JP4408275B2 - Cu-Ni-Si alloy with excellent strength and bending workability - Google Patents

Description

  The present invention relates to a copper alloy, and more particularly to a copper alloy used for conductive spring materials such as connectors, terminals, relays and switches.

As electronic devices have become lighter, thinner and shorter in recent years, terminals and connectors have become smaller and thinner, and copper alloys for electronic materials used are required to have higher strength and bending workability than ever before. . In response to this requirement, instead of the conventional solid solution strengthened copper alloys such as phosphor bronze and brass, precipitation strengthened copper alloys such as Cu—Ni—Si based Corson alloy and titanium copper are used, and the demand is increasing. Among precipitation-strengthened copper alloys, Cu-Ni-Si-based alloys are alloy systems that have both high strength and relatively high electrical conductivity, and the strengthening mechanism consists of Ni-Si-based intermetallic compound particles in the Cu matrix. The strength is improved by precipitation.
Generally, strength and bending workability are contradictory properties, and it has been conventionally desired to improve bending workability while maintaining high strength even in a Cu-Ni-Si alloy.

As a method for improving the bending workability, Patent Document 1 improves the bending workability by adding Co to the Cu—Ni—Si based alloy system and adjusting the solution conditions. However, increasing the additive element may increase the manufacturing cost. On the other hand, Patent Document 2 discloses a method for improving the bending workability by controlling the crystal orientation. In this invention, a texture satisfying the following formula is formed with the X-ray diffraction intensities of the (200) plane, (220) plane, and (311) plane being I ₍₂₀₀₎ , I ₍₂₂₀₎ , I _(311). As a result, bending workability is improved.
(I ₍₂₀₀₎ + I ₍₃₁₁₎ ) / I ₍₂₂₀₎ ≧ 0.5

JP-A-5-179377 JP 2000-80428 A

However, considering that I ₍₂₀₀₎ and I ₍₃₁₁₎ increase due to grain size increase during recrystallization, and I ₍₂₂₀₎ increases due to an increase in the degree of cold rolling, the above equation is satisfied. Requires coarsening of the crystal grain size and reduction of workability of cold rolling, which causes strength reduction. Therefore, there has been a demand for a method that can improve the bending workability without requiring adjustment of the manufacturing process such as the coarsening of the crystal grain size causing the strength reduction and the reduction of the workability of the cold rolling.

The present invention aims to solve the above problems. Specifically, it is an object to provide a Cu—Ni—Si alloy having good bending workability while maintaining high strength by adjusting the manufacturing process and controlling the texture.

The inventor investigated the correlation between the measurement result of the texture of the Cu—Ni—Si alloy using an X-ray diffractometer and the bending workability. As a result, it was found that bending workability can be improved by controlling the maximum value of the X-ray intensity in the two regions including the {123} <412> orientation on the {111} positive electrode diagram. That is, the Cu—Ni—Si based alloy in which the maximum value in the above region is controlled within a certain range is more resistant to bending cracking than the Cu—Ni—Si based alloy having the same strength and other textures. Is good and bending wrinkles are reduced.

(A) The present invention is based on the above knowledge and contains 1.0 to 4.5 mass% Ni and 0.25 to 1.5 mass% Si, with the balance being copper and inevitable impurities. In the {111} positive electrode diagram, the maximum value of the X-ray random intensity ratio in the following ranges (1) to (2) is 2.0 or more and 10.0 or less. It is a Cu—Ni—Si based alloy having a texture and excellent bending workability.
(1) α = 20 ± 10 °, β = 90 ± 10 °
(2) α = 20 ± 10 °, β = 270 ± 10 °
Where α is an axis perpendicular to the rotation axis of the diffraction goniometer defined in the Schulz method, and β is an angle around an axis parallel to the rotation axis.

(B) Furthermore, this invention is a Cu-Ni-Si type alloy as described in said (A) containing 0.005-0.3 mass% of Mg.

(C) Further, the present invention further comprises (A), containing 0.005 to 2.0 mass% in total of one or more of Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, and Ag. It is a Cu-Ni-Si alloy described in (B).

  From the above, the Cu-Ni-Si alloy of the example of the present invention is less susceptible to bending cracking and has less bending wrinkles than the Cu-Ni-Si alloy having the same 0.2% proof stress. Therefore, it is suitable for applications such as terminals and connectors as a copper alloy having improved bending cracking resistance and bending wrinkles while maintaining high strength.

  Hereinafter, the reasons for defining the component composition and texture of the present invention will be described in detail together with the action thereof.

[Ni and Si concentration]
Ni and Si are precipitated as Ni ₂ Si intermetallic compounds by performing an aging treatment. Precipitation of Ni ₂ Si particles remarkably improves the strength of the alloy, and Ni and Si dissolved in the base material decrease along with the precipitation, thereby improving conductivity. However, if the Ni concentration is less than 1.0% by mass or the Si concentration is less than 0.25% by mass, the desired strength cannot be obtained even if the other component is added. Moreover, when Ni concentration exceeds 4.5 mass%, or when Si concentration exceeds 1.5 mass%, sufficient strength can be obtained, but the conductivity becomes low, and further coarseness that does not contribute to improvement of strength. Ni-Si-based particles (crystallized substances and precipitates) are formed in the matrix phase, which causes a decrease in bending crack resistance, etching properties and plating properties. Therefore, the Ni concentration was set to 1.0 to 4.5 mass%, and the Si concentration was set to 0.25 to 1.5 mass%.

[Mg concentration]
Mg has the effect of improving stress relaxation properties and hot workability, but if it is less than 0.005% by mass, the desired effect cannot be obtained, and if it exceeds 0.30%, castability (decrease in casting surface quality) , Hot workability and plating heat-resistant peelability are reduced. Therefore, the Mg concentration is determined to be 0.005 to 0.3% by mass.

[Other additives]
Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, and Ag have an effect of improving the strength and heat resistance of the Cu—Ni—Si based alloy. Of these, Zn also has an effect of improving the heat resistance of the solder joint, and Fe has an effect of refining the structure. Furthermore, Ti, Zr, Al, and Mn have an effect of improving hot rollability. This is because these elements have a strong affinity for sulfur and form a compound with sulfur to reduce the segregation of sulfide to the ingot grain boundaries, which is the cause of hot rolling cracks. When the total concentration of Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, and Ag is less than 0.005% by mass, the above effect cannot be obtained, and the total content is 2.0% by mass. If it exceeds, the conductivity will be significantly reduced. Therefore, these contents are determined to be 0.005 to 2.0 mass% in total.

[Organization]
In general, a texture is a statistical deviation of crystal orientation formed by processing and heat treatment, and greatly depends on processing conditions and heat treatment conditions. The present inventors measured the texture of Cu—Ni—Si alloys having different manufacturing processes using an X-ray diffractometer (RINT 2500 manufactured by Rigaku Corporation), and the texture and bending workability of Cu—Ni—Si alloys. The relationship between (bending crack resistance and bending wrinkles) was investigated. As a result, there was a correlation between the two, and it was found that the formation of the {123} <412> orientation in the texture was closely related to the resistance to bending cracking and the size of bending wrinkles. In the {111} positive electrode diagram, the {123} <412> orientation corresponds to α = 22 °, β = 90 °, α = 22 °, and β = 270 °. Here, α is an angle around the axis perpendicular to the rotation axis of the diffraction goniometer defined in the Schulz method, and β is an angle around the axis parallel to the rotation axis.

The reason why the bending crack resistance and the bending wrinkle are improved by suppressing the strength of the {123} <412> orientation is not clear, but the {123} <412> orientation is a rolling deformation of the Cu—Ni—Si based alloy. This is considered to be one of the causes because it is less stable and has less crystallized orientation than other crystal orientations. The reason why the ranges of α and β are defined as in the claims (1) and (2) is that the X-ray intensity ratio corresponding to the {123} <412> orientation is determined from processing, heat treatment conditions, measurement errors, and the like. It was determined in consideration of the fluctuation of the peak position. The reason why the maximum value of the intensity ratio is set to 2.0 or more and 10.0 or less is shown below. When the maximum value of the strength ratio is less than 2.0, the bending cracking resistance is good, but the desired strength cannot be obtained, and the bending wrinkle becomes large. This is because the material having a maximum value of less than 2.0 has a small orientation ratio that deteriorates the bending workability, but the crystal grain size becomes coarse during the solution treatment. On the other hand, if the maximum value of the strength ratio exceeds 10.0, the ratio of {123} <412> orientation increases, and bending cracks are likely to occur or bending wrinkles also increase. Therefore, the maximum value of the intensity ratio is set to 2.0 or more and 10.0 or less.

In a general manufacturing process of a Cu—Ni—Si based alloy, after melting an ingot in a high frequency melting furnace, raw materials such as electrolytic copper, Ni, Si, etc. are melted under a charcoal coating to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. Thereafter, hot rolling is performed, and cold rolling and heat treatment are repeated to finish a strip or foil having a desired thickness and characteristics. Heat treatment includes solution treatment and aging treatment. In the solution treatment, heating is performed at a high temperature of 700 to 1000 ° C., so that the Ni—Si-based compound is dissolved in the Cu matrix, and at the same time, the Cu matrix is recrystallized. The solution treatment may be combined with hot rolling. In the aging treatment, Ni and Si heated in a temperature range of 350 to 550 ° C. for 1 h or more and solid-dissolved by the solution treatment are precipitated as fine particles mainly composed of Ni ₂ Si. This aging treatment improves strength and conductivity. In order to obtain higher strength, cold rolling may be performed before aging treatment and / or after aging treatment. Moreover, when performing cold rolling after an aging treatment, strain relief annealing (low temperature annealing) may be performed after cold rolling.

  Among the series of processes, the processes that have an important influence on the texture control were cold rolling and solution treatment before solution treatment. The {123} <412> orientation that adversely affects the bending cracking resistance and bending wrinkles of the Cu—Ni—Si based alloy is a recrystallized texture with a high degree of aggregation formed during solution treatment. It is formed by changing the crystal orientation by lattice rotation. That is, it was important to suppress the aggregation degree of the recrystallization texture formed at the time of the solution treatment to suppress the aggregation degree of the {123} <412> orientation. The degree of aggregation of the recrystallized texture can be controlled in the range of 2.0 to 10.0 by adjusting the degree of processing before the solution treatment and the plate thickness reduction rate, and appropriately performing the solution treatment. The conditions for cold rolling and solution treatment before solution treatment will be described in detail below.

(A) Cold rolling before solution treatment: The degree of cold rolling performed before the solution treatment is 40% or more and less than 80%, and the amount of reduction in sheet thickness and the initial stage in one rolling pass The ratio of the plate thickness (plate thickness after hot rolling) is defined as the plate thickness reduction rate, which is within 25%. When the degree of cold rolling is less than 40%, the degree of assembly is less than 2.0 and the bending cracking resistance is good, but the strength is lowered and the bending wrinkle is also increased. On the other hand, when the cold rolling work degree is 80% or more, the deformed texture having a high degree of aggregation formed by cold rolling is changed to a recrystallized texture by recrystallization during the solution treatment, and thereafter The degree of aggregation of {123} <412> orientations exceeds 10.0 due to lattice rotation during cold rolling. For this reason, bending cracking resistance deteriorates and bending wrinkles also increase. Further, if the sheet thickness reduction rate exceeds 25%, even if the cold rolling workability is within the specified range, a deformed texture with a high degree of aggregation is formed, and the degree of aggregation exceeds 10.0. Bending cracking properties deteriorate and bending wrinkles also increase.

(B) Solution treatment: The solution treatment temperature is 720 ° C. or more and less than 900 ° C., and the treatment time (material holding time) is less than 300 seconds. If processing temperature is less than 720 degreeC, the quantity of Ni and Si which dissolves is inadequate, and the strength after an aging treatment falls. Furthermore, the degree of assembly exceeds 10.0, and the bending wrinkle becomes large. On the other hand, when the treatment temperature is 900 ° C. or higher, the degree of aggregation becomes less than 2.0 due to the coarsening of the crystal grains, the strength decreases, and the bending wrinkle also increases. Further, even when the treatment time is 300 seconds or longer, the crystal grains become coarse, so that the strength is lowered and the bending wrinkles are also increased.

(C) Cold rolling between solution treatment and aging treatment (hereinafter referred to as rolling A), cold rolling after aging treatment (hereinafter referred to as rolling B), and aging treatment: rolling A and rolling The processing degree of B, the temperature and time of aging treatment may be arbitrarily set as long as the texture of the present invention can be obtained. Regarding the aging treatment, it is appropriate that the aging temperature is 350 ° C. or more and less than 550 ° C. and the aging time is 1 hour or more and less than 10 hours in the alloy of the present invention.

Hereinafter, in order to clarify the features of the present invention and the best mode for carrying out the present invention, the present invention will be specifically described with reference to examples. The experiment of the example was performed using the following two types of alloys.
Alloy A: Cu-1.6 mass% Ni-0.35 mass% Si-0.5 mass% Sn-0.4 mass% Zn
Alloy B: Cu-2.5 mass% Ni-0.5 mass% Si-0.1 mass% Mg

Using a high-frequency induction furnace, 2 kg of electrolytic copper was melted in a graphite crucible having an inner diameter of 60 mm, and Ni, Si, Mg, Sn and Zn were added to adjust the molten metal components. After adjusting the molten metal to 1200 ° C., an ingot having a thickness of 30 mm × width of 60 mm × length of 120 mm was cast. Next, this ingot was processed and heat-treated in the following order to obtain a sample having a plate thickness of 0.3 mm.
(1) The ingot was heated at 800 ° C. for 3 hours and then hot-rolled to a predetermined plate thickness shown in Table 1.
(2) The oxidized scale on the surface of the hot rolled material was removed with a grinder.
(3) It cold-rolled on the predetermined conditions shown by Table 1, and finished plate | board thickness to 1 mm.
(4) As a solution treatment, the solution was heated at a predetermined temperature shown in Table 1 for 30 seconds and rapidly cooled in water.
(5) The surface oxide film was removed by chemical polishing.
(6) Cold rolled to a plate thickness of 0.3 mm.
(7) Heated at 450 ° C. for 5 hours in hydrogen as an aging treatment.
(8) The surface oxide film was removed by chemical polishing.

The following evaluation was performed about the sample produced in this way.
(A) Maximum value of X-ray random intensity ratio: {111} positive electrode spot measurement of each sample was performed with an X-ray diffractometer (RINT 2500 manufactured by Rigaku Corporation), and a {111} positive electrode dot diagram was prepared. In the reflection method, when the incident angle of X-rays on the sample surface becomes shallow, measurement becomes difficult. Therefore, the range of angles that can be actually measured is 0 ° ≦ α ≦ 75 °, 0 ° ≦ β ≦ 360 ° on the positive dot diagram. It becomes. In this measurement, scanning within the aforementioned angle range was performed with the rotation intervals Δα and Δβ of α and β being 5 °, and the X-ray intensity at 16 × 73 = 1168 points was measured. At this time, the positive point diagram was normalized by assuming that the state having no texture, that is, the state where the crystal orientation was random, as 1. As the crystal orientation was in a random state, the {111} positive electrode point measurement result of the copper powder sample was used. The X-ray irradiation conditions were a Co tube, tube voltage 30 KV, and tube current 100 mA. The maximum value of the X-ray intensity is selected from 50 points included in the regions (1) and (2) in FIG. 1, and the maximum value is 2.0 or more and 10.0 or less for both alloy A and alloy B. ○, otherwise determined as x.

(B) 0.2% yield strength: A JIS13B test piece was prepared using a press so that the tensile direction was parallel to the rolling direction, a tensile test was performed, and the 0.2% yield strength was measured. For alloy A, the strength was determined to be good when the 0.2% yield strength exceeded 650 MPa, and for alloy B, the 0.2% yield strength exceeded 700 MPa.

(C) Bending crack resistance: After collecting a strip test piece having a width of 10 mm and a length of 30 mm so that the bending axis is parallel to the rolling direction (BadWay), a W bending test (JIS H 3130) was performed to Evaluation was made based on the ratio MBR / t between the minimum bending radius MBR (Minimum Bend Radius) and the thickness t. For alloy A, the case where MBR / t was 0.5 or less, and for alloy B, the case where MBR / t was 1.0 or less were judged to have good bending crack resistance.

(D) Bending wrinkle width: In a W bending test, after taking an SEM image of a wrinkle observed on the surface of a bending convex portion of a test piece bent at a minimum bending radius, measurement of the width of the wrinkle on the photograph And the maximum wrinkle width in the test piece was obtained. This was performed on three test pieces for each specimen, and the average value was taken as the wrinkle width. For both Alloy A and Alloy B, the wrinkle width was determined to be small when the wrinkle width was 30 μm or less.

Table 2 shows the evaluation results of the alloy A manufactured under the conditions of Table 1, and Table 3 shows the evaluation results of the alloy B manufactured under the conditions of Table 1. The 0.2% proof stress is higher in alloy B and the bending crack resistance is better in alloy A, but the influence of manufacturing conditions on the characteristics is the same in both alloys A and B. That is, as shown in Tables 2 and 3, according to the present invention, it is possible to obtain an alloy having good bending cracking resistance and reduced bending wrinkles while maintaining high strength. (Table 1 No. 1-7)

  On the other hand, Comparative Example No. No. 8 has a rolling degree before solution treatment is lower than that of the invention example, so that the maximum value of the texture becomes less than 2.0, the strength decreases, and the bending crack resistance is good, but the width of the bending wrinkle Exceeded 30 μm. No. No. 9 has a higher degree of rolling before solution treatment than the invention example, so the maximum value of the texture exceeds 10.0, the bending crack resistance is inferior to the invention example, and the width of the bending wrinkle is 30 μm. Beyond.

  Comparative Example No. No. 10 had a higher plate thickness reduction rate than the inventive example, the maximum value of the texture exceeded 10.0, the bending crack resistance was inferior to the inventive example, and the width of the bending wrinkle exceeded 30 μm. Comparative Example No. No. 11 has a solution treatment temperature lower than that of the inventive example, and therefore the maximum value of the texture exceeded 10.0. As a result, although the bending cracking resistance was good, the width of the bending wrinkle exceeded 30 μm, and the strength was inferior to that of the inventive examples because the amount of Ni and Si dissolved was small.

  Comparative Example No. In No. 12, the temperature of the solution treatment was higher than that of the inventive example. During the solution treatment, the crystal grains were coarsened, and the maximum value of the texture was less than 2.0. Therefore, although the bending crack resistance was good, the width of the bending wrinkle exceeded 30 μm, and the strength was inferior to that of the inventive examples.

It is explanatory drawing regarding two area | regions of (1) and (2) prescribed | regulated on the prescribed | regulated {111} positive electrode point figure.

Explanation of symbols

RD Rolling direction of sample TD Transverse direction of sample α Axis perpendicular to rotation axis of diffraction goniometer specified by Schulz method β Axis parallel to previous rotation axis

Claims (3)

Containing 1.0 to 4.5 mass% of Ni and 0.25 to 1.5 wt% Si, balance Ri Rana or copper and inevitable impurities, {111} in the pole figure, following ( Cu-Ni-Si excellent in strength and bending workability having a texture, wherein the maximum value of the X-ray random intensity ratio in the range of 1) to (2) is 2.0 or more and 10.0 or less Alloy.
(1) α = 20 ± 10 °, β = 90 ± 10 °
(2) α = 20 ± 10 °, β = 270 ± 10 °
(Where α: axis perpendicular to the rotation axis of the goniometer for diffraction defined in the Schulz method, β: axis parallel to the rotation axis) The Cu-Ni-Si-based alloy according to claim 1, containing 0.005 to 0.3 mass% of Mg. Cu-Ni- of Claim 1 and 2 which contains 0.005-2.0 mass% of 1 or more types in total in Zn, Sn, Fe, Ti, Zr, Cr, Al, P, Mn, and Ag. Si-based alloy.