Cu-Ni-Co-Si copper alloy sheet material, its manufacturing method, and electrical components.

Abstract

To provide a Cu-Ni-Co-Si based copper alloy sheet material which materializes strength / conductivity balance, that is, tensile strength of 900 MPa or more and conductivity of 40% IACS or more, and has significantly improved press punchability.SOLUTION: A copper alloy sheet material is provided which has a chemical composition composed of, in mass%, the total of Ni and Co: 1.50 to 5.50%, Si: 0.50 to 1.20%, S: 0.0005 to 0.20%, Mg: 0.01 to 0.20%, Cr: 0 to 0.50%, Zn: 0 to 1.00%, Sn: 0 to 1.00%, Mn: 0 to 0.20%, B: 0 to 0.10%, P: 0 to 0.10%, Ag: 0 to 0.20%, Al: 0 to 0.20%, Zr: 0 to 0.20%, Ti: 0 to 0.50%, Fe: 0 to 0.30%, the balance composed of Cu and unavoidable impurities, and in which Mg-S based particles having a circle-equivalent diameter of 0.5 μm or more are present at a number density of 300 pieces / mm2 or more, and the average particle size of the Mg-S based particles is 3.0 μm or less in terms of the circle-equivalent diameter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-strength Cu-Ni-Co-Si copper alloy sheet material with improved press-punching properties, a method for manufacturing the same, and an electrical component using the Cu-Ni-Co-Si copper alloy sheet material. [Background technology]

[0002] Cu-Ni-Co-Si copper alloys offer a relatively good balance of strength and conductivity among copper alloys, making them useful for conductive components such as connectors and lead frames. In recent years, with the miniaturization and weight reduction of electronic devices, connector materials have become thinner, requiring even higher strength from the copper alloy sheets used as their material. In the case of Cu-Ni-Co-Si copper alloy sheets, it is expected that a high level of strength-conductivity balance can be achieved, such as high strength of 900 MPa or more in the rolling direction and conductivity of 40% IACS or more. However, strength and conductivity generally have a trade-off relationship, and achieving such high levels of both strength and conductivity in copper alloy sheets is not easy.

[0003] On the other hand, when processing copper alloy sheets into electrically conductive components, the process generally involves press punching. Recently, with the miniaturization and narrowing of component pitches, high dimensional accuracy of punched parts is required. Extending the life of the die is important to improve dimensional accuracy in the punching process. The cut surface (edge) of a metal sheet formed by press punching usually has both a shear surface and a fracture surface (see Figure 2). When punching is performed with the appropriate clearance, materials with a smaller proportion of shear surfaces are advantageous for extending die life. In this specification, when punching materials of the same sheet thickness with the appropriate clearance using a press die, materials with a smaller proportion of shear surfaces on the cut surface are considered to have good "press punchability." There is room for improvement in press punchability for high-strength Cu-Ni-Co-Si copper alloy sheets.

[0004] Patent Document 1 describes a Cu-Ni-Co-Si copper alloy sheet material that achieves both bendability and high strength by controlling the texture. However, it does not describe a material that achieves high strength of 900 MPa or more with an electrical conductivity of 40% IACS or more. It does not intend to improve press punchability, and there is no mention of sulfur content.

[0005] Patent Document 2 describes a Cu-(Ni)-Co-Si copper alloy sheet material that achieves high conductivity and reduced mold wear by controlling the particle size and number density of precipitates in the surface and central parts. Although the conductivity is increased to 55% IACS or higher, the tensile strength remains below 750 MPa. Mold life is evaluated based on burr height and sagging amount. There is no consideration of reducing the proportion of shear surfaces or utilizing sulfur-containing particles.

[0006] Patent Document 3 describes a Cu-Ni-Co-Si copper alloy sheet material whose stress relaxation resistance has been improved by adjusting the microstructure using a method for controlling the heating rate and cooling rate during solution treatment. It is not intended to improve press punchability, and there is no mention of the sulfur content.

[0007] Patent Document 4 describes a Cu-Ni-Co-Si copper alloy sheet material whose spring limit value is improved by controlling the morphology of precipitates using a three-stage aging treatment method. Among the sheet materials specifically described, some have a conductivity of 40%IACS or higher and a relatively high 0.2% yield strength (YS) of 882 MPa (Table 2-7, Example 138), but no method is disclosed for stably obtaining a strength level of tensile strength of 900 MPa or higher. Improvement of press punchability is not intended, and there is no mention of sulfur content.

[0008] Patent document 5 describes a Cu-(Ni)-Co-Si copper alloy sheet material with an S content of approximately 0.002%. The solution treatment temperature is 750°C (paragraph 0033). These materials have low strength levels and low electrical conductivity.

[0009] Patent Document 6 describes manufacturing examples No. 6, 8, 15, 19, 38, 41, and 46 in the specification table for Cu-(Ni)-Co-Si copper alloy sheet materials containing S in the range of 50 ppm (0.005%) or less and Mg. Of these, No. 8 has a relatively high conductivity of 46% IACS. However, there is no particular description regarding hot rolling, and the temperature of the finishing heat treatment, which is equivalent to solution treatment, is low at 775°C, so it is insufficient for significant improvement in strength and press punchability. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2011-117034 [Patent Document 2] Japanese Patent Publication No. 2012-224922 [Patent Document 3] Japanese Patent Publication No. 2015-187308 [Patent Document 4] Japanese Patent Publication No. 2011-214088 [Patent Document 5] Japanese Patent Application Publication No. 11-222641 [Patent Document 6] Japanese Patent Publication No. 2016-44344 [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention aims to achieve a high level of strength and conductivity balance in a Cu-Ni-Co-Si copper alloy sheet material, with a tensile strength of 900 MPa or more in the rolling direction and an conductivity of 40% IACS or more, while also significantly improving press-punching properties. [Means for solving the problem]

[0012] The inventors discovered that the above objective can be achieved by incorporating trace amounts of Mg and S into a Cu-Ni-Co-Si copper alloy, thereby creating a microstructure in which Mg-S inclusions of a predetermined size are dispersed.

[0013] In other words, the objective is to produce a material with a chemical composition consisting of, by mass%, a total of Ni and Co: 1.50-5.50%, more preferably 2.00-4.00%, Si: 0.50-1.20%, S: 0.0005-0.20%, Mg: 0.01-0.20%, Cr: 0-0.50%, Zn: 0-1.00%, Sn: 0-1.00%, Mn: 0-0.20%, B: 0-0.10%, P: 0-0.10%, Ag: 0-0.20%, Al: 0-0.20%, Zr: 0-0.20%, Ti: 0-0.50%, Fe: 0-0.30%, with the remainder being Cu and unavoidable impurities, and having 300 Mg-S particles / mm² with an equivalent circular diameter of 0.5 μm or more in a cross-section parallel to the rolling direction and thickness direction (referred to as the "TD surface"). 2 This is achieved by a copper alloy sheet material having the above number density, an average particle diameter of the Mg-S system particles being 3.0 μm or less in equivalent circular diameter, and a tensile strength in the rolling direction of 900 MPa or more. In such a microstructure, an electrical conductivity of 40% IACS or more can be obtained. In a cross-section (LD plane) perpendicular to the rolling direction of this sheet material, the average grain size according to the cutting method in accordance with JIS H0501-1986 is, for example, 1 to 20 μm.

[0014] Furthermore, in the present invention, as a method for manufacturing the Cu-Ni-Co-Si copper alloy sheet material, when manufacturing the sheet material from a cast slab having the above chemical composition in the above order, the process includes hot rolling, cold rolling, solution treatment, and aging treatment, In the hot rolling process, the rolling rate per pass in all rolling passes performed at temperatures of 800°C or higher is 20% or less, and the total rolling rate in rolling passes performed at temperatures of 900°C or higher is 38% or more. A method for manufacturing copper alloy sheets is provided, in which, during the solution treatment process, the average heating rate from 300°C to 800°C is set to 10°C / s or more, the temperature is held at 800-1020°C for 10 seconds or more, and the average cooling rate from 800°C to 500°C is set to 50°C or more. The temperature of the aging treatment can be, for example, 400 to 550°C.

[0015] Furthermore, in the present invention, an electrical component using the above copper alloy sheet is provided. Particularly, an electrical component having a press punching part is a suitable object.

Effects of the Invention

[0016] According to the present invention, in a copper alloy sheet of Cu-Ni-Co-Si system, it has become possible to stably impart a high-level strength-conductivity balance of a tensile strength of 900 MPa or more and a conductivity of 40% IACS or more in the rolling direction. Furthermore, during press punching, it is possible to significantly reduce the ratio of the sheared cross section generated at the cut edge, thereby improving the life of the press die. The improvement of the die life brings about the stabilization of quality by maintaining high dimensional accuracy in the mass production of press punched parts. The present invention realizes the simultaneous improvement of conductivity, strength, and press punching property, which has been desired for a sheet material for manufacturing electrical components with thinning and narrow pitch progress.

Brief Description of the Drawings

[0017] [Figure 1] SEM image of the cross section of the Cu-Ni-Co-Si system copper alloy sheet according to the present invention, in which particles are clarified by binarization treatment. [Figure 2] A diagram schematically showing the shape of the cut edge of the metal plate after press punching.

Embodiments for Carrying Out the Invention

[0018] [Chemical Composition] In the present invention, a Cu-Ni-Co-Si system copper alloy is applied. Hereinafter, “%” regarding alloy components means “mass %” unless otherwise specified.

[0019] Ni and Co form Ni-Co-Si precipitates, Co-Si precipitates, and Ni-Si precipitates, improving the strength and conductivity of the copper alloy sheet material. The Ni-Co-Si precipitate is thought to be a compound mainly composed of (Ni,Co)2Si. The Co-Si precipitate and the Ni-Si precipitate are thought to be precipitates mainly composed of Co2Si and Ni2Si, respectively. In order to sufficiently disperse the fine precipitate particles that are effective in improving strength, the total content of Ni and Co needs to be 1.50% or more, and more preferably 2.00% or more. The Ni content is more preferably 0.50% or more, even more preferably 0.75% or more, and may be controlled to 1.00% or more. Similarly, the Co content is more preferably 0.50% or more, and even more preferably 1.00% or more. On the other hand, if the total content of Ni and Co is excessive, coarse precipitates tend to form, which is detrimental to improving strength. The total content of Ni and Co is limited to 5.50% or less, and may be controlled to 4.00% or less.

[0020] Si forms Ni-Co-Si precipitates. To adequately disperse the fine precipitate particles effective in improving strength, the Si content needs to be 0.50% or higher. On the other hand, excessive Si tends to produce coarse precipitates, making the material prone to cracking during hot rolling. The Si content should be limited to 1.20% or less. It may also be controlled to less than 1.00%.

[0021] S is an important component element in this invention. Generally, in copper alloys, S is often treated as an impurity from the viewpoint of suppressing deterioration of hot workability and reduction of material properties. In the manufacturing process of copper alloys, the S content is usually reduced by methods such as degreasing of raw materials and flotation separation in molten metal. However, in this invention, the press punching performance is improved by dispersing Mg-S particles in the material. Therefore, a predetermined amount of S is included in the copper alloy as a source for generating Mg-S particles. After various studies, it was found that the S content needs to be controlled in the range of 0.0005 to 0.20%. If the S content is too low, the amount of Mg-S particles generated will be insufficient, and the improvement effect on press punching performance will not be obtained. A S content of 0.01% or more is more effective. When compared with copper alloys with equivalent content of alloying elements other than S and the same manufacturing conditions applied, a S content of 0.01% or more is advantageous in obtaining an even better improvement effect on press punching performance. Excessive sulfur content leads to poor hot workability and increased cracking during hot rolling. Furthermore, excessive sulfur addition can easily cause coarsening of Mg-S particles, resulting in reduced strength.

[0022] Mg is an element that improves the stress relaxation resistance of Cu-Ni-Co-Si copper alloys and has conventionally been added as needed. However, in this invention, Mg content is essential because it is used as a source for generating Mg-S particles. Furthermore, Mg content is important for achieving high strength of 900 MPa or more in tensile strength while suppressing a decrease in conductivity by utilizing solid solution strengthening of Mg. After various studies, it is necessary to ensure an Mg content of 0.01% or more. A large amount of Mg content will cause a decrease in hot workability or cold workability. The Mg content is limited to a range of 0.20% or less, and may be controlled to 0.15% or less.

[0023] Other elements such as Cr, Zn, Sn, Mn, B, P, Ag, Al, Zr, Ti, and Fe may be included as needed. The preferred content ranges for these elements are: Cr: 0-0.50%, Zn: 0-1.00%, Sn: 0-1.00%, Mn: 0-0.20%, B: 0-0.10%, P: 0-0.10%, Ag: 0-0.20%, Al: 0-0.20%, Zr: 0-0.20%, Ti: 0-0.50%, and Fe: 0-0.30%.

[0024] Cr, Mn, B, P, Al, Zr, and Ti have the effect of further increasing alloy strength and reducing stress relaxation. Sn and Ag are effective in improving stress relaxation resistance. Zn improves the solderability and castability of copper alloy sheets. Cr, Mn, Zr, Ti, and Fe readily form high-melting-point compounds with unavoidable impurities such as Pb, and B, P, Zr, and Ti have a refinement effect on the cast structure, each contributing to improved hot workability.

[0025] When including one or more of the following elements: Cr, Zn, Sn, Mn, B, P, Ag, Al, Zr, Ti, and Fe, it is more effective to have a total content of 0.01% or more. However, including large amounts will negatively affect hot or cold workability and will also be cost-ineffective. It is more desirable to keep the total amount of these optional additive elements to 1.0% or less, or 0.5% or less.

[0026] [Mg-S particles] In this specification, "Mg-S particles" refer to compound particles present in a copper alloy in which Mg and S are observed by EDX (energy-dispersive X-ray fluorescence analysis) when an electron beam is irradiated to the center of the particle. These particles are considered to be mainly composed of the compound MgS. The dispersion of Mg-S particles with a particle diameter of approximately 0.5 to 3.0 μm improves press formability. In this specification, the particle diameter of Mg-S particles refers to the equivalent diameter of a circle unless otherwise specified. That is, the area of ​​a certain particle observed in the cross-section of a copper alloy sheet is S (μm). 2 If we assume that S = π × D, then the diameter D (μm) of a perfect circle with area S is called the equivalent diameter of the particle. Here, S = π × D2 It is / 4.

[0027] According to the inventors' research, in a cross-section parallel to the rolling direction and thickness direction (TD plane), there are 300 Mg-S particles with an equivalent circular diameter of 0.5 μm or more per mm. 2 When present at the above number density, it was found that the proportion of the shear surface area in the cut formed when shearing (press punching) is performed with appropriate clearance is significantly reduced. In other words, the press punching performance is significantly improved. This extends the life of the press die, maintains high dimensional accuracy of punched parts in mass production, and stabilizes the quality of the parts. However, if the average particle size of Mg-S particles with an equivalent circle diameter of 0.5 μm or more exceeds 3.0 μm in equivalent circle diameter, the increase in strength is hindered, and in some cases, the improvement in press punching performance may not be fully obtained. The average particle size and number density of Mg-S particles can be determined by the following analytical method.

[0028] (Analysis method for Mg-S particles) The cross-section (TD surface) of the copper alloy sheet material, parallel to the rolling direction and thickness direction, is polished to obtain a sample surface for EDX measurement. The sample surface is observed using an FE-SEM (Field Emission Scanning Electron Microscope) equipped with an EDX device, and a measurement area is randomly determined. EDX analysis is performed on all particles with an equivalent circle diameter of 0.5 μm or more that are present in the measurement area. Particles in which Mg and S are detected are identified as "Mg-S particles," and their number is counted. In EDX analysis, the electron beam is irradiated to the center of the particle. In addition, the equivalent circle diameter of individual particles present in the measurement area is measured by processing the FE-SEM image of the measurement area with software. This operation is performed for multiple non-overlapping measurement areas, and the total number of particles with an equivalent circle diameter of 0.5 μm or more identified as "Mg-S particles" is divided by the total area of ​​the measurement area to obtain the "number density of Mg-S particles with an equivalent circle diameter of 0.5 μm or more (particles / mm²)." 2 The arithmetic mean of the equivalent circle diameters for these particles is calculated, and this value is defined as the "average particle diameter (μm) of Mg-S particles with an equivalent circle diameter of 0.5 μm or more". Here, the area of ​​one measurement region is 0.03 mm². 2The total area of ​​the measurement region is 0.75 mm². 2 The above is intended to be the case. In the FE-SEM observation described above, one field of view may be used as one measurement area, or a region created by seamlessly connecting several adjacent fields of view may be set as one measurement area.

[0029] [Tensile strength, electrical conductivity] This invention focuses on copper alloy sheet materials having a tensile strength of 900 MPa or more in the rolling direction. By applying a manufacturing method described later to a Cu-Ni-Co-Si copper alloy adjusted to the above-mentioned chemical composition, a high strength of 900 MPa or more can be obtained. At the same time, an electrical conductivity of 40% IACS or more can be obtained. Such a high level of strength-conductivity balance can meet the needs for thinner and smaller conductive components. Regarding electrical conductivity, it is also possible to obtain materials with a conductivity of 43% IACS or more, or even 46% IACS or more.

[0030] [Average grain size] Generally, reducing the grain size is advantageous for improving strength and bendability. On the other hand, if stress relaxation characteristics, a type of creep phenomenon, are important, an excessively small grain size is disadvantageous. When considering processing for conductive parts where thinning and narrow pitch are required, the average grain size of the cross section perpendicular to the rolling direction (LD plane) according to the cutting method in accordance with JIS H0501-1986 is preferably in the range of 1 to 20 μm. The average grain size can be measured by the following method.

[0031] (Method for measuring average crystal grain size) The cross-section perpendicular to the rolling direction (LD surface) of the sheet material is polished and then etched to create an observation surface. This observation surface is observed with an optical microscope, and an observation image is obtained. On the obtained observation image, a total of three straight lines parallel to the rolling surface are drawn at positions in the thickness direction of the sheet material at 1 / 4, 1 / 2 (center of the sheet material), and 3 / 4 of the sheet thickness. The average grain size is calculated by counting the number of grain boundaries cut by each straight line using a cutting method compliant with JIS H0501-1986. This operation is performed for five randomly selected fields of view, and the arithmetic mean of the average grain size obtained for each field of view is adopted as the average grain size of the sheet material. A confocal laser microscope can be used as the optical microscope.

[0032] [Manufacturing method] The copper alloy sheet material described above can be manufactured, for example, by the following process. Melting and casting → Hot rolling → Cold rolling → (Intermediate annealing → Cold rolling) → Solution treatment → Aging treatment → Finish cold rolling → Low-temperature annealing Although not mentioned in the above process, surface milling is performed as needed after hot rolling, and pickling, polishing, or further degreasing is performed as needed after each heat treatment. The following describes each process.

[0033] [Melting and Casting] Cast slabs can be manufactured by continuous casting, semi-continuous casting, etc. To prevent oxidation of Si, Mg, etc., it is preferable to carry out the process in an inert gas atmosphere or a vacuum melting furnace. In the melting of copper alloys, sulfur is generally treated as an impurity, and the raw materials and refining methods are usually controlled to reduce its content as much as possible. In contrast, in the present invention, it is necessary to strictly control the sulfur content so that sulfur within the predetermined content range described above is incorporated into the copper alloy. For example, a pre-prepared Cu-S master alloy can be used to add sulfur.

[0034] [Hot rolling] Since sulfur (S) easily leads to the formation of a coarse Mg-S compound phase in the cast slab, it is important to break up this coarse compound phase during the hot rolling process in order to obtain the desired metallic structure in which Mg-S particles are dispersed. To break up the coarse compound phase, it is advantageous to achieve the greatest possible degree of workability in the high-temperature range where deformation resistance is low. However, since sulfur (S) is also an element that reduces hot workability, it is necessary to carefully manage the pass schedule during hot rolling to prevent cracking. Therefore, the inventors conducted detailed hot rolling experiments. As a result, they found that by following the conditions below, it is possible to break up the coarse compound phase and prevent cracking during hot rolling for copper alloys within the composition range mentioned above.

[0035] (i) The rolling rate per pass in all rolling passes performed at temperatures of 800°C or higher shall be 20% or less. (ii) Furthermore, the total rolling rate from the rolling pass performed at a temperature of 900°C or higher shall be 38% or higher. Here, the rolling temperature in each rolling pass can be determined by using the surface temperature of the material measured by an infrared thermometer just before it is caught in the rolling rolls. The rolling ratio from plate thickness t0 (mm) to plate thickness t1 (mm) is determined by the following equation (1). Rolling ratio (%) = 100 × (t0 - t1) / t0 ... (1) The rolling ratio per pass in a given rolling pass can be determined by substituting the thickness of the sheet before rolling in that rolling pass into t0 and the thickness of the sheet after rolling in that rolling pass into t1, and applying equation (1). Furthermore, the total rolling ratio for rolling passes performed at a temperature of 900°C or higher can be determined by substituting the initial thickness of the sheet before the start of rolling into t0 and the thickness of the sheet after rolling in the last rolling pass at a rolling temperature of 900°C or higher into t1, and applying equation (1).

[0036] The heating before hot rolling can be carried out, for example, by holding the material at 920-1060°C for 60-600 minutes. There is no specific lower limit for the rolling rate per pass in (i) above, but since it becomes uneconomical if the number of passes increases, it is fine to set it in the range of 5-20% for example. It is more preferable to set it in the range of 10-20%. It is more effective to set the total rolling rate by the rolling passes performed at temperatures of 900°C or higher in (ii) above to 40% or higher. There is no specific upper limit for the total rolling rate by the rolling passes performed at temperatures of 900°C or higher, but it is fine to set it in the range of 65% or less for example. It is preferable that the rolling temperature of the final pass be 700°C or higher. After the completion of hot rolling, it is preferable to rapidly cool the material by water cooling or the like.

[0037] [Cold rolling] The material is cold-rolled using a conventional method to obtain an intermediate sheet material for the subsequent solution treatment. If necessary, intermediate annealing and cold rolling may be performed one or more times to adjust the sheet thickness. The rolling ratio for cold rolling is preferably set in the range of 90.0 to 99.5%.

[0038] [Solution treatment] The solution treatment is performed under the following conditions to maximize precipitation strengthening and to obtain a distribution morphology of Mg-S particles that ultimately leads to improved press punchability: an average heating rate of 10°C / s or more from 300°C to 800°C, holding at 800-1020°C for 10 seconds or more, and an average cooling rate of 50°C / s or more from 800°C to 500°C. Water cooling or oil cooling can be used to increase the average cooling rate. If the heating rate or cooling rate is slower than the above range, it becomes difficult to stably achieve high strength of 900 MPa or more. The reason for this is not entirely clear at present, but it is presumed that the presence of Mg-S precipitates in the matrix phase causes the solid solution behavior of Ni, Co, and Si to be different from normal, requiring more precise control of the heat pattern, including the heating and cooling processes, than before. If the heating or cooling rate is slow, or if the holding temperature during the solution treatment is lower than 800°C, or if the holding time at 800°C or above is too short, the solution treatment will be insufficient, making it difficult to stably obtain high strength of 900 MPa or more. In addition, the final result will be 300 Mg-S particles / mm² with an equivalent circular diameter of 0.5 μm or more. 2 It becomes difficult to obtain a microstructure in which the above number density exists and the average particle size of Mg-S particles with an equivalent circle diameter of 0.5 μm or more is 3.0 μm or less, making it impossible to achieve both high strength and improved press formability. In addition, these Mg-S particles also have the effect of suppressing grain coarsening, preventing a decrease in strength and a decrease in bendability. If the holding time for the solution treatment exceeds 1020°C, the grains may coarseen, potentially leading to a decrease in strength and a decrease in bendability. Holding times above 800°C are uneconomical if they are too long. It is preferable to set the holding time at 800-1020°C in the range of 10-600 seconds.

[0039] [Statute of limitations treatment] Next, the aging process is performed. The aging conditions should be set according to the required characteristics, within the range of an aging temperature of 400 to 550°C and a holding time of 1 to 24 hours in that temperature range.

[0040] [Finishing cold rolling] In this specification, the final cold rolling performed after aging treatment is referred to as "finish cold rolling." The rolling ratio for finish cold rolling is preferably set in the range of 10 to 80%. Considering applications for processing into small conductive components such as connectors, the final sheet thickness is preferably set in the range of, for example, 0.05 to 0.40 mm. The sheet thickness setting range may also be 0.05 to 0.25 mm or 0.06 to 0.15 mm.

[0041] [Low-temperature annealing] For the final heat treatment, it is preferable to perform low-temperature annealing with the aim of reducing residual stress, improving bendability, and improving stress relaxation resistance by reducing voids and dislocations on slip surfaces. The conditions for low-temperature annealing should be such that no recrystallization occurs, with a holding temperature of 150 to 500°C and a holding time of 5 seconds to 5 hours. [Examples]

[0042] Copper alloys with the chemical compositions shown in Tables 1A, 1B, 2A, and 2B (hereinafter abbreviated as "Tables 1A to 2B") were melted and cast using a vertical semi-continuous casting machine. Cu-20.1 mass%S alloy was used for the sulfur addition. The obtained cast slabs were heated at 1000°C for 3 hours, then extracted, hot-rolled to a thickness of 10 mm, and water-cooled. The hot-rolling conditions are shown in Tables 1A to 2B. The total hot-rolling rate was 90-95%. The rolling temperature of the final pass of hot-rolling was 700°C or higher in all cases. Except for some comparative examples (No. 41) in which cracking occurred during hot-rolling, the oxide layer on the surface was removed by mechanical polishing (surface grinding) after hot-rolling, and the intermediate product sheets were cold-rolled to be used for solution treatment. Each intermediate product sheet was subjected to solution treatment under the conditions shown in Tables 1A to 2B. Subsequently, aging treatment, finish cold rolling, and low-temperature annealing were performed to obtain a plate product (test specimen) with a thickness of 0.10 mm. The main manufacturing conditions for processes other than hot rolling and solution treatment are shown in Tables 1A to 2B. Note that the rolling ratios for hot rolling and cold rolling listed in the tables have been rounded to the nearest whole number.

[0043] The following investigations were conducted on each test specimen.

[0044] [Number density and average particle diameter of Mg-S particles] Following the aforementioned "Analysis Method for Mg-S Particles," the cross-section (TD plane) of the test material parallel to the rolling direction and thickness direction was observed using a FE-SEM equipped with an EDX device, and EDX analysis was performed. The sample surface was prepared by mechanical polishing using 0.04 μm colloidal silica, followed by ion milling. The ion milling conditions were: SVM-741 (Sanyu Electronics Co., Ltd.), acceleration voltage 6 kV, irradiation current 120 μA, time 30 minutes, and tilt angle 60°. For FE-SEM observation, backscattered electron images were obtained using a JEOL JSM-7200F (JEOL Ltd.), magnification 500x, voltage 15 kV, current level 12-14, and dead time 30-60%. One field of view is a rectangular region of 170 μm × 240 μm. Since the constituent elements of the particles, Mg, S, Co, Ni, and Si, are lighter than the metallic substrate Cu, the Mg-S, Ni-Co-Si, Ni-Si, and Co-Si particles all appear darker than the metallic substrate in the backscattered electron image. By binarizing the backscattered electron image, the particles present in the metallic substrate can be clearly identified. Here, the above backscattered electron image was binarized with a contrast of 3800-4000 and a brightness of 300-800.

[0045] For all particles with an equivalent circle diameter of 0.5 μm or more among the particles present in the visual field, elemental analysis was performed by EDX. The EDX device used was an X-MaxN50 manufactured by Oxford Instruments. The analysis software used was AZtec (Ver. 4.0 SP2 HF1) manufactured by the same company. The measurement conditions were an exposure time of 2 seconds per particle, an energy range of 0 to 20 keV, and a channel number of 2048, and mode 4 was selected for the process time. In the EDX measurement of particles using this device, it is programmed to automatically align the electron beam to the center of each measurement target particle present in the visual field. Particles with an equivalent circle diameter of 0.5 μm or more in which both Mg and S were detected were selected as "Mg-S-based particles". Here, a region where four consecutive visual fields were connected so as to overlap by 10% in the long side direction was set as one measurement region. Since the area of one measurement region is the area obtained by subtracting the overlapping area from the area of four visual fields, (0.17 mm × 0.24 mm × 4) - (0.17 mm × 0.24 mm × 0.1 × 3) = 0.151 mm 2 is. For this measurement region, the number density (number / mm 2 ) and the average particle diameter (μm) according to the equivalent circle diameter of Mg-S-based particles were calculated. This operation was performed for non-overlapping different measurement regions randomly set with a repetition number n = 5. The total area of the measurement regions is 0.151 mm 2 × 5 = 0.755 mm 2 is.

[0046] For reference, FIG. 1 illustrates a SEM image of one measurement region in which particles were clarified by binarization processing. This is a combination of four visual fields as described above for the test material No. 1 of the present invention example. The original image in which Mg-S-based particles are displayed in red among the particles is shown in black and white. Among the displayed particles, approximately 42% by number ratio are Mg-S-based particles displayed in red. The remaining particles were almost any of Ni-Co-Si-based particles, Ni-Si-based particles, and Co-Si-based particles.

[0047] [Average crystal grain size] In accordance with the "Method for Measuring Average Crystal Grain Size" described above, the average crystal grain size was determined for the cross-section (LD plane) perpendicular to the rolling direction of the test material sheet using a cutting method compliant with JIS H0501-1986.

[0048] [conductivity] The conductivity of each test material was measured using the double-bridge and average cross-sectional area methods in accordance with JIS H0505. Considering the conductivity required for conductive components such as small connectors, materials with a conductivity of 40% IACS or higher were judged to be acceptable.

[0049] [Tensile strength] Tensile test specimens (JIS No. 5) were taken from each test material in the rolling direction, and tensile tests were performed in accordance with JIS Z2241 with n=3 tests to measure the tensile strength. The average value of n=3 was taken as the performance value for the test material. From the perspective of ensuring high reliability as electrical components such as connectors, which are becoming thinner, specimens with a tensile strength of 900 MPa or higher in the rolling direction were judged to be acceptable.

[0050] [Press punching capability] A test was conducted in which 5mm x 5mm square test pieces were punched out of a 0.10mm thick sheet metal using a press die. The clearance was set to two levels: 4% and 10% of the sheet metal thickness. Of the four cuts (end faces) formed on the square test piece, two opposing cuts were punched out so as to be parallel to the rolling direction. Figure 2 schematically shows the shape of the cuts of the punched test piece. The size of the burrs, etc., are depicted in an exaggerated manner. For the cuts parallel to the rolling direction of the test piece, the surface height viewed in the direction normal to the cut was measured along the entire length in the sheet metal thickness direction (punch axis direction) using a laser microscope, and a surface roughness profile was created. From this profile, the length of the shear surface indicated by symbol A in Figure 2 was determined, and the ratio of the shear surface to the fracture surface was calculated. Here, for the sake of ease of measurement, the length including the burr portion indicated by symbol B in Figure 2 was considered as the length of the fracture surface, and the "shear ratio" was calculated using the following formula (2). In this press punching test, the burr height is usually less than 1 μm, so including the burr in the length of the fracture surface does not hinder the evaluation of press punchability. Shear area ratio (%) = 100 × A / (A + B) …(2) This measurement was performed at 10 locations within the cross-section (end face) parallel to the rolling direction of the test specimen. The shear area ratio was determined at each location using equation (2), and the arithmetic mean of these ratios was calculated. This average value was then adopted as the shear area ratio of the test material. In conventional Cu-Ni-(Co)-Si copper alloy sheet materials, the shear area ratio in this test is approximately 50-60%. Test materials with a shear area ratio of 40% or less under both 4% and 10% clearance conditions can be judged to have a significant improvement in press punchability.

[0051] The results are shown in Tables 1A to 2B.

[0052] [Table 1A]

[0053] [Table 1B]

[0054] [Table 2A]

[0055] [Table 2B]

[0056] In the test materials of the present invention, which contained predetermined amounts of Mg and S and underwent hot rolling and solution treatment under conditions within the range specified by the present invention, all exhibited high strength with a tensile strength of 900 MPa or more in the rolling direction, an electrical conductivity of 40% IACS or more, and a shear surface ratio of 40% or less, demonstrating a significant improvement in press punchability.

[0057] In contrast, Comparative Examples No. 31, 32, and 46 had low Mg and S content, resulting in insufficient number density of Mg-S particles with an equivalent circular diameter of 0.5 μm or larger, and thus inadequate improvement in press punching properties (reduction of shear area ratio). Of these, No. 31 and 32 also had low Si content, resulting in insufficient formation of precipitates that contribute to strength, and thus low tensile strength. Numbers 33, 34, 36, and 40 had low sulfur content, resulting in insufficient number density of Mg-S particles with an equivalent circular diameter of 0.5 μm or larger, and thus inadequate improvement in press punchability (reduction of shear area ratio). Of these, number 34 had insufficient solid solution due to a short holding time during the solution treatment, resulting in low strength. It is thought that the strength-enhancing effect from fine Mg-S precipitates was not fully realized due to the very low sulfur content, resulting in insufficient strength. In No. 35, the solid solution behavior of Ni, Co, and Si differed from the norm due to the presence of the Mg-S phase. However, the heating rate during the solution treatment was slower than the range specified in the present invention, which likely resulted in insufficient solid solution of Ni, Co, and Si. Furthermore, the excessive S content led to the formation of many coarse Mg-S particles. For these reasons, the strength was reduced. In samples No. 37, 43, and 45, the total rolling rate in the hot rolling pass above 900°C was low, resulting in insufficient fragmentation of the Mg-S phase in the cast slab. This led to an excessively large average particle size of the Mg-S particles. Consequently, the strength was low. In particular, No. 43 suffered a significant decrease in strength due to the slow cooling rate during the solution treatment. Because No. 38 had a low Mg content, the strength-enhancing effect from the solid solution strengthening of Mg and the synergistic effect with (Ni,Co)2Si, Ni2Si, and Co2Si precipitates was not fully realized, resulting in low strength. Sample No. 39 had low conductivity due to its excessively high Mg content. Additionally, it contained many coarse Mg-S particles, resulting in low strength. No. 41 had a high sulfur content and a large rolling rate per pass during hot rolling at temperatures above 800°C, which caused cracking during hot rolling, so the experiment was stopped. In samples No. 42 and 44, the low sulfur content resulted in insufficient number density of Mg-S particles with an equivalent circular diameter of 0.5 μm or larger, leading to inadequate improvement in press punchability. Of these, No. 42 had low strength because the cooling rate during the solution treatment was slow, resulting in insufficient formation of precipitates that contribute to strength. In No. 44, the total content of Ni and Co was too low, which is thought to have resulted in insufficient formation of fine (Ni,Co)2Si precipitates that contribute to strength, thus resulting in low strength. No. 47 had insufficient solution treatment due to a low holding temperature during the solution treatment, resulting in low strength. Furthermore, because a method was not adopted to ensure a sufficient total rolling rate at temperatures above 900°C during hot rolling, the Mg-S phase in the cast slab was not sufficiently fragmented, and the effect of improving press punchability was not fully realized.

Claims

1. In mass%, the total of Ni and Co is 1.50-5.50%, Ni is 1.00% or more, Si is 0.50-1.20%, S is 0.001-0.20%, and Mg is 0.01-0.20%. Furthermore, one or more of Cr, Zn, Mn, B, P, Ag, Al, Zr, and Ti are included in a total amount of 0.01% to 0.5%, with Cr being 0.03% or less and Zn being 0.01%. The chemical composition contains Mn: 0.20% or less, B: 0.10% or less, P: 0.10% or less, Ag: 0.20% or less, Al: 0.20% or less, Zr: 0.20% or less, and Ti: 0.02% or less, with the remainder being Cu and unavoidable impurities. In a cross-section parallel to the rolling direction and the thickness direction, there are 300 Mg-S particles per mm with an equivalent circular diameter of 0.5 μm or more. ２ A copper alloy sheet material having the above number density, an average particle diameter of the Mg-S particles being 3.0 μm or less in terms of equivalent circular diameter, an electrical conductivity of 40% IACS or more, and a tensile strength in the rolling direction of 900 MPa or more.

2. The copper alloy plate material according to claim 1, wherein the total amount of Ni and Co in the aforementioned chemical composition is 2.00 to 4.00%.

3. The copper alloy sheet material according to claim 1 or 2, wherein the average grain size in a cross section perpendicular to the rolling direction, measured by a cutting method in accordance with JIS H0501-1986, is 1 to 20 μm.

4. In mass%, the total of Ni and Co is 1.50-5.50%, with Ni being 1.00% or more, Si 0.50-1.20%, S 0.001-0.20%, and Mg 0.01-0.20%. Furthermore, one or more of Cr, Zn, Mn, B, P, Ag, Al, Zr, and Ti are included in a total of 0.01% to 0.5%, with Cr being 0.03% or less and Zn 0. When manufacturing sheet metal from a cast slab with a chemical composition containing 0.1% or less of Mn, 0.20% or less, B, 0.10% or less, P, 0.10% or less, Ag, 0.20% or less, Al, 0.20% or less, Zr, and Ti in the range of 0.02% or less, with the remainder being Cu and unavoidable impurities, the process involves hot rolling, cold rolling, solution treatment, and aging treatment in the order described above. In the hot rolling process, the rolling rate per pass in all rolling passes performed at temperatures of 800°C or higher is 20% or less, and the total rolling rate in rolling passes performed at temperatures of 900°C or higher is 38% or more. In the solution treatment process, the average heating rate from 300°C to 800°C is set to 10°C / s or more, the temperature is maintained at 800-1020°C for 10 seconds or more, and the average cooling rate from 800°C to 500°C is set to 50°C / s or more. A method for manufacturing a copper alloy sheet according to any one of claims 1 to 3.

5. The method for manufacturing a copper alloy plate according to claim 4, wherein the temperature of the aging treatment is 400 to 550°C.

6. An electrical component using a copper alloy plate material according to any one of claims 1 to 3.

7. An electrical component having a press-punched portion, using a copper alloy sheet material according to any one of claims 1 to 3.

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