the punch was set to 50% of the plate thickness. Further, punches and dies having different hardnesses were used, and the punch hardness was set to be 60 to 80% of the die hardness.

As shown in FIG. 1, the wear amount of the punch blade is an area S1 in which a height difference is generated between the cross-sectional profile P1 of the punch blade before pressing and the cross-sectional profile P2 of the punch blade after pressing, as shown in FIG. The area was calculated as the worn area. A symbol D in FIG. 1 indicates a pressing direction. The mold wear was evaluated according to the following criteria. If the evaluation is ◯, the mold wear is excellent, and if it is ◎, it is further excellent.
◎: Wear area is 1000 .mu.m ² or less ○: wear area exceeds 1000 .mu.m ² 1500 .mu.m ² less ×: wear area is 1500 .mu.m ² or more

  The obtained results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, in each Example in which the number of the first Ni—Si particles to the second Ni—Si particles was regulated within a predetermined range, the mold wear was excellent. Further, those with a finish rolling workability of 15 to 30% were further excellent in mold wear, yield ratio YS / TS was 0.9 or more, and work hardening coefficient n value was 0.05 or less. This is probably because the contact time between the mold and the material has decreased.
In Examples 5, 7, and 9 in which the workability of finish rolling was 10% or more and less than 15%, the yield ratio was 0.9 or more, but the n value was larger than 0.05. Further, in Examples 2, 3, 10, and 11 in which the workability of finish rolling exceeds 30% and is 40% or less, the n value was 0.05 or less, but the yield ratio was smaller than 0.9. . However, these examples also have no practical problem.

On the other hand, Comparative Example 1 in which the first Ni—Si particles exceeded 1.4 × 10 ³ particles / mm ² and the number of the second Ni—Si particles became 4.0 × 10 ³ particles / mm ² or more. In the case of? 4 and Comparative Example 6, the number of punch scratches exceeded 20, the scratch wear of the mold was promoted, and the mold wear was inferior.
In the case of Comparative Example 5 in which the first Ni—Si particles are less than 0.04 × 10 ³ particles / mm ² and the number of second Ni—Si particles is less than the number of first Ni—Si particles, adhesive wear is caused. As a result, the mold wear was inferior.

Claims (3)

In mass%, Ni: 2.0 to 5.0%, Si: 0.3 to 1.5%, Ni / Si ratio is 1.3 or more and 6.7 or less, and the balance is Cu and inevitable impurities 0.2% proof stress YS is 700 MPa or more, and the first Ni—Si particles having a diameter of 0.5 to 0.6 μm are 0.04 × 10 ^{3 to} 1.4 × 10 ³ particles / mm ² , A Cu—Ni—Si based copper alloy in which the number of second Ni—Si particles having a diameter of less than 0.5 μm is equal to or more than the number of first Ni—Si particles and less than 4.0 × 10 ³ / mm ² .   The Cu-Ni-Si based copper alloy according to claim 1, wherein the yield ratio YS / TS is 0.9 or more and the work hardening coefficient n value is 0.05 or less.   Furthermore, the Cu-Ni-Si type | system | group copper alloy of Claim 1 which contains 0.005-1.0 mass% of at least 1 sort (s) chosen from the group of Mg, Mn, Sn, Zn, and Cr in a total amount.