Cu-[Ni,Co]-Si copper alloy sheet material, conductive components, and heat dissipation components

Abstract

To provide a technology improving press blanking property while maintaining good bending workability and capable of obtaining a versatile, medium strength plate material in a Cu-[Ni, Co]-Si system alloy.SOLUTION: A copper alloy plate material includes, in mass%, a total of Ni and Co: 1.00-3.60%, Si: 0.20-2.00%, S: 0.005-0.10%, Ag: 0-1.00%, Al: 0-3.00%, B: 0-0.50%, Cr: 0-1.00%, Fe: 0-3.00%, Mg: 0-1.50%, Mn: 0-1.50%, P: 0-0.50%, Sn: 0-3.00%, Ti: 0-1.00%, Zn: 0-3.00%, Zr: 0-1.00%, with the balance essentially consisting of Cu. A number density of S-containing phase particles with long diameters of 2.0 μm or more and less than 5.0 μm is 50 particles / mm2 or more, and a number density of S-containing phase particles with long diameters of 5.0 μm or more is 50 particles / mm2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Cu-[Ni,Co]-Si copper alloy sheet material with improved press-punching and bendability, and to electrical and heat-dissipating components using the Cu-[Ni,Co]-Si copper alloy sheet material. Here, Cu-[Ni,Co]-Si copper alloy is a general term for Cu-Ni-Si copper alloys, Cu-Co-Si copper alloys, and Cu-Ni-Co-Si copper alloys. [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, as well as heat dissipation components in electronic equipment. When processing copper alloy sheets into conductive or heat dissipation components, press punching and bending processes are commonly used. Various studies have been conducted to improve the press punching and bending properties of Cu-[Ni,Co]-Si copper alloys.

[0003] Patent Document 1 discloses a technique for improving the strength and bendability of a Cu-[Ni,Co]-Si copper alloy by optimizing its texture. Materials with added sulfur are not shown, and there are no specific teachings regarding the improvement of press-punching properties. Patent Document 2 discloses a technique for improving the press-punching properties of a Cu-[Ni,Co]-Si copper alloy by increasing the number density of precipitates near the surface of the plate compared to the central part. In this document, materials with less burring and burrs on the cut surface are evaluated as having good press-punching properties (paragraph 0091). Materials with added sulfur are not shown. Patent document 3 discloses a technique for improving the strength and bendability of a Cu-[Ni,Co]-Si copper alloy by controlling the cooling rate during solution treatment. Materials with added sulfur are not shown, and there are no specific teachings regarding the improvement of press punchability.

[0004] Patent Document 4 discloses a technique for improving solder wettability and spring properties in a Cu-[Ni,Co]-Si copper alloy by optimizing the size and number density of precipitates using a three-stage aging treatment process. Materials with added sulfur are not shown, and there are no specific teachings regarding improvements in press punching properties or bendability. Patent document 5 discloses a technique for improving the strength and press-punching properties of a Cu-[Ni,Co]-Si copper alloy by adding sulfur and controlling the number density of Mg-S particles. There is no particular teaching regarding the improvement of bendability. Patent document 6 discloses a technique for improving the bendability and stress relaxation properties of a Cu-[Ni,Co]-Si copper alloy by optimizing the grain size and the degree of softening before and after pre-annealing. Materials with added sulfur are not shown, and there are no specific teachings regarding the improvement of press punching properties. [Prior art documents] [Patent Documents]

[0005] [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 Publication No. 2021-134376 [Patent Document 6] Japanese Patent Publication No. 2013-95977 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Recently, with the miniaturization, narrowing of the pitch of parts, and the advancement of mass production, the importance of suppressing wear on dies used in bending and other processes has increased. According to the technology in Patent Document 5, in Cu-[Ni,Co]-Si copper alloys, it was possible to significantly improve strength and press punchability by creating a microstructure in which Mg-S inclusions are dispersed. In other words, it was shown that the addition of S is extremely effective in improving press punchability. However, improving press punchability by adding S can sometimes reduce bendability, and further improvement was desired. Also, while the technology in Patent Document 5 results in a very high strength level, there are many applications such as conductive parts and heat dissipation parts that do not require such high strength. Excessive strength increases the manufacturing burden of parts and can lead to a lack of proper balance between required characteristics and manufacturing costs.

[0007] The present invention provides a technology for improving press-punching properties while maintaining good bendability in Cu-[Ni,Co]-Si copper alloys by using a sulfur addition method, and aims to provide a technology that can obtain sheet material with a versatile moderate strength level (tensile strength in the rolling direction of 500 MPa or more and less than 900 MPa). [Means for solving the problem]

[0008] To achieve the above objectives, the following inventions are disclosed herein.

[0009] [1] The chemical composition, in mass%, consists of Ni and Co total: 1.00-3.60%, Si: 0.20-2.00%, S: 0.005-0.10%, Ag: 0-1.00%, Al: 0-3.00%, B: 0-0.50%, Cr: 0-1.00%, Fe: 0-3.00%, Mg: 0-1.50%, Mn: 0-1.50%, P: 0-0.50%, Sn: 0-3.00%, Ti: 0-1.00%, Zn: 0-3.00%, Zr: 0-1.00%, with the remainder being Cu and unavoidable impurities, and the number density of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm is 50 particles / mm 2 The above results indicate that the number density of S-containing phase particles with a major axis of 5.0 μm or larger is 50 particles / mm². 2 The copper alloy sheet material is as follows: [2] The copper alloy sheet material described in [1] above, wherein the total content of Ag, Al, B, Cr, Fe, Mg, Mn, P, Sn, Ti, Zn, and Zr is 4.00% by mass or less. [3] The copper alloy sheet material described in [1] or [2] above, wherein the Ni content is 0.80 to 3.50 mass%. [4] A copper alloy sheet material as described in any of [1] to [3] above, having a tensile strength in the rolling direction of 500 MPa or more and less than 900 MPa. [5] A copper alloy plate material according to any of the above [1] to [4], wherein the conductivity is 40% IACS or higher. [6] A copper alloy sheet material as described in any of [1] to [5] above, wherein the ratio MBR / t of the minimum bending radius MBR to the sheet thickness t, as determined by a 90°W bending test in BW in accordance with the Japan Copper Alloy Association Technical Standard JCBA T307:2007, is 2.5 or less. [7] In a cantilever resonance fatigue test using a specimen with its longitudinal direction perpendicular to the rolling direction, the fatigue limit at a load stress of 300 MPa was 10 6 A copper alloy sheet material as described in any of the above [1] to [6], having a cycle of 100% or more. [8] A casting process to obtain a cast slab by pouring molten copper alloy having the chemical composition described in [1] above into a mold and allowing it to solidify, and then cooling it from 1100°C to 600°C under conditions where the average cooling rate is 65°C / s or more, A hot rolling process is performed in which the cast slab is heated to 880-1100°C, and then subjected to hot rolling with a total rolling ratio of 85% or more to obtain a hot-rolled sheet. A first intermediate cold rolling step in which the hot-rolled sheet is subjected to cold rolling with a total rolling ratio of 60% or more, An intermediate annealing step is performed on the sheet material obtained in the first intermediate cold rolling step, by heat treatment by holding it at 430 to 620°C for 0.1 to 20 hours. A final intermediate cold rolling step is performed on the sheet material obtained in the intermediate annealing step, in which cold rolling is performed to a total rolling ratio of 75% or more. A solution treatment step is performed on the sheet material obtained in the final intermediate cold rolling step, which is heat-treated by holding it at 800 to 1020°C for 10 to 600 seconds. An aging treatment step of subjecting the sheet material obtained in the solution treatment step to a heat treatment by holding it at 400 to 550°C for 1 to 24 hours, A final cold rolling step of subjecting the sheet material obtained in the aging treatment step to cold rolling with a total rolling reduction rate of 10 to 80%, A final heat treatment step of subjecting the sheet material obtained in the final cold rolling step to a heat treatment by holding it at 140 to 500°C for 5 to 3600 seconds, A method for manufacturing a copper alloy sheet material according to any one of [1] to [7] above, including these steps. [9] In the chemical composition of the copper alloy molten metal injected into the mold in the casting step, the total content of Ag, Al, B, Cr, Fe, Mg, Mn, P, Sn, Ti, Zn, Zr is 4.00% by mass or less. The method for manufacturing a copper alloy sheet material according to [8] above.

[10] In the chemical composition of the copper alloy molten metal injected into the mold in the casting step, the Ni content is 0.80 to 3.50% by mass. The method for manufacturing a copper alloy sheet material according to [8] or [9] above.

[11] An electrical component using the copper alloy sheet material according to any one of [1] to [7] above as a material.

[12] A heat dissipation component using the copper alloy sheet material according to any one of [1] to [7] above as a material.

[0010] In this specification, "sheet material" means a sheet-like metal material. A thin sheet-like metal material may also be called "foil", and such "foil" is also included in the "sheet material" referred to here. A long sheet-like metal material wound in a coil shape is also included in the "sheet material". Also, in this specification, the thickness of the sheet-like metal material is called "sheet thickness". Also, "sheet surface" means the surface perpendicular to the sheet thickness direction of the sheet material. The sheet surface may also be called the "rolling surface". In this specification, the notation "n1~n2" indicating a numerical range means "n1 or more and n2 or less". Here, n1 and n2 are numerical values satisfying n1 < n2.

[0011] In this specification, "press punching property" is an index evaluated by the area ratio of the "sheared surface" in the cut surface (cut edge) when punching is performed using a press die with appropriate clearance. In order to stabilize the quality in the punching process, it is important to extend the die life. On the cut surface of a metal plate formed by press punching, usually, a sheared surface and a fracture surface are formed (see Figure 1). When punching is performed with appropriate clearance, materials with a smaller proportion of the sheared surface are more advantageous for extending the die life. Therefore, in this specification, it is assumed that materials with a smaller proportion of the sheared surface in the cut surface when punching is performed under the same conditions have better press punching properties.

[0012] The "major axis length" is the maximum possible length of a line segment connecting two points on the contour line of a particle on the image plane (limited to those that do not extend outside the particle).

[0013] The total rolling ratio (%) in a certain rolling process is determined by the following formula (1). Total rolling ratio (%) = 100×(h0 - h1) / h0…(1) h0: Plate thickness (mm) before being subjected to the first pass of rolling in that rolling process h1: Plate thickness (mm) when the final rolling pass of that rolling process is completed

Advantages of the Invention

[0014] According to the present invention, a Cu-[Ni,Co]-Si-based copper alloy sheet having improved press punching properties while ensuring good bending workability has been realized, and a medium-strength level sheet with high versatility has been achieved.

Brief Description of the Drawings

[0015] [Figure 1] A diagram schematically showing the shape of the cut edge of a metal plate after press punching.

Embodiments for Carrying Out the Invention

[0016] [Chemical Composition] Hereinafter, "%" regarding the component composition means "mass%" unless otherwise specified.

[0017] This invention focuses on a Cu (copper)-[Ni,Co]-Si copper alloy containing at least one of Ni (nickel) and Co (cobalt), and also containing Si (silicon). Ni, Co, and Si form precipitates mainly composed of (Ni,Co)2Si, contributing to improved strength and conductivity. Furthermore, they also contribute to improved fatigue properties. The total content of Ni and Co can be set in the range of 1.00 to 3.60%, and the Si content can be set in the range of 0.20 to 2.00%. Within this range, an appropriate strength level, as described later, can be obtained. It is more preferable to include Ni in the range of 0.80 to 3.50%.

[0018] S (sulfur) is an important component element in this invention. Generally, in copper alloys, sulfur 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, sulfur 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 properties are improved by dispersing sulfur-containing phase particles in the material. Therefore, a predetermined amount of sulfur is included in the copper alloy as a source for generating sulfur-containing phase particles. As a result of various studies, it has been found that controlling the sulfur content in the range of S:0.005~0.10% is effective. If the sulfur content is too low, the amount of sulfur-containing phase particles generated will be insufficient, and the improvement effect on press punching properties will not be obtained. It is more preferable that the sulfur content be 0.006% or more, and even more preferable that it be 0.008% or more. If the sulfur content is excessive, the hot workability will worsen, and cracks will easily occur during hot rolling. Also, from the viewpoint of obtaining good bendability, a lower sulfur content is more effective. The sulfur content is preferably adjusted to a range of 0.05% or less, and more preferably to 0.03% or less.

[0019] As additional optional elements, one or more of the following can be included as needed: Ag (silver), Al (aluminum), B (boron), Cr (chromium), Fe (iron), Mg (magnesium), Mn (manganese), P (phosphorus), Sn (tin), Ti (titanium), Zn (zinc), and Zr (zirconium). The content of these optional elements can be set within the following ranges: Ag: 0-1.00%, Al: 0-3.00%, B: 0-0.50%, Cr: 0-1.00%, Fe: 0-3.00%, Mg: 0-1.50%, Mn: 0-1.50%, P: 0-0.50%, Sn: 0-3.00%, Ti: 0-1.00%, Zn: 0-3.00%, and Zr: 0-1.00%. The total content of these optional elements is preferably 4.00% by mass or less, from the viewpoint of a good balance of press-punchability, bendability, strength, and fatigue properties.

[0020] Considering economic and manufacturability, it is more preferable that the content of the above-mentioned arbitrary elements be within the range of Ag: 0-0.40%, Al: 0-2.00%, B: 0-0.20%, Cr: 0-0.70%, Fe: 0-2.00%, Mg: 0-1.20%, Mn: 0-1.20%, P: 0-0.20%, Sn: 0-2.00%, Ti: 0-0.80%, Zn: 0-2.00%, and Zr: 0-0.40%. In this case, it is more preferable that the total amount of these elements be 2.50 mass% or less.

[0021] Furthermore, the content of the above-mentioned optional elements may be controlled within the following ranges: Ag: 0-0.20%, Al: 0-1.00%, B: 0-0.10%, Cr: 0-0.30%, Fe: 0-1.00%, Mg: 0-0.60%, Mn: 0-0.60%, P: 0-0.10%, Sn: 0-1.00%, Ti: 0-0.40%, Zn: 0-1.00%, and Zr: 0-0.20%. In this case, the total content of these elements may be controlled to 1.20 mass% or less.

[0022] Other elements are also permissible to be included as long as they do not hinder the objective of the present invention (improving press-punching performance while maintaining good bendability). Specifically, the total content of elements other than Ni, Co, Si, S, Ag, Al, B, Cr, Fe, Mg, Mn, P, Sn, Ti, Zn, Zr, and Cu (hereinafter sometimes referred to as "non-specified elements") is preferably 0.50% or less, and may be controlled to 0.10% or less. The content of non-specified elements can be determined, for example, by quantifying substantially all elements that may be contained in the copper alloy sheet using the following analytical method.

[0023] (Example of a method for quantifying alloying elements) Oxygen (O) and nitrogen (N) are quantified using an oxygen-nitrogen-hydrogen analyzer (e.g., LECO ONH-836), hydrogen (H) is quantified using a hydrogen analyzer (e.g., Horiba EMGA-921), carbon (C) and sulfur (S) are quantified using a carbon-sulfur analyzer (e.g., LECO CS844), elements from the 2nd to 6th periods (excluding C, N, O, group 17 elements, group 18 elements, technetium (Tc), polonium (Po), and promethium (Pm)) are quantified using ICP-MS (e.g., Agilent 7900), and fluorine (F), chlorine (Cl), and bromine (Br) are quantified using a combustion-ion chromatography apparatus (e.g., Thermo Scientific DIONEX ICS-1600).

[0024] The chemical composition of the copper alloy sheet material according to the present invention can be specified as "one or more of Ni and Co, Si, S, the above arbitrary elements (including cases where the total is 0% by mass), the remainder being Cu and unavoidable impurities," or it can be specified as "one or more of Ni and Co, Si, S, the above arbitrary elements (including cases where the total is 0% by mass), the above non-specified elements (including cases where the total is 0%), the remainder being Cu."

[0025] [S-containing phase particles] In this specification, "S-containing phase particles" refer to second-phase particles present in a copper alloy in which the presence of sulfur (S) is observed by EDX (energy-dispersive X-ray fluorescence analysis). These particles include particles of S alone and compound particles containing S. Depending on the alloying elements present, compound particles are thought to be mainly composed of sulfides with metals that readily bond with S, such as MgS, MnS, and CrS.

[0026] According to the inventors' research, S-containing phase particles with a major axis particle size of 2.0 μm or more and less than 5.0 μm, as observed in the sample surface parallel to the plate surface, were found to be extremely effective in improving press punching performance. S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm are thought to act as the starting point for fracture during press working, which is thought to contribute to reducing the proportion of the shear surface. On the other hand, coarse S-containing phase particles with a major axis particle size of 5.0 μm or more are factors that reduce bendability and fatigue characteristics. Such coarse S particles are prone to becoming the starting point for cracks during bending.

[0027] Detailed analysis revealed that the number density of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm is 50 particles / mm³. 2 By implementing the above, it was found that the proportion of the shear surface in the cut formed when shearing (press punching) is performed with the appropriate clearance is significantly reduced. As a result, the life of the press die is extended, reducing die failures in mass production and stabilizing the quality of parts. In other words, the press punching performance is significantly improved. Increasing the number density of S-containing phase particles with a major diameter of 2.0 μm or more and less than 5.0 μm is difficult in terms of manufacturing. The number density of such S-containing phase particles is usually 1500 particles / mm 2 The following applies: 70-1200 pieces / mm 2 It may be controlled within this range. On the other hand, the number density of S-containing phase particles with a major axis of 5.0 μm or larger should be 50 particles / mm 2 By controlling the following parameters, good bendability is ensured, and at the same time, good fatigue properties are achieved. This microstructure can be realized by following the chemical composition described above and the manufacturing method described later.

[0028] (Method for Measuring Number Density of S-containing Phase Particles) The surface of the copper alloy sheet is polished to obtain a sample surface for EDX measurement. The sample surface is observed with a FE-SEM (field emission scanning electron microscope) equipped with an EDX device, and a measurement area with a size of, for example, 300 μm × 400 μm is randomly determined. In the FE-SEM observation, JSM-7,200F manufactured by JEOL Ltd. is used, and a secondary electron image is obtained under the conditions of an acceleration voltage of 15 kV and Irradiation current number 13 , WD (working distance) of 10 mm. For particles with a major axis of 1 μm or more in this secondary electron image, point analysis of EDX is performed to determine whether these particles are S-containing phase particles. The major axis is the length of the longest line segment that can be drawn within the particle (limited to those that do not extend outside the contour of the particle). In the point analysis of the EDX, those with an analysis concentration of S of 0.5 mass% or more are treated as S-containing phase particles. For the obtained secondary electron image, the number of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm and the number of S-containing phase particles with a major axis of 5.0 μm or more existing in the measurement area are counted. For particles whose part is cut by the boundary of the measurement area, the boundary part is regarded as a part of the contour of the particle, and the major axis is measured in the particle part within the measurement area. This operation is performed for a plurality of non-overlapping measurement areas, and the total number of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm and the total number of S-containing phase particles with a major axis of 5.0 μm or more counted are divided by the total area of the measurement area (mm 2 ) respectively, so as to obtain the number density (number / mm 2The number density is calculated. This number density calculation operation is performed for three or more non-overlapping measurement areas. The arithmetic mean of the number density values ​​of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm obtained in each measurement area is calculated and adopted as the number density of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm in the plate material. Similarly, the arithmetic mean of the number density values ​​of S-containing phase particles with a major axis of 5.0 μm or more obtained in each measurement area is calculated and adopted as the number density of S-containing phase particles with a major axis of 5.0 μm or more in the plate material. Note that the measurement of the major axis of each S-containing phase particle and the counting of the number of particles can be performed using image processing software (e.g., ImageJ).

[0029] [Tensile strength, electrical conductivity] The required strength level for copper alloy sheet materials used in electrical components such as connectors and heat dissipation components in electronic equipment varies depending on the application, and excessively high strength increases the manufacturing burden of the parts, leading to increased manufacturing costs. Patent document 5 describes an invention that improves press punchability using Mg-S particles, targeting high-strength sheet materials with a tensile strength of 900 MPa or more in the rolling direction. In the present invention, it is possible to improve press punchability even in Cu-[Ni,Co]-Si copper alloy sheet materials with a moderate strength level, for example, a tensile strength of 500 MPa or more and less than 900 MPa in the rolling direction, while also ensuring good bendability. Furthermore, an conductivity of 40% IACS or more can be obtained at the same time. The conductivity of copper alloy sheet materials according to the present invention is usually in the range of 70% IACS or less.

[0030] Ni, Co, and Si increase the strength of copper alloy sheets through the formation of precipitates. Mg and S also contribute to increasing the strength of copper alloy sheets through the formation of Mg-S particles. Furthermore, in the copper alloy sheet manufacturing method of the present invention, described later, the amount of precipitate formation can be adjusted by the aging treatment time, and the final strength of the sheet can be adjusted by the total rolling ratio of the finish cold rolling. In the present invention, by appropriately combining these elemental technologies that affect strength, a moderate strength level of 500 MPa to less than 900 MPa is achieved while ensuring a sufficient number density of S-containing phase particles with a major diameter of 2.0 μm or more and less than 5.0 μm.

[0031] [Bendability] Bending is often involved when processing materials into electrical components and the like. Considering the applications of Cu-[Ni,Co]-Si copper alloy sheets, in order to obtain high reliability when processing them into electrical components and heat dissipation components, it is desirable that the material has bendability such that the ratio of the minimum bending radius MBR to the sheet thickness t, MBR / t, is 2.5 or less, as measured by a BW (Bad Way) bending test according to the Japan Copper Association Technical Standard JCBA T307:2007. It is more preferable that the MBR / t in BW be 2.0 or less, and even more preferable that it be 1.5 or less. It is also possible to obtain a material with an MBR / t in BW of 0.0 (no cracking in tight bending). BW (Bad Way) means that the bending axis is in the direction parallel to the rolling direction.

[0032] Furthermore, JCBA T307:2007 states that "This standard applies to the evaluation of the bendability of copper and copper alloy sheets and strips with a thickness of 0.1 mm or more and 0.8 mm or less." According to the inventors' studies, it was confirmed that even for Cu-[Ni,Co]-Si copper alloy sheets with a thickness of less than 0.1 mm, the bendability can be evaluated by the W bending test using the method described in the said standard. Therefore, in this invention, the W bending test method using BW as shown in JCBA T307:2007 is extended to cases where the sheet thickness is less than 0.1 mm (for example, 0.02 mm or more and less than 0.1 mm) and applied as is.

[0033] [Fatigue characteristics] Since electrical components such as connectors are sometimes subjected to repeated stress, using sheet materials with good fatigue characteristics is advantageous for improving the reliability of these components. It was found that in Cu-[Ni,Co]-Si copper alloy sheet materials with dispersed sulfur-containing phase particles, good fatigue characteristics can be obtained by adjusting the total content of Ni and Co and the Si content to the appropriate range mentioned above to fully exhibit precipitation strengthening, and by controlling the number density of coarse sulfur-containing phase particles to a low level. Considering the applications of Cu-[Ni,Co]-Si copper alloy sheet materials, in a cantilever resonance fatigue test using a specimen with the longitudinal direction perpendicular to the rolling direction (TD), the fatigue limit at a load stress of 300 MPa was 1.0 × 10⁻⁶. 6 A cycle count of over one million cycles is desirable. "Fatigue" can be determined by monitoring the decrease in resonant frequency associated with a decrease in Young's modulus.

[0034] [Manufacturing method] The copper alloy sheet material described above can be manufactured, for example, by the following manufacturing process. Casting → Hot rolling → First intermediate cold rolling → Intermediate annealing → Final intermediate cold rolling → Solution treatment → Aging treatment → Finish cold rolling → Finish heat treatment Although not mentioned in the above process, surface machining is performed as needed after hot working, and pickling, polishing, or further degreasing is performed as needed after each heat treatment. The following describes each of the above processes.

[0035] [casting] The copper alloy molten metal having the chemical composition described above is poured into a mold at a temperature of 1180-1420°C for casting. It is desirable to hold the copper alloy molten metal at the above temperature range for, for example, 2-8 hours before casting. If the molten metal temperature before casting falls below 1180°C, a large amount of coarse sulfur-containing phase (single sulfur phase or sulfur compounds) tends to form in the cast slab, which reduces bendability and fatigue properties. Raising the molten metal temperature before casting is advantageous for homogenizing the molten metal, but if the temperature is too high it becomes uneconomical, so it is preferable to keep it in the range of 1420°C or lower. As for the casting method, general methods such as continuous casting, semi-continuous casting, and ingot casting can be applied, but in this invention, controlling the cooling rate is important. Specifically, after pouring the copper alloy molten metal at the above temperature into the mold and allowing it to solidify, it is cooled under conditions where the average cooling rate from 1100°C to 600°C is 65°C / s or higher. Therefore, casting equipment with sufficient cooling capacity should be used. If the average cooling rate from 1100°C to 600°C falls below 65°C / s, a large amount of coarse sulfur-containing phase tends to form in the resulting slab, which reduces bendability and fatigue properties. However, excessively high cooling rates place a heavy burden on the equipment and are uneconomical. It is preferable to adjust the average cooling rate from 1100°C to 600°C to a range of, for example, 230°C / s or less.

[0036] In the melting of copper alloys, sulfur (S) 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, the present invention requires strict control of the S content so that S within the predetermined content range described above is incorporated into the copper alloy. For example, a pre-prepared Cu-S matrix alloy can be used to add S.

[0037] [Hot rolling] After heating the cast slab to 880-1100°C, a hot-rolled sheet is obtained by hot-rolling the slab to a total rolling ratio of 85% or more. From the viewpoint of promoting the homogenization of the structure, it is more preferable to heat the cast slab to 950-1100°C. The heating and holding time of the cast slab is preferably set in the range of 0.5-12 hours. In order to obtain the desired metallic structure in which sulfur-containing phase particles are dispersed, it is effective to break up the coarse sulfur-containing phase during the hot-rolling process. For this purpose, the total rolling ratio in hot rolling is set to 85% or more. The upper limit of the total rolling ratio in hot rolling can be set according to the capacity of the hot-rolling mill. Usually, it is sufficient to set it in the range of 95% or less.

[0038] [First intermediate cold rolling, intermediate annealing, final intermediate cold rolling] In this invention, a process is employed in which multiple cold rolling steps, interspersed with intermediate annealing, are performed before the solution treatment. The first cold rolling step performed after hot rolling is called the "first intermediate cold rolling step," and the final cold rolling step performed before the solution treatment is called the "final intermediate cold rolling step." For the first intermediate cold rolling, it is desirable to achieve a total rolling ratio of 60% or more. For the final intermediate cold rolling, it is desirable to achieve a total rolling ratio of 75% or more in order to introduce strain that promotes recrystallization in the subsequent solution treatment. In each of these cold rolling processes, the upper limit of the total rolling ratio can be set according to the capacity of the rolling mill. It is usually sufficient to set it within a range of 99% or less. Intermediate annealing, performed between the first and final intermediate cold rolling processes, is carried out under conditions of holding the material at 430-620°C for 0.1-20 hours. If the temperature is too low or the holding time is too short, the strain may not be sufficiently removed, leading to problems such as cracking during subsequent cold rolling. If the temperature is too high or the holding time is too long, the material strength will decrease. If necessary, one or more intermediate cold rolling and intermediate annealing steps may be inserted between the above-mentioned intermediate annealing and the above-mentioned final intermediate cold rolling. In that case, the same conditions as the above-mentioned intermediate treatment may be used for the inserted intermediate annealing, and the same conditions as the above-mentioned first intermediate cold rolling may be used for the inserted intermediate cold rolling.

[0039] [Solution treatment, aging treatment] Next, a solution treatment is performed under conditions of holding at 800-1020°C for 10-600 seconds. After that, an aging treatment is performed under conditions of holding at 400-550°C for 1-24 hours.

[0040] [Finishing cold rolling, finishing heat treatment] After aging treatment, finish cold rolling is performed under conditions of a total rolling ratio of 10-80%. Subsequently, finish heat treatment is performed with the aim of reducing residual stress, improving bendability, and improving stress relaxation resistance by reducing voids and dislocations on the slip surface. For the finish heat treatment, heating conditions that do not cause recrystallization should be adopted within the range of holding temperature 140-500°C and holding time 5-3600 seconds. The final plate thickness can be, for example, in the range of 0.02-0.40 mm.

[0041] [Electrical components and heat dissipation components] The Cu-[Ni,Co]-Si copper alloy sheet material obtained as described above exhibits excellent press-punching properties and good bendability, and its strength can be adjusted to a moderate level. Therefore, it can be processed into electrical components such as connectors and heat dissipation components for electronic equipment using a processing process that improves mold life and reduces manufacturing costs by avoiding excessive manufacturing load. Furthermore, the resulting parts also exhibit good fatigue characteristics. [Examples]

[0042] Copper alloys with the chemical compositions shown in Tables 1 to 4 were melted and cast using a vertical semi-continuous casting machine. The gas phase space in contact with the molten metal during casting was an atmospheric environment. Cu-20.1 mass%S alloy was used for sulfur addition. The molten metal temperature before casting and the holding time of the molten metal at that temperature are shown in Tables 1 to 4. Thermocouples were placed inside the mold, and the temperature of the cast slab during cooling was monitored by incorporating the thermocouples into the solidified slab after the molten metal was poured in, and the average cooling rate from 1100°C to 600°C was determined. The cooling rate of the cast slab was controlled by the amount of water used to cool the mold and the amount of water used to cool the cast slab after it was removed from the mold. Furthermore, the analytical samples taken from the cast slabs were analyzed for the elements listed in Tables 1-4 using the method described in "Examples of Quantitative Methods for Alloy Elements" above.

[0043] The obtained slabs were held at the temperatures shown in Tables 1 to 4 for 1 to 10 hours, then removed from the furnace and subjected to hot rolling with the total rolling ratios shown in Tables 1 to 4. After hot rolling, the surface oxide layer was removed by mechanical polishing (surface grinding). Subsequently, with the exception of some examples (No. 51 and 54), the first intermediate cold rolling, intermediate annealing, final intermediate cold rolling, solution treatment, aging treatment, finish cold rolling, and finish heat treatment were performed in the order shown in Tables 1 to 4. Intermediate annealing and final intermediate cold rolling were omitted in No. 51 and 54. The total rolling ratio (%) values ​​for each rolling process listed in the tables have been rounded to the nearest whole number. In each case, sheet metal obtained by finishing heat treatment was used as the test material for the following investigation. The thickness of the test material was 0.2 mm in each case.

[0044] (Number density of S-containing phase particles) Following the aforementioned "Method for Measuring the Number Density of S-Containing Phase Particles," the test surface parallel to the plate surface of the test material was observed using an FE-SEM (JSM-7200F, JEOL Ltd.) equipped with an EDX device. S-containing phase particles were confirmed by EDX analysis, and secondary electron images were captured. The sample surface was prepared by mechanical polishing using #1000 grit abrasive paper, followed by electrolytic polishing. Electrolytic polishing was performed at 15V for 20 seconds. Each measurement area was a rectangular area of ​​300 μm × 400 μm, and measurements were taken at three non-overlapping measurement areas. The total area of ​​the measurement areas was 0.36 mm². 2 The measurement of the major axis of S-containing phase particles and the counting of the number of particles whose major axis falls within a predetermined range were performed using the image analysis software ImageJ (National Institutes of Health (NIH), Version 1.52a) in the following manner.

[0045] First, in the secondary electron image shown above, particles that were determined not to be S-containing phase particles were blacked out. Then, the analysis conditions using the software were set by sequentially selecting Analyze and Set Scale, and on the "Set Scale" screen that appeared, the number of pixels representing the scale bar length of the captured FE-SEM image was measured and entered into Distance in pixels. Next, the scale bar length (μm) was entered into Known distance, the Pixel aspect ratio was set to 1.0, and the Unit of length was set to μm, so that the software could recognize the size of the precipitate. After that, on the "Resize Image Canvas" screen, the Width was set to 1280 pixels, the Height to 950 pixels, and the Position to Top-Center, and the image of the FE-SEM image portion excluding the scale bar was displayed. After setting the scale and removing the scale bar display, the "Threshold" screen, accessed by sequentially selecting Image, Adjust, and Threshold, inverted the brightness so that the pixel with the lowest brightness among all pixels had a brightness of 255 and the pixel with the highest brightness had a brightness of 0. The threshold was then set to a value that brought the percentage of pixels below that value to 5% of all pixels as close to 5% as possible, and the areas containing precipitate particles were binarized and identified. Subsequently, in the "Analyze Particles" screen of the same software, the area of ​​a single independent precipitate region was 0.1 μm². 2 To exclude particles below a certain value, the Size was set to "0.10-Infinity". Furthermore, the Circularity was set to 0.00-1.00, and the Fit Ellipse item was checked on the "Set Measurements" screen. Particle analysis was then performed, and the number of S-containing phase particles with a major axis (displayed under the item name "Major") of 2.0 μm or more and less than 5.0 μm, and S-containing phase particles with a major axis of 5.0 μm or more were determined for that field of view.

[0046] (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.

[0047] (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 viewpoint of ensuring bendability and high reliability in electrically conductive components such as connectors, specimens with a tensile strength in the rolling direction of 500 MPa or more and less than 900 MPa were judged to be acceptable.

[0048] (Bendability) In accordance with the Japan Copper Association (JCBA) technical standard JCBA T307:2007, the ratio MBR / t (minimum bending radius MBR to plate thickness t) was determined by a W bending test on a BW (Ballwood) plate to prevent cracking. The test specimen size was 30 mm in the direction perpendicular to rolling on the plate surface and 10 mm in the rolling direction (width of the specimen). The presence or absence of cracks on the bent surface was determined according to JCBA T307:2007. For samples judged as "large wrinkles" based on the visual inspection of the bent surface, a sample was prepared by cutting the deepest wrinkled part perpendicular to the bending axis, and the polished cross-section was observed with an optical microscope to check whether cracks had occurred that had propagated into the plate thickness. If no such cracks were found, it was judged as "no cracks observed". Considering the intended use of the material of this invention, samples with an MBR / t of 2.5 or less in this test were judged as acceptable.

[0049] (Press punching capability) A test was conducted in which 5mm x 5mm square test pieces were punched out of a 0.2mm thick sheet metal using a press die. The clearance was set to two levels: 5% 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 perpendicular to the rolling direction. Figure 1 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 when the cut is viewed in the direction normal to the cut (in this case, the direction perpendicular to the rolling direction and the sheet metal thickness direction) 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 1 was determined, and the ratio of the shear surface to the fracture surface was calculated. For the sake of measurement, the length including the burr portion indicated by symbol B in Figure 1 was considered as the length of the fracture surface, and the "shear area ratio" was calculated using the following formula (2). In this press punching test, the height of the burr is usually less than 1 μm, so including the burr in the length of the fracture surface does not hinder the evaluation of the press punching performance. Shear area ratio (%) = 100 × A / (A + B) …(2) This measurement was performed at 10 locations within the cut surface (end face) parallel to the rolling direction of the test specimen. The shear area ratio was calculated at each location using equation (2), and the arithmetic mean of these ratios was adopted as the shear area ratio of the test material. In this test, if the shear area ratio at a 5% clearance is 40% or less, and the shear area ratio at a 10% clearance is 30% or less, it can be judged that a significant improvement in press punchability is observed compared to conventional Cu-[Ni,Co]-Si copper alloy sheet material. Therefore, specimens with a shear area ratio of 40% or less at a 5% clearance and a shear area ratio of 30% or less at a 10% clearance were judged to be acceptable.

[0050] (Fatigue characteristics) A 3mm wide, 20mm long specimen was cut from the material, with the width direction being the rolling direction (LD) and the length direction being perpendicular to the rolling direction (TD). A cantilever resonance fatigue test was performed using a fatigue testing apparatus (RF-RT, manufactured by Nippon Techno Plus Co., Ltd.) at a load stress of 300 MPa. The change in resonance frequency was monitored during the test, and the number of cycles at which the resonance frequency reached 98% of the initial value was defined as the fatigue limit of the specimen. This procedure was performed on five specimens prepared from one material, and the average of their fatigue limits was adopted as the fatigue limit of the material in question. 6 We judged items that met the cycle requirement to be acceptable. The results are shown in Tables 1 to 4.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] In the test materials of the present invention, in which a predetermined amount of sulfur was included and the number density of sulfur-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm was controlled to the above-mentioned appropriate range, a remarkable improvement in press punchability was obtained while maintaining good bendability, and good fatigue characteristics were achieved at a moderate strength level (tensile strength in the rolling direction of 500 MPa or more and less than 900 MPa). The electrical conductivity was also good, at 40% IACS or higher.

[0056] In contrast, in comparative example No. 41, the high sulfur content prevented a sufficient reduction in the number density of sulfur-containing phase particles with a major axis of 5.0 μm or larger, resulting in poor bendability and fatigue characteristics. In samples No. 42, 43, 44, 45, 46, 51, 52, 53, 54, and 55, the low sulfur content resulted in a low number density of sulfur-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm, leading to insufficient improvement in press punching properties. Of these, samples No. 45 and 53 had a high total content of Ni and Co, resulting in high strength levels, poor bendability, and poor conductivity. In No. 47, the low cooling rate during casting resulted in a high number density of sulfur-containing phase particles with a major diameter of 5.0 μm or more, leading to poor bendability and fatigue characteristics. In No. 48, the low molten metal temperature during casting prevented sufficient solid dissolution of sulfur (S), resulting in a high number density of S-containing phase particles with a major axis of 5.0 μm or larger, leading to poor bendability and fatigue properties. In No. 49, the low total content of Ni and Co resulted in insufficient precipitation strengthening, leading to a low strength level and poor fatigue properties. In No. 50, the low Si content resulted in insufficient precipitation strengthening, leading to a low strength level and poor fatigue properties.

Claims

1. The chemical composition, in mass%, consists of Ni: 0.80–3.50%, total Ni and Co: 1.00–3.60%, Si: 0.20–2.00%, S: 0.005–0.10%, Ag: 0–1.00%, Al: 0–3.00%, B: 0–0.50%, Cr: 0–1.00%, Fe: 0–3.00%, Mg: 0–1.50%, Mn: 0–1.50%, P: 0–0.50%, Sn: 0–3.00%, Ti: 0–1.00%, Zn: 0–3.00%, Zr: 0–1.00%, with the remainder being Cu and unavoidable impurities. The number density of S-containing phase particles with a major axis of 2.0 μm or more and less than 5.0 μm is 50 particles / mm². ２ The above results indicate that the number density of S-containing phase particles with a major axis of 5.0 μm or larger is 50 particles / mm². ２ The copper alloy sheet material is as follows:

2. The copper alloy sheet material according to claim 1, wherein the total content of Ag, Al, B, Cr, Fe, Mg, Mn, P, Sn, Ti, Zn, and Zr is 4.00% by mass or less.

3. The copper alloy sheet material according to claim 1, wherein the tensile strength in the rolling direction is 500 MPa or more and less than 900 MPa.

4. The copper alloy plate material according to claim 1, wherein the conductivity is 40% IACS or higher.

5. The copper alloy sheet material according to claim 1, wherein the ratio MBR / t of the minimum bending radius MBR (where no crack occurs) to the sheet thickness t, as determined by a 90° W bending test in B.W. in accordance with the Japan Copper Alloy Association Technical Standard JCBA T307:2007, is 2.5 or less.

6. In a cantilever resonance fatigue test using a specimen with its longitudinal direction perpendicular to the rolling direction, the fatigue limit at a load stress of 300 MPa was 10 ６ The copper alloy plate material according to claim 1, which is more than 10

7. An electrical component using a copper alloy plate material as described in any one of claims 1 to 6.

8. A heat dissipation component made using a copper alloy plate material as described in any one of claims 1 to 6.

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