CN102105611B - Cu-Ni-Si-Mg-based alloy having improved electrical conductivity and bendability - Google Patents

Abstract

A Cu-Ni-Si-Mg alloy 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, and the rest is composed of Cu and unavoidable impurities. Ni-Si-Mg precipitate X and Ni-Si precipitate Y, the average particle size of the precipitate X is 0.05 to 3.0 μm, there is no precipitate X with a particle size exceeding 10 μm, and the average particle size of the precipitate Y is 0.01 to 0.10 μm, and may contain a total of 0.01 to 2.0% by mass of Cr, P, Mn, Ag, Co, Mo, As, Sb, Al, Hf, Zr, Ti, C, Fe, In, Ta, Sn, or Zn. Preferably, the precipitate X is 10 ³ to 10 ⁵ particles/mm ² , and the precipitate Y is 1.0×10 ⁸ to 1.0×10 ¹¹ particles/mm ² . The Cu-Ni-Si-Mg alloy of the present invention can maintain high strength, high electrical conductivity, and good bending processing properties, and also exhibits excellent stress relaxation resistance properties at high temperatures.

Description

Cu-Ni-Si-Mg Alloys with Improved Conductivity and Flexibility

technical field

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.

Background technique

Copper alloys for electronic materials used in terminals, connectors, etc. are required to have both high strength and high electrical conductivity or thermal conductivity in terms of basic characteristics. In addition to these properties, bending workability, stress relaxation resistance, heat resistance, adhesion to plating, etching workability, punchability, and corrosion resistance are also required.

From the viewpoint of high strength and high conductivity, in recent years, the use of age-hardening copper alloys has gradually increased in terms of alloys for electronic materials, replacing solid-solution-strengthened copper represented by phosphor bronze and brass. alloy. Age-hardening copper alloy, through the aging treatment of the solution-treated supersaturated solid solution, the fine precipitates are evenly dispersed, and the strength of the alloy is improved. At the same time, the amount of added elements dissolved in copper will be reduced to improve electrical conductivity. Therefore, a material having excellent mechanical properties such as strength and elasticity and good electrical conductivity and thermal conductivity can be obtained. Among the age-hardening copper alloys, Cu-Ni-Si alloys are known as Corson alloys, which are representative copper alloys having both high strength and high conductivity, and have been put into practical use as materials for electronic devices. In this copper alloy, fine Ni—Si-based intermetallic compounds (precipitates Y) are precipitated in the form of particles in the copper matrix to improve strength and conductivity.

Cu-Ni-Si-Mg alloys have been studied in the past (Patent Documents 1 to 4), and the Cu-Ni-Si-Mg alloys can maintain the excellent properties of the above-mentioned Cu-Ni-Si alloys, especially high strength. With good bending processability, it has excellent stress relaxation resistance at high temperature (the ability to maintain proper contact pressure in the connector for a long time). In a general method for producing Cu-Ni-Si-Mg alloys, raw materials such as electrolytic copper, Ni, Si, etc. are first melted in an atmospheric melting furnace under a charcoal covering to obtain a molten solution having a desired composition. Next, the melt is cast into an ingot. Then, heat treatment, hot rolling, cold rolling, and heat treatment are performed, and finished into a strip or foil having desired thickness and properties.

Patent Document 1: Japanese Patent Laid-Open No. 2008-127668

Patent Document 2: JP 2005-307223

Patent Document 3: Japanese Patent Application Laid-Open No. 10-110228

Patent Document 4: Japanese Patent Laid-Open No. 2004-307905

Contents of the invention

In the production of Cu-Ni-Si-Mg alloys, Mg is easier to oxidize than other additive elements, so it reacts with oxygen in the melt to form oxides and suspends on the melt. Therefore, Mg is usually added in excess in consideration of the amount of Mg loss due to oxidation. On the other hand, since the Ni-Si-Mg compound (precipitate X) is a primary crystal in this alloy system, it will crystallize first in the cast ingot. However, in the homogenization heat treatment to make the heterogeneous structure of the internal structure of the metal after casting uniform, the precipitate X is dissolved, and the solution treatment is also performed thereafter, so the conventional Cu-Ni- The Mg component of the Si—Mg-based alloy is in a state of solid solution in the base material, and the precipitate X does not exist. Conventional Cu-Ni-Si-Mg alloys in which Mg is added in excess in this way and Mg is in a solid solution state prevent electrons from passing through the metal lattice due to the presence of Mg, so it is difficult to obtain Cu-Ni-Si alloys of the same grade. High electrical conductivity.

However, with the miniaturization of products in recent years, conductive spring materials such as connectors, terminals, relays, and switches are required to maintain high electrical conductivity, smaller and severe bending, and strength.

The present inventor, in the Cu-Ni-Si-Mg alloy, improved the conventional technology of complete solid solution of Mg after homogenization heat treatment, and by adjusting the casting conditions and homogenization heat treatment conditions, the alloy has a specific It was found that the size of the Mg-containing precipitate X was reduced while maintaining the same size and distribution of the precipitate Y as in the past, and it was found that an excellent effect can be achieved. Based on this finding, the Ni-Si-Mg compound (precipitate X) and the Ni-Si compound (precipitate Y) were adjusted in size and their preferred amounts and ratios to complete the electrical conductivity and bendability of the present invention. Cu-Ni-Si-Mg alloy.

The present invention is as follows.

(1) A copper alloy comprising 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, the remainder being Cu and unavoidable impurities. A Ni-Si-Mg alloy containing Ni-Si-Mg precipitates X and Ni-Si precipitates Y, the average particle size of the precipitates X is 0.05 to 3.0 μm, and there is no precipitate X with a particle size exceeding 10 μm, In addition, 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 contains 1.0×10 ³ to 1.0×10 ⁵ per 1 square mm of a cross section perpendicular to the rolling direction.

(3) The copper alloy according to (1) or (2), wherein the precipitate Y contains 1.0×10 ⁸ to 1.0×10 ¹¹ per 1 square mm of a cross section perpendicular to the rolling direction.

(4) The copper alloy according to any one of the above, which contains a total of 0.01 to 2.0% by mass selected from Cr, P, Mn, Ag, Co, Mo, As, Sb, Al, Hf, Zr, Ti, C, Fe , At least one element of In, Ta, Sn and Zn.

Invention effect

The Cu-Ni-Si-Mg alloy of the present invention maintains the high strength, high electrical conductivity, good bending workability, and stress relaxation characteristics of the same level as the Cu-Ni-Si alloy, and has excellent resistance to stress at high temperatures. Hot-dip peelability.

Description of drawings

Figure 1 schematically shows a 2-stage homogenization heat treatment showing the thermal history of the material being processed.

Detailed ways

(1) Ni concentration

In the Cu-Ni-Si-Mg alloy of the present invention, if the Ni concentration is less than 1.0% by mass, the precipitate X or Y will not be sufficiently precipitated, and thus the target strength cannot be obtained. If the Ni concentration exceeds 4.5% by mass, coarse precipitates are likely to be formed in the cast ingot, and cracks are likely to be generated during hot rolling.

(2) Si concentration

The addition concentration of Si is set to be 0.16 to 1.13% by mass. If the amount of Si is less than 0.16% by mass, the precipitate X or Y will not be sufficiently precipitated and the solid solution amount of Ni will increase, so that high conductivity cannot be obtained. If the amount of Si exceeds 1.13% by mass, the concentration of Si on the surface of the base material increases, deteriorating the heat-resistant plating peelability.

(3) Mg concentration

If the Mg concentration is less than 0.05% by mass, the target stress relaxation resistance characteristic (resistance to creep deformation) due to the effect of Mg addition cannot be obtained. If it exceeds 0.30% by mass, the size or number of precipitates X will increase, resulting in deterioration of hot workability. Furthermore, since the amount of solid-solution Mg increases, the conductivity is poor.

(4) Precipitate X (Ni-Si-Mg precipitate)

The 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 ratio of Mg in the precipitate X is usually about 0.5 to 16% by mass. When the content 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, those containing precipitates of Ni and Si and having a Mg ratio of less than 0.5% are treated as precipitates Y. As a result of analyzing many precipitates X, the amount of Mg in the precipitate X is within 16% by mass if the alloy composition of the present invention and the target particle diameters of the precipitates X and Y are used.

The precipitates X and Y in the present invention are crystals during casting and also precipitates during aging treatment. In the present invention, by making the precipitate X exist, the Mg concentration of the base material is reduced to improve the electrical conductivity, and the existence of the precipitate X that remains even after the solution treatment after the homogenization heat treatment exerts the influence on grain growth. The pinning effect can be given a good influence, and the average crystal grain size can be finer than that of the conventional example.

The average particle size of the precipitate X in the present invention is 0.05 to 3.0 μm, more preferably 0.50 to 3.0 μm. If the average particle size is less than 0.05 μm, the size of the precipitates is too small to contribute to the strength, and the amount of Mg solid-dissolved in the matrix phase increases, so that the intended conductivity cannot be obtained. On the other hand, when the average particle diameter of the precipitates X exceeds 3.0 μm, the precipitates are coarsened and do not contribute to the strength, and hot cracks are likely to occur, resulting in poor workability. Furthermore, when the precipitate X with a particle diameter exceeding 10 μm exists, the bending workability deteriorates remarkably.

The number of precipitates X in the alloy of the present invention is preferably 1.0×10 ³ to 1.0×10 ⁵ per 1 square mm of a cross section perpendicular to the rolling direction. When the number of precipitates X is less than 10 ³ , even if the number of precipitates X is precipitated because the number is too small, it does not contribute to the improvement of electrical conductivity and flexibility. On the other hand, if the number of precipitates X exceeds 10 ⁵ , Ni and Si to be formed into precipitates Y will be consumed, resulting in insufficient formation of precipitates Y and failure to ensure the original high strength of the Cu-Ni-Si alloy. .

The precipitate X in the present invention is mainly derived from precipitates generated during alloy casting. Conventionally, in order to prevent cracks in the rolling stage, heating is performed in the post-casting step, thereby performing homogenization heat treatment to solid-solve all precipitates. In the present invention, the homogenization heat treatment conditions are controlled so that the cast structure of the ingot is homogenized and crystallized matter remains so as to form precipitates X of a target size and number. In addition, since the precipitate X has a high melting point, even after the solution heat treatment step or aging step after the homogenization heat treatment, the particle size will change slightly due to the diffusion of thermal influence, but it will not disappear.

(5) Precipitate Y (Ni-Si Precipitate)

The 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 the usual composition is represented by Ni ₂ Si or the like.

The precipitate Y is formed by performing solution treatment in the production process, sufficiently dissolving Ni and Si in the base material in advance, and then precipitating it from the base material by aging treatment, as in the production of ordinary Corson alloys. Also, the particle size or 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 diameter 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 diameter of the precipitate Y is 0.10 μm or more, it is coarse and does not contribute to the strength. In addition, when there are precipitates Y having a particle size exceeding 3.0 μm, the strength and stress relaxation properties tend 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 if it is less than 1×10 ⁸ , the number of precipitates is small, so Doesn't help the intensity. On the other hand, when the number of precipitates exceeds 1×10 ¹¹ , bending workability decreases.

(6) Additional elements other than Ni, Si, and Mg

Cr, P, Mn, Ag, Co, and Mo are effective in improving strength and heat resistance, As, 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 crystal grain size during solution treatment.

If the addition amount of these elements is less than 0.01 mass %, the addition effect cannot be obtained, and if it exceeds 2.0 mass %, electrical conductivity will fall.

(7) Manufacturing method

The production method of the copper alloy of the present invention uses a general production procedure of a precipitation-strengthened copper alloy (melting/casting→homogenization heat treatment→hot rolling→intermediate cold rolling→intermediate solid solution→final cold rolling→aging, or melting/casting→ Casting→homogenization heat treatment→hot rolling→intermediate cold rolling→intermediate solid solution→aging→final cold rolling), in this step adjust the homogenization heat treatment conditions to manufacture the target copper alloy. In addition, intermediate rolling and intermediate solid solution may be repeated several times as necessary.

When producing the copper alloy of the present invention, it is important to strictly control the conditions of homogenization heat treatment, solution treatment and annealing. That is, the homogenization heat treatment must be carried out under conditions such that the Ni-Si-Mg precipitate X produced by casting remains within the range of the present invention and the Ni-Si precipitate Y is sufficiently eliminated. In addition, in the solution treatment, it is preferable that Ni and Si are sufficiently solid-dissolved and the precipitate Y does not exist, as long as the remaining precipitate X is not eliminated. The final aging is only required to be a condition under which the precipitate Y having a small average particle diameter can be sufficiently precipitated, and the condition may be the same as the conventional aging condition.

In the melting/casting step, raw materials such as electrolytic copper, Ni, Si, Mg, etc. are melted to obtain a molten solution having a desired composition, and then cast into an ingot. During the homogenization heat treatment and hot rolling of the ingot, in order to eliminate the Ni-Si precipitate Y generated in the casting and adjust the Ni-Si-Mg precipitate X within the range of the present invention, two stages can be used. for homogenization heat treatment. At this time, as the homogenization heat treatment of the first stage, the atmosphere temperature in the furnace is set to 800° C. or higher and not to 890° C., and the temperature of the material is maintained for 0.5 to 2.5 hours after reaching the set temperature. In addition, in order to reduce the average particle size of the remaining coarse Ni-Si-Mg precipitates X, as the second-stage homogenization heat treatment, the atmosphere temperature in the furnace was set at 890°C to 980°C, After keeping the temperature for 0.5 to 1.2 hours, hot rolling can be performed immediately. The heating of the first stage and the second stage can be performed continuously in one furnace by moving from the heat treatment area of the first stage to the heat treatment area of the second stage. A schematic diagram of the thermal history of the material subjected to the two-stage homogenization heat treatment is shown in FIG. 1 . Moreover, it is also possible to use a different furnace to immediately insert the second-stage furnace after taking out the first-stage furnace to start the second-stage heating without lowering the temperature of the ingot.

If the holding temperature in the first stage is lower than 800°C, the Ni-Si precipitate Y cannot be sufficiently solid-dissolved, and the precipitate X remains with a large average particle size. On the other hand, if it is 890°C or higher, then The precipitate X also dissolves and disappears. Moreover, if the holding temperature in the second stage does not reach 890°C, the precipitate X will not disappear, but the particles of the precipitate X may remain in a large state, and a part of the precipitate Y may not be solid-dissolved and residual. On the other hand, if the holding temperature in the second stage exceeds 980° C., all the precipitates X may be solid-dissolved.

In this homogenization heat treatment, heating can be performed by a known method such as a burner or a dielectric. During heating, care should be taken to keep the output energy and the weight of the ingot in the furnace constant respectively. Even at the same set temperature, there is a risk of overheating in the case of a light ingot weight and insufficient heating in the case of a heavy ingot weight.

By keeping the atmosphere temperature in the furnace in the first stage of the homogenization heat treatment at 800°C or higher and not reaching 890°C for 0.5 to 2.5 hours, the Ni-Si-Mg precipitate X hardly changes, while the Ni-Si-Mg precipitate X hardly changes. However, the average particle size of the Si-based precipitate Y becomes smaller. Next, by setting 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 precipitates X becomes small and partially disappears, but the remaining precipitates X On the other hand, the Ni-Si-based precipitates Y remaining even after the first-stage heat treatment disappear completely. After hot rolling after the above-mentioned two-stage homogenization heat treatment, the Ni—Si—Mg-based precipitates X exist to the end in the size and number after hot rolling. On the other hand, Ni—Si-based precipitates Y are precipitated in a predetermined size and number by solution/cold rolling and aging treatment.

After hot rolling, intermediate rolling and intermediate solid solution can be performed by appropriately selecting the number of times and order within the scope of the objective of the present invention. If the working degree of the final pass of the intermediate rolling is less than 30%, since the amount of rearrangement which becomes the precipitation origin of the precipitate Y is small, the number of the precipitate Y decreases and the strength decreases. On the other hand, if the workability exceeds 99%, the amount of rearrangement 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 last pass is preferably 30% to 99%.

The intermediate solid solution is sufficiently performed in order to dissolve the crystal particles during melting casting or the precipitated particles after hot rolling to eliminate the precipitate Y as much as possible. For example, if the solution treatment temperature is lower than 500° C., the solution will be insufficient and the desired strength will not be obtained. On the other hand, if the solution treatment temperature exceeds 850° C., the material may be melted. Therefore, it is preferable to perform solution treatment by heating the material temperature to 500°C to 850°C. The time for solution treatment is preferably 60 seconds to 2 hours.

In addition, in terms of the relationship between solution treatment temperature and time, in order to obtain the same heat treatment effect (for example, the same average particle size of the precipitate Y), it is known that the time must be shorter at high temperatures, and at low temperatures The time must be longer. For example, in the present invention, it is preferably 1 hour at 600°C, and 2, 3 minutes to 30 minutes at 750°C.

The cooling rate after solution treatment is generally rapid cooling so that the solid solution components do not precipitate into second phase particles (precipitate Y).

The working degree of the final rolling is 0 to 50%, preferably 5 to 20%. If it exceeds 50%, bending workability will fall.

The final aging step of the present invention is carried out in the same manner as the conventional technique, and the fine second-phase particles within the range of the present invention (precipitate Y and optionally, precipitate X) are uniformly precipitated.

Example

Embodiment 1 (manufacture of copper alloy)

5 kg of high-purity copper was melted using a high-frequency induction furnace. After covering the surface of the molten copper with charcoal sheets, add a specified amount of Ni, Si and Mg, and then adjust the temperature of the molten copper to 1200°C. Then, the melt was cast into a mold to manufacture an ingot with a width of 65 mm and a thickness of 20 mm. Regarding the composition of the produced ingot, samples were cut out from the ingot in accordance with JIS H1292, and the amounts of constituent elements were analyzed by fluorescent X-ray analysis.

Next, the ingot was subjected to the homogenization heat treatment described in Table 1, and then hot-rolled to a thickness of 8 mm. At this stage, Ni-Si and Ni-Si-Mg precipitates generated during casting also remain. After grinding and removing the oxide scale on the surface of the hot-rolled plate, it is cold-rolled until the plate thickness is 0.2 mm. After heating at 750° C. to 800° C. for 20 seconds as a solution treatment and rapidly cooling in water, the surface oxide film was removed by chemical polishing. Then, cold rolling with a working degree of 25%, and heating at 460° C. for 7.5 hours under an inert atmosphere was used as an aging treatment.

The samples produced in this way were evaluated as follows.

(1) Measurement of the number and size of precipitates

The cross-section perpendicular to the rolling direction is finished into a mirror surface by mechanical grinding using diamond abrasive grains with a diameter of 1 μm, and then the precipitation with a length of 0.05 mm or more is measured at a magnification of 400 times using FE-SEM (Field Emission Scanning Electron Microscope) number of objects. The observation area was set to 60 mm ² , and the number of precipitates in the observation area was counted. And, by using FE-SEM (Field Emission Scanning Electron Microscope) EDS (Energy Dispersive X-ray Analysis) to analyze the components of all the precipitates, it was confirmed that the components of the precipitates to be measured contain Ni and Si, or Ni, Si and Mg. Here, the difference between the precipitates X and Y is due to the problem of detection accuracy. Even if the precipitates contain Ni, Si, and Mg, if the ratio of Mg is less than 0.5%, they are treated as precipitates Y.

In addition, when the average particle diameter was measured, the presence or absence of Ni—Si—Mg precipitates X having an average particle diameter of 10 μm or more was confirmed. The particle diameter is the length of the longest part of the precipitate in the photograph taken by FE-SEM. The average particle size was obtained by adding up all the crystal particle sizes in the observation area and dividing by the arithmetic mean of the number of crystal particles.

(2) Conductivity measurement of base metal

The test piece was cut out from the sample, and the surface oxide layer was completely removed by mechanical grinding and chemical etching, and then the conductivity (%IACS) was measured by the 4-terminal method. The preferred conductivity targeted by the present invention is above 45% IACS.

(3) Bending workability

The W bending test described in JIS H 3130 is performed so that the bending radius R becomes 0. The test direction is set to Bad Way (the bending axis is parallel to the rolling direction). The test piece was in the form of a strip with a width of 10 mm and a length of 30 mm. Next, the cross-section of the bent portion was visually observed using an optical microscope for the test piece subjected to the W-bend at the above-mentioned bend R, and the quality of the bending workability was judged. Evaluation criteria are as follows. ○: No wrinkles or cracks, △: Wrinkles on the surface of the material, ×: Cracks occurred.

(4) Tensile strength

Take the test piece No. 13B specified in JIS Z 2201 (2003) along the direction parallel to the stretching direction and rolling direction. Using this test piece, a tensile test was carried out in accordance with JIS Z 2241 (2003) to determine the tensile strength. The preferred tensile strength targeted by the present invention is 760 MPa or more.

(5) Stress relaxation characteristics

As the stress relaxation resistance characteristic at high temperature, the stress relaxation rate (Technical Standard of Japan Copper Association (JCBA): JCBA T309) was measured. This test is a method for evaluating fatigue caused by temperature. It installs a strip-shaped test piece with a width of 10 mm on a cantilever beam, and compares the deflection displacement (free end of displacement of the specified position). When the deflection after the test is the same as the initial state, the value of the stress relaxation rate is 0%, and the greater the deflection after the test than the initial state, the greater the value of the stress relaxation rate (stress reduction). The stress relaxation rate was calculated by the following formula (wherein, y=deflection displacement (mm) after a predetermined time has elapsed, y ₁ =initial deflection (mm), y ₀ =set height (mm)).

Stress relaxation rate = (yy ₁ )/y ₀ ×100(%)

Furthermore, the set height y ₀ is calculated by the following formula (wherein, L=punctuation distance (mm), σ ₀ =load stress (kg/mm ² ); 80% of 0.2% yield strength or any stress below 0.2% yield strength, E=Young's modulus (kg/mm ² ), t=plate thickness (mm)).

y ₀ =(2/3)×L×L×σ ₀ /(E×t)

Measurement of Stress Relaxation The sample was set at 150° C., and the measurement was performed until a constant relaxation rate appeared. Since a substantially constant stress relaxation rate was exhibited at approximately 1000 hours, this value was used as the stress relaxation rate.

Generally used Corson alloy has a stress relaxation rate of about 10% after 150°C×1000h. Therefore, in the evaluation of each of the following Examples and Comparative Examples, those with a stress relaxation rate of 9% or less were deemed to have good stress relaxation resistance at high temperatures.

[Table 1]

"-*" in the above table indicates that no other elements are added.

With respect to embodiment 1～10, because the homogenization heat treatment of the first stage is from 800 ℃ to less than 890 ℃ × 2 hours, the heat treatment of the second stage is 890 ℃～980 ℃ × 0.5～1.2 hours, so in After hot rolling, the precipitate X has no coarse particles exceeding 10 μm and has an average particle size of 0.05 to 3.0 μm, while the precipitate Y completely dissolves and disappears. Then, through solution/cold rolling, during the aging treatment, the precipitate Y can be precipitated under the aging condition that the average particle diameter becomes 0.01 to 0.10 μm. As a result, high strength, high electrical conductivity, good bending workability and stress relaxation properties can be 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 could not be reduced during the heat treatment, and the coarse precipitate X of 10 μm or more remained in the product. On the other hand, the large-sized precipitate Y before the homogenization heat treatment remained without disappearing at the homogenization heat treatment temperature of 870°C. The precipitate Y that remained even after hot rolling after the homogenization heat treatment did not disappear even after solid solution, rolling, and aging treatment (the same conditions as in Examples 1 to 10). Therefore, even if there is no coarse precipitate Y and the precipitate Y is precipitated under the aging condition that the average particle size becomes 0.1 μm or less, since the coarse precipitate Y exists before aging, the average particle size exceeds 0.10 μm and The number of precipitates Y also decreased. Therefore, in Comparative Example 11, the bending workability was poor due to the presence of large precipitates of the precipitate X, and the strength was also poor due to the small number of precipitates Y. Furthermore, since a large amount of Mg exists in a large amount of precipitates X, the amount of solid-solution Mg decreases, and the stress relaxation property is also poor.

In Comparative Examples 12 and 13, since the homogenization heat treatment temperature is higher than that of Comparative Example 11, there is no coarse precipitate X of 10 μm or more, but because the time is short, the average particle size of the precipitate X is not below 3.0 μm, The large-sized precipitate Y does not disappear even after homogenization heat treatment. As a result, in Comparative Examples 12 and 13, since the average particle size of the precipitates Y exceeded 0.10 μm and the number was small, the strength was poor, and since the number of the precipitates X was large and the average particle size was also large, the stress relaxation characteristics were also poor. .

In Comparative Examples 14 and 15, the homogenization heat treatment was performed under the conditions that all the precipitates X and Y disappeared in the same manner as in the conventional technique. After the subsequent aging treatment, 1.7×10 ⁸ and 1.2×10 ⁸ precipitates Y were precipitated respectively, so high strength can be obtained, but since there is no precipitate X, the amount of Mg in the base material becomes excessive, resulting in poor conductivity.

In the homogenization heat treatment of Comparative Example 16, the average particle diameter and maximum particle diameter of the precipitate X could be controlled. However, since the heat treatment temperature in the first stage is relatively low, even if the temperature in the second stage is 900°C, the large-sized precipitate Y before the heat treatment becomes smaller but does not disappear, so the average particle size of the precipitate Y It exceeds 0.10 μm, and the number of precipitates Y is also small. As a result, the strength is poor.

In Comparative Example 17, since the time of the second-stage homogenization heat treatment is too short, coarse precipitates X will remain after hot rolling, and the average particle diameter of precipitates X also exceeds 3.0 μm. Furthermore, although the remaining size Larger precipitates Y, but the number of precipitates Y as a whole is small. As a result, the strength, bending workability, and stress relaxation characteristics are poor.

In Comparative Example 18, since the heat treatment time in the second stage was too long, the average particle size of the precipitate X did not reach 0.05 μm and the number of precipitates was small, resulting in poor electrical conductivity.

From Examples 19 to 22 and Comparative Examples 23 to 30, it can be seen that the present invention is effective also in alloys obtained by adding other elements to Cu—Ni—Mg alloys. In Comparative Examples 23 to 26, since the homogenization heat treatment was performed in one stage, and the precipitate X did not exist, the electrical conductivity was low. In Comparative Examples 27 and 28, since the homogenization heat treatment temperature in the first stage was low, the number of precipitates Y was small, but the average particle size was large. Therefore, the tensile strength is poor. In Comparative Examples 29 and 30, because the homogenization heat treatment time in the second stage was short, the particle size of the precipitate X was large, and the coarse precipitate X of 10 μm or more remained in the product, but the number of the precipitate Y was small. Therefore, tensile strength, bending workability, and stress relaxation characteristics are poor. In addition, in Comparative Example 29, since the number of precipitates X was large, the stress relaxation characteristics were worse.

In addition, regarding the heat-resistant plating peelability, the examples have heat-resistant plating peelability that does not cause problems in practical use, and Example 20 has heat-resistant plating peelability that is more excellent than other examples.

Claims (2)

1. A copper alloy comprising 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, the remainder being Cu-Ni composed of Cu and unavoidable impurities - a Si-Mg alloy containing Ni-Si-Mg precipitates X and Ni-Si precipitates Y, the average particle size of the precipitates X is 0.05 to 3.0 μm, and there is no precipitate X with a particle size exceeding 10 μm, and The average particle size of the precipitate Y is 0.01-0.10 μm, wherein the precipitate X contains 1.0×10 ³ to 1.0×10 ⁵ per 1 square mm in the cross-section perpendicular to the rolling direction, and the precipitate Y is perpendicular to the rolling direction. The cross section in the direction contains 1.0×10 ⁸ to 1.0×10 ¹¹ per 1 square mm. 2. A copper alloy containing a total of 0.01 to 2.0% by mass selected from Cr, P, Mn, Ag, Co, Mo, As, Sb, Al, Hf, Zr, Ti, C, Fe, In, Ta , at least one of Sn and Zn, 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, and the rest is composed of Cu and unavoidable impurities, which contains Ni-Si-Mg precipitate X and Ni-Si precipitate Y, the average particle size of the precipitate X is 0.05 to 3.0 μm, there is no precipitate X with a particle size exceeding 10 μm, and the average particle size of the precipitate Y is 0.01 ~0.10 μm, wherein the precipitate X contains 1.0×10 ³ to 1.0×10 ⁵ per 1 square mm in the cross section perpendicular to the rolling direction, and the precipitate Y contains 1.0×10 5 per 1 square mm in the cross section perpendicular to the rolling direction ×10 ⁸ to 1.0×10 ¹¹ pieces.