JP3871064B2 - Copper alloy plate for electrical connection parts - Google Patents

Description

  The present invention relates to a copper alloy plate that is excellent in bending workability and shear punchability, and is particularly suitable for use in electrical connection parts such as automobile terminals and connectors.

In recent years, connection parts such as automobile terminals and connectors have been required to have low cost performance capable of ensuring reliability in a high temperature environment such as an engine room. One of the most important characteristics in reliability under this high temperature environment is a contact fitting force maintaining characteristic, so-called stress relaxation resistance characteristic. That is, when a steady displacement is applied to a spring-shaped component made of a copper alloy, for example, when a tab of a male terminal is fitted with a spring-shaped contact of a female terminal, these connecting components are like an engine room. If the contact fitting force is maintained in a high temperature environment, the contact fitting force will be lost with time, but this is a resistance characteristic.
Cu-Ni-Si-based alloys, Cu-Ti-based alloys, Cu-Be-based alloys, and the like are known as alloy systems having excellent stress relaxation characteristics, all of which are strong oxidizing elements (Si, Ti, Be). Etc.) cannot be melted in a large-scale melting furnace with a wide opening to the atmosphere, and high cost is inevitable from the viewpoint of productivity. On the other hand, Cu-Ni-Sn-P-based alloys with a small amount of addition can be so-called shaft furnace ingot, and can be greatly reduced in cost because of its high productivity. In addition, it is a very promising alloy system that can exhibit stress relaxation properties up to a Cu-Be-based alloy equivalent level depending on the production method and the amount of added elements.

Patent Document 1 below discloses a method for producing a copper-based alloy for connectors having excellent stress relaxation resistance. This manufacturing method is a Cu-Ni-Sn-P alloy in which Ni-P intermetallic compounds are uniformly and finely dispersed in a matrix to improve electrical conductivity and at the same time improve stress relaxation resistance. Yes, according to the document, in order to obtain desired characteristics, the cooling start and end temperatures of the hot rolling, the cooling rate, and the temperature of the heat treatment for 5 to 720 minutes applied during the subsequent cold rolling process. And time must be strictly controlled.
Patent Documents 2 and 3 below disclose Cu-Ni-Sn alloys having excellent stress relaxation resistance and a method for producing the same, but the P content is reduced as much as possible to reduce the Ni-P compound. The present invention relates to a solid solution type copper alloy that suppresses precipitation, and does not require an advanced heat treatment technique, and has an advantage that it can be manufactured by an extremely short annealing heat treatment.

Japanese Patent No. 2844120 JP-A-11-293367 JP 2002-294368 A

However, the formation energy of Ni-P intermetallic compound is extremely low, and it is easily coarsened by heat treatment during the copper alloy manufacturing process, and the accuracy of terminal shape is achieved while exhibiting the stress relaxation characteristics required by the current automobile technology. There have also been problems such as deterioration of the bending workability that backs up and enlargement of the punching burr that wears the terminal punching die.
Here, looking at the cross-sectional structure of a typical box-shaped connector (female terminal 3), as shown in FIG. 2, when the pressing piece 5 is cantilevered and supported by the upper holder part 4 and the male terminal 6 is inserted. The pressing piece 5 is elastically deformed, and the male terminal 6 is fixed by the reaction force. In FIG. 2, 7 is a wire barrel portion, and 8 is a fixing tongue piece. When manufacturing such a connector from a copper alloy material board, bending and shear punching are frequently used. In order to manufacture a small and precise connector, it is necessary to have excellent bending workability in both the direction parallel to and perpendicular to the rolling direction. In addition, if large burrs are generated in the shear punching process, the burrs are sandwiched between the bent parts and the precise bending process is hindered. If the burrs are generated in the wire barrel part, the wire is cut during the bending process. Promotes wear of punching dies. Therefore, this type of copper alloy sheet is required to have excellent bending workability and shear punchability.
On the other hand, the bending workability and the shear punchability of the conventional Cu—Ni—Sn solid solution type copper alloy are still not sufficient.

  Therefore, the present invention provides an electrical connection component having excellent bending workability in the perpendicular and perpendicular directions to the rolling direction and simultaneously having excellent shear punching properties in a Cu-Ni-Sn solid solution type copper alloy. An object is to obtain a copper alloy sheet.

The copper alloy plate for electrical connection parts according to the present invention has Ni: 0.4 to 1.6%, Sn: 0.4 to 1.6%, P: 0.027 to 0.15%, Fe: 0.0. Including 0005 to 0.15%, Ni / P ratio Ni / P is less than 15, the balance is composed of Cu and impurities, and Ni-P precipitates are dispersed in the copper alloy matrix The precipitate has a diameter of 60 nm or less, and 20 or more particles having a diameter of 5 nm to 60 nm are observed in a field of view of 500 nm × 500 nm.
The composition of the copper alloy plate is, as required, any one or more of Zn: 1% or less, Mn: 0.1% or less, Si: 0.1% or less, Mg: 0.3% or less, or / And Cr, Co, Ag, In, Be, Al, Ti, V, Zr, Mo, Hf, Ta, and B may be included in a total amount of 0.1% or less.

  According to the present invention, a Cu-Ni-Sn solid solution type copper alloy has an excellent bending workability in the direction perpendicular to and perpendicular to the rolling direction, and at the same time has an excellent shear punching property. Copper alloy sheets can be obtained.

Hereinafter, the copper alloy plate according to the present invention will be described. First, the composition of the copper alloy according to the present invention will be described.
Ni is an element that dissolves in a copper alloy to strengthen the stress relaxation resistance and improve the strength. However, if it is 0.4% or less, there is no effect, and if it exceeds 1.6%, an intermetallic compound is easily precipitated with P added at the same time, so that solid solution Ni is reduced and stress relaxation resistance is lowered. . Therefore, the content is set to 0.4 to 1.6%. A range of 0.7 to 0.9% is more desirable.

  Sn is an element that dissolves in a copper alloy and improves strength by work hardening. Furthermore, in this alloy system, it is an element contributing to heat resistance. In the copper alloy plate according to the present invention, in order to improve the bending workability and the shear punchability, it is necessary to perform finish annealing at a high temperature, but if the Sn content is less than 0.4%, the heat resistance decreases, Since recrystallization softening proceeds in finish annealing, the temperature of finish annealing cannot be raised sufficiently. On the other hand, if it exceeds 1.6%, the electrical conductivity is lowered, and 30% IACS cannot be achieved in the final copper alloy sheet product. Therefore, the Sn content is set to 0.4 to 1.6%. A range of 0.6 to 1.3% is more desirable. In addition, there is also an advantage that solid solution Ni necessary for improving the stress relaxation resistance can be sufficiently obtained by performing the finish annealing at a high temperature.

  P is an element that expresses Ni-P precipitates during the manufacturing process and improves heat resistance during finish annealing. As a result, finish annealing at a high temperature is possible, and bending workability and shear punchability are improved. However, if it is less than 0.027%, it becomes easy to combine with Ni having a relatively large addition amount compared to the P addition amount, and a strong Ni-P intermetallic compound is formed, while P is 0.15%. If added in excess, the precipitation amount of Ni-P intermetallic compound further increases, and in any case, Ni-P intermetallic compound does not re-dissolve in finish annealing, and bending workability and shear punching workability decrease. In addition, solid solution Ni for improving the stress relaxation resistance cannot be obtained sufficiently. Therefore, the P content is 0.027 to 0.15%. 0.05 to 0.08% is more preferable.

Moreover, the reason why the Ni / P ratio is less than 15 is that the Ni-P precipitates are improved in heat resistance due to Ni re-solution and dislocation fixation at a high finish annealing temperature, and during recrystallization softening by finish annealing. This is for achieving both decomposition and re-solution of the Ni-P precipitate. When the Ni / P ratio is 15 or more, the heat resistance is not improved sufficiently, and finish annealing at a relatively low temperature is unavoidable, the bending workability and the shear punchability are not improved, and sufficient stress relaxation resistance is obtained. I can't.
Fe is an element that suppresses the coarsening of recrystallized grains in finish annealing. By adding 0.0005% or more to the copper alloy, the copper alloy is heated to a high temperature in the final annealing to sufficiently dissolve the added element, and at the same time, coarsening of recrystallized grains can be suppressed. However, if it exceeds 0.15%, the conductivity decreases and about 30% IACS cannot be achieved.

The copper alloy of the present invention may further contain Zn, Mn, Mg, Si and others as subcomponents.
Zn can be added in an amount of 1% or less to prevent peeling of the tin plating. However, if it is the temperature range (about 150-180 degreeC) used as a terminal for motor vehicles, it is enough if 0.05% or less is added. Furthermore, when ingot-making in a shaft furnace, 0.05% or less is desirable.
Mn and Si can be added in amounts of 0.01% or less as deoxidizers, respectively, but 0.001% or less and 0.002% or less are desirable, respectively.
Mg has the effect of improving the stress relaxation resistance and can be added in an amount of 0.3% or less. However, when ingot forming in a shaft furnace, 0.001% or less is desirable.
Cr, Co, Ag, In, Be, Al, Ti, V, Zr, Mo, Hf, Ta, B, etc. have the effect of preventing coarsening of crystal grains, and should be added in a total amount of 0.1% or less. Can do.
Pb is preferably limited to 0.001% or less as an impurity.

Next, the structure of the copper alloy plate according to the present invention will be described.
The copper alloy sheet according to the present invention has a structure in which precipitates of Ni-P intermetallic compounds are dispersed in a copper alloy matrix. Among the precipitates, particles having a diameter exceeding 60 nm cause cracking in bending with a small R / t (R: bending radius, t: plate thickness), and if this exists, bending workability deteriorates. In addition, when a deposit particle remove | deviates from a spherical form, let the diameter (major axis) of the circumscribed circle of this deposit particle be the diameter of the deposit referred to in the present invention.
On the other hand, the precipitate becomes a starting point of cracking at the time of shear punching, and if this is distributed at a high density, the shear punching property is excellent. Fine precipitates with a diameter of less than 5 nm cause local work hardening characteristics with dislocations in the shear stress field and contribute to the propagation and progression of shear punching, but precipitates with a diameter of 5 nm or more are finely dispersed. In this case, since the fracture surface of the shear punching proceeds along the existing location, the punching property is further improved, which helps to reduce the flash. Accordingly, with respect to particles having a diameter of 60 nm or less that do not deteriorate the bending workability, it is desirable that 20 or more particles having a diameter of 5 nm or more exist on average within a field of view of 500 nm × 500 nm, and more preferably 30 or more.

Next, the manufacturing method of the copper alloy plate which concerns on this invention is demonstrated.
The copper alloy plate according to the present invention is obtained by homogenizing the copper alloy ingot, performing hot rolling and cold rough rolling, and subsequently subjecting the copper alloy plate after cold rough rolling to finish continuous annealing, and further cooling. It can be manufactured by hot rolling and stabilizing annealing.
Since the copper alloy of the present invention is not a precipitation-type copper alloy, specially strict management in terms of conditions is not required in homogenization, hot rolling, and cold rough rolling. For example, the homogenization treatment is performed at 800 to 1000 ° C. for 0.5 to 4 hours, the hot rolling is performed at 800 to 950 ° C., and after the hot rolling, it is cooled with water or allowed to cool. In the cold rough rolling, the processing rate is selected so that a processing rate of about 30 to 80% is obtained in the final finish rolling. An intermediate recrystallization annealing can be appropriately interposed during the cold rough rolling.

On the other hand, it is necessary to strictly manage the continuous annealing of the copper alloy sheet after the rough cold rolling, and to set an appropriate holding temperature and holding time.
One of the major characteristics of the alloy system within the provisions of the present invention is that the precipitation phase is transformed by annealing at a holding time of several tens of seconds and exceeding 650 ° C. As described above, when the holding temperature is low, a relatively large number of coarse precipitates are observed. In terms of thermodynamics, when the holding temperature is further increased, the precipitates are usually further aggregated and coarsened. However, in this alloy system, the precipitation phase transitions from 600 to 650 ° C., that is, the coarse precipitates generated in the low temperature region from the temperature of 600 to 650 ° C. are decomposed and re-dissolved as fine particles. A new phase that precipitates the Ni-P compound appears. This precipitate contributes to improvement of bending workability and reduction of punching burrs.
When the holding temperature is low, precipitate particles having a diameter of more than 60 nm are easily observed, and in a composition region where the contents of Ni and P are very small, particles having a diameter of 60 nm or less are insufficient. On the other hand, even if the annealing temperature exceeds 650 ° C., if the holding time is short, the coarse precipitates are not sufficiently decomposed and re-dissolved, and the fine precipitates are difficult to be expressed. Remains. On the other hand, if the length is too long, the recrystallized grains may be coarsened to cause a decrease in bending workability.
In the case of the copper alloy composition of the present invention, it is maintained at a temperature exceeding 650 ° C. as a substantial temperature, and the holding time is 15 to 30 seconds. A structure in which compound precipitates are appropriately dispersed can be obtained. After annealing, it is desirable to rapidly cool at a cooling rate of 10 ° C./second or more.
In addition, by performing the final annealing temperature under the conditions of high temperature and short time as described above, the precipitate of Ni-P intermetallic compound precipitated in the temperature rising process is re-dissolved, and the solid solution necessary for improving the stress relaxation resistance is obtained. There is also an advantage that Ni can be sufficiently obtained.

  The stabilizing annealing after the final finish rolling is desirably performed at 250 to 450 ° C. for 20 to 40 seconds. This is because the distortion introduced in the final finish rolling is removed, the material is not softened, and the strength is hardly lowered.

Next, examples of the copper alloy plate according to the present invention will be described.
The copper alloy was melted under a charcoal coating in the atmosphere in a kryptor furnace to obtain 45 mm-thick ingots (Nos. 1 to 9) having the compositions shown in Table 1. Subsequently, after soaking at 965 ° C. for 3 hours or 850 ° C. for 30 minutes, it is hot-rolled to a thickness of 15 mm, quenched at 830 ° C. or higher (water-cooled), and both sides are faced by 1 mm each. After the thickness of 13 mm, cold rough rolling was performed to obtain the thicknesses shown in Table 1.
Subsequently, no. For Nos. 1-8, finish continuous annealing was performed. For No. 9, batch-type intermediate and finish annealing were performed with cold rolling in between, and after finishing cold rolling, low temperature annealing (stabilized annealing) was performed. The conditions for each step are shown in Table 1. The final product plate thickness is 0.25 mm.

  For each test material in the final product state obtained, conductivity, hardness, mechanical properties (tensile strength, proof stress, elongation), spring limit value, stress relaxation resistance, bending workability and shear punchability, The measurement was performed as follows, and the distribution of precipitates was observed with a scanning electron microscope (TEM). The results are shown in Table 2.

Conductivity: Conductivity was measured by a four-terminal method using a double bridge in accordance with a nonferrous metal material conductivity measuring method defined in JIS-H0505.
Hardness: The hardness was measured in accordance with the microhardness test method defined in JIS-Z2251, and the Vickers hardness was measured at a test load of 100 g (0.9807 N).
Mechanical properties: JIS No. 5 tensile test specimen was prepared by machining so that the longitudinal direction was parallel (LD) and perpendicular (TD) to the rolling direction of the plate, and was pulled according to JIS-Z2241 Tests were performed and measured. The yield strength is a tensile strength corresponding to a permanent elongation of 0.2%.
Spring limit value: It was determined by a moment type test using a spring limit value tester manufactured by Akashi (MODEL: APT). The test direction of the material was a parallel direction (LD) and a vertical direction (TD) with respect to the rolling direction of the plate material.

  Stress relaxation resistance: Stress relaxation rate was measured using the cantilever method shown in FIG. A strip-shaped test piece 1 having a width of 10 mm is cut out so that the length direction is parallel to the rolling direction of the plate (LD) and the direction perpendicular to the plate direction (TD), and one end thereof is fixed to the rigid body test stand 2. A deflection amount having a size of d (= 10 mm) is given to a portion having a span length L of 1. At this time, L is determined so that a surface stress corresponding to 80% of the material yield strength is applied to the material. This is held in an oven at 180 ° C. for 30 hours and then taken out. The permanent distortion δ when the deflection d is removed is measured, and the stress relaxation rate (RS) is calculated by RS = (δ / d) × 100. In addition, holding | maintenance of 180 degreeC x 30 hours is equivalent to holding | maintenance of about 150 degreeC x 1000 hours, when it calculates with a Larson Miller parameter.

  Bending workability: A specimen having a width of 10 mm and a length of 35 mm was cut out so that the length direction was parallel (LD) and perpendicular to the rolling direction of the plate (TD), and the bending line was perpendicular to the length direction. Scissors using a B-type bending jig specified in the CESM0002 metal material W bending test, and R / t = 2 (R with a load of 1 t using a Shimadzu universal testing machine RH-30 : Bending radius, t: plate thickness), 90 ° W bending was performed, and then the presence or absence of cracks in the bent portion was evaluated.

  Shear punchability: A circular punching test in accordance with Japan Copper and Brass Association standard JCBAT310 (a shear test method for copper and copper alloy sheet strips) was performed, and the shear burr height was measured. Specifically, a test material to which Nisseki Mitsubishi Unipres PA-5 lubricating oil is applied in advance with a brush is punched into a circle with a punching press having a punch diameter of 10.000 mmφ and a die diameter of 10.040 mmφ. The clearance of this punching press is (interval on one side (distance between die cutting blade and outer periphery of punch) / plate thickness of test material) × 100 (%)) = 8%, and shear rate is 50 mm / min. The burrs generated around the punched circular holes were measured at four locations every 90 degrees in circumference, and the average value was taken as the burr height.

  Observation of the distribution of precipitates: The specimen is finished into a thin film for TEM observation by the electrolytic thin film method (twin jet method). This is photographed with TEM H-800 (acceleration voltage 200 kV) manufactured by Hitachi, Ltd. at photographing magnifications of 40000 times and 100000 times, and further magnified by 1.5 times and printed on photographic paper. The number of precipitates having a diameter exceeding 60 nm in a square field equivalent to 1000 nm × 1000 nm on the photographic paper having a magnification of 60000 times, and the precipitate having a diameter of 5 nm to 60 nm in a square field having a size equivalent to 500 nm × 500 nm on the photographic paper having a magnification of 150,000 times. Count the number. A plurality of visual fields are observed, and an average value is calculated. The precipitate particles observed in the visual field were all spherical.

  As shown in Table 2, no precipitate with a diameter exceeding 60 nm was observed. Nos. 1 to 7 are excellent in bending workability in both the LD and TD directions. In addition, 20 or more precipitates having a diameter of 5 nm or more and 60 nm or less were observed in a 500 nm × 500 nm visual field. 1-4 and No.1. No. 8 has a small average burr height. The burr height of 1-4 is small. Furthermore, no. In 1-4, the stress relaxation rate was 15% or less in both the LD and TD directions.

In contrast, no. Nos. 5 to 7 have a small Ni addition amount, and coarse precipitates exceeding 60 nm are less likely to be generated. However, since the finish annealing temperature is low, the fine Ni-P compound does not transition to the fine precipitation new phase that occurs around 650 ° C. However, the number of precipitates does not reach the specified value. Since the fine precipitates of 60 nm or less that improve the shearing property are insufficient, the burr height exceeds 10 μm and the shear punching property is inferior. Since the amount of added Ni is small and the solid solution Ni in the matrix is taken away by the precipitate, the amount of Ni solid solution does not reach the amount capable of maintaining the stress relaxation characteristics, and the stress relaxation rate is high (particularly TD direction).
No. In No. 8, since the final annealing temperatures did not reach 600 ° C. and 650 ° C., coarse precipitates exceeding 60 nm were not sufficiently decomposed and re-dissolved, and partly remained, resulting in poor bending workability. Although it is not completely transferred to the new fine precipitation phase that occurs around 650 ° C., a small amount of fine precipitates are generated due to the large amount of Ni added, and the burr height is kept low. Further, since the total amount of Ni-P precipitates is large and the amount of Ni re-solution is insufficient, sufficient solid solution Ni necessary for improving the stress relaxation resistance is not obtained, and the stress relaxation rate in the TD direction is high.
No. In No. 9, precipitates remain aggregated to 60 nm or more by batch annealing below 650 ° C. Although recrystallization is completed by performing batch annealing twice, it does not reach the temperature at which the aggregated precipitates are decomposed and fine precipitates are expressed, so the bending workability is lowered and the burr height is also reduced. It is high.

It is sectional drawing explaining a stress relaxation test. It is the front view (a) and sectional view (b) which show the structure of a female terminal.

Explanation of symbols

1 Test piece 3 Female terminal

Claims (3)

Ni: 0.62 to 1.02% (mass%, the same applies hereinafter), Sn: 0.52 to 1.3% , P: 0.046 to 0.092 %, Fe: 0.0005 to 0.15 % The ratio Ni / P of Ni content and P content is less than 15, the balance is a composition consisting of Cu and impurities, and a structure in which Ni-P precipitates are dispersed in the copper alloy matrix, The said deposit is 60 nm or less in diameter, and 20 or more things of diameter 5 nm or more and 60 nm or less are observed within a 500 nm x 500 nm visual field, The copper alloy plate for electrical-connection components characterized by the above-mentioned. The composition of the copper alloy includes any one or more of Zn: 1% or less, Mn: 0.1% or less, Si: 0.1% or less, and Mg: 0.3% or less. Item 4. A copper alloy plate for electrical connection parts according to item 1. The composition of the copper alloy includes Cr, Co, Ag, In, Be, Al, Ti, V, Zr, Mo, Hf, Ta, and B in a total amount of 0.1% or less. The copper alloy plate for electrical connection parts described in 2.

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