KR102121180B1 - Cu-Ni-Si BASED COPPER ALLOY HAVING EXCELLENT WEAR-RESISTANCE OF MOLDING - Google Patents

Abstract

(Task) Provide a Cu-Ni-Si-based copper alloy having excellent mold abrasion resistance.
(Solution) As a mass%, Ni: 2.0-5.0%, Si: 0.3-1.5%, Ni/Si ratio is 1.3 or more and 6.7 or less, the balance is made of Cu and unavoidable impurities, and 0.2% yield strength YS is 700 ㎫ or more, 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 /mm 2, and the number of second Ni-Si particles having a diameter of less than 0.5 µm is the first Ni-Si It is a Cu-Ni-Si-based copper alloy with a number of particles greater than 4.0 × 10 ³ particles/mm 2.

Description

Cu-Ni-Si-based copper alloy with excellent mold wearability {Cu-Ni-Si BASED COPPER ALLOY HAVING EXCELLENT WEAR-RESISTANCE OF MOLDING}

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

Conventionally, as a material for a terminal or a connector, brass or phosphor bronze, which is a solid solution strengthening alloy, has been used. By the way, with the high performance of electronic devices, high current is required for the copper alloy used. Therefore, compared with the conventional solid solution strengthened copper alloy, a precipitation strengthened copper alloy excellent in strength, electrical conductivity, and thermal conductivity has been used. The precipitation-enhanced copper alloy is treated by aging the solution-saturated supersaturated solid solution, whereby fine precipitates are uniformly dispersed, the strength of the alloy is increased, and the amount of the dissolved element in copper is reduced to improve electrical conductivity. For this reason, mechanical properties, such as strength and spring properties, are excellent, and electrical conductivity and thermal conductivity become good.

As a precipitation strengthening type copper alloy, a Cu-Ni-Si type copper alloy has been developed (Patent Document 1). However, in general, the Cu-Ni-Si-based copper alloy has a large shear surface of the press punching surface in continuous press working, and thus increases the area where tools such as punches in the mold come into contact with the material, thereby increasing wear. . For this reason, there is a problem that the frequency of maintenance of the mold increases and productivity decreases, and suppression thereof is desired.

Therefore, recently, as a technique for improving the mold abrasiveness of the Colson alloy, a measure for controlling the number and distribution of precipitates has been proposed. For example, in the invention of Patent Document 2, (1) hot rolling (2) cold rolling (3) solution treatment (4) aging treatment (5) final cold rolling (6) stress relief annealing in this order In, cooling after the end of the hot rolling final pass is performed at a starting temperature of 300 to 450°C, cold rolling before the solution treatment is performed at an average rolling rate per pass of 15 to 30%, and a total rolling rate of 70% or more, 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.

Thereby, the number of Ni-Si precipitate particles having a particle diameter of 20 to 80 nm on the surface is 1.5×10 ⁶ to 5.0×10 ⁶ particles/mm 2, and the number of Ni-Si precipitate particles exceeding 100 nm on the surface particle diameter is 0.5×10. The number of Ni-Si precipitate particles having a particle size of 20 to 80 nm in the surface layer controlled from ⁵ to 4.0 x 10 ⁵ particles/mm 2 and the thickness from the surface being 20% of the total plate thickness is a/mm 2, and the surface layer When the number of Ni-Si precipitate particles having a particle size of 20 to 80 nm in the inner portion is set to b/mm 2, a/b is controlled to be 0.5 to 1.5 to improve mold abrasion resistance.

In the invention of Patent Document 3, (1) casting (casting at a cooling rate of 10 to 30°C/sec) (2) reheat treatment (2 to 8 hours at 850 to 950°C) (3) hot rolling (finish temperature 680 to 780 ℃, rolling time 180 to 450 sec, cooling time 40 to 180°C/sec) (4) Face milling (5) Cold rolling (6) Solution treatment (20 sec at 950°C, water immediately after that) (7) Aging heat treatment (temperature 425 to 500°C, performed for 1 to 6 hours) (8) Cold rolling (rolling rate of 10%) was performed in a process comprising this sequence.

Thereby, (a) (three types of intermetallic compounds A (diameter: 0.3 µm or more and 2 µm or less), B (diameter: 0.05 µm or more and less than 0.3 µm), C (containing Ni and Si in total, 50 mass% or more) Diameter: more than 0.001 µm and less than 0.05 µm), (b) (horizontal length x (µm) and vertical length y (µm) of the crystal grain diameter in the cross section perpendicular to the rolling direction of the copper alloy sheet, the relational formula [x /y ≥ 2]), and (c) (the dispersion density a of the compound A, the dispersion density b of the intermetallic compound B, and the dispersion density c of the intermetallic compound C are represented by the relational formula [a/(b + c) ≤ 0.010] and [0.001 ≤ (b/c) ≤ 0.10]), thereby improving the wear resistance of the mold.

International Publication No. WO2011/068134 International Publication No. WO2013/094061 Japanese Patent Application Publication No. 2008-95185

However, the conventional Cu-Ni-Si-based copper alloy improves mold abrasion resistance, but has not been sufficiently studied in a region with higher strength.

In view of these circumstances, the present invention has been made to solve the above problems, and aims to provide a Cu-Ni-Si-based copper alloy having excellent mold abrasion resistance.

The precipitation-enhanced Cu-Ni-Si-based copper alloy precipitates Ni-Si particles having a particle size of nm level as a precipitate in a large amount by aging treatment, but does not contribute to the improvement of strength. Si particles are also present.

When the content of Ni is 2.0% or more, the Ni/Si ratio is 1.3 or more and 6.7 or less, and the 0.2% yield strength YS is 700 MPa or more, when the material of the Cu-Ni-Si-based copper alloy is pressed, It has been found that when the Ni-Si particles of the µm level existing on the surface and the wavefront of the material come into contact with the mold, scratch wear occurs from the particles. Then, it was found that the number of Ni-Si particles having a diameter of 0.5 to 0.6 µm correlates with the number of scratches. Therefore, it was found that mold abrasion resistance can be improved by suppressing Ni-Si precipitates having a diameter of 0.5 to 0.6 µm.

Further, when the yield ratio YS/TS, which is the ratio of the tensile strength TS (㎫) of the product to 0.2% proof stress YS (㎫), is 0.9 or more, and the work hardening index n value (hereinafter, n value) is 0.05 or less, the inner mold is further molded. It was found that the abrasion resistance was improved.

In addition, adhesion wear is promoted 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, and the number of Ni-Si particles exceeding 0.6 μm in diameter is 0.5. It was also found that scratch wear was promoted when the number of Ni-Si particles of -0.6 µm was increased.

In addition, when the content of Ni is less than 2.0% and the 0.2% yield strength YS is less than 700 MPa, a phenomenon in which the number of Ni-Si particles affects mold abrasion is not remarkably confirmed.

And if it is Ni-Si particles having a particle size of nm level, it is possible to control and adjust the conditions of solution treatment and aging treatment. However, when controlling Ni-Si particles at a µm level, overaging or the like must be performed, such as strength. Properties. Therefore, it was 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 Ni: 2.0 to 5.0% and Si: 0.3 to 1.5% in mass%, and the Ni/Si ratio is 1.3 or more and 6.7 or less, The remainder is composed of Cu and unavoidable 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 /mm 2, and the diameter is less than 0.5 µm. The number of the second Ni-Si particles of the number of the first Ni-Si particles is greater than or equal to 4.0×10 ³ pieces/mm 2.

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.

It is preferable that the Cu-Ni-Si-based copper alloy of the present invention further contains at least one selected from the group of Mg, Mn, Sn, Zn, and Cr in a total amount of 0.005 to 1.0 mass%.

According to the present invention, a Cu-Ni-Si-based copper alloy having excellent mold abrasion properties is obtained.

1 is a view illustrating a wear area of a punch for quantifying mold wear.

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

(Furtherance)

[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 to 6.7. Ni and Si form an intermetallic compound by appropriate heat treatment, thereby improving strength without deteriorating the electrical conductivity.

When the content of Ni and Si is less than the above range, an effect of improving the strength is not obtained, and when it exceeds the above range, conductivity decreases and hot workability decreases.

When the Ni/Si ratio is less than 1.3, and when the Ni/Si ratio exceeds 6.7, the conductivity is significantly reduced.

[Other additive elements]

In the alloy, at least one selected from the group of Mg, Mn, Sn, Zn and Cr may be contained in an amount of 0.005 to 1.0% by mass in a total amount.

Mg improves the strength and stress relaxation characteristics. Mn improves strength and hot workability. Sn improves strength. Zn improves the heat resistance of the solder joint. Since Cr forms a compound with Si in the same way as Ni, it improves strength without deteriorating the electrical conductivity by precipitation hardening.

In addition, when the total amount of each element described above is less than the above-mentioned range, the above-described effect is not obtained, and if it exceeds the above-mentioned 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 /mm ³ .

As described above, the first Ni-Si particles generate scratch wear on the mold.

Therefore, it is preferable that the number of the first Ni-Si particles is small, but when the first Ni-Si particles are less than 0.04 x 10 ³ pieces/mm 2 per unit area of the Cu-Ni-Si-based copper alloy, Cu-Ni- is formed in the mold. Adhesion abrasion in which the Si-based copper alloy adheres is promoted.

Here, the Ni-Si particles are concentrated in stress at the time of pressing and become a starting point for cracking, so the ratio of the material to the shear surface of the Ni-Si particles is large or small enough to be distributed. This is because the larger the number of Ni-Si particles, the greater the concentration of stress areas, and the earlier the crack propagates, the smaller the proportion of the material to the shear surface. In addition, since the front end surface is a surface in contact with the metal mold in the press, when the area is increased, the contact time between the metal mold and the material becomes long, so that the adhesive material easily adheres to the metal mold from the material.

On the other hand, when the first Ni-Si particles exceed 1.4×10 ³ /mm ³ , scratch wear of the mold is promoted.

The number of second Ni-Si particles having a diameter of less than 0.5 µm contained in the Cu-Ni-Si-based copper alloy is greater than or equal to the number of first Ni-Si particles and less than 4.0 x 10 ³ /mm 2.

When the number of second Ni-Si particles is less than the number of first Ni-Si particles, adhesion abrasion is promoted. On the other hand, when the number of the second Ni-Si particles is 4.0 × 10 ³ /mm 2 or more, scratch wear is promoted.

Here, since 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, if the number of the second Ni-Si particles is small, adhesion Wear is promoted, and a large number promotes scratch wear.

In addition, the increase or decrease in the number of second Ni-Si particles tends to change with the increase or decrease in the number of first Ni-Si particles.

The particle size and number of the first to second Ni-Si particles are 1500 to 5000 using a FE-SEM (electrolyte radial scanning electron microscope) after grinding a parallel rolling section of a Cu-Ni-Si-based copper alloy and etching. It is measured on the basis of an image at a magnification of about 2 times. 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, Image J published by the National Institute of Sanitation in the United States). Here, the diameter of the circle circumscribed to the precipitate is taken as the particle diameter of each Ni-Si particle.

It is preferable that the yield ratio YS/TS of the Cu-Ni-Si-based copper alloy is 0.9 or more, and the work hardening coefficient (n value) is 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, and as soon as it starts to elongate, it breaks soon. That is, when the yield ratio is high, the material breaks immediately during press, thereby shortening the contact time between the mold and the material, thereby improving mold wear resistance.

Moreover, the work hardening coefficient (n value) is a value correlated with the uniform elongation of a material. The smaller this value, the smaller the plastic deformation area required for punching when the material is pressed. That is, when the value of n is 0.05 or less, the contact time between the mold and the material is shortened, so that the mold wear resistance is improved.

In addition, the work hardening coefficient (n value) is calculated|required as follows.

In the tensile test, when the test piece is stretched and a load is applied, each part of the test piece is uniformly stretched (uniformly elongated) in the plastic strain region that exceeds the elastic limit and reaches the highest load point. In the plastic strain region where this uniform elongation occurs, Equation 1 is between the true stress (σ _t ) and the true strain (ε _t ).

σ _t = Kε _t ⁿ

The relationship of is established, and this is called the nth power curing rule. Let "n" be the work hardening coefficient (Sudo Hajime: Material Test Method, Rochikuho Uchida, (1976), p. 34). n takes a value of 0 ≤ n ≤ 1, and the larger n, the greater the degree of work hardening, and when the part subjected to local deformation is work hardened, the deformation moves to another part, making it difficult to produce a constricted part. For this reason, a material with a large n value exhibits uniform elongation.

The yield ratio and the n value are each correlated with the finish rolling workability, and the yield ratio and the n value can be adjusted by controlling the rolling workability of the finish rolling described later.

When the rolling degree of finish rolling is less than 10%, the yield ratio becomes smaller than 0.9, and the n value becomes 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 increases to 0.9 or more by increasing the value of YS by work hardening. On the other hand, the value of n is greater than 0.05.

When the rolling workability of finish rolling is 15% or more and 30% or less, the yield ratio becomes 0.9 or more, and the uniform elongation decreases, so that the n value becomes 0.05 or less, which is the most preferable condition.

In the range in which the rolling workability of the finish rolling exceeds 30% and is 40% or less, the yield ratio becomes less than 0.9 and the n value becomes 0.05 or less because the strength of YS is prematurely saturated as compared with TS. Even if the rolling workability exceeds 40%, it is the same tendency, but the mold wearability deteriorates as the yield ratio becomes smaller.

[0.2% proof strength]

The 0.2% yield strength in the rolling parallel direction of the Cu-Ni-Si copper alloy is 700 MPa or more, for example. When the 0.2% yield strength is 700 MPa or more, the strength is improved.

In addition, tensile strength is calculated|required by the tensile test according to JIS-Z2241. The conditions for 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 50 mm.

[kidney]

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%.

In addition, the elongation was a breaking elongation, and the tensile strength described above was measured and measured by a tensile tester in accordance with JIS-Z2241. Then, the difference between the length L (gauge length) between the marks when the test piece was broken and the distance L0 before the test was determined as %.

The conditions of the tensile test are 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 tensile testing is performed in the rolling direction of the copper foil.

[Conductivity]

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

<manufacturing method>

The Cu-Ni-Si-based copper alloy of the present invention can usually be produced by performing ingots in the order of hot rolling, cold rolling, solution treatment, aging treatment, finish rolling, and stress relief annealing. Cold rolling or recrystallization annealing prior to solution treatment is not essential, and may be performed as necessary.

<Hot rolling>

Here, hot rolling is set so that the third Ni-Si particles having a diameter of 1.0 µm or more and 3.5 µm or less in the material before cold rolling after hot rolling are within a range of 3.5 × 10 ³ to 8.5 × 10 ³ /mm ³ . This is because, if the conditions of solution treatment and aging treatment are to be controlled to control the Ni-Si particles at the µm level, overaging and the like must be performed, thereby impairing properties such as strength.

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 in the final product.

When the third Ni-Si particles are less than 3.5 x 10 ³ particles/mm 2, the first Ni-Si particles become less than 0.04 x 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 wear is promoted.

The conditions of the hot rolling for regulating the diameter and number of the third Ni-Si particles can be adjusted, for example, within a range of a hot rolling temperature of 800 to 1000°C and a holding time of 1 to 5 h.

[Example 1]

The electric copper was dissolved in an air melting furnace, and a predetermined amount of the additive element shown in Table 1 was added as necessary, and the molten metal was stirred. Thereafter, it was poured into a mold at an injection temperature of 1200°C to obtain a copper alloy ingot having the composition shown in Table 1. The ingot was hot rolled to make the plate thickness 10 mm. Subsequently, it was carried out in the order of chamfering, cold rolling, solution treatment, aging treatment, low temperature heat treatment, and finish rolling to obtain samples having a plate thickness of 0.05 to 0.4 mm. After the finish cold rolling, stress relief annealing was performed in a temperature range of 200°C to 500°C for 1 second to 1000 seconds.

Moreover, hot rolling was performed at 1000 degreeC for 3 hours, and solution treatment was performed at 700-900 degreeC. The aging treatment was performed at 400°C to 550°C in a range of 1 to 15 hours, at a temperature and time at which the tensile strength after finish rolling was maximum, and finish rolling was performed within a range of 10 to 40% of the working rate.

<Evaluation>

The following items were evaluated about the obtained sample.

[Conductivity]

About the sample in the rolling parallel direction after stress relief annealing, electrical conductivity (%IACS) was computed from the volume resistivity calculated|required by the tetragonal method using a double bridge apparatus based on JISH0505.

[The tensile strength]

For the sample after the stress relief annealing, a JIS 13B test piece was prepared using a press machine so that the tensile direction was parallel to the rolling direction. The tensile test of this test piece was performed according to JIS-Z2241, and the tensile strength TS was measured. The conditions of the tensile test were a test piece width of 12.7 mm, room temperature (15 to 35°C), a tensile rate of 5 mm/min, and a gauge length L = 50 mm, and tensile testing was performed in the rolling direction of the copper foil.

[kidney]

The elongation at break was determined by the tensile test. The difference between the length L between the marks when the test piece was broken and the target distance L0 before the test was determined as %, and was taken as elongation.

[Evaluation of scratch wear]

No. of punches: Punch side after punching 1 shot (10 shots in total) for 10 samples cut into 5 × 15 mm in the lengthwise direction of the rolling parallel direction of each sample using a punch having a width of 5 mm The number of scratches on the surface was counted visually. When the number of punch scratches is 20 or less, there is little scratch wear of the mold and excellent mold abrasion resistance.

[Evaluation of adhesion wear]

The adhesion wear was judged using a ball-on-disk friction wear tester. The test was conducted with a load of 1 N and a sliding distance of 125 m, and the material of the ball (relative member) was SUJ2.

Before and after the abrasion test, the profile of the cross-section of the sliding portion of the ball was measured with a laser microscope, and it was judged that adhesion wear occurred when the height of the cross-sectional profile after the test was higher than that before the test with respect to a portion of the sliding portion having a length of 1 µm or more.

[Evaluation of mold abrasion property]

The mold abrasion property cannot be judged only by the scratch wear evaluation and adhesion wear evaluation, and is influenced by the mechanical properties of the material. In order to comprehensively judge the effects of these, mold abrasion was evaluated by measuring the amount of abrasion of the punch blade after 100,000 shots of each sample, for 5 samples cut by 200 × 300 mm using a turret punch press. The amount of wear of the punch blade was measured on the basis of before pressing.

Using a cylindrical punch, the clearance was set to 5% of the plate thickness, the press speed was 290 shots/min, and the punching depth was set to 50% of the plate thickness. In addition, punches and dies each having a different hardness were used, and the punch hardness was set to a value of 60 to 80% of the die hardness.

The amount of wear of the punch blade, using a laser microscope, as shown in Fig. 1, the area S1 where the height difference occurred between the cross-sectional profile P1 of the punch blade before press and the cross-sectional profile P2 of the punch blade after press was regarded as the worn area , The area was calculated. Reference numeral D in Fig. 1 indicates the press direction. The mold wearability was evaluated according to the following criteria. If the evaluation is ○, the mold abrasion resistance is excellent, and if ◎, it is more excellent.

◎: wear area is 1000 μm ² or less

○: Wear area is more than 1000 μm ² and less than 1500 μm ²

×: wear area is 1500 μm ² or more

Table 1 and Table 2 show the obtained results.

As is apparent from Table 1 and Table 2, the mold wear resistance was excellent in each of the examples in which the number of the first Ni-Si particles to the second Ni-Si particles was regulated within a predetermined range. Moreover, the workability of finish rolling being 15 to 30% is more excellent in mold abrasion, yield ratio YS/TS is 0.9 or more, and work hardening coefficient n value is 0.05 or less. This is considered to be because the contact time between the mold and the material is reduced.

In addition, in Examples 5 and 7, 9 in which the working degree of finish rolling was 10% or more and less than 15%, the yield ratio was 0.9 or more, but the n value was greater than 0.05. Further, in Examples 2, 3, 10, and 11 in which the workability of finish rolling was more than 30% and 40% or less, the n value was 0.05 or less, but the yield ratio was less than 0.9. However, these examples have no practical problems.

On the other hand, in the case of Comparative Examples 1 to 4 and Comparative Example 6, the first Ni-Si particles exceeded 1.4 × 10 ³ particles/mm 2 and the number of second Ni-Si particles became 4.0 × 10 ³ particles/mm 2 or more. , The number of punch scratches exceeded 20, and the scratch wear of the mold was promoted, resulting in poor mold abrasion.

In Comparative Example 5, in which the first Ni-Si particles were less than 0.04×10 ³ particles/mm 2 and the number of second Ni-Si particles was less than the number of first Ni-Si particles, adhesion abrasion was promoted and mold abrasion was inferior. .

Claims (3)

In mass%, Ni: 2.0 to 5.0%, Si: 0.3 to 1.5%, Ni/Si ratio is 1.3 to 6.7 or less, the balance is made of Cu and unavoidable impurities, 0.2% proof stress YS is 700 MPa or more, 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 pieces/mm 2, and the number of second Ni-Si particles having a diameter of less than 0.5 μm is equal to or greater than the number of the first Ni-Si particles. Cu-Ni-Si-based copper alloy having a number of Ni-Si particles of less than 4.0 x 10 ³ pieces/mm 2 and a diameter of more than 0.6 µm, which is less than or equal to the number of the first Ni-Si particles. According to claim 1,
Cu-Ni-Si-based copper alloy having a yield ratio YS/TS of 0.9 or more and a work hardening coefficient n of 0.05 or less. According to claim 1,
Further, a Cu-Ni-Si-based copper alloy containing 0.005 to 1.0 mass% of at least one or more selected from the group of Mg, Mn, Sn, Zn and Cr in a total amount.

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