JP5261500B2 - Cu-Ni-Si-Mg alloy with improved conductivity and bendability - Google Patents

Description

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

Copper alloys for electronic materials used for terminals, connectors, and the like are required to have both high strength, high electrical conductivity, and thermal conductivity as basic characteristics. In addition to these characteristics, bending workability, stress relaxation resistance, heat resistance, adhesion to plating, etching workability, press punching, and corrosion resistance are required.
From the viewpoint of high strength and high conductivity, the amount of age-hardened copper alloys has increased in recent years as an alloy for electronic materials, replacing solid solution strengthened copper alloys represented by conventional phosphor bronze, brass, etc. Yes. In age-hardened copper alloys, by aging the solution-treated supersaturated solid solution, fine precipitates are uniformly dispersed to increase the strength of the alloy, and at the same time, the amount of additive elements dissolved in copper Decreases and conductivity is improved. For this reason, it is possible to obtain a material having excellent mechanical properties such as strength and spring property and excellent electrical conductivity and thermal conductivity. Among these age-hardening-type copper alloys, Cu-Ni-Si-based alloys are known as Corson alloys, and are representative copper alloys that have both high strength and high conductivity, and have been put into practical use as materials for electronic devices. . In this copper alloy, the strength and conductivity are increased by the precipitation of fine Ni—Si intermetallic compounds (precipitates Y) in the form of particles in the copper matrix.

  Excellent properties of the above Cu-Ni-Si alloys, especially high strength and good bending workability, and excellent stress relaxation resistance at high temperatures (ability to maintain an appropriate contact pressure for a long time in the connector) Cu-Ni-Si-Mg based alloys exhibiting the above have been studied (Patent Documents 1 to 4). In a general manufacturing process of a Cu—Ni—Si—Mg alloy, first, raw materials such as electrolytic copper, Ni, and Si are melted under a charcoal coating in an atmospheric melting furnace to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. Thereafter, heat treatment, hot rolling, cold rolling and heat treatment are performed to finish the strips and foils having a desired thickness and characteristics.

JP2008-127668 JP 2005-307223 A JP-A-10-110228 JP 2004-307905 A

In the production of a Cu—Ni—Si—Mg based alloy, Mg is easily oxidized as compared with other additive elements, and therefore reacts with oxygen in the molten metal to become an oxide and float on the molten metal. Therefore, considering the amount of Mg loss due to oxidation, Mg is usually added excessively. On the other hand, since the Ni—Si—Mg compound (precipitate X) is a primary crystal in this alloy system, it is first crystallized in the cast ingot. However, in the homogenization heat treatment performed in order to make the non-uniform structure of the internal structure of the metal after casting uniform, the precipitate X is solid-solutioned, and further solution treatment is performed after that, so that conventional Cu-Ni-Si is used. The Mg component of the Mg-based alloy is in a state of being dissolved in the base material, and is usually not present as the precipitate X. In the conventional Cu-Ni-Si-Mg-based alloy in which Mg is excessively added and Mg is in a solid solution, the presence of Mg inhibits electrons from passing through the metal lattice. It was difficult to obtain the same high electrical conductivity as that of the Cu—Ni—Si alloy.
However, in accordance with recent miniaturization of products, conductive spring materials such as connectors, terminals, relays, and switches are required to have smaller and severe bending and strength while maintaining high conductivity.

The present inventor has improved the prior art in which Mg is completely dissolved in a Cu-Ni-Si-Mg alloy after the homogenization heat treatment, and adjusted the casting conditions and the homogenization heat treatment conditions to adjust the specific size. It was discovered that while the Mg-containing precipitate X has in the alloy, the precipitate Y exhibits an excellent effect by keeping the same size and distribution as the conventional one. Based on the knowledge, the size and preferably the amount and ratio of each of the Ni—Si—Mg compound (precipitate X) and the Ni—Si compound (precipitate Y) are adjusted, and Cu having excellent conductivity and bendability of the present invention. A Ni—Si—Mg alloy was completed.
The present invention is as follows.
(1) 1.0 to 4.5 mass% Ni, 0.16 to 1.13 mass% Si, and 0.05 to 0.30 mass% Mg, with the balance being Cu and inevitable impurities A Cu—Ni—Si—Mg based alloy comprising Ni—Si—Mg precipitates X and Ni—Si precipitates Y, the average particle size of the precipitates X being 0.05 to 3.0 μm, A copper alloy in which no precipitate X having a particle size of more than 10 μm exists and the average particle size of the precipitate Y is 0.01 to 0.10 μm.
(2) The copper alloy according to (1), wherein the precipitate X is included in an amount of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ per square mm of the cross section perpendicular to the rolling direction.
(3) The precipitate Y is a copper alloy according to (1) or (2) containing 1.0 × 10 ^{8 to} 1.0 × 10 ¹¹ per square mm of the cross section perpendicular to the rolling direction.
(4) At least one selected from the group consisting of Cr, P, Mn, Ag, Co, Mo, As, Sb, Al, Hf, Zr, Ti, C, Fe, In, Ta, Sn, and Zn is 0 in total. Any one of the above copper alloys containing 0.01 to 2.0% by mass.

  The Cu—Ni—Si—Mg based alloy of the present invention retains the same high strength, high conductivity, good bending workability and stress relaxation properties as the Cu—Ni—Si based alloy, and is excellent at high temperatures. Excellent heat-resistant plating peelability.

2 is a schematic of a two-stage homogenization heat treatment, showing the temperature history of the material being processed.

(1) Ni concentration In the Cu-Ni-Si-Mg-based alloy of the present invention, if the Ni concentration is less than 1.0 mass%, the precipitate X or Y does not sufficiently precipitate, so that the intended strength cannot be obtained. . If the Ni concentration exceeds 4.5% by mass, coarse precipitates are likely to be formed in the casting ingot, and cracks are likely to occur during hot rolling.

(2) Si concentration The additive concentration of Si is 0.16 to 1.13% by mass. When the amount of Si is less than 0.16% by mass, the precipitate X or Y does not sufficiently precipitate and the amount of Ni solid solution increases, so that high conductivity cannot be obtained. When the amount of Si exceeds 1.13% by mass, the Si concentration on the surface of the base material increases, so that the heat-resistant plating peelability deteriorates.

(3) Mg concentration When the Mg concentration is less than 0.05% by mass, the intended stress relaxation resistance (resistance to creep deformation), which is the effect of adding Mg, cannot be obtained. When it exceeds 0.30 mass%, the size of the precipitate X is large or the number of the precipitates X is large, so that hot workability is deteriorated. Moreover, since the amount of solid solution Mg increases, electroconductivity is inferior.

(4) Precipitate X (Ni-Si-Mg precipitate)
Precipitate X (Ni—Si—Mg precipitate) refers to a precipitate (second phase particle) containing Ni, Si and Mg formed in the copper alloy of the present invention. The Mg ratio in the precipitate X is usually about 0.5 to 16% by mass. When the amount is less than 0.5% by mass, the presence of Mg cannot be detected by component analysis and cannot be distinguished from the precipitate Y (Ni—Si precipitate). Therefore, in the present invention, a precipitate containing Ni and Si and having a Mg ratio of less than 0.5% is treated as a precipitate Y. As a result of analyzing a large number of precipitates X, the amount of Mg in the precipitates X was within 16% by mass with the alloy composition of the present invention and the particle sizes of the target precipitates X and Y.
The precipitate X and precipitate Y of the present invention are crystallized products during casting and also precipitates during aging treatment. In the present invention, the presence of the precipitate X reduces the Mg concentration of the base material and improves the conductivity, and pinning of the crystal growth is caused by the presence of the precipitate X remaining in the solution treatment after the homogenization heat treatment. It has a good effect as an effect, and an average crystal grain size finer than that of the conventional example can be obtained.

  The average particle size of the precipitate X of the present invention is 0.05 to 3.0 μm, more preferably 0.50 to 3.0 μm. When the average particle size is less than 0.05 μm, the size of the precipitate is too small to contribute to the strength, and the amount of Mg dissolved in the matrix increases, so that the intended conductivity cannot be obtained. On the other hand, when the average particle size of the precipitate X exceeds 3.0 μm, the precipitate becomes coarse and does not contribute to the strength, and hot cracking is likely to occur, resulting in poor workability. Further, when the precipitate X having a particle size exceeding 10 μm exists, the bending workability is remarkably deteriorated.

The number of precipitates X in the alloy of the present invention is preferably 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ per square mm of the cross section perpendicular to the rolling direction. When the number of the precipitates X is less than 10 ³ , the number is too small, so that even if the precipitates X are precipitated, they do not contribute to the improvement of conductivity and bendability. On the other hand, when the number of the precipitates X exceeds 10 ^5, Ni and Si that should form the precipitates Y are consumed, and the precipitates Y are not sufficiently formed, and the Cu—Ni—Si based alloy inherently high Strength cannot be secured.

  The precipitate X of the present invention is mainly derived from precipitates generated during alloy casting. Conventionally, in order to prevent cracking in the rolling stage, the homogenization heat treatment was performed by heating in the next process of casting, and all precipitates were dissolved. In the present invention, this homogenization heat treatment condition is controlled, and the crystallized matter is left so that the desired size and number of precipitates X can be obtained while homogenizing the cast structure of the ingot. In addition, since the precipitate X has a high melting point, even though it undergoes a solution heat treatment step and an aging step after the homogenization heat treatment, the particle size slightly changes due to diffusion of the heat effect, but does not disappear.

(5) Precipitate Y (Ni-Si precipitate)
Precipitate Y (Ni-Si precipitate) refers to a precipitate (second phase particle) containing Ni and Si formed in the copper alloy of the present invention, and its normal composition is represented by Ni ₂ Si or the like. The
Precipitate Y is formed by solution treatment in the manufacturing process, Ni and Si are sufficiently dissolved in the base material, and precipitated from the base material by aging treatment, in the same manner as in the manufacture of ordinary Corson alloy. To do. The particle size and density can be controlled by these heat treatment conditions. The average particle size of the precipitate Y is 0.01 to 0.10 μm, preferably 0.05 to 0.10 μm. When the average particle size of the precipitate Y is less than 0.01 μm, the size is too small and does not contribute to the strength. On the other hand, when the average particle size of the precipitate Y is 0.10 μm or more, the precipitate Y is coarse and does not contribute to the strength. In addition, when the precipitate Y with a particle size exceeding 3.0 μm exists, the strength and the stress relaxation property are likely to deteriorate.
The number of precipitates Y is preferably 1 × 10 ⁸ to 1 × 10 ^11, more preferably 1 × 10 ⁹ to 1 × 10 ¹¹ , and when the number is less than 1 × 10 ⁸ , the number of precipitates is Does not contribute to strength because it is small. On the other hand, when the number of precipitates exceeds 1 × 10 ^11, bending workability is lowered.

(6) Additive elements other than Ni, Si and Mg Cr, P, Mn, Ag, Co and Mo are effective in improving strength and heat resistance, and As and Sb are effective in improving plating peelability. , Al, Hf, Zr, Ti, C, Fe, In, Ta, Sn, and Zn are effective in preventing the coarsening of the crystal grain size in the solution treatment.
If the addition amount of these elements is less than 0.01% by mass, the effect of addition cannot be obtained, and if it exceeds 2.0% by mass, the conductivity is lowered.

(7) Manufacturing Method The manufacturing method of the copper alloy of the present invention is a general manufacturing process (melting / casting → homogenization heat treatment → hot rolling → intermediate cold rolling → intermediate solution forming → final cooling) with a precipitation strengthened copper alloy. Hot rolling → intermediate cold rolling → intermediate solution rolling → aging → final cold rolling), but the homogenization heat treatment conditions are adjusted within the process. Thus, the target copper alloy is manufactured. In addition, about intermediate rolling and intermediate solution forming, you may repeat several times as needed.
In order to produce the copper alloy of the present invention, it is important to strictly control the conditions for the homogenization heat treatment, the solution treatment, and the annealing. That is, in the homogenization heat treatment, the Ni—Si—Mg precipitate X generated by casting is left so as to be within the scope of the present invention, and the Ni—Si precipitate Y must be sufficiently removed. In the solution treatment, it is desirable that Ni and Si are sufficiently solid-solubilized so that the precipitate Y does not exist. However, the condition may be such that the remaining precipitate X does not disappear. About the last aging, what is necessary is just the conditions which precipitate Y with a small average particle diameter fully precipitates, and this conditions may be the same as the conventional aging conditions.

In the melting / casting step, raw materials such as electrolytic copper, Ni, Si, and Mg are melted to obtain a molten metal having a desired composition and cast into an ingot. In the homogenization heat treatment and hot rolling of the ingot, in order to eliminate the Ni-Si precipitate Y generated by casting and adjust the Ni-Si-Mg precipitate X within the scope of the present invention, the homogenization is performed. Heat treatment is preferably performed in two stages. In that case, the atmosphere temperature in the furnace is set at 800 ° C. or more and less than 890 ° C. as the first stage homogenization heat treatment, and is held for 0.5 to 2.5 hours after the material temperature reaches the set temperature. Furthermore, in order to reduce the average particle size of the remaining coarse Ni—Si—Mg precipitate X, the atmosphere temperature in the furnace was set to 890 ° C. to 980 ° C. as the second stage homogenization heat treatment, and the material temperature was It is preferable to perform hot rolling immediately after holding for 0.5 to 1.2 hours after reaching the set temperature. The first and second stage heating may be performed continuously in one furnace, and is performed by moving from the first stage heat treatment zone to the second stage heat treatment zone. An outline of the temperature history of the material of this two-stage homogenization heat treatment is shown in FIG. Alternatively, in order to prevent the temperature of the ingot from decreasing in a separate furnace, it may be inserted into the second stage furnace as soon as it is taken out from the first stage furnace, and the second stage heating may be started.
When the first stage holding temperature is less than 800 ° C., the Ni—Si precipitate Y is not sufficiently dissolved, and the precipitate X remains with a large average particle diameter, whereas at 890 ° C. or higher, the precipitate X is also solid. Dissolve and disappear. In addition, when the second stage holding temperature is less than 890 ° C., the precipitate X does not disappear, but the particles of the precipitate X may remain large, and some of the precipitate Y remains without being dissolved. there's a possibility that. On the other hand, if the second stage holding temperature exceeds 980 ° C., the precipitate X may be completely dissolved.
In this homogenization heat treatment, heating is performed by a known means such as a burner or a dielectric. When heating, care is taken to keep the output energy and the ingot weight in the furnace constant. If the ingot weight is light even at the same set temperature, it will be overheated, and if the ingot weight is heavy, there is a risk that the heating will be insufficient.

  The Ni—Si—Mg-based precipitate X is hardly changed by maintaining the atmosphere temperature in the first stage furnace of the homogenization heat treatment at 800 ° C. or more and less than 890 ° C. for 0.5 to 2.5 hours. The average particle diameter of the Ni—Si based precipitate Y becomes small. Subsequently, by performing the second stage heat treatment at 890 ° C. to 980 ° C. for 0.5 to 1.2 hours, the average particle size of the Ni—Si—Mg based precipitate X becomes small, and part of Although it disappears, the remaining precipitates X have a predetermined size and number, while all the Ni—Si based precipitates Y that have remained after the first heat treatment disappear. After hot rolling is performed after the two-stage homogenization heat treatment, Ni—Si—Mg-based precipitates X exist to the end in the size and number after hot rolling. On the other hand, the Ni-Si-based precipitate Y undergoes solution treatment and cold rolling, and a predetermined size and number are precipitated by aging treatment.

After the hot rolling, intermediate rolling and intermediate solution forming are performed by appropriately selecting the number of times and the order within the range of the object of the present invention. If the degree of work in the final pass of the intermediate rolling is less than 30%, the number of precipitates Y is reduced because the amount of dislocations that are the starting points of precipitation Y is reduced, and the strength is lowered. On the other hand, when the degree of work exceeds 99%, the amount of dislocations increases and the number of precipitates Y increases, but the average particle size of the precipitates Y becomes too small and the strength decreases. Therefore, the intermediate rolling degree of the final pass is preferably 30% to 99%.
The intermediate solution treatment is sufficiently performed to eliminate the precipitate Y as much as possible by dissolving the crystallized particles during melt casting and the precipitated particles after hot rolling. For example, when the solution treatment temperature is less than 500 ° C., the solid solution is insufficient and the desired strength cannot be obtained. On the other hand, when the solution treatment temperature exceeds 850 ° C., the material may be dissolved. Therefore, it is preferable to perform a solution treatment in which the material temperature is heated to 500 ° C to 850 ° C. The solution treatment time is preferably 60 seconds to 2 hours.

As a relation between the solution treatment temperature and time, in order to obtain the same heat treatment effect (for example, the same average particle diameter of the precipitate Y), it is common sense that the time is short at a high temperature and at a low temperature. It must be long. For example, in the present invention, 1 hour is desirable at 600 ° C. and 2 to 3 minutes to 30 minutes at 750 ° C.
The cooling rate after the solution treatment is generally rapidly cooled so that the solid solution component does not precipitate as second phase particles (precipitate Y).
The degree of work of final rolling is 0 to 50%, preferably 5 to 20%. If it exceeds 50%, the bending workability deteriorates.
The final aging step of the present invention is performed in the same manner as in the prior art, and fine second-phase particles (including the precipitate Y and, optionally, the precipitate X) within the scope of the present invention are uniformly precipitated.

Example 1 (Manufacture of copper alloy)
Using a high frequency induction furnace, 5 kg of high purity copper was dissolved. After covering the molten copper surface with charcoal pieces, predetermined amounts of Ni, Si and Mg were added to adjust the molten copper temperature to 1200 ° C. Thereafter, the molten metal was cast into a mold to produce an ingot having a width of 65 mm and a thickness of 20 mm. About the component of the manufactured ingot, according to JISH1292, the sample was cut out from the ingot and the quantity of the structural element was analyzed by the fluorescent X ray analysis.
Next, this ingot was subjected to homogenization heat treatment described in Table 1, and then hot-rolled to a thickness of 8 mm. Even at this stage, precipitates of Ni—Si and Ni—Si—Mg generated during casting remain. The hot-rolled plate surface oxidized scale was ground and removed, and then cold-rolled to a plate thickness of 0.2 mm. As a solution treatment, the surface oxide film was removed by chemical polishing after heating at 750 ° C. to 800 ° C. for 20 seconds and quenching in water. Thereafter, cold rolling with a workability of 25% was performed, and the aging treatment was performed at 460 ° C. for 7.5 hours in an inert atmosphere.

The following evaluation was performed on the sample thus fabricated.
(1) Measurement of the number and size of precipitates A cross section perpendicular to the rolling direction is mirror-finished by mechanical polishing using diamond abrasive grains having a diameter of 1 μm, and an FE-SEM (electrolytic emission scanning electron microscope) is used. The number of precipitates having a length of 0.05 mm or more was measured at a magnification of 400 times. The observation area was 60 mm ² and the number of precipitates in the observation area was counted. In addition, the use of EDS (energy dispersive X-ray analysis) of FE-SEM (electrolytic emission scanning electron microscope) that Ni and Si or Ni, Si and Mg are included as components of precipitates to be measured. It confirmed by analyzing a component with respect to all the deposits. Here, the distinction between the precipitates X and Y is a precipitate containing Ni, Si, and Mg because of the problem of detection accuracy.
Moreover, when measuring an average particle diameter, the presence or absence of the Ni-Si-Mg precipitate X with an average particle diameter of 10 micrometers or more was confirmed. The particle diameter was the length of the longest part of the deposit of the photograph image | photographed with FE-SEM. The average grain size is obtained by a simple average obtained by adding all crystal grain sizes in the observation area and dividing by the number of crystal grains.

(2) Conductivity measurement of base material A test piece was cut out from a sample, and the surface oxide layer was completely removed by mechanical polishing and chemical etching, and then the conductivity (% IACS) was measured by a four-terminal method. The preferred electrical conductivity aimed at in the present invention is 45% IACS or higher.

(3) Bending workability The W bending test described in JIS H 3130 was performed so that the bending radius R was zero. The test direction was Bad Way (the direction in which the bending axis was parallel to the rolling direction). The test piece was a strip having a width of 10 mm and a length of 30 mm. Next, the cross section of the bending part was visually observed using an optical microscope with respect to the test piece subjected to the W bending with the bending R, and the quality of the bending workability was judged. The evaluation criteria are as follows. ○: No wrinkles or cracks, Δ: Wrinkles on the material surface, ×: Cracks occurred.

(4) Tensile strength No. 13B test piece defined in JIS Z 2201 (2003) was collected in a direction in which the tensile direction was parallel to the rolling direction. Using this test piece, a tensile test was performed according to JIS Z 2241 (2003) to obtain a tensile strength. The preferable tensile strength aimed at in the present invention is 760 MPa or more.

(5) Stress relaxation property As the stress relaxation property at high temperature, the stress relaxation rate (Technical Standard of Japan Copper and Brass Association (JCBA): JCBA T309) was measured. In this test, a strip test piece having a width of 10 mm is attached to a cantilever beam, the deflection displacement (displacement at a predetermined position at the free end) after being held for a predetermined time in a high temperature bent state is compared with the initial state, and the sag due to temperature It is a method to evaluate. When the deflection after the test and the initial state does not change, the value of the stress relaxation rate is 0%, and as the deflection after the test becomes larger than the initial state, the value of the stress relaxation rate increases (stress decreases). The stress relaxation rate is given by the following equation (where, y = deflection displacement (mm) after elapse of a predetermined time, y ₁ = initial deflection (mm), y ₀ = set height (mm)).
Stress relaxation rate = (y−y ₁ ) / y ₀ × 100 (%)

Further, the set height y ₀ is given by the following equation (where L = target distance (mm), σ ₀ = load stress (kg / mm ² ); 0.2% proof stress 80% or 0.2% Arbitrary stress below yield strength, E = Young's modulus (kg / mm ² ), t = plate thickness (mm)).
y ₀ = (2/3) × L × L × σ ₀ / (E × t)

The stress relaxation was measured until the sample was 150 ° C. and showed a certain relaxation rate. Since a substantially constant stress relaxation rate was exhibited in about 1000 hours, this value was taken as the stress relaxation rate.
The stress relaxation rate after 150 ° C. × 1000 h of a commonly used Corson alloy is about 10%. Therefore, in the evaluation of each of the following invention examples and comparative examples, those having a stress relaxation rate of 9% or less were considered to have good stress relaxation resistance at high temperatures.

In the above table, “-*” represents no addition of other elements.
In Invention Examples 1 to 10, the first stage homogenization heat treatment is 800 ° C. to less than 890 ° C. × 2 hours, and the second stage heat treatment is 890 ° C. to 980 ° C. × 0.5 to 1.2 h. After the hot rolling, the precipitate X had no coarse particles exceeding 10 μm, the average particle size was 0.05 to 3.0 μm, and all the precipitate Y was dissolved and disappeared. Thereafter, in the aging treatment after solution heat treatment and cold rolling, the precipitate Y could be precipitated under the aging conditions such that the average particle diameter was 0.01 to 0.10 μm. As a result, high strength, high conductivity, good bending workability and stress relaxation were obtained.

  In Comparative Examples 11 to 15, the homogenization heat treatment was performed in one stage. In Comparative Example 11, since the homogenization heat treatment temperature was as low as 870 ° C., the size of the precipitate X was not reduced by the heat treatment, and coarse precipitates X of 10 μm or more remained in the product. On the other hand, the precipitate Y having a large size before the homogenization heat treatment remains without disappearing at the homogenization heat treatment temperature of 870 ° C. Precipitate Y remaining after hot rolling after homogenization heat treatment does not disappear even after solution treatment, rolling, and aging treatment (same conditions as in Invention Examples 1 to 10). Therefore, even if the precipitate Y is precipitated under aging conditions such that the average particle size is 0.1 μm or less if the coarse precipitate Y is not present, the coarse precipitate Y exists from before the aging, so the average The particle size exceeds 0.10 μm, and the number of precipitates Y decreases. For this reason, Comparative Example 11 has poor bending workability due to the presence of large precipitates X, and the strength is inferior due to the small number of precipitates Y. Furthermore, since a large amount of Mg is present in a large number of precipitates X, the amount of solid solution Mg is reduced and the stress relaxation characteristics are also poor.

In Comparative Examples 12 and 13, since the homogenization heat treatment temperature is higher than that in Comparative Example 11, there is no coarse precipitate X of 10 μm or more, but since the time is relatively short, the average particle size of the precipitate X is 3.0 μm or less. The precipitate Y having a large size did not disappear even after the homogenization heat treatment. As a result, Comparative Examples 12 and 13 were inferior in strength because the average particle size of the precipitate Y exceeded 0.10 μm and the number was small, and the stress relaxation characteristics were also poor because the number of precipitates X was large and the average particle size was large. .
In Comparative Examples 14 and 15, the homogenization heat treatment was performed under the conditions such that all of the precipitate X and the precipitate Y disappeared as in the prior art. In the subsequent aging treatment, 1.7 × 10 ⁸ precipitates and 1.2 × 10 ⁸ precipitates were precipitated, respectively, so that high strength could be obtained. However, since the precipitate X does not exist, The amount of Mg was excessive and the conductivity was inferior.
In the homogenization heat treatment of Comparative Example 16, the average particle size and maximum particle size of the precipitate X could be controlled. However, since the heat treatment temperature of the first stage is low, the precipitate Y which was large before the heat treatment becomes small but does not disappear even if the temperature of the second stage is 900 ° C. Therefore, the average particle size of the precipitate Y is The number of precipitates Y was less than 0.10 μm. As a result, the strength was inferior.
In Comparative Example 17, since the time for the second stage homogenization heat treatment is too short, coarse precipitates X remain after hot rolling, and the average particle size of the precipitates X exceeds 3.0 μm, and the size Large precipitates Y remained, but the total number of precipitates Y was small. As a result, the strength, bending workability, and stress relaxation characteristics were inferior.
In Comparative Example 18, the heat treatment time in the second stage is too long, so the average particle size of the precipitate X is less than 0.05 μm, the number is small, and the conductivity is inferior.

The invention examples 19-22 and the comparative examples 23-30 show that this invention is effective also in the alloy which added another element to the Cu-Ni-Mg type alloy. In Comparative Examples 23 to 26, the homogenization heat treatment was performed in one stage, and since the precipitate X was not present, the conductivity was low. In Comparative Examples 27 and 28, the number of precipitates Y was small because the first-stage homogenization heat treatment temperature was low, but the average particle size was large. Therefore, it was inferior in tensile strength. In Comparative Examples 29 and 30, the second stage homogenization heat treatment time was short, so the particle size of the precipitate X was large, and coarse precipitates X of 10 μm or more remained in the product, but the number of precipitates Y was small. It was. Therefore, it was inferior in tensile strength, bending workability, and stress relaxation characteristics. Furthermore, in Comparative Example 29, since the number of precipitates X was large, the stress relaxation characteristics were inferior.
In addition, regarding the heat-resistant plating peelability, the invention example showed a heat-resistant plating peelability that does not cause a problem in actual use, but the invention example 20 showed a further excellent heat-resistant plating peelability compared to other examples. .

Claims (4)

  Cu containing 1.0 to 4.5% by mass of Ni, 0.16 to 1.13% by mass of Si, and 0.05 to 0.30% by mass of Mg with the balance being Cu and inevitable impurities -Ni-Si-Mg based alloy, including Ni-Si-Mg precipitate X and Ni-Si precipitate Y, the average particle diameter of the precipitate X being 0.05 to 3.0 m, the particle diameter being A copper alloy in which no precipitate X exceeding 10 μm exists and the average particle size of the precipitate Y is 0.01 to 0.10 μm. 2. The copper alloy according to claim 1, wherein the precipitate X is included in an amount of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ per square mm of a cross section perpendicular to the rolling direction. 3. The copper alloy according to claim 1, wherein the precipitate Y is contained in an amount of 1.0 × 10 ^{8 to} 1.0 × 10 ¹¹ per square mm of a cross section perpendicular to the rolling direction.   A total of 0.01 to at least one selected from the group consisting of Cr, P, Mn, Ag, Co, Mo, As, Sb, Al, Hf, Zr, Ti, C, Fe, In, Ta, Sn, and Zn. The copper alloy according to any one of claims 1 to 3, comprising 2.0% by mass.

Images