JPH0689440B2 - Manufacturing method of high-strength conductive copper-based alloy with excellent press formability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high-strength conductive copper-based alloy suitable as a material for a terminal of a wire harness used for electric components of automobile parts.

[Conventional technology]

As is well known, the automobile industry has come to play a major role as a key industry in Japan, and due to the increase in the number of production and the recent development of car electronics, the number of copper alloy products used for it has been increasing. . The wire harness that plays a role in the electric components of the car does not leak to this, and 1k per unit
A length of 20 m and a weight of 20 kg were used. Recently, demands for weight reduction, high reliability, and cost reduction for automobiles are becoming more and more severe. Therefore, wire harnesses are also required to be lightweight, highly reliable, and low cost. Here, the wire harness is an integrated wire and terminal, and it is essential to improve the material characteristics and reliability of the terminal material in order to reduce the weight and increase the density of power distribution.

Against this background, in practice, the terminal material is thinned and pressed into a complicated shape, so good strength, elasticity, conductivity, and press formability are essential. In addition to good corrosion resistance and stress corrosion cracking resistance, it must also have excellent stress relaxation resistance because thermal loads are applied around the engine room and exhaust gas system.

In order to meet such demands, the present inventors have filed Japanese Patent Application No. 62-10.
No. 6426 has proposed copper alloys for wire harness terminals and methods of manufacturing the same. Japanese Patent Application Sho 62-1
The invention described in No. 06426 has exhibited excellent properties by uniformly and finely depositing Ni-Ti intermetallic compounds in a Cu matrix. As a copper-based alloy in which a compound is deposited, Japanese Patent Publication No. 34-1253, Japanese Patent Publication No. 62-8491, and Japanese Patent Publication No.
The ones described in JP-A-63-4890, JP-B-62-54048 and the like are known, and the manufacturing method thereof is, for example, JP-A
The method described in JP 62-50453 is known.

[Problems to be solved by the invention]

In the Cu-Ni-Ti alloys disclosed in the above publications,
In many cases, manufacturing methods suitable for improving strength and conductivity are mainly used. Therefore, in these conventional manufacturing methods, Cu-Ni-Ti alloy wire for press forming into complicated shapes is used. It is often not always suitable when manufacturing terminals for harnesses.

For example, in the example of Japanese Examined Patent Publication No. 341253, “a wire having a diameter of 5.2 mm, water quenched at 1000 ° C., and further cold worked to have a diameter of 1.6 mm.
mm wire and finally tempered at 500 ° C for 1 hour to obtain a finish wire. "a. As a result, the invention alloy (2) (Cu-2.3
Ni-0.7Ti alloy) has the following values: tensile strength 71.0 kgf / mm ² , elongation 3.5%, Vickers hardness 214, conductivity 60.6%.
However, the material obtained by this method is excellent in material property values such as strength and conductivity, but has a drawback that it is inferior in workability. Therefore, the process of solution treatment-quenching-strong cold working-aging treatment is advantageous in improving strength and conductivity, but has a problem that workability is extremely deteriorated.

The method described in JP-A-62-50453 is disclosed in
Strength and conductivity are improved by using more restrictive heat treatment conditions, cooling conditions and cold working rate than those described in JP 34-1253, but the basic manufacturing method is solution treatment. It is a process of treatment-quenching-strong cold working-aging treatment and is similar to that of Japanese Patent Publication No. 34-1253. Therefore, there is a problem in that workability is poor with respect to strength and conductivity.

On the other hand, in JP-B-62-8491, JP-B-63-4890, and JP-A-62-54048, soft annealing and cold rolling are repeated, and in some cases after the final cold rolling. Aging treatment is applied to improve strength and conductivity. However, according to such a manufacturing method, in order to improve the strength and elasticity, it is necessary to make the cold working rate after the softening annealing relatively large, and in this case, the press formability is greatly reduced. Further, it has lower elasticity and inferior stress relaxation resistance as compared with the material manufactured by the solution treatment and the quenching process.

Therefore, the present inventors have previously proposed Japanese Patent Application No. 62-10642.
In No. 6, we proposed a method to improve strength, elasticity, conductivity, press formability, and stress relaxation resistance property. This manufacturing method is solution treatment-quenching-cold working-aging treatment-cold working- In the process represented by aging treatment, the characteristics are expressed by strictly limiting the processing and heat treatment conditions. However, such a manufacturing method has a problem in that the number of steps required to obtain a product after solution treatment is large and the economy is low.

Therefore, an object of the present invention is to produce at low cost a copper-based alloy suitable for a terminal material of a wire harness, which is excellent in press formability, strength, elasticity, conductivity, and stress relaxation resistance. It is in.

[Means for solving problems]

The gist of the present invention to achieve the above-mentioned object is that, in weight%, Ni; 1.0 to 3.0%, Ti; 0.1 to 1.5%, provided that the weight percentage ratio of Ni / Ti is in the range of 1 to 10. , Oxygen; 50
ppm or less, and if necessary, the total amount of one or more elements selected from the group consisting of Zn, Mg, Ca, Be, Zr and Cr.
After heating a copper-based alloy containing 0.01 to 1.0% and the balance Cu and unavoidable impurities to a temperature of 800 to 970 ℃, 400 to 650
400 to 65 at a cooling rate of 10 ° C / sec or more to a temperature of ° C.
Heat and hold at 0 ℃ for 5 to 360 minutes, then cool to room temperature, and if necessary, cold work within 3% and heat at 400 to 600 ℃ for 1 to 360 minutes. , Is a method for producing a high-strength conductive copper-based alloy with excellent press formability.

The contents of the present invention will be specifically described below.

[Detailed Description of the Invention]

(1) Concerning the composition of the alloy of the present invention, the copper-based alloy of the present invention has a basic feature in that precipitation strengthening and dispersion strengthening by Ni-Ti intermetallic compounds are aimed at. It is an essential element in invention alloys.

Ni is an element that contributes to the improvement of properties such as strength, elasticity, heat resistance, and stress relaxation resistance when a compound is formed with Ti. Further, it has the effect of making the cast structure and the hot structure fine and preventing the crystal grains from becoming coarse during the solution treatment. To achieve this effect, the content must be 1.0% (weight%, the same applies below) or more, but if it exceeds 3.0%, the electrical conductivity will be significantly reduced and the solution treatment temperature will be high. It is disadvantageous in manufacturing, and is not preferable in terms of economy. Therefore, the Ni content is set to the range of 1.0 to 3.0%.

When the Ti content is less than 0.1%, the effect of improving strength, elasticity, heat resistance, stress relaxation resistance, etc. is small even when coexisting with Ni.
On the other hand, when the Ti content exceeds 1.5%, the electrical conductivity is lowered and the press formability is extremely lowered. In addition, since the manufacturability such as castability decreases, the Ti content is 0.1-
The range is 1.5%.

Further, the objects of the present invention are advantageously achieved when Ni and Ti are precipitated as Ni—Ti based intermetallic compounds. In order to fully exert the strengthening by this Ni-Ti intermetallic compound, it is necessary to set the ratio by weight percentage of Ni / Ti within the range of 1-10. When the Ni / Ti ratio is less than 1, the Ti-Ni based intermetallic compound which is a compound of Ti and Cu is aged and precipitated. This T
Even if the i-Cu intermetallic compound is deposited, the improvement in strength and elasticity can be expected, but the improvement in electrical conductivity is small, and
The crystal grains are likely to become coarse during the solution heat treatment, and thus the bent surface is likely to be roughened during press forming. Therefore, the Ni / Ti ratio needs to be 1 or more. On the other hand, the Ni / Ti ratio is
If it is more than 10, the amount of Ni remaining in the matrix increases and the electrical conductivity decreases. For this reason, the Ni / Ti ratio is 1 to 1 in order to sufficiently exhibit the characteristics of the present invention.
Must be in the 0 range.

Zn improves the plating reliability of the alloy of the present invention. Specifically, it improves the heat-resistant adhesion of Sn plating and Sn-Pb plating. The terminal of the wire harness may be Sn-plated or Sn-Pb-plated, but if it is heated for a long time by electricity or heat of the engine system, the effect of the environment is added and the additive elements Ni and Ti are plated. It diffuses to the interface and forms a reaction diffusion layer with Sn. This reaction diffusion layer is fragile, and the plating is easily peeled off, which lowers the plating reliability. When Zn is added, the diffusion of Ni or Ti in Cu is suppressed, and the formation of the reaction diffusion layer at the interface can be efficiently prevented. In addition, Zn has a deoxidizing effect, acts as a deoxidizing agent for the molten metal, and improves the flowability of the molten metal, thus improving the castability. In order to exert such effect, 0.1% or more of Zn
However, if the content exceeds 1.0%, the electrical conductivity will be significantly reduced.
It is necessary to be in the range of ~ 1.0%.

Like Zn, Mg and Ca are elements that contribute to the improvement of plating reliability and deoxidation. It also has the effect of improving the elasticity of the alloy. In order to exert such effects, it is necessary to contain 0.01% or more, but if it exceeds 0.5%, the electrical conductivity and press formability of the alloy will be significantly reduced, and it is economically disadvantageous. Therefore, the Mg and Ca contents are preferably in the range of 0.01 to 0.5%.

Be is an element that further improves the strength, elasticity, and stress relaxation resistance of this alloy. It also has a deoxidizing effect and also serves as a deoxidizing agent for the molten metal. In order to exert such effects, it is necessary to contain 0.01% or more, but if it exceeds 0.5%, the electrical conductivity and press formability of the alloy will be significantly reduced, and it is also economically disadvantageous. Becomes Therefore, the Be content is preferably in the range of 0.01 to 0.5%.

Similar to Be, Zr and Cr are elements that contribute to the improvement of strength, elasticity, stress relaxation resistance and deoxidation. In order to exert such effects, it is necessary to contain 0.01% or more, but if it exceeds 0.5%, the electrical conductivity and press formability will be significantly reduced, and it will be economically disadvantageous. Become.
Therefore, the Zr and Cr contents are preferably in the range of 0.01 to 0.5%.

In addition, Zn, Mg, Ca, Be, Zr, and Cr can contain two or more kinds in total up to 1.0%. If the content exceeds 1.0%, the electrical conductivity and the press formability are significantly deteriorated and it is economically disadvantageous. Therefore, the total amount of one or more selected from the group of Zn, Mg, Ca, Be, Zr, Cr is 0.01-1.
It can be added in the range of 0%.

Regarding the oxygen content, the precipitated Ni-Ti-based intermetallic compound contained in the alloy in an amount of more than 50 ppm forms a ternary compound with oxygen to become a Ni-Ti-O-based compound, and the strength, elasticity, press forming It reduces the material properties such as conductivity and plating reliability. Also, if the oxygen content is high, hydrogen embrittlement may occur on the surface and inside when H ₂ gas is used in the alloy manufacturing process. Therefore, the oxygen content should be 50 ppm or less.

(2) Regarding manufacturing conditions of the alloy of the present invention.

The copper-based alloy of the present invention adjusted to the component composition as described above is Ni
By uniformly and finely dispersing and precipitating the Ti-based intermetallic compound, it is possible to obtain a material having various characteristics required for the terminal of the recent wire harness. Such various characteristics can be advantageously exhibited especially by a production method in which heat treatment is appropriately controlled. The details of the manufacturing method will be described below.

First, a slab of a copper-based alloy in which the alloy composition and the oxygen content are adjusted to have the above-described composition is melt-cast and manufactured. It is desirable that this melting and casting be performed in an inert gas or reducing gas atmosphere. Further, it is preferable that the cooling rate during casting is as high as possible. Then, the slab is subjected to hot rolling or homogenization annealing and then cold rolling to reduce the plate thickness. Then, if necessary, cold rolling with intermediate annealing and pickling is performed to obtain the plate thickness before finishing.

Then, the obtained raw material is heated to a temperature of 800 to 970 ° C,
Perform solution treatment. If the temperature of this solution heat treatment is less than 800 ° C, the solution will not be sufficiently solutionized, and therefore casting, hot rolling,
Coarse precipitates generated in the annealing process do not disappear sufficiently, so the characteristics cannot be improved. Also, it is difficult to control the crystal grains at temperatures below 800 ° C. However, if the temperature exceeds 970 ° C., the crystal grains become coarse in a short time, which is not preferable.
Therefore, in the present invention, the temperature range of solution treatment is
Set to 800-970 ℃.

After solution treatment, cooling rate is 10 ℃ / sec or more, preferably 50
Cool to 400-650 ℃ at a cooling rate of ℃ / sec or more. 10 ° C
When the cooling rate is less than / sec, precipitation occurs during the cooling process, and the precipitate generated at this stage does not contribute much to strengthening. The temperature range for cooling is sufficient from the solution treatment temperature to a temperature of 400 to 650 ° C. If the temperature exceeds 650 ° C, the precipitate will grow and become coarse, and the characteristics cannot be further improved. The temperature range of the subsequent aging treatment of the present invention is 400 to 650 ° C., and reheating for aging is not required by rapidly cooling from the solution treatment temperature to 400 to 650 ° C. and subsequently performing aging treatment at this temperature. Will be economically advantageous.

The aging treatment is performed by heating at a temperature of 400 to 650 ° C for 5 to 360 minutes. In this process, the Ni-Ti intermetallic compound is uniformly and finely precipitated. At temperatures below 400 ° C, the time required for precipitation is long, while at temperatures above 650 ° C, precipitates grow. As a result, the particles become coarse, and further improvement in characteristics cannot be expected. Therefore, the aging temperature should be in the range of 400-650 ° C. If the aging time is less than 5 minutes, the formation of precipitates is insufficient, and if the aging time is longer than 360 minutes, it is not preferable in terms of growth of the precipitates and economical efficiency.

The plate material obtained by the above-mentioned steps has excellent press formability and also has an excellent balance of strength, elasticity, conductivity, and stress relaxation resistance.

The material properties can be further improved by cold-rolling the plate material that has undergone this treatment at a working rate of 30% or less and heating it at a temperature of 400 to 600 ° C for 1 to 360 minutes. If the cold working rate exceeds 30%, the press formability is extremely reduced, so it is necessary to keep the cold working rate within 30%. The strength, elasticity, conductivity, and stress relaxation resistance of the alloy are further improved by the increase of internal strain given by this cold working and final aging treatment, but the temperature of this final aging treatment is less than 400 ° C. And the effect of improving elasticity is small, and 600
If the temperature exceeds ℃, it will be over-aged and the material properties will deteriorate.
If the holding time is less than 1 minute, the effect of improving elasticity is small, and if the holding time is more than 360 minutes, it is not preferable in terms of growth of precipitates and economy.

Through the above steps, the Ni-Ti-based intermetallic compound becomes C
A thin plate can be manufactured from a copper-based alloy having a structure in which it is uniformly and finely dispersed and precipitated in a u matrix. This can be used for strength, elasticity, conductivity, stress relaxation resistance, and press formability, as shown in Examples below. Since it is excellent, it can satisfy the characteristics required for the terminal material of the recent wire harness.

The characteristics of the alloy of the present invention will be specifically shown below with reference to representative examples of the present invention.

[Example 1] Copper-based alloy No. 1 having the chemical composition values (% by weight) shown in Table 1 was melted using a high frequency induction melting furnace and cast into a 15 mm x 50 mm x 300 mm ingot. The melting and casting atmosphere was completely shielded with an inert gas. After cutting this ingot into 15 mm × 50 mm × 200 mm, 90
After hot rolling at 0 ° C to a thickness of 5 mm, it was chamfered to a thickness of 4.
It was set to 2 mm. This was cold-rolled to a thickness of 0.5 mm by a cold-rolling process in which intermediate annealing (700 ° C x 1 hr) was performed when the thickness was 2 mm and 1 mm. This plate material was heat-treated under the conditions shown in Table 2 to produce a test material.

These heat treatments were performed in an inert gas, and the quenching gas used was cooled Ar gas. The cooling rate was the average cooling rate from the solution heat treatment temperature to the subsequent aging treatment temperature.

Table 2 also shows the results of examining the hardness, tensile strength, elongation, conductivity, and press formability of the obtained test materials. Hardness, tensile strength and elongation, and conductivity are measured according to JIS Z 2244 and JIS Z, respectively.
2241, JIS H 0505. Press formability was evaluated by bending at right angles with an inner radius of 0 on axes parallel and perpendicular to the rolling direction and observing the bent surface and its cross-section in a magnified manner.

The following is clear from the results in Table 2.

The alloys (1) and (2) produced according to the method of the present invention have an excellent balance of hardness, tensile strength, elongation and conductivity and good press formability. Therefore, it can be seen that the plate material manufactured by the method of the present invention has good material properties and excellent press formability, and is also suitable as a terminal material for a wire harness having a complicated shape.

On the other hand, Comparative Example (3) having a low solution treatment temperature has low hardness, tensile strength, and elongation, while Comparative Example (4) having a high solution treatment temperature is inferior in press formability. The comparative example (5) having a slow average cooling rate has low hardness and tensile strength, the comparative example (6) having a low aging temperature has low conductivity, and the comparative example (7) having a high aging temperature has a hardness of The tensile strength is low.

Example 2 An alloy having the components shown in Table 1 of Example 1 was subjected to the same intermediate step as in Example 1 to obtain a plate material having a thickness of 2 mm. 700 ℃ × 60
After annealing for 1 minute, it was used as the material plate of the following manufacturing method.

[Manufacturing method 1] After cold rolling the above material plate to a thickness of 1 mm, 700 ° C x 60
Annealing was performed for a minute. Then, after cold rolling to a thickness of 0.45 mm, solution heat treatment was performed for 2 minutes at 950 ° C, and the average cooling rate was 60
The sample was cooled to 550 ° C at ℃ / sec, then subjected to an aging treatment at this temperature for 60 minutes and cooled to room temperature. The obtained aging-treated material was cold-rolled to 0.4 mm and subjected to a final aging treatment at a temperature of 480 ° C for 60 minutes.

[Manufacturing Method 2] The material plate was cold-rolled to a thickness of 0.8 mm. 950 this
After solution treatment at ℃ × 2 minutes, the average cooling rate is 60 ℃ / sec
After cooling to 550 ° C, aging treatment was performed at this temperature for 60 minutes, and the temperature was cooled to room temperature. The obtained aging treated material is 0.
It was cold-rolled to 4 mm and subjected to a final aging treatment at 480 ℃ x 60 minutes.

[Manufacturing Method 3] The material plate was cold-rolled to a thickness of 1 mm. 950 ° C
After the solution treatment for 2 minutes, it was quenched with water. Then, after cold rolling to 0.4 mm, aging treatment was performed at 500 ° C for 60 minutes.

As shown in Table 3, 1 is an example within the range of conditions regulated by the present invention, and 2 and 3 are comparative examples that deviate from the above conditions.

Table 4 shows the results obtained by measuring the hardness, tensile strength, elongation, spring limit value, conductivity, stress relaxation rate and press formability of the materials obtained by each method. The measurement of hardness, tensile strength, elongation, and conductivity is the same as in Example 1. Spring limit is JIS H 31
Made on the basis of 30. The stress relaxation rate was calculated by the following equation as the stress relaxation rate, which was the bending behavior after 500-hour holding at 150 ° C by U-bending so that the stress at the center of the test piece was 40 kgf / mm ² .

Stress relaxation rate (%) = [(L ₁ -L ₂ ) / (L ₁ -L ₀ )] × 100 where L _{0 is} the length of the jig (mm) L _{1 is the} length of the sample at the start (mm) L ₂ ： Horizontal distance between sample ends after processing (mm) For press formability, 90 ° w bending test (CES-M
OOO2-6, R = 0.2mm rolling direction and vertical direction) were observed by magnifying and observing the central mountain surface and its cross section, and those without cracks were evaluated as ○, and those with cracks were evaluated as ×.

As is clear from the results in Table 4, the alloy of the production method (1) according to the present invention is excellent in hardness, tensile strength, elongation, spring limit value, conductivity, stress relaxation resistance and press formability. Therefore, it can be seen that it is an alloy with excellent properties as a terminal material for wire harnesses.

On the other hand, the alloy of the comparative method (2) having a cold working ratio higher than the range specified by the method of the present invention is inferior in press formability, and as in the comparative method (3), the solution treatment-quick cooling-strong cold working is performed. The alloy using the conventional process of working-aging treatment is generally inferior in material properties to the alloy obtained by the method (1) of the present invention and also has poor press formability.

[Example 5] Copper-based alloys No. 1 to N whose chemical composition values (% by weight) are shown in Table 5
All o.12 were produced according to the production method (1) of Example 2 above. The hardness, tensile strength, elongation, conductivity and press formability of the obtained material were measured, and the results are shown in Table 6. The method of measuring these characteristics was the same as in Example 2.

From Table 6, it can be seen that the alloy obtained by the method of the present invention is excellent in hardness, tensile strength, elongation, spring limit value, conductivity and press formability.

As described above, according to the present invention, a copper alloy for a terminal of a wire harness, which is excellent in strength, elasticity, conductivity, stress relaxation resistance, and press formability, can be economically manufactured,
The purpose of the present invention is to provide a terminal material that can sufficiently cope with the recent reduction in size and weight of automobile electrical components and the increase in wiring density.

Claims (2)

[Claims] 1. In weight%, Ni; 1.0-3.0%, Ti; 0.1-
1.5%, but the weight percentage ratio of Ni / Ti is in the range of 1 to 10, oxygen; 50 ppm or less, and if necessary Zn, Mg, Ca, Be,
After heating a copper-based alloy containing one or more elements selected from the group consisting of Zr and Cr in a total amount of 0.01 to 1.0% and the balance of Cu and inevitable impurities to a temperature of 800 to 970 ° C. Excellent in press formability, characterized by cooling to a temperature of 400 to 650 ℃ at a cooling rate of 10 ℃ / sec or more, heating and holding at a temperature of 400 to 650 ℃ for 5 to 360 minutes, and then cooling to room temperature. Manufacturing method of high strength conductive copper base alloy. 2. In weight%, Ni; 1.0-3.0%, Ti; 0.1-
1.5%, but the weight percentage ratio of Ni / Ti is in the range of 1 to 10, oxygen; 50 ppm or less, and if necessary Zn, Mg, Ca, Be,
After heating a copper-based alloy containing one or more elements selected from the group consisting of Zr and Cr in a total amount of 0.01 to 1.0% and the balance of Cu and inevitable impurities to a temperature of 800 to 970 ° C. Cooling to a temperature of 400 to 650 ℃ at a cooling rate of 10 ℃ / sec or more, heating and holding at a temperature of 400 to 650 ℃ for 5 to 360 minutes, then cooling to room temperature, and then cold working within a working rate of 30% The method for producing a high-strength conductive copper-based alloy with excellent press formability, which comprises heating at 400 to 600 ° C for 1 to 360 minutes.