Cu-Ni-Al copper alloy plate, manufacturing method thereof and conductive spring component

Abstract

The present invention relates to a copper alloy plate having the following chemical composition: in mass %, Ni: 10.0-30.0%, Al: 1.00-6.50%, Ag: 0-0.50%, B: 0-0.1%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, Mg: 0-2.0%, Mn: 0-2.0%, P: 0-0.2%, Si: 0-2.0%, Sn: 0-2.0%, Ti: 0-2.0%, Zn: 0-2.0%, Zr: 0-0.3%, the balance being Cu and unavoidable impurities, and satisfying Ni / Al≤9.0, and using X Cu Cu concentration in the precipitate represented by (mass %) = [Cu / (Cu+Ni+Al)] × 100 Cu The content is 15 to 50% by mass, and the Vickers hardness is 300 HV or higher.

Description

Technical Field

[0001] The present invention relates to a Cu-Ni-Al alloy sheet material having excellent performance in suppressing the generation of smut during etching, a method for producing the same, and a conductive spring member using the sheet material. Background Art

[0002] Cu-Ni-Al alloys are characterized by their high strength due to Ni-Al precipitates. Furthermore, they exhibit a metallic appearance with a light copper hue. These alloys are used as conductive spring components for lead frames, connectors, and other applications, as well as non-magnetic, high-strength components.

[0003] With the miniaturization and high density of electronic devices, the demand for miniaturization of conductive spring components used therein has also increased. In order to develop the miniaturization of conductive spring components, further high strength is required. In Cu-Ni-Al copper alloys, a large amount of precipitates need to be formed in order to achieve high strength. On the other hand, small conductive spring components that require high dimensional accuracy are mostly made through an etching process. When etching a copper alloy containing a large amount of precipitates, particles from the precipitates that are difficult to dissolve in the etching solution form stains (residual attachments to the material surface), which become the main cause of the reduction in etching properties and the contamination of components. In addition, in order to obtain raw materials for thin-walled components, it is easy to cause an increase in the number of passes and rolling load in the final cold rolling process, thereby reducing productivity and increasing the risk of reduced yield caused by edge cutting, breakage, etc.

[0004] Various studies have been conducted so far to improve other properties while effectively utilizing the high strength properties of Cu-Ni-Al based copper alloys.

[0005] For example, Patent Document 1 discloses a technique for subjecting a Cu-Ni-Al copper alloy containing a specified amount of Si to solution treatment at 700-1020°C and aging at 400-650°C, thereby causing Si-containing γ' phases to precipitate with an average grain size of 100 nm or less. This results in a material exhibiting high strength, excellent workability, and high electrical conductivity. However, Patent Document 1 does not disclose any effective technique for suppressing the occurrence of stains.

[0006] Patent Document 2 discloses a technique for producing a sheet material with an excellent "strength-bending workability balance" and excellent discoloration resistance from a Cu-Ni-Al copper alloy. In its manufacturing process, a method is adopted in which a material that has undergone solid solution treatment is subjected to cold rolling deformation as needed, followed by a first aging treatment in a higher temperature range and a second aging treatment in a conventional temperature range. This two-stage aging treatment makes it difficult to produce discontinuous precipitation of grain boundary reaction type, and fully induces the intragranular precipitation of fine second phase particles that contribute to improving strength, thereby achieving an excellent strength-bending workability balance. However, Patent Document 2 does not disclose a technique effective for suppressing the occurrence of stains.

[0007] Patent Document 3 discloses a technology for producing a sheet material with a high Young's modulus in a Cu-Ni-Al copper alloy. Specifically, cold rolling with intermediate annealing is performed under specific conditions, followed by solution treatment at a slow temperature increase rate, and final cold rolling is performed at a low reduction ratio, followed by aging treatment. This results in a specific crystal orientation and achieves a high Young's modulus. However, Patent Document 3 does not disclose any effective technology for suppressing the occurrence of stains.

[0008] Patent Document 4 discloses a technology for producing a sheet material with excellent etching properties in a Cu-Ni-Al copper alloy. The manufacturing process employs the following method: rapid heating during solution treatment, cold rolling after aging treatment, and final heat treatment at a controlled rate of temperature increase. This results in a microstructure with a high KAM value, resulting in a smooth etched surface. Furthermore, Patent Document 4 teaches that reducing the formation of coarse precipitates is also effective in improving etching properties. However, Patent Document 4 does not teach effective techniques for suppressing the formation of stains.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication No. 2012 / 081573

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-50923

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-79436

[0014] Patent Document 4: Japanese Patent Application Publication No. 2019-2042 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] Cu-Ni-Al alloys are useful for conductive spring components such as connectors, but effective solutions for suppressing smut during etching have yet to be found. The present invention aims to provide a Cu-Ni-Al alloy sheet material that exhibits high strength and significantly reduces smut during etching compared to conventional methods. Furthermore, a manufacturing process is disclosed that is effective in reducing the load during final cold rolling when producing high-strength thin sheet material.

[0017] Means for solving problems

[0018] Ni-Al precipitates contribute to the high strength of Cu-Ni-Al copper alloys and are primarily composed of intermetallic compounds of Ni and Al. However, Cu is also present in these precipitate particles. The present inventors have discovered that increasing the Cu concentration in the Ni-Al precipitates significantly suppresses the generation of stains during etching, leading to the completion of the present invention.

[0019] Specifically, the above object is achieved by the following copper alloy plate, which has the following chemical composition: in mass%, Ni: 10.0-30.0%, Al: 1.00-6.50%, Ag: 0-0.50%, B: 0-0.10%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, M The Cu concentration X in the precipitate is determined by the following formula (2) based on the analysis of the residue obtained by electrolytic extraction in a 7 mol / L aqueous phosphoric acid solution, and the balance is composed of Cu and unavoidable impurities. Cu The content is 15 to 50% by mass, and the Vickers hardness is 300 HV or higher.

[0020] Ni / Al≤9.0…(1)

[0021] In the formula (1), the element content expressed in mass % is substituted in place of the element symbol.

[0022] X Cu (mass %)=[Cu / (Cu+Ni+Al)]×100…(2)

[0023] Here, the value of the mass ratio of the element in the residue is substituted in place of the element symbol in formula (2).

[0024] In the above-mentioned plate material, the number density of fine precipitate particles with a major diameter of 5 to 50 nm in an observation plane parallel to the plate surface is preferably 1.0×10 7 Pieces / mm 2 The full width at half maximum of the X-ray diffraction peak of the {220} crystal plane in the plate surface is preferably 0.5° or more. The number density of coarse precipitate particles with a major diameter of 1.0 μm or more in the observation plane parallel to the plate surface is preferably 3.0×10 4 Pieces / mm 2 the following.

[0025] As a method for manufacturing the above-mentioned plate, a method for manufacturing a copper alloy plate is provided, which obtains a plate having a Vickers hardness of 300 HV or higher by a manufacturing process comprising the following steps in sequence:

[0026] The step of heating the slab having the above chemical composition at 1000-1150° C. (slab heating step),

[0027] A process of hot rolling with the rolling temperature in the final rolling pass being 800°C or higher (hot rolling process),

[0028] A cold rolling process with a rolling reduction of 80% or more (cold rolling process) is performed.

[0029] A step (solution treatment step) of cooling the steel at 950-1100°C for 30-360 seconds and then cooling the steel from 900°C to 700°C at an average cooling rate of 110-150°C / s.

[0030] A step of cooling the steel sheet at 400 to 650°C for 0.5 to 75 hours and at an average cooling rate of 40 to 80°C / h from 400 to 300°C (aging treatment step).

[0031] A cold rolling process with a rolling reduction of 30% or more (final cold rolling process) is performed.

[0032] A step (final heat treatment step) in which the steel is cooled at an average cooling rate of 50 to 90°C / s from 400°C to 300°C after holding at 400 to 700°C for 10 to 600 seconds. In this case, it is preferable that the steel be produced in a manufacturing process in which the M value of the following formula (4), which represents the relationship between the Vickers hardness H1 (HV) after the aging treatment step, the Vickers hardness H2 (HV) after the final cold rolling step, and the Vickers hardness H3 (HV) after the final heat treatment step, is not less than -0.2 and not more than 1.2, thereby obtaining a steel sheet having a Vickers hardness H3 of not less than 300 HV.

[0033] M=(H2-H1) / (H3-H2)…(4)

[0034] Furthermore, the present invention provides a conductive spring member using the copper alloy sheet material.

[0035] In this specification, "plate surface" refers to the surface perpendicular to the thickness direction of the plate. "Plate surface" is sometimes also called "rolled surface". The Vickers hardness can be the Vickers hardness of the plate surface measured in accordance with JIS Z2244: 2009. The full width at half maximum of the X-ray diffraction peak of the {220} crystal plane in the plate surface is measured by measuring the X-ray diffraction pattern of the plate surface under the conditions of Cu-Kα radiation, tube voltage 30kV, and tube current 10mA, and calculating after removing Kα2 radiation using X-ray diffraction pattern analysis software. The "long diameter" of the particle is defined as the diameter (nm or μm) of the smallest circle surrounding the particle. The "number density of fine precipitate particles with a long diameter of 5 to 50 nm" and the "number density of coarse precipitate particles with a long diameter of 1.0 μm or more" can be calculated as follows.

[0036] [Method for calculating the number density of fine precipitate particles]

[0037] For the observation surface obtained by electrolytically polishing the plate surface under the following electrolytic polishing conditions and then ultrasonically cleaning it in ethanol for 20 minutes, FE-SEM (field emission scanning electron microscope) was used to observe at a magnification of 100,000 times, and an observation field was randomly set in which part or all of the particles with a long diameter of more than 1.0 μm were not included in the field of view. For this observation field, the number of precipitate particles with a long diameter of 5 to 50 nm in the particles where the entire outline of the particles can be seen was counted. This operation was performed for more than 10 observation fields in which the areas were not repeated, and the total number of the above counts in all the observed fields was N. 合计 The value obtained by dividing by the total area of ​​the observation field is converted into per 1mm 2 The number of particles is taken as the number density of fine precipitate particles (particles / mm 2 ).

[0038] (Electrolytic grinding conditions)

[0039] Electrolyte: Distilled water, phosphoric acid, ethanol, and 2-propanol mixed in a volume ratio of 10:5:5:1

[0040] ·Liquid temperature: 20℃

[0041] Voltage: 15V

[0042] Electrolysis time: 20 seconds

[0043] [Method for calculating the number density of coarse precipitate particles]

[0044] The plate surface was electrolytically polished under the following electrolytic polishing conditions to dissolve only the Cu base, thereby exposing the precipitate particles. The plate surface was then ultrasonically cleaned in ethanol for 20 minutes. The obtained observation surface was observed using a FE-SEM (field emission scanning electron microscope). The total number of precipitate particles with a major diameter of 1.0 μm or more observed on the FE-SEM image was divided by the total observation area (mm). 2 ) and the obtained value is set as the particle number density of coarse precipitate particles (particles / mm 2 The total observation area is set to 0.1 mm using multiple observation fields that are randomly set and do not repeat. 2 Precipitated particles that partially overflowed from the observation field were counted if the major diameter of the portion appearing within the observation field was 1.0 μm or more.

[0045] (Electrolytic grinding conditions)

[0046] Electrolyte: Distilled water, phosphoric acid, ethanol, and 2-propanol mixed in a volume ratio of 10:5:5:1

[0047] ·Liquid temperature: 20℃

[0048] Voltage: 15V

[0049] Electrolysis time: 20 seconds

[0050] The rolling reduction from a certain plate thickness t0 (mm) to a certain plate thickness t1 (mm) is calculated using the following formula (3).

[0051] Rolling rate (%) = [(t0-t1) / t0] × 100 (3)

[0052] Effects of the Invention

[0053] According to the present invention, a sheet material can be provided that has a very high strength level and significantly reduces the generation of stains during etching compared to conventional methods, within a composition range of a Cu-Ni-Al alloy exhibiting a white metallic appearance. Furthermore, in the final cold rolling process to obtain such a high-strength thin sheet material, the phenomenon of work softening can be utilized to reduce the rolling load. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The diagram shows a photograph of the appearance of a test piece after an etching test (upper row) and a photograph of the appearance of a cellophane tape subjected to a peeling test on the surface of the test piece (lower row) for the test material of Example No. 1 of the present invention.

[0055] Figure 2The diagram shows a photograph of the appearance of a test piece after an etching test (upper row) and a photograph of the appearance of a cellophane tape subjected to a peeling test on the surface thereof (lower row) for the test material of Example No. 7 of the present invention.

[0056] Figure 3 The diagram shows a photograph of the appearance of a test piece after an etching test (upper row) and a photograph of the appearance of a cellophane tape subjected to a peeling test on the surface of the test piece (lower row) for the test material of Comparative Example No. 34. DETAILED DESCRIPTION

[0057] [Chemical composition]

[0058] In the present invention, the Cu-Ni-Al copper alloy is the object. Hereinafter, unless otherwise specified, "%" related to the alloy composition means "mass %".

[0059] Ni, along with Cu, is a major element that forms the matrix (metal base) of Cu-Ni-Al copper alloys. Furthermore, a portion of the Ni in the alloy combines with Al to form Ni-Al precipitates, and these fine particles contribute to increased strength. To achieve sufficient strength, a Ni content of 10% or more is preferred. Furthermore, increasing the Ni content results in a metallic appearance that appears whiter than other common copper alloys. However, as with other copper alloys, exposure to high humidity can result in a thin oxide film forming on the metal surface, sometimes discoloring to a degree that is discernible from the outside. In this case, the beautiful white appearance is compromised. In particular, when discoloration resistance is important, it is more preferable to increase the Ni content to 12.0% or more, while ensuring the Al content as described below. A Ni content of 15.0% or more is more effective. On the other hand, increasing the Ni content deteriorates hot workability. The Ni content is limited to 30.0% or less, and can be limited to 25.0% or less. Alternatively, the Ni content can be managed to a value between 18.0% and 22.0%.

[0060] Al is an element that forms Ni-Al precipitates. If the Al content is too low, the strength improvement becomes insufficient. On the other hand, if the Al content is too high, the hot workability deteriorates. In addition, by increasing the Al content as the Ni content increases, the discoloration resistance can be improved. As a result of various studies, it is necessary to make the Al content in the range of 1.00 to 6.50%, and to set the Ni / Al ratio to satisfy the following formula (1). It is more preferable to satisfy the following formula (1)'.

[0061] Ni / Al≤9.0…(1)

[0062] 2.0≤Ni / Al≤8.0…(1)'

[0063] In the formula (1) and the formula (1)', the content of the element expressed in mass % is substituted in place of the element symbol.

[0064] Other elements may be included as needed, such as Ag, B, Co, Cr, Fe, Ga, Ge, In, Mg, Mn, P, Si, Sn, Ti, Zn, and Zr. The content of these elements is as follows: Ag: 0-0.50%, B: 0-0.10%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, Mg: 0-2.0%, Mn: 0-2.0%, P: 0-0.2%, Si: 0-2.0%, Sn: 0-2.0%, Ti: 0-2.0%, Zn: 0-2.0%, and Zr: 0-0.3%. The total amount of these optional elements is preferably 2.0% or less, and may be 1.2% or less, or 0.5% or less.

[0065] [Cu concentration in precipitate X Cu ]

[0066] It is known that by controlling the Cu concentration in the precipitate, it is possible to significantly suppress the generation of stains during etching while maintaining high strength. In Ni-Al based precipitates, Cu is present together with Ni and Al, and the Cu concentration is increased compared to normal. Specifically, the composition of the precipitate is controlled so that the Cu concentration in the precipitate X is determined by the following formula (2) based on the analysis of the residue obtained by electrolytic extraction in a 7 mol / L phosphoric acid aqueous solution. Cu It is 15 to 50% by mass.

[0067] X Cu (mass %)=[Cu / (Cu+Ni+Al)]×100…(2)

[0068] In the position of the element symbol in formula (2), the value of the mass ratio of the element in the residue is substituted.

[0069] By adding the above X Cu When X is set to 15 or more, the stain generation inhibitory effect is significantly shown. The mechanism is not clear at present, but it is speculated that the amount of Cu dissolved in the precipitate increases, and the precipitate is easily dissolved in the etching solution (such as ferric chloride aqueous solution). Cu Improving to 15 or more can be achieved by the manufacturing method described below. Cu More preferably, it is 20 or more. Cu If it exceeds 50, it cannot maintain high strength, so X Cu Adjust within the range of 50 or less. You can also adjust within the range of 45 or less or 40 or less.

[0070] [Vickers hardness]

[0071] In order to be suitable for small conductive spring components, it is advantageous to have high strength at a high level. The Vickers hardness is preferably 300 HV or higher, more preferably 320 HV or higher. In addition, it can be adjusted to a strength level of 340 HV or higher or 380 HV or higher, which is extremely high for a Cu-Ni-Al copper alloy. There is no particular upper limit for the hardness, but it can usually be adjusted within a range of 450 HV or lower. The strength level can be adjusted by setting the chemical composition and the conditions in the manufacturing process described below.

[0072] [Number density of fine precipitate particles with a long diameter of 5 to 50 nm]

[0073] Fine precipitate particles with a long diameter of 5 to 50 nm are dispersed in the matrix (metal base), thereby contributing to the improvement of strength. The fine precipitates generated in the Cu-Ni-Al copper alloy of the present invention are Ni-Al precipitates mainly composed of Ni and Al. From the perspective of improving strength, the number density of fine precipitate particles with a long diameter of 5 to 50 nm is preferably 1.0×10 7 Pieces / mm 2 More than 2.5×10 7 Pieces / mm 2 Usually, at 5.0×10 10 Pieces / mm 2 It should be noted that the Ni—Al precipitate particles also contain Cu, and in the copper alloy sheet material of the present invention, the effect of suppressing the generation of stains is achieved by controlling the Cu concentration to be high as described above.

[0074] [Number density of coarse precipitate particles with a major diameter of 1.0 μm or more]

[0075] In order to form a smooth etched surface by etching, it is advantageous to minimize the amount of coarse precipitates. Specifically, the density of coarse precipitate particles with a major diameter of 1.0 μm or more is preferably 3.0×10 4 Pieces / mm 2 Below, more preferably 1.0×10 4 Pieces / mm 2 the following.

[0076] [Full width at half maximum of the X-ray diffraction peak of the {220} crystal plane]

[0077] In the Cu-Ni-Al copper alloy sheet material according to the present invention, the full width at half maximum of the X-ray diffraction peak of the {220} crystal plane on the sheet surface is, for example, 0.5° or greater. This copper alloy sheet material introduces sufficient lattice strain, which is advantageous in achieving high-strength and smooth etched surfaces.

[0078] [Manufacturing method]

[0079] The copper alloy sheet material described above can be produced, for example, through the following production steps.

[0080] Melting and casting → Slab heating → Hot rolling → Cold rolling → (Intermediate annealing → Cold rolling) → Solution treatment → Aging treatment → Final cold rolling → Final heat treatment

[0081] It should be noted that, although not described in the above steps, face cutting is performed as needed after hot rolling, and pickling, grinding, or degreasing is performed as needed after each heat treatment.

[0082] [Melting and Casting]

[0083] Cast slabs can be produced by continuous casting, semi-continuous casting, etc. From the viewpoint of preventing oxidation of Al, it is preferable to carry out melting in an inert gas atmosphere or under vacuum in a chamber.

[0084] [Casting Slab Heating]

[0085] The slab is heated and maintained at 1000-1150°C. This heating can be implemented by utilizing the slab heating process during hot rolling. In the past, the heating of Cu-Ni-Al copper alloy slabs was mostly carried out at a temperature below 950°C. In the present invention, it is necessary to control the Cu concentration in the precipitate in the subsequent process. Therefore, it is effective to heat the slab to the above-mentioned high temperature so that the coarse second phase present in the casting structure is dissolved as much as possible. However, if it exceeds 1150°C, the part with a low melting point in the casting structure becomes brittle and cracks may occur during hot rolling. It is more effective to set the heating holding time in the above-mentioned temperature range to more than 1.5 hours, and more effective to set it to more than 2 hours. Taking into account the economy, the slab heating time in the above-mentioned temperature range is preferably set within the range of less than 5 hours.

[0086] [Hot Rolling]

[0087] In hot rolling, the rolling temperature of the final pass is set to 800°C or above. The temperature of each rolling pass can be expressed by the surface temperature of the material immediately after it comes out of the work roll in the rolling pass. By heating the slab in the above-mentioned high temperature region and hot rolling above 800°C, the amount of coarse second phase present is sufficiently reduced. As a result, the Cu concentration in the precipitate can be controlled within an appropriate range in the subsequent process. In the plate after hot rolling (hot-rolled plate), it is preferred to suppress the number density of coarse second phase particles with a long diameter of more than 5 μm in the observation plane parallel to the plate surface to, for example, 10 / mm 2 From the viewpoint of stably achieving a final-pass rolling temperature of 800° C. or higher in mass production operations, the plate thickness after hot rolling (final plate thickness) is preferably in the range of 5 to 20 mm, more preferably in the range of 7 to 20 mm.

[0088] [Cold Rolling]

[0089] Before solution treatment, cold rolling can be performed to adjust the plate thickness. One or more "intermediate annealing → cold rolling" steps can be added as needed. The reduction ratio in the cold rolling performed before solution treatment (or, if intermediate annealing is performed, the reduction ratio in the cold rolling after the final intermediate annealing) can be set to, for example, 80% or higher. The upper limit of the reduction ratio depends on the capacity of the rolling mill and can be set, for example, within a range of 99.5% or lower.

[0090] [Solution treatment]

[0091] In the solution treatment of the present invention, heating is performed to a temperature higher than the solution treatment temperature (about 800 to 900°C) of a general Cu-Ni-Al copper alloy. Specifically, the time for holding the material in the temperature range of 950 to 1100°C is set to 30 to 360 seconds. If heated to such a high temperature region, the second phase can be fully dissolved even if the holding time is as short as mentioned above. In the present invention, in addition to the above-mentioned heating temperature and holding time, it is also important to control the cooling rate after the solution treatment within a narrow range. Specifically, the average cooling rate from 900°C to 700°C is in the range of 110 to 150°C / s. If the cooling rate in this temperature range is slow, the effect of suppressing the generation of stains cannot be fully obtained. On the other hand, it is known that if the cooling rate is too fast, it is difficult to stably obtain a structure with a sufficient amount of fine precipitates dispersed in the subsequent process, which becomes disadvantageous in achieving a very high strength level. It is speculated that when the cooling rate in the above-mentioned temperature region after solution treatment is controlled within a narrow range of 110 to 150°C / s, a plurality of fine precipitation nuclei are generated within the grains during the cooling process, and growth toward the precipitated particles is appropriately performed, thereby obtaining a "precursor structure state" suitable for dispersing a large amount of fine precipitates with a high Cu concentration in a subsequent series of steps. In actual operation, it is effective to continue forced cooling until a temperature region of 10°C or more and 100°C or less is reached under cooling conditions in which the average cooling rate from 900°C to 700°C is in the range of 110 to 150°C / s, and it is more preferable to continue forced cooling until a temperature region of 20°C or more and 50°C or less is reached.

[0092] [Aging Processing]

[0093] Next, aging treatment is performed. After solution treatment, aging treatment can be performed directly in the structural state where the solution treatment process is completed without introducing processing strain such as cold rolling. The aging treatment is carried out under the condition that the average cooling rate from 400°C to 300°C is 40 to 80°C / h after being maintained at 400 to 650°C for 0.5 to 75 hours. After that, it is preferably continued to cool in the furnace until the temperature range of 10°C or more and 200°C or less is reached, and more preferably, the temperature range of 20°C or more and 100°C or less is reached. Strictly controlling the cooling conditions as described above is extremely effective in adjusting the Cu concentration of the precipitate to the specified range. If the cooling rate is too fast, it is difficult to fully ensure the amount of fine precipitates after the final heat treatment described later, which becomes disadvantageous in obtaining high strength. If the cooling rate is too slow, the concentration of Cu dissolved in the precipitate phase is reduced, and it is difficult to obtain a plate with a high Cu concentration in the precipitate after the final heat treatment described later, and the work softening effect cannot be fully exerted in the final cold rolling of the next process.

[0094] [Final cold rolling]

[0095] After aging treatment, cold rolling is performed until the final target plate thickness. In this specification, this cold rolling is referred to as "final cold rolling". In addition to adjusting the target plate thickness, the final cold rolling also has the purpose of imparting rolling strain so that sufficient hardening phenomenon is exhibited in the final heat treatment of the next process. From the viewpoint of imparting rolling strain, it is necessary to make the rolling rate in the final cold rolling more than 30%. It is more effective to set it to more than 50%. The upper limit of the rolling rate depends on the capacity of the rolling mill and can usually be set in the range of less than 99%. The final plate thickness can be adjusted in the range of 0.01 to 0.50 mm, for example.

[0096] Generally speaking, the higher the cold rolling rate is, the greater the deformation resistance is due to work hardening. For example, when finishing is a thin plate with a thickness of 0.1mm or less, the increase in the number of rolling passes and the edge cutting of the material easily become problems. However, when cold rolling is implemented for the aging treated material according to the above-mentioned manufacturing conditions, work hardening is significantly suppressed, and the above-mentioned problems are greatly improved. The reason is unclear. It is speculated that at the moment of finishing the above-mentioned aging treatment, the precipitate with the high concentration of Cu is formed. Cu is solid-dissolved in the precipitate, and the composition of the precipitate is close to the parent phase. Thus, when the plastic deformation caused by rolling (i.e., when giving rolling strain), the precipitated particles are easily quasi-solid-dissolved (quasi-solid-dissolved). As a result, although it is cold working, the rise of hardness is very small, and even the phenomenon of hardness reduction is produced on the contrary. Such phenomenon is referred to as "work softening" in this manual.

[0097] [Final heat treatment]

[0098] The final heat treatment is performed on the sheet material after the final cold rolling to increase the strength while controlling the Cu concentration of the precipitate. The final heat treatment is carried out under the conditions of maintaining the temperature at 400-700°C, more preferably 420-700°C, for 10-600 seconds, and then cooling the sheet material at an average rate of 50-90°C / s from 400°C to 300°C. In this heat treatment, it is speculated that the solute atoms in the quasi-solid solution during the final cold rolling are finely precipitated, thereby obtaining a structural state in which dislocations are difficult to move. If the cooling rate is slow, the Cu concentration in the precipitate decreases, making it difficult to stably obtain a sheet material with a high effect of suppressing the generation of stains. If the cooling rate is too fast, precipitation from the quasi-solid solution state cannot be fully carried out, resulting in an inability to obtain a high strength level. In actual operation, it is effective to continue forced cooling until the temperature reaches a range of 10°C or more and 100°C or less under the cooling condition of an average cooling rate of 50-90°C / s from 400°C to 300°C. It is more preferable to continue forced cooling until the temperature reaches a range of 20°C or more and 50°C or less.

[0099] By using the plate material of the present invention obtained as described above as a raw material and performing processing including etching, a conductive spring member with high dimensional accuracy can be obtained.

[0100] Example

[0101] The copper alloy with the chemical composition shown in Table 1 was melted and cast using a vertical semi-continuous casting machine. The resulting cast sheet was heated and maintained at the temperature and time shown in Tables 2 and 3, then withdrawn, hot rolled, and water-cooled. The total hot rolling rate was 85-95%. The rolling temperature of the final pass and the final plate thickness after hot rolling are shown in Tables 2 and 3. For some examples (No. 35, 37, 39) in which cracks were generated during hot rolling, the production was terminated at that point. After hot rolling, the surface oxide layer was removed by mechanical grinding (face cutting), and cold rolling was performed at the rolling rate shown in Tables 2 and 3.

[0102] For each cold-rolled material obtained, a continuous annealing furnace equipped with a heating zone and a forced cooling zone was used to carry out solution treatment under the conditions shown in Tables 2 and 3. After heating at a specified temperature for a specified time in the heating zone, forced cooling was carried out in the forced cooling zone by blowing nitrogen gas for forced convection using a fan onto the surface of the plate in the through plate. The cooling rate can be controlled by adjusting the convection intensity. In the through plate, the plate surface temperature T0 (°C) immediately before the forced cooling began and the plate surface temperature T1 (°C) immediately after the forced cooling were measured. In each case, it was confirmed that T0 was above 900°C and T1 was below 700°C. Therefore, based on the cooling curve determined by the above-mentioned T0, T1 and plate passing speed, the average cooling rate from 900°C to 700°C was calculated.

[0103] After the solution treatment, aging treatment is directly performed without applying cold rolling strain (cold rolling deformation). The aging treatment is performed using a batch annealing furnace under the conditions of maintaining the temperature described in Table 2 and Table 3 for the time described in the table. The atmosphere is nitrogen. After heating and maintaining, cooling is performed in the furnace at a substantially constant cooling rate until the temperature becomes lower than 300°C. Next, final cold rolling is performed at the rolling rate described in Table 2 and Table 3. Then, a continuous annealing furnace having a heating zone and a forced cooling zone is used to perform the final heat treatment under the conditions shown in Table 2 and Table 3. After heating at a specified temperature for a specified time in the heating zone, forced cooling is performed in the forced cooling zone by blowing nitrogen gas that is forced convected by a fan onto the surface of the plate in the through plate. The cooling rate can be controlled by adjusting the convection intensity. In the through plate, the plate surface temperature T0 (°C) immediately before the forced cooling begins and the plate surface temperature T1 (°C) immediately after the forced cooling ends are measured. In each case, T0 was confirmed to be 400° C. or higher and T1 was confirmed to be 300° C. or lower. Therefore, the average cooling rate from 400° C. to 300° C. was determined based on the cooling curve determined by T0, T1, and the sheet passing rate.

[0104] In this way, plate products (test materials) having the final plate thickness shown in Tables 2 and 3 were obtained. The following investigations were conducted on each test material. It should be noted that "hardness" was measured not only on the test materials after the final heat treatment, but also on the materials after the aging treatment and the materials after the final cold rolling.

[0105] (Cu concentration in precipitate X Cu )

[0106] A sample was collected from the test material, and after removing the surface oxide layer by dry grinding using corundum sandpaper with a number 1000 (grain size P1000 specified in JIS R6010:2000), a voltage of about 2.0 V was applied for 15 minutes in a phosphoric acid aqueous solution with a concentration of 7 mol / L at 25°C to dissolve the matrix (metal substrate). The residue (precipitate) extracted (extracted) into the solution was filtered using a filter with a pore size of 50 nm to recover it. At this time, the residue and the filter were washed with pure water until the pH of the extracted liquid became 6.2. The recovered residue was analyzed for Cu, Ni, and Al using ICP emission spectrometry, and the Cu concentration X in the precipitate determined by the following formula (2) was determined based on the analysis. Cu To dissolve the residue, a mixed acid consisting of equal volumes of nitric acid and hydrochloric acid was used.

[0107] X Cu (mass %)=[Cu / (Cu+Ni+Al)]×100…(2)

[0108] In the position of the element symbol in formula (2), the value of the mass ratio of the element in the residue is substituted.

[0109] (Full width at half maximum of the X-ray diffraction peak of the {220} crystal plane)

[0110] An X-ray diffraction apparatus (manufactured by Bruker AXS; D2 Phaser) was used to measure the X-ray diffraction pattern of the plate surface under the conditions of Cu-Kα radiation, tube voltage of 30 kV, and tube current of 10 mA. The Kα2 line was removed using the Kα2 removal function of the X-ray diffraction pattern analysis software (manufactured by Bruker AXS; DIFFRAC.EVA) under the conditions of "maximum: 1, intensity ratio: 0.5, minimum: 0", and the full width at half maximum of the X-ray diffraction peak of the {220} crystal plane was calculated.

[0111] (Number density of fine precipitate particles)

[0112] According to the above-mentioned "method for determining the number density of fine precipitate particles", the observation surface prepared by electrolytic grinding and ultrasonic cleaning was observed using FE-SEM (manufactured by JEOL Ltd.; JSM-7200F), and the number density (number / mm2) of fine second phase particles with a major diameter of 5 to 50 nm was determined. 2 The electrolytic polishing was performed using an electrolytic polishing device (ELECTROPOLISHER POWER SUPPLUY, ELECTROPOLISHER CELL MODULE) manufactured by BUEHLER. The ultrasonic cleaning was performed in ethanol using an ultrasonic cleaning machine "BRANSONIC M2800-J" for 20 minutes.

[0113] (hardness)

[0114] The Vickers hardness of the plate surface was measured using a method in accordance with JIS Z2244:2009. The test force F (N) was measured at seven points, with the average d (mm) of the diagonal lengths d1 and d2 of the resulting indentation being less than two-thirds of the specimen thickness. The average of the five values, excluding the maximum and minimum values, was used as the hardness of the test material.

[0115] In each case, the hardness H1 (HV) after aging treatment, the hardness H2 (HV) after final cold rolling, and the hardness H3 (HV) of the test material after final heat treatment were measured, and the manufacturability index M represented by the following formula (4) was obtained.

[0116] M=(H2-H1) / (H3-H2)…(4)

[0117] The manufacturability index M represents the ratio of the "hardness increase in the final cold rolling" to the "hardness increase after the final heat treatment". The smaller the value, the more "material strengthening" that can effectively suppress the work hardening in the final cold rolling can be achieved. That is, the smaller the manufacturability index M is, the smaller the load in the final cold rolling is in the strengthening process that combines aging treatment, final cold rolling and final heat treatment, and the manufacturability is evaluated to be good. The results of various studies have shown that in this alloy system, if the manufacturability index M is below 1.2, it is judged that high-strength plates can be efficiently manufactured with a high yield using the above-mentioned strengthening process. It should be noted that when the hardness is reduced by the final cold rolling, the manufacturability index M becomes a negative value, which can be evaluated as the load in the rolling being particularly reduced. However, if the hardness reduction in the final cold rolling is too large, then in order to ensure sufficient strength, it is necessary to increase the hardness rise in the final heat treatment to a considerable extent, and the constraints of the final heat treatment conditions become strict. In addition, after significant work hardening in the final cold rolling, when softening in the final heat treatment, the manufacturability index M may become a large negative value, which is not preferable from the perspective of reducing the load in the final cold rolling. Considering the load balance in each step and the load reduction in the final cold rolling, the M value shown in the above formula (4) is preferably in the range of not less than -0.2 and not more than 1.2.

[0118] (Amount of stain generated)

[0119] A test piece with a width of about 10 mm and a length of about 40 to 60 mm was cut out from the test material, and its surface was subjected to an etching test using a jet etching device. The etching liquid was an aqueous solution of ferric chloride with a Baume degree of 42 Bh. The liquid temperature was set to 50°C, the spray pressure was set to 0.15 MPa, and the spray time was set to 120 seconds. After the etching test, the sample was washed with water and dried, and a "peel test" was performed on the surface of the sample in accordance with the method of peeling off the transparent tape after affixing it in accordance with JIS Z1522:2009. The stains generated by etching adhere to the surface of the sample after washing and drying. According to the amount of stains transferred to the surface of the peeled transparent tape in the peeling test (the degree of black dirt on the tape), the performance of suppressing the generation of stains can be evaluated.

[0120] exist Figures 1 to 3 , there are shown a photograph of the appearance of a test piece after an etching test (upper row), and a photograph of the appearance of a cellophane tape subjected to a peeling test on the surface thereof (lower row). Figure 1 This is Example No. 1 of the present invention, Figure 2 This invention No. 7, Figure 3 This is Comparative Example No. 34. The results of two test pieces are shown. Figure 3 ) compared to the test piece of the present invention ( Figure 1 、 Figure 2) significantly inhibited the generation of stains. Here, by visually observing the appearance of the test piece after the etching test and the degree of black dirt on the transparent tape peeled off in the peeling test, compared with Comparative Example No. 34 ( Figure 3 ), the situation where the stain generation inhibitory effect is clearly seen is evaluated as ○ (stain generation inhibitory ability: good), the situation where the stain generation inhibitory effect is particularly significant is evaluated as ◎ (stain generation inhibitory ability: excellent), and the situations other than these are evaluated as × (stain generation inhibitory ability: insufficient improvement).

[0121] These survey results are shown in Tables 4 and 5.

[0122] [Table 1]

[0123] Table 1

[0124]

[0125] Underline: outside the scope of the present invention

[0126]

[0127]

[0128]

[0129]

[0130] The Cu-Ni-Al copper alloy sheets of the present invention all have high strength, and the Cu concentration in the precipitate is Cu In the range of 15 to 50 mass %, the performance of suppressing the generation of stains is excellent. The manufacturability index M is also low, and the manufacturability is also good in the strengthening process combining aging treatment, final cold rolling, and final heat treatment.

[0131] In the comparative examples No. 31 to 34, 40, and 41, the Cu concentration in the precipitate was X 0. Cu Examples of performance in suppressing stain generation that becomes lower than the range specified in the present invention and fails to improve. Specifically, the slab heating temperature and the rolling temperature of the final hot rolling pass of Comparative Example No. 31 are low. The solution treatment temperature of No. 32 is low. The average cooling rate from 900°C to 700°C in the solution treatment process of No. 33 is slow. The cooling rate from 400°C to 300°C in the aging treatment process of No. 34 is too slow. The rolling temperature of the final hot rolling pass of No. 40 is low, and the heating holding time of the solution treatment is short. The average cooling rate from 400°C to 300°C in the final heat treatment process of No. 41 is slow.

[0132] No.36, 38, 42 to 44 are examples in which the number density of fine precipitate particles is reduced due to the deviation of the chemical composition or manufacturing conditions from the range specified in the present invention, and the strength level equivalent to 300HV is not achieved. Specifically, the Ni content of No.36 is too low. The Al content of No.38 is low and the Ni / Al ratio is high. The average cooling rate from 900°C to 700°C in the solution treatment process of No.42 is too fast. The cooling rate from 400°C to 300°C in the aging treatment process of No.43 is too fast. The cooling rate from 400°C to 300°C in the final heat treatment process of No.44 is too fast.

[0133] Examples No. 35, 37, and 39 were produced during hot rolling, and production was terminated at that point. The Ni content in No. 35 was too high, the Al content in No. 37 was too high, and the slab heating temperature in No. 39 was too high.

[0134] (Number density of coarse precipitate particles)

[0135] In order to obtain an etched surface with less unevenness and high smoothness, it is advantageous to have fewer coarse precipitates. Therefore, the number density of coarse precipitate particles was investigated using the following method for the plate material obtained in the present invention (test material after final heat treatment).

[0136] According to the "Method for Determining the Number Density of Coarse Precipitated Particles" described above, the observation surface prepared by electrolytic polishing and ultrasonic cleaning was observed using FE-SEM to determine the number density of coarse precipitated particles with a major diameter of 1.0 μm or greater. The electrolytic polishing was performed using an electrolytic polishing device (ELECTROPOLISHER POWER SUPPLUY, ELECTROPOLISHER CELL MODULE) manufactured by BUEHLER. The ultrasonic cleaning was performed in ethanol for 20 minutes using a BRANSONIC M2800-J ultrasonic cleaner.

[0137] The results show that the number density of coarse precipitates in the plate materials of the examples of the present invention was very low.

[0138] [Table 6]

[0139] Table 6

[0140]

Claims

1. A copper alloy plate having the following chemical composition: in mass %, Ni: 10.0-30.0%, Al: 1.00-6.50%, Ag: 0-0.50%, B: 0-0.10%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, Mg: 0-2.0%, Mn: 0-2.0%, P: 0-0.2%, Si: 0-2.0%, Sn: 0-2.0%, Ti: 0-2.0%, Zn: 0-2.0%, Zr: 0-0.3%, the balance being Cu and unavoidable impurities, and satisfying the following formula (1). The Cu concentration X in the precipitate was determined by analyzing the residue obtained by electrolytic extraction in a 7 mol / L phosphoric acid aqueous solution using the following formula (2): Cu 15 to 50% by mass Vickers hardness is above 300HV, Ni / Al≤9.0 … (1) in, Substitute the element content expressed in mass % in the place of the element symbol in formula (1). X Cu (Mass%) = [Cu / (Cu+Ni+Al)] × 100… (2) In the place of the element symbol in formula (2), the value of the mass ratio of the element in the residue is substituted.

2. The copper alloy sheet according to claim 1, wherein In the observation plane parallel to the plate surface, the number density of fine precipitate particles with a long diameter of 5 to 50 nm is 1.0×10 7 Pieces / mm 2 above.

3. The copper alloy sheet material according to claim 1 or 2, wherein: The full width at half maximum of the X-ray diffraction peak of the {220} crystal plane in the plate surface is 0.5° or more.

4. A method for producing a copper alloy sheet, wherein: A plate having a Vickers hardness of 300 HV or more is obtained by a manufacturing process including the following steps in sequence: A casting heating step of heating a casting at 1000-1150° C., wherein the casting has the following chemical composition: in mass %, Ni: 10.0-30.0%, Al: 1.00-6.50%, Ag: 0-0.50%, B: 0-0.10%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, Mg: 0-2.0%, Mn: 0-2.0%, P: 0-0.2%, Si: 0-2.0%, Sn: 0-2.0%, Ti: 0-2.0%, Zn: 0-2.0%, Zr: 0-0.3%, and the balance consisting of Cu and unavoidable impurities, and satisfies the following formula (1); The hot rolling process is performed under the condition that the rolling temperature in the final rolling pass is 800°C or higher. The cold rolling process is carried out with a rolling reduction of more than 80%. The solution treatment step is to hold the temperature at 950-1100°C for 30-360 seconds and then cool the steel from 900°C to 700°C at an average cooling rate of 110-150°C / s. An aging treatment step in which the temperature is maintained at 400-650°C for 0.5-75 hours and then cooled at an average cooling rate of 40-80°C / h from 400°C to 300°C. The final cold rolling process is carried out with a rolling rate of more than 30%. The final heat treatment step is to hold the temperature at 400-700°C for 10-600 seconds and then cool the steel sheet from 400°C to 300°C at an average cooling rate of 50-90°C / s. Ni / Al≤9.0 … (1) In the formula (1), the element content value expressed in mass % is substituted in place of the element symbol.

5. The method for manufacturing a copper alloy sheet material according to claim 4, wherein: A sheet material having a Vickers hardness H3 of 300 HV or higher is obtained by a manufacturing process in which the M value of the following formula (4) representing the relationship between the Vickers hardness H1 (HV) after the aging treatment step, the Vickers hardness H2 (HV) after the final cold rolling step, and the Vickers hardness H3 (HV) after the final heat treatment step is -0.2 or more and 1.2 or less. M=(H2-H1) / (H3-H2)…(4).

6. A method for producing a copper alloy sheet, wherein the copper alloy sheet comprises a Cu concentration X in a precipitate determined by the following formula (2) based on analysis of a residue obtained by electrolytic extraction in a 7 mol / L phosphoric acid aqueous solution. Cu 15 to 50% by mass X Cu (Mass%) = [Cu / (Cu+Ni+Al)] × 100… (2) in, Substitute the element symbol in the position of the element in the residue into the value of the mass ratio of the element. The manufacturing method manufactures the plate from the cast piece through the steps including cast piece heating, hot rolling, cold rolling, solution treatment, aging treatment, final cold rolling and final heat treatment in sequence. When the Vickers hardness after the aging treatment step is set to H1 (HV), the Vickers hardness after the final cold rolling step is set to H2 (HV), and the Vickers hardness after the final heat treatment step is set to H3 (HV), a plate having a Vickers hardness H3 of 300 HV or more is obtained by a manufacturing process in which the M value of the following formula (4) is set to be greater than or equal to -0.2 and less than or equal to 1.

2. The cast piece has the following chemical composition: in mass %, Ni: 10.0-30.0%, Al: 1.00-6.50%, Ag: 0-0.50%, B: 0-0.10%, Co: 0-2.0%, Cr: 0-0.5%, Fe: 0-2.0%, Ga: 0-0.5%, Ge: 0-0.5%, In: 0-0.5%, Mg: 0-2.0%, Mn: 0-2.0%, P: 0-0.2%, Si: 0-2.0%, Sn: 0-2.0%, Ti: 0-2.0%, Zn: 0-2.0%, Zr: 0-0.3%, and the balance is Cu and unavoidable impurities, and satisfies the following formula (1): Ni / Al≤9.0 … (1) Wherein, the content value of the element expressed in mass % is substituted in the place of the element symbol in formula (1). M=(H2-H1) / (H3-H2)…(4).

7. A conductive spring member using the copper alloy sheet material according to claim 1 as a material.

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