JP6974250B2 - Copper alloy material and terminals for terminals of aluminum wire harness - Google Patents

Description

The present invention relates to a copper alloy material which is excellent in contact corrosion resistance to aluminum and is suitably used for terminals of an aluminum wire harness (a wire harness using an aluminum wire as an electric wire).

Connectors for automobiles can be classified into high-performance terminals used for connecting ECUs (Electrical Control Units) installed directly above the engine and general-purpose terminals used for interconnecting wire harnesses stretched throughout the vehicle. .. Cu-Ni-Si alloys, Cu-Ni-Sn-P alloys, Cu-Mg alloys and the like are used for high-performance terminals. On the other hand, 7/3 brass (C2600) and 6/4 brass (C2800) are used in large quantities for general-purpose terminals.

Generally, copper wire is used for the wire harness, but since there is a strong demand for weight reduction of automobiles, weight reduction of the wire harness is considered, and aluminum wire (pure aluminum wire or aluminum alloy wire) which is lighter than copper wire is considered. ) Is being developed as a wire harness (aluminum wire harness). In this aluminum wire harness, the aluminum wire and the copper alloy terminal come into contact with each other. At this time, there is a concern that the press cut surface (exposed base material) of the Sn-plated copper alloy terminal and the aluminum wire may come into contact with each other, causing contact corrosion of dissimilar metals between the copper alloy terminal (base material) and the aluminum wire. ing.

Patent Documents 1 and 2 disclose a technique for forming a coating layer having an electrode potential close to that of aluminum on the surface of a copper alloy terminal to prevent contact corrosion of aluminum wire. However, in this case as well, as in the case of Sn plating, the base material is exposed on the cut surface by the press punching performed in the process of manufacturing the terminal, and the base material and the aluminum wire come into contact with each other, which causes contact corrosion to the aluminum wire. May occur.

On the other hand, in order to prevent contact corrosion of dissimilar metals of aluminum, after press punching, the press cut surface is covered by post-plating or sealed with waterproof resin to eliminate the exposed part of the base material, and the base material of the terminal and the aluminum wire are removed. A method of preventing contact with is also conceivable. However, this method is costly to manufacture, and if there is a non-plating or a defect in the resin sealing, contact corrosion of the aluminum wire progresses from there. As many as 1000 to 3000 wire harness terminals are used per automobile, and it cannot be said that sufficient reliability can be ensured by the above method in order to prevent contact corrosion of aluminum wires.

Japanese Unexamined Patent Publication No. 2013-20862 Japanese Unexamined Patent Publication No. 2017-2021414

It is preferable that the copper alloy terminal of the aluminum wire harness can suppress contact corrosion of the aluminum wire due to copper-aluminum dissimilar metal contact even when the entire or part of the surface is not covered with a coating layer such as plating or waterproof resin.
In order to suppress the corrosion of the aluminum wire due to such contact with dissimilar metals, a method of adding a large amount of alloying elements having an electrode potential closer to that of aluminum than copper to the copper alloy for terminals can be considered first. However, since the electrode potential of most practical copper alloys reflects the Fermi level of copper, which is a solvent element, this method is less effective. In addition, high-concentration alloying causes a decrease in conductivity.

In the performance evaluation test of the wire harness, an overcurrent is applied to the entire wire harness for a specified time, and a test is performed to see if there is a place where it ignites or smokes. If it is low, heat generation will be concentrated there. Therefore, if the conductivity of the copper alloy terminal is lower than that of brass, it becomes necessary to review the design of the entire wire harness.
Therefore, an object of the present invention is to provide a copper alloy material for terminals, which has a conductivity equal to or higher than that of brass and can reduce galvanic corrosion of aluminum wires more than brass.

The copper alloy material according to the present invention is used as a terminal of an aluminum wire harness, contains Al: 0.4 to 2.2% by mass, Ni: 0.4 to 4.0% by mass, and the balance Cu and It is composed of unavoidable impurities, is characterized by having a conductivity of 23% IACS or more, and has excellent contact corrosion resistance to aluminum (it can suppress contact corrosion of aluminum).
This copper alloy material has any form of a plate material, a strip material, a wire material, and a bar material. In the present invention, aluminum means pure aluminum and an aluminum alloy.

The copper alloy material according to the present invention has better contact corrosion resistance to aluminum than brass, and when this copper alloy material is used as a crimp terminal for an aluminum wire in an aluminum wire harness, the contact corrosion of the aluminum wire is conventional copper. It is reduced compared to the terminal. This makes it possible to improve the reliability of the entire aluminum wire harness. Since the copper alloy material according to the present invention has a conductivity equal to or higher than that of brass, when this copper alloy material is used as a terminal for an aluminum wire, the conventional wire harness can be used as it is without any design change. .. Further, the copper alloy material according to the present invention has a smaller stress relaxation rate than brass, and when used as a crimp terminal for an aluminum wire, when the terminal is heated by a high temperature atmosphere and energization heat generation, it is connected to the aluminum wire. The bond strength is unlikely to decrease.

It is an electric circuit diagram in the measurement of the voltage between electrodes of an Example.

Subsequently, the copper alloy material according to the present invention will be described in detail.
[Composition of copper alloy material]
The copper alloy material according to the present invention contains Al: 0.4 to 2.2% by mass and Ni: 0.4 to 4.0% by mass, and the balance is basically composed of Cu and unavoidable impurities, and is an aluminum wire harness. It is for the terminal of. Hereinafter, the action of each of the above elements will be described.

(Al)
In the equilibrium phase diagram of the Cu—Al binary alloy, Cu and Al are completely solid-solved in the dilute region of Al, but Al in the copper alloy is the same as P in phosphor deoxidized copper. It is significantly segregated into line defects such as dislocations or surface defects such as stacking defects. That is, there are shades of Al concentration in the copper alloy. Then, the shading portion itself becomes a local battery in the electrolyte solution, and the contact potential difference with Al is alleviated. This reduces contact corrosion of the aluminum wire in the wire harness. In addition, Al improves the work hardening ability of the copper alloy, contributes to the strengthening of the copper alloy, and further contributes to the reduction of the stress relaxation rate of the copper alloy because it acts as a solid dissolving element. However, when the Al content is less than 0.4% by mass, the effect is insufficient. On the other hand, Al significantly lowers the conductivity of the copper alloy, and when the content exceeds 2.2% by mass, the conductivity is lower than 23% IACS under the co-addition of Ni.
Therefore, the Al content is in the range of 0.4 to 2.2% by mass. The lower limit of the Al content is preferably 0.5% by mass from the viewpoint of reducing contact corrosion of the aluminum wire and reducing the stress relaxation rate, and the upper limit is preferably from the viewpoint of suppressing the decrease in conductivity. Is 1.8% by mass.

(Ni)
Al in the copper alloy adheres strongly to dislocations, but the interaction disappears with increasing temperature. This phenomenon is observed as a recovery process (hardness and elastic modulus decrease with the passage of time). This phenomenon becomes remarkable at 80 ° C. or higher, and stress relaxation is likely to occur accordingly. Further, since the localization (segregation) of Al is alleviated by this phenomenon, the effect of reducing the contact corrosion of the aluminum wire is also reduced. In order to prevent such a phenomenon, an element that suppresses Al adhering to dislocations from being separated by diffusion is required. The element having this action is Ni. Further, since Ni acts as a solid solution element, it also contributes to a decrease in the stress relaxation rate of the copper alloy. However, if the Ni content is less than 0.4% by mass, the action of suppressing the withdrawal of Al is insufficient. On the other hand, when it exceeds 4.0% by mass, the conductivity is lower than 23% IACS under the co-addition of Al.
Therefore, the Ni content is in the range of 0.4 to 4.0% by mass. The lower limit of the Ni content is preferably 0.5% by mass from the viewpoint of reducing contact corrosion of the aluminum wire and reducing the stress relaxation rate, and the upper limit is preferably from the viewpoint of suppressing the decrease in conductivity. Is 3.5% by mass, more preferably 2.8% by mass.

[Characteristics of copper alloy material]
(conductivity)
Most of the brass used for automobiles is C2600 (Cu-30% by mass Zn) and C2800 (Cu-40% by mass Zn), and the actual conductivity thereof is about 26 to 28% IACS. On the other hand, the non-patent document "Mechanical / Metallic Materials for Young Engineers 2nd Edition (Maruzen Co., Ltd., published on March 10, 2002)", p. According to 311 the minimum conductivity of a Cu—Zn alloy with a Zn content of 30-40% by mass is 23% IACS. Therefore, in the present invention, the lower limit of the conductivity is set to 23% IACS from the viewpoint of providing a copper alloy terminal that can be applied to an aluminum wire harness constructed on the premise of the conductivity of a copper terminal without changing the overall design. I set it. In the copper alloy material according to the present invention, each alloy element or unavoidable impurity is contained within a range in which the conductivity of the copper alloy material does not decrease to less than 23% IACS.

(Resistant to contact corrosion)
When the copper alloy material has the composition described above, the copper alloy material has better contact corrosion resistance to aluminum than brass (contact corrosion of aluminum is suppressed). In the examples described later, the contact corrosion resistance to aluminum is (1) the amount of contact corrosion (weight reduction rate) of the aluminum when the aluminum and the copper alloy material are brought into contact with each other in salt water maintained at room temperature. And (2) the energization voltage measured when aluminum and the copper alloy material are immersed in salt water kept at room temperature in a non-contact manner and energized is evaluated. Here, the room temperature means that the equipment and materials used for each measurement are in equilibrium with this temperature while the air temperature is maintained at 20 ° C to 40 ° C.

(Stress relaxation rate)
When the copper alloy material has the composition described above, the stress relaxation rate of the copper alloy material is smaller than that of brass. When the stress relaxation rate of the copper alloy material is small, when the terminal is used as a crimp terminal for an aluminum wire, the bonding strength with the aluminum wire is unlikely to decrease even when the terminal is heated by a high temperature atmosphere and heat generation.

[Copper alloy coating layer]
The copper alloy material according to the present invention can be used as a bare material as it is, but a surface coating layer can be formed as needed by using the copper alloy material as a base material (base material). The surface coating layer itself may be a well-known one in copper alloy materials for terminals and the like, and for example, the following ones are suitable.
Sn or Sn alloy layer formed on the surface of a copper alloy material.
A Cu—Sn alloy layer and a Sn or Sn alloy layer formed on the surface of a copper alloy material. This surface coating layer is formed by, for example, performing Cu plating and Sn or Sn alloy plating on the surface of a copper alloy material in this order, and then performing a reflow treatment. The Cu—Sn alloy layer is formed by Cu of Cu plating and Sn or Sn of Sn alloy plating.
A Ni layer and a Sn or Sn alloy layer formed on the surface of a copper alloy material.
A Ni layer, a Cu—Sn alloy layer, and a Sn or Sn alloy layer formed on the surface of a copper alloy material. This surface coating layer is formed, for example, by subjecting the surface of a copper alloy material to Ni plating, Cu plating, Sn or Sn alloy plating in this order, and then performing a reflow treatment.
A Ni layer, a Cu layer, a Cu—Sn alloy layer, and a Sn or Sn alloy layer formed on the surface of a copper alloy material. The Cu—Sn alloy layer can be formed, for example, by plating the surface of a copper alloy material with Ni plating, Cu plating, Sn or Sn alloy plating, and then performing a reflow treatment. The Cu plating that was not used to form the Cu—Sn alloy layer remains as a copper layer.

[Manufacturing method of copper alloy material]
The copper alloy material according to the present invention can be produced, for example, by homogenizing and heat-treating an ingot, then hot rolling, and then repeating cold rolling and annealing. After the start of cold rolling, while cold rolling to the final plate thickness, annealing (softening annealing) may be performed only once, but due to the path schedule and the like, annealing may be performed twice or more. The annealing after the final cold rolling is low temperature annealing. Examples of preferable conditions for each heating step are as follows.
The homogenization heat treatment is selected from the range of an atmospheric temperature of 800 to 950 ° C. and a holding time of 30 minutes to 2 hours. After the homogenization heat treatment, hot rolling is performed as it is. The annealing conditions before the final cold rolling are selected from the range of an atmospheric temperature of 350 to 400 ° C. and a holding time of 1 to 3 hours for batch annealing, and a physical temperature of 500 to 700 ° C. for continuous annealing. Choose from a range of hours 10-60 seconds. When annealing two or more times during cold rolling, the annealing conditions performed in the upper step should be selected from the same range as above for batch annealing, and the body temperature should be 650-700 ° C for continuous annealing. Choose from a holding time range of 10-60 seconds.

Copper alloys (Nos. 1 to 18) were melted in a crypto furnace in the air under charcoal coating to obtain ingots having the compositions shown in Tables 1 to 3 and having a thickness of 45 mm, a width of 180 mm and a length of 45 mm. Subsequently, after homogenization treatment under the conditions shown in Tables 1 to 3, hot rolling was started at that temperature to obtain a hot rolled plate having a thickness of 15 mm.
The hot-rolled plate was cold-rolled and annealed under the steps and conditions shown in the columns of the hot-rolled process in Tables 1 to 3, and both were finally cold-rolled to a plate thickness of 0.25 mm, and finally. Low temperature annealing was performed. This low-temperature annealing was carried out by immersing the material in a niter furnace that had been heated and held for 20 seconds and cooling it in water. In the columns of the steps after hot spreading in Tables 1 to 3, t is the plate thickness (unit: mm).
Using the obtained cold-rolled material with a plate thickness of 0.25 mm as a test material, at room temperature (about 25 ° C), mechanical properties (0.2% proof stress, elongation), conductivity, stress relaxation rate, as described below. Contact corrosion resistance (aluminum corrosion reduction rate, energization voltage) was measured. Ni base-plated and Sn-plated test materials were used for the measurement test of the aluminum corrosion reduction rate, and the test material (bare material) without surface coating was used for the other measurement tests.

(Measurement of mechanical properties)
From each test material, a JIS No. 5 tensile test piece was machined so that the longitudinal direction was the rolling direction, and a tensile test was conducted in accordance with JIS-Z2241 to obtain 0.2% proof stress and elongation. (Breaking elongation) was measured. The proof stress is a tensile strength corresponding to a permanent elongation of 0.2%.
(Measurement of conductivity)
The conductivity was measured by a four-terminal method using a double bridge in accordance with the non-ferrous metal material conductivity measuring method specified in JIS-H0505.

(Measurement of stress relaxation rate)
The stress relaxation rate was measured by the cantilever method. A test piece (width 10 mm, length 60 mm) having a longitudinal direction perpendicular to the rolling direction was cut out from each test material. One end of the test piece is fixed to a rigid body test table, the test piece is given an initial deflection displacement d of 10 mm at a position at a certain distance (span length) from the fixed end, and the fixed end is equivalent to 80% of 0.2% proof stress. Surface stress was applied. The span length was calculated by the "stress relaxation test method by bending copper and copper alloy thin strips" specified in the technical standard of the Japan Copper and Brass Association (JCBA-T309: 2004). With the test piece attached to the rigid body test stand, it was placed in an oven held at 150 ° C., held for 1000 hours, then taken out, and the permanent deflection displacement δ was measured when the initial deflection displacement d (10 mm) was removed. Then, the stress relaxation rate SRRT = (δ / d) × 100 was calculated.

(Measurement of contact corrosion resistance)
(1) Measurement of aluminum corrosion reduction rate The aluminum corrosion reduction rate is the amount of contact corrosion (weight reduction) of aluminum when a test piece made of a copper alloy material and aluminum are brought into contact with each other in salt water maintained at room temperature. Means the percentage of.
After performing 0.1 μm thick Ni base plating and 1 μm thick electric gloss Sn plating on the entire surface of each test material, reflow treatment is performed at 270 ° C., and then shear cutting is performed on all four sides assuming press working in actual operation. , A square (side length 1 cm) test piece was prepared. The base material (copper alloy) is exposed on the end surface (shear-cut surface) of this test piece. For the measurement of the aluminum reduction rate, the test piece collected from each test material and a rectangular (2 cm × 1.5 cm) aluminum plate (pure aluminum plate: commercially available JIS A1050P) having a plate thickness of 0.5 mm were used. After degreasing the test piece and the aluminum plate with absolute ethanol, the test piece was placed on the center of the plane of the aluminum plate and sandwiched between resin clips having ^{a surface pressure of 1.5 kg / cm 2.} The test piece was placed on the aluminum plate so that the cutting burr did not face the aluminum plate. In addition, the weight of the aluminum plate was measured before the test. The test piece sandwiched between the clips and the aluminum plate were immersed in a 4% NaCl aqueous solution for 24 hours and then taken out. Corrosion products and salts were removed from the aluminum plate with a nylon brush under running water, and the aluminum plate was dried and weighed. From the weight w0 of the aluminum plate before the test and the weight w of the aluminum plate after the test, the reduction rate (100 × (w0-w) / w0) of the weight of the aluminum plate after the test was calculated.

(2) Measurement of energization voltage This test is a test assuming that the aluminum is corroded and thinned when the copper alloy material and aluminum are not in direct contact but are electrically contacted via salt water. be. To measure the energizing voltage, use a rectangular (5 cm x 2 cm) test piece collected from each test material and a rectangular (5 cm x 2 cm) aluminum plate (pure aluminum plate: commercially available JIS A1050P) with a plate thickness of 0.5 mm. Using. An electric circuit for measuring the energizing voltage is shown in FIG.
The aluminum plate 1 was wrapped with a Teflon (registered trademark) sheet 2 having a circular hole 2a having a diameter of 1 cm. An aluminum plate 1 and a 0.25 W incandescent light bulb 4 assuming a load are connected in parallel to the + pole of a 14 V constant voltage power supply 3 assuming an automobile battery, and the minus pole is connected to the ground. The aluminum plate 1 is not connected to anything other than the positive pole of the power supply 3. The other wire connected to the light bulb 4 (the wire not connected to the positive pole of the power supply 3) is connected to the ground. The aluminum plate 1 and the test piece 6 wrapped in the Teflon sheet 2 are fixed to the nylon plate 5 having the ribs 5a having a height of 2 mm and a width of 2 mm in the central portion along the ribs 5a. At this time, the aluminum plate 1 and the test piece 6 are fixed so that the rolled surfaces face the same direction and there is as little gap as possible between the rib 5a and the aluminum plate 1 and between the rib 5a and the test piece 6. One electric wire of the 0.25 W incandescent light bulb 7 is attached to the test piece 6, the other electric wire is connected to the ground, and the voltmeter 8 is connected in parallel with the light bulb 7.

The voltage measured by the voltmeter 8 was monitored, and the voltage at 150 seconds after the start of energization after immersion in salt water was measured. When the nylon plate 5 to which the aluminum plate 1 and the test piece 6 are fixed is immersed in the tank 10 containing the 150 ppm NaCl aqueous solution 9 and energized, the aluminum plate 1 and the test piece 6 are not directly connected, so that most of the current is generated. It is consumed by the light bulb 4 connected to the power supply 3. When the aluminum plate 1 is corroded and hydrogen is generated in the test piece 6, an electric current easily flows between the aluminum plate 1 and the test piece 6 which are electrically in contact with each other via the NaCl aqueous solution, and is connected to the test piece 6 side. The voltage across the light bulb 7 is increased. The reason why the aluminum plate 1 is covered with the Teflon (registered trademark) sheet 2 is to promote corrosion. The smaller the exposed area of the aluminum plate 1 is compared to the test piece 6, the more easily the corrosion progresses.

As shown in Tables 1 to 3, the conventional materials No. 17 (C2600) has an aluminum corrosion reduction rate of 0.009% by mass and an energization voltage of 0.021V. In 18 (C2800), the aluminum corrosion reduction rate was 0.008% by mass, and the energization voltage was 0.020V.
Invention Example No. In Nos. 1 to 11, the contents of Al and Ni are within the specified range, the conductivity is 23% IACS or more, and the contact corrosion resistance to aluminum is superior to that of the conventional material brass (No. 17 and 18). .. More specifically, No. Nos. 1 to 11 have an aluminum corrosion reduction rate of 0.008% by mass or less, an electrode-to-electrode voltage of 0.019 V or less, and No. Compared with 17, both the aluminum corrosion reduction rate and the energizing voltage are lower. In addition, No. Nos. 1 to 9 and 11 are No. Compared with 18, both the aluminum corrosion reduction rate and the energizing voltage are lower, and No. No. 10 is No. Compared with 18, the aluminum corrosion reduction rate is the same, but the energizing voltage is low.

On the other hand, Comparative Example No. Since the Al content of No. 12 was excessive, the conductivity was as low as 22% IACS.
Comparative Example No. Since the Ni content of No. 13 was insufficient, the contact corrosion resistance exceeding that of brass (Nos. 17 and 18) could not be obtained. Moreover, the stress relaxation rate is larger than that of brass.
Comparative Example No. Since the Al content of No. 14 was insufficient, the contact corrosion resistance exceeding that of brass (Nos. 17 and 18) could not be obtained. Moreover, the stress relaxation rate is larger than that of brass.
Comparative Example No. Since the Ni content of No. 15 was excessive, the conductivity was as low as 21% IACS.
Comparative Example No. In No. 16, since the Ni content is insufficient, the diffusion of Al cannot be suppressed, the segregation of Al becomes small, the contact corrosion resistance exceeding that of brass (Nos. 17 and 18) cannot be obtained, and the stress relaxation rate is reduced. Is larger than brass.

1 Aluminum plate 3 Power supply 6 Test piece 8 Voltmeter

Claims (2)

An aluminum wire containing Al: 0.4 to 2.2% by mass and Ni: 0.4 to 4.0% by mass, composed of the balance Cu and unavoidable impurities, and having a conductivity of 23% IACS or more. Copper alloy material for harness terminals. It is made of a copper alloy material containing Al: 0.4 to 2.2% by mass, Ni: 0.4 to 4.0% by mass, the balance Cu and unavoidable impurities, and the conductivity is 23% IACS or more. Features copper alloy terminals for aluminum wire harnesses.

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