KR101249107B1 - Cu-ni-si alloy to be used in electrically conductive spring material - Google Patents

Abstract

Cu-Ni-Si-based alloy containing 1.0 to 4.0 mass% of Ni and Si at a concentration of 1/6 to 1/4 with respect to Ni, wherein the frequency of the twin crystal boundary (Σ3 boundary) in all grain boundaries is 15 to 60%. Group alloy. The base alloy may further contain Mg 0.2% or less, Sn 0.2-1%, Zn 0.2-1%, Co 1-1.5%, and Cr 0.05-0.2%.

Description

Cu-Ni-Si-based alloy used in conductive spring materials {CU-NI-SI ALLOY TO BE USED IN ELECTRICALLY CONDUCTIVE SPRING MATERIAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Cu-Ni-Si based alloys used in conductive spring materials for electronic components, and is particularly used for electronic components such as connectors, terminals, relays, and switches, and has excellent balance of strength, bending workability, and conductivity. It relates to a Cu-Ni-Si-based alloy.

In recent years, with light and short size reduction of electronic devices, miniaturization and thinning of terminals, connectors, and the like also progress, strength and bending workability are required, and instead of conventional solid solution copper alloys such as phosphor bronze and brass, corson There is an increasing demand for precipitation-reinforced copper alloys such as (Cu-Ni-Si) alloys, beryllium copper and titanium copper. Among them, Corson alloy is excellent in balance between strength and electrical conductivity, and is frequently used for electronic parts such as connectors.

In general, strength and bending workability are incompatible with each other. Therefore, it has been studied to improve bending workability while maintaining high strength even in a Corson alloy, and the manufacturing process is adjusted to adjust the crystal grain size, the number, shape, and collection of precipitates. The measures to improve the bending workability by controlling the tissues individually or mutually have been widely practiced.

In patent document 1, in the Corson alloy which Co, Zn, Mn, Cr, and Al were further added, grain growth at the time of solution formation is suppressed and bending workability is improved. In patent document 2, punching workability and bending workability are improved by containing a suitable amount of Ti, Zr, Hf, or Th in a Corson alloy, and refine | miniaturizing the crystal grain size preferably. In patent document 3, bending workability is improved by restricting S and O content in a Corson alloy to less than 0.005%, optimizing content of Sn and Mg, Zn arbitrarily, and also controlling a crystal grain size.

In Patent Literatures 4 and 5, bending workability, stress relaxation property, and the like are improved by limiting the S content in the Corson alloy, optimizing the content of Mg, Sn, and Zn, and controlling the aspect ratio of the crystal grain size and the crystal grain. have. In patent document 6, bending workability is improved by controlling the texture of corson alloy and controlling the pole density of # 123 '<412> orientation to a prescribed range.

In Patent Literature 7, the texture of the corson alloy is controlled, the texture of the aggregate is controlled so as to satisfy (I ₍₁₁₁₎ + I ₍₃₁₁₎ ) / I ₍₂₂₀₎ > 2.0, thereby improving bending workability. In patent document 8, the conditions of the hot rolling and solution treatment process in a Corson alloy are adjusted, and the bending workability is improved so that a yield point effect may not be expressed by a tensile strength test.

Japanese Patent Laid-Open No. 5-179377 Japanese Patent Laid-Open No. 6-184681 Japanese Patent Application Laid-Open No. 11-222641 Japanese Unexamined Patent Publication No. 2002-38228 Japanese Unexamined Patent Publication No. 2002-180161 Japanese Unexamined Patent Publication No. 2007-92135 Japanese Laid-Open Patent Publication 2006-16629 Japanese Unexamined Patent Publication No. 2007-169781

In recent years, with the miniaturization of electronic components, in addition to the presence or absence of cracks (cracks) in the evaluation of bending workability, the size of wrinkles occurring in the bends also becomes a problem. This is because, in the case where the bent portion is an electrical contact, a large wrinkle causes contact resistance to be unstable and the reliability of the electrical connection is impaired.

However, the bending workability evaluated in the prior art is hardly considered for bending cracking resistance and bending wrinkles, and a Cu-Ni-Si-based alloy excellent in bending wrinkle resistance has not been obtained. In patent document 3, although the description of wrinkles exists in bending workability evaluation, the quantitative evaluation about the magnitude | size of bending wrinkles was not performed, and the invention example without wrinkles was not obtained. In Patent Literature 6, bending wrinkle evaluation was performed. In order to obtain a Cu-Ni-Si-based alloy having excellent strength and bending workability, attention was paid to the direction of 123 123 <412> on a 111 111 positive electrode viscosity ( Patent document 6 "0016") and the conditions of the cold rolling and solution treatment before a solution treatment are adjusted (patent document 6 "0019"). Bending wrinkle evaluation was also performed in patent document 8, but in order to obtain the Cu-Ni-Si type alloy excellent in strength and bending workability, it paid attention to residual Ni-Si particle | grains (patent document 8 "0009"), and the amount of Ni, Si, and hot Rolling and solution treatment conditions are adjusted (patent document 8 "0019").

In order to achieve the above object, the present inventors have conducted studies on bending workability from the viewpoint of grain boundary control of polycrystalline metals differently from the prior art, and as a result, annealing twins generated during work heat treatment of Cu-Ni-Si alloys By controlling the frequency of occurrence of Cu-Ni-Si-based alloys having high strength and having good bending workability even in bending wrinkle evaluation.

The Cu-Ni-Si-based alloy of the present invention is a copper alloy having good bending workability and reduced bending wrinkles while maintaining high strength, and is suitable for use in terminals, connectors, and the like.

Best Mode for Carrying Out the Invention

Next, the requirements of the present invention will be described together with the operation thereof.

[Ni, Si]

Ni and Si is, by carrying out a suitable heat treatment, to form fine particles of the intermetallic compound to the Ni ₂ Si mainly. As a result, the strength of the alloy is significantly increased, and at the same time, the electrical conductivity is also increased.

Ni is 1.0-4.0 mass%, Preferably it adds in the range of 1.5-3 mass%. If Ni is less than 1.0 mass%, sufficient strength will not be obtained. When Ni exceeds 4.0 mass%, a crack will generate | occur | produce in hot rolling.

The addition concentration (mass%) of Si shall be 1/6-1/4 of the addition concentration (mass%) of Ni. When Si addition concentration is less than 1/6 of Ni addition concentration, intensity | strength falls, and when it is more than 1/4 of Ni addition concentration, not only it does not contribute to strength but electroconductivity falls by excess Si.

[Mg, Sn, Zn, Co, Cr]

Although Mg has the effect of improving stress relaxation characteristics and hot workability, when it exceeds 0.2% by mass, castability (decrease in cast surface quality), hot workability and plating heat-peelability are deteriorated. Therefore, the density | concentration of Mg was prescribed | regulated to 0.2% or less.

Sn and Zn have an effect of improving strength and heat resistance, Sn has an effect of improving stress relaxation resistance, and Zn has an effect of improving heat resistance of solder joints. Sn is added in the range of 0.2-1 mass%, and Zn is 0.2-1 mass%. If it is less than the above-mentioned range, a desired effect will not be obtained, and if it exceeds, electroconductivity will fall.

Co and Cr have the effect | action which produces | generates a compound with Si, and improves strength by precipitation. Co has an effect of preventing coarsening of crystal grains during heat treatment, and Cr has an effect of improving heat resistance.

Co is added in the range of 1-1.5 mass% and Cr is 0.05-0.2 mass%. If it is less than the above-mentioned range, a desired effect will not be obtained, and if it exceeds, electroconductivity will fall.

Twin boundary

Metallic materials are usually aggregates of crystal grains having various crystal orientations, that is, polycrystals, and boundaries, that is, grain boundaries exist in the metallic material due to differences in the arrangement of atoms. Grain boundaries are classified into diagonal grain boundaries, incineration grain boundaries, and sub-grain boundaries according to the orientation difference between adjacent grains. Generally, grain boundaries refer to diagonal grain boundaries having an orientation difference of 15 ° or more between adjacent grains. On the other hand, grain boundaries are classified into random grain boundaries and corresponding grain boundaries according to the consistency between adjacent grains. The annealing twins generated by the work heat treatment of the Cu-Ni-Si-based alloy have a corresponding grain boundary of Σ3 and have high compatibility between crystal grains.

The value of Σ is an index indicating the consistency of grain boundaries, and when the right and left crystal lattices intersecting grain boundaries are superimposed, they have a corresponding relationship of Σ = n when the overlapping lattice points and the density ratio of lattice points are 1 / n. It is called. Since the twin boundary has good atom matching, non-uniform deformation hardly occurs in the vicinity of the boundary, and cracks and wrinkles originating near the boundary do not easily occur during bending deformation. For this reason, bending workability can be improved by controlling the ratio of the twin boundary in the whole boundary which combined the grain boundary and twin boundary (except an incineration grain boundary and a sub grain boundary here).

In the Cu-Ni-Si-based alloy of the present invention, the bending workability is improved by controlling the frequency (ratio) of the twin boundary (Σ3 boundary) in the entire boundary to 15% or more and 60% or less, preferably 30% or more and 60% or less. do. If it is less than 15%, desired bending workability will not be obtained, and if it exceeds 60%, the crystal grain at the time of solution formation will coarsen and the strength will fall.

As a method of calculating the ratio of twin boundaries, there is an EBSP (Electron Back Scattering Pattern) method by FESEM (Field Emission Scanning Electron Microscope). This method is a method of analyzing a crystal orientation based on the backscattered electron diffraction pattern (Kikuchi pattern) generated when an electron beam is projected obliquely on a sample surface. After analyzing the crystal orientation by this method, the orientation difference between adjacent crystal orientations can be obtained, and the ratio of the random grain boundary and each corresponding grain boundary (grain boundary distribution) can be determined. Since the twin boundary corresponds to the Σ3 corresponding grain boundary, the ratio of the twin boundary is calculated as (total of the length of the corresponding grain boundary Σ3) / (total of the length of the grain boundary) × 100. In addition, a grain boundary refers to the boundary where the orientation difference between adjacent grains becomes 15 degrees or more, and does not include an incineration grain boundary or a sub grain boundary.

The twin in the present invention is an annealing twin, which is a twin twin that is generated by recrystallization generated by annealing after rolling. The frequency of twinning is correlated with the stacking defect energy of the material. If the stacking defect energy is low, the twining frequency generated during annealing is increased, and if it is high, the frequency is decreased. On the other hand, the lamination defect energy is lowered by increasing the amount of solid solution Ni.Si (exactly, by increasing the amount of solid solution Si). Therefore, to increase the twin boundary frequency, the amount of solid solution Ni.Si may be increased in order to lower the stacking defect energy before the final recrystallization annealing (corresponding to the solution treatment in the present invention).

However, in the conventional method for producing a corson alloy, it is customary to carry out solid solution of Ni and Si at the time of solution treatment, and unnecessarily performing hot rolling at a high temperature cracks at the time of hot rolling in addition to the cost increase. It was not carried out because of an increased risk. In addition, there was also a manufacturing method that doubles the solution treatment by hot rolling. However, even after hot rolling after annealing corresponding to the solution treatment, the Ni-Si crystallized substance produced during casting cannot be completely dissolved, resulting in lamination defects. The energy could not be lowered sufficiently. As a result, the twin boundary frequency obtained by the conventional method was about 12%. On the other hand, in the present invention, by increasing the cooling rate at the time of casting, the number and particle diameter of the Ni-Si crystals are reduced, and the conditions of high temperature and long time annealing are adopted within the limit that cracking does not occur in the hot rolling process, and the material is cooled. By doing so, the amount of solid solution Ni.Si was increased in comparison with the conventional method to obtain a desired twin boundary frequency.

[Manufacturing method]

The corson alloy of this invention is manufactured by the general manufacturing process which combined the solution treatment, cold rolling, and an aging treatment after "melting, casting-> hot rolling-> face-fining", and stress relief annealing after final cold rolling In some cases, the solution treatment may be combined with hot rolling. Since annealing twinning occurs with recrystallization at the time of solution treatment, in order to achieve the frequency of twinning boundary of 15% or more and 60% or less, the conditions from the casting to hot rolling are carried out within the following ranges. Ni and Si may be sufficiently dissolved before recrystallization annealing, that is, solution treatment.

Ingot cooling rate at the time of casting is 300-500 degreeC / min, and crystallization of coarse Ni-Si particle | grains is suppressed at the time of casting cooling. The speed | rate exceeding ingot cooling rate 500 degreeC / min is not practical in cost. Next, after annealing at a heating temperature of 940 to 1000 ° C, preferably at 950 to 980 ° C for 3 to 6 h of heating time to solidify the Ni-Si particles remaining in the ingot, hot rolling is performed. If the heating temperature is less than 940 ° C or less than 3 hours, the solid solution of the remaining Ni-Si particles is insufficient. On the other hand, annealing at high temperatures exceeding 1000 ° C. during hot rolling increases the risk of hot rolling cracking. Annealing in excess of 6 hours results in excessive annealing for the desired effect in the above temperature range, which is undesirable in terms of cost. The material temperature at the end of hot rolling shall be 650 degreeC or more. If it is less than 650 ℃ to the Ni ₂ Si amount to be precipitated in the hot rolling is increased, because it is not possible to ensure sufficient employment Ni · Si amount, the boundary frequency is lowered twin crystal.

After roughing, cold rolling of 85% or more of workability is performed, and solution treatment for 5 sec to 30 min (in this case, final recrystallization annealing) is performed at 700 to 820 ° C., followed by 2 at 350 to 550 ° C. Aging treatment of -30 h is performed. In addition, cold rolling is performed at a degree of processing of 5% to 50%.

Example 1

(Production of sample)

Electrical copper was dissolved, a predetermined amount was added to the air melting furnace, and the molten metal was stirred. Thereafter, the ingot was obtained by tapping with a mold at an injection temperature of 1250 ° C. By changing the water cooling conditions of the mold, the ingot cooling rate at the time of casting was adjusted to the conditions in the table. The ingot cooling rate at the time of casting is the average cooling rate (degreeC / min) from ingot temperature to 500 degreeC after a molten metal solidifies. Next, this ingot was processed and heat-treated in the following procedure, and the sample of 0.25 mm of plate | board thickness was obtained.

(1) The ingot was annealed and hot rolled under the conditions shown in the table, and the plate thickness was finished to a predetermined thickness, followed by water cooling.

(2) Oxidation scale of the surface layer was removed by roughing.

(3) Cold rolling was performed to a plate thickness of 0.3 mm.

(4) The solution treatment was performed for 1 minute at the solution temperature in the table.

(5) Aging treatment was performed under the conditions of 450 ° C × 10 h.

(6) The aging material was cold rolled to 0.25 mm.

For this material, EBSP measurements, tensile tests, and W bending tests on twin boundaries were performed according to the following criteria.

Twin boundary

As a method of calculating the ratio of twin boundaries, an EBSP (Electron Back Scattering Pattern) method by FESEM (Field Emission Scanning Electron Microscope) was used. After analyzing the crystal orientation by this method, the grain boundary distribution was determined by determining the orientation difference between adjacent crystal orientations. Observation magnification was 1000 times, and the sum total of the observation visual field was 2 mm <2>. Corresponding grain boundaries are represented using? Values, and twin boundaries correspond to? 3 corresponding grain boundaries. The ratio (%) of the twin boundary is calculated as (total of the length of the corresponding grain boundary Σ3) / (total of the length of the grain boundary) x 100. In addition, the grain boundary in a formula indicates the boundary which the orientation difference between adjacent grains becomes 15 degrees or more, and does not contain an incineration grain boundary or a grain boundary.

[The tensile strength]

About each copper alloy plate, the tension test was done in the direction parallel to a rolling direction, and it calculated | required based on JISZ22241. In the following examples, high strength means that the alloy A has a tensile strength of 700 MPa or more, that of the alloy B is 650 MPa or more, and that of the alloy C is 600 MPa or more.

[Bending Crack]

The single test piece of width 10mm x length 30mm was extract | collected so that a bending axis might be parallel to a rolling direction. The W bending test (JIS H 3130) of this test piece was performed, and the minimum bending radius which a crack does not produce was made into MBR (Minimum Bend Radius), and it evaluated by the ratio MBR / t with plate | board thickness t (mm). Regarding alloy A, when MBR / t in the bad way (B.W.) direction was 1 or less, the crack evaluation of bending workability was good (○), and the other was judged to be bad (×).

Regarding alloys B and C, when MBR / t was 0.5 or less, it was determined that bending workability was good.

[Bending wrinkles]

In the said W bending test, the SEM image of the wrinkle observed in the surface of the bending convex part of the test piece bent with MBR was photographed. The width | variety of the bending wrinkles was measured on the photograph, and the width | variety of the largest bending wrinkles in the test piece was calculated | required. Three test pieces were measured about each specimen and the average value was made into the width | variety of a bending wrinkle. B.W. When the width | variety of the bending wrinkle of the direction is 30 micrometers or less, the wrinkle evaluation of bending workability was favorable ((circle)), and when it exceeded 30 micrometers, it judged that it was defect (x). In addition, "-" in a table | surface shows the evaluation impossibility.

Table 1 shows an example of Ni-Si-based copper alloy A (Cu-2% Ni-0.5% Si-0.1% Mg) according to the present invention.

Table 2 shows an example of Ni-Si-based copper alloy B (Cu-1.6% Ni-0.4% Si-0.4% Sn-0.5% Zn) according to the present invention.

Table 3 shows an example of Ni-Si-based copper alloy C (Cu-1.6% Ni-0.4% Si) according to the present invention.

In Comparative Examples 1, 8 and 15, since the cooling rate at the time of casting is less than 300 degree-C / min, coarse Ni-Si grain crystals generate | occur | produce in an ingot, and the solid-solution amount of Ni and Si with respect to a mother phase falls, Since the lamination defect energy was not sufficiently lowered, the twin boundary frequency was less than 15%.

In Comparative Examples 2-4, 9-11, and 16-18, since the hot-rolling conditions do not satisfy any of 940 degreeC or more, 3 h or more, and end temperature 650 degreeC or more, Ni-Si particle inclusions are not fully dissolved. Since the lamination defect energy did not decrease, the twin boundary frequency was less than 15%.

In the comparative examples 5, 12, and 19, since the cold workability was 85% or less, recrystallization at the time of solutionization was inadequate and the twinning frequency became less than 15%.

In Comparative Examples 6, 13 and 20, since the solution temperature was 700 degrees C or less, recrystallization was inadequate, twin boundary frequency became less than 15%, and intensity also fell.

In Comparative Examples 7, 14 and 21, since the solution temperature exceeded 820 degreeC, since the twin boundary frequency exceeded 60% and the crystal grain size became large, the width | variety of the bending wrinkles became large.

Example 2

(Production of sample)

Electrocopper was melt | dissolved, the predetermined amount was added to the desired composition shown in Table 4 in the atmospheric melting furnace, and the molten metal was stirred. Thereafter, the mixture was heated in a mold at an injection temperature of 1250 ° C, the cooling rate was adjusted to 400 ° C / min, and an ingot was obtained. Next, this ingot was processed and heat-treated in the following procedure, and the sample of 0.25 mm of plate | board thickness was obtained.

(1) After ingot was annealed at 950 degreeC for 4 hours, hot rolling was performed so that the finishing temperature after rolling might be 700 degreeC.

(2) Oxidation scale of the surface layer was surface-treated, and plate | board thickness was finished to 5 mm.

(3) Cold rolling was performed to a plate thickness of 0.3 mm.

(4) The solution treatment was performed for 1 minute at 750 degreeC.

(5) Aging treatment was performed under the conditions of 450 ° C × 10 h.

(6) The aging material was cold rolled to 0.25 mm.

The material was subjected to EBSP measurements, tensile tests, conductivity and W bending tests on twin boundaries. Evaluation of twin boundary frequency and W bending test was performed similarly to Example 1 mentioned above, and since tensile strength is largely influenced by a composition, 600 Mpa or more was determined as high strength.

The results are shown in Table 5. As shown in Table 5, Inventive Examples 13-24 obtained the desired twin boundary frequency, the bending workability was favorable, and the strength was also favorable. In Comparative Example 22, the amount of Ni was lower than the prescribed amount and the bending workability was good, but the tensile strength was lowered. In Comparative Example 23, the amount of Ni was higher than the prescribed amount, hot rolling cracking occurred, and sample preparation became impossible.

Claims (4)

As a Cu-Ni-Si type alloy containing 1.0-4.0 mass% of Ni, containing 1/6-1/4 concentration of Si with respect to the mass% concentration of Ni, and remainder consists of Cu and an unavoidable impurity, The Cu-Ni-Si type alloy which controlled the frequency of the twin boundary (Σ3 boundary) in the whole grain boundary as 15% or more and 60% or less as a result of observation of the texture by EBSP measurement. The method of claim 1,
Furthermore, Cu-Ni-Si type | system | group alloy containing 0.2 mass% or less of Mg. The method of claim 1,
Cu-Ni-Si type alloy which contains 0.2-1 mass% of Sn and 0.2-1 mass% of Zn further. The method of claim 1,
Cu-Ni-Si type alloy which contains 1-1.5 mass% of Co and 0.05-0.2 mass% of Cr further.