Copper alloy molding with excellent electrical conductivity

Abstract

To provide a copper alloy molding having excellent electrical conductivity.SOLUTION: A copper alloy molding comprises, in mass%, C: 0.01-3.00% and, as an optional additional component, an element M: 0.0-5.0% or less (where the element M is one or more selected from Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, and Al) with the balance being Cu and inevitable impurities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper alloy shaped product formed using a copper alloy powder suitable for processes involving rapid melting and rapid solidification, such as three-dimensional additive manufacturing, thermal spraying, laser coating, build-up welding, etc. In particular, the present invention relates to a copper alloy shaped product having excellent electrical conductivity, formed using a copper alloy powder suitable for additive manufacturing using a powder bed method (powder bed fusion method). [Background technology]

[0002] 3D printers are beginning to be used to create metal objects. These 3D printers create objects using additive manufacturing, and typical metal additive manufacturing methods include the powder bed method (powder bed fusion method) and the metal deposition method (directed energy deposition method). In the powder bed method, a laser beam or electron beam is irradiated to melt and solidify the irradiated areas of a spread powder. This melting and solidification causes the powder particles to bond together. Irradiation is selectively applied to parts of the metal powder; the unirradiated areas do not melt, and a bond layer is formed only in the irradiated areas.

[0003] New metal powder is then laid on top of the bonded layer, and the powder is irradiated with a laser or electron beam. The irradiation melts and solidifies the metal particles, forming a new bonded layer. The new bonded layer also bonds with the existing bonded layer.

[0004] As the melting and solidification processes are repeated, the bonding layers gradually grow. This growth results in a three-dimensional object. Using this additive manufacturing method, it is easy to create objects with complex shapes.

[0005] A powder bed type additive manufacturing method discloses a procedure in which a mixture of "iron-based powder" and "one or more types of powder selected from the group consisting of nickel, nickel-based alloys, copper, copper-based alloys, and graphite" is used as the metal powder for metal laser sintering, and a sintered layer is formed by repeating a powder layer formation step in which the metal powder is spread, a sintered layer formation step in which a beam is irradiated onto the powder layer to form a sintered layer, and a removal step in which the surface of the object is cut to form a sintered layer, thereby producing a three-dimensional shaped object (see Patent Document 1).

[0006] High conductivity is required for alloys used in high-frequency induction heating devices, heat sinks for motor cooling, etc. Cu-based alloys are suitable for such applications. Because the parts used for these applications have complex shapes, additive manufacturing methods have attracted attention, and the advantages of additive manufacturing can be utilized.

[0007] However, copper has low light absorption at the 1064 nm laser wavelength used in general-purpose laser additive manufacturing, making it difficult to obtain the energy required for melting and solidifying, making it difficult to produce objects. For this reason, copper alloys with improved light absorption and excellent formability are being developed. For example, a copper alloy has been proposed in which the main component is copper and the amount of solid solubility in copper is less than 0.2 at% (see Patent Document 2). This proposal aims to obtain mechanical strength while reducing the decrease in electrical conductivity due to solid solubility in copper by using an additive element that has a low amount of solid solubility in copper, and involves adding an element that is difficult to dissolve in copper in a solid solution state according to a binary phase diagram, etc. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-81840 [Patent Document 2] International Publication No. 2019 / 039058 Summary of the Invention [Problem to be solved by the invention]

[0009] Additive manufacturing is a process of forming a shaped object by irradiating it with an electron beam or laser, and energy absorption by metal powder is an important factor in the manufacturing process. For example, in the case of laser additive manufacturing, the lower the laser light reflectance for the irradiated laser wavelength, the easier the energy absorption, resulting in highly efficient manufacturing.

[0010] However, copper has a high laser beam reflectivity, making it difficult to absorb energy and increasing efficiency, making it difficult to achieve high-density molding. Adding additional elements makes it easier to absorb laser beams and facilitates high-density molding, but the amount of these elements dissolved in the copper alloy matrix increases, reducing electrical conductivity.

[0011] The object of the present invention is to provide a molded object having excellent electrical conductivity, which is formed using a copper alloy powder that is suitable for processes involving rapid melting, rapid cooling and solidification, such as additive manufacturing, and which enables the production of high-density molded objects and which can yield molded objects with high electrical conductivity. [Means for solving the problem]

[0012] As a result of extensive research, the inventors have focused on carbon (including carbon black, activated carbon, and graphite), which has excellent light absorption, and have invented a copper alloy shaped product with excellent electrical conductivity, which is produced using copper alloy powder with a carbon layer non-chemically adhered to the powder surface. By adhering a carbon layer to the surface of the copper alloy powder, the laser light absorption rate is increased, making it possible to obtain a high-density shaped product.

[0013] Furthermore, during the production of molded products, the C component of the powder surface carbide layer reacts with the M element solid-solubilized in the copper alloy powder to form carbides, resulting in a matrix structure in the molded product that is close to pure Cu, resulting in a molded product with excellent electrical conductivity. In other words, by expelling the added elements as carbides to the grain boundaries, the amount of solid solution in the matrix is ​​reduced, resulting in an electrical conductivity close to that of pure Cu. Furthermore, because these carbides are fine, they contribute to improved strength, resulting in copper alloy molded products with excellent moldability, electrical conductivity, and strength.

[0014] Therefore, a first means for solving the problems of the present invention is a copper alloy shaped product containing, in mass %, 0.01 to 3.00% C, 0.0 to 5.0% or less of element M as an optional added component (wherein element M is one or more components selected from Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, and Al), and the remainder being Cu and unavoidable impurities.

[0015] The second aspect of the present invention is the copper alloy shaped product according to the first aspect, which contains at least one of precipitates of carbide of element M and elemental carbon.

[0016] The third means is the copper alloy shaped article according to the second means, characterized in that the precipitates and elemental carbon have particle sizes of 1000 nm or less.

[0017] These copper alloy shaped products may be copper alloy shaped products formed using a Cu-based powder comprising an element M (M: one or more selected from Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, and Al) in an amount of 0.0 to 5.0% by mass as an optional added component, with the remainder being Cu and unavoidable impurities, and further comprising a carbon layer powder that is a non-chemically reactive layer coated with 0.01 to 3.00% carbon on the surface of the Cu-based powder.

[0018] These copper alloy shaped articles may be copper alloy shaped articles formed by layering these Cu-based powders by an additive manufacturing method. When a carbon layer is adhered to the surface of the powder used in additive manufacturing, the energy efficiency during additive manufacturing is excellent, allowing for the production of high-density copper alloy objects.In addition, the powder also has excellent electrical conductivity.

[0019] Preferably, the copper alloy shaped article has a relative density of 97% or more.

[0020] Preferably, the copper alloy shaped article has an electrical conductivity of 70% IACS or more. [Effects of the Invention]

[0021] The copper alloy shaped product of the present invention has excellent electrical conductivity due to the inclusion of carbon and precipitates of carbides of element M. This is because the aging heat treatment causes element components and compounds of element group M to precipitate at grain boundaries, thereby increasing the purity of Cu in the matrix of the copper alloy shaped product. Copper alloy molded objects are made using powder in which a carbon layer, a non-chemically reactive layer, is adhered to the surface of the Cu-based powder. Since the added elements that are dissolved in the matrix of the Cu-based powder are released as carbides of 1000 nm or less in the copper alloy molded object, the copper alloy molded object has a matrix structure close to that of pure Cu and has excellent electrical conductivity. Furthermore, if the particle size of the precipitates or carbon element in the copper alloy molded product is 1000 nm or less, the element M that was dissolved in the matrix is ​​expelled from the matrix as a carbide, and the molded product has excellent electrical conductivity. DETAILED DESCRIPTION OF THE INVENTION

[0022] Before describing the embodiments of the shaped product of the present invention, the reasons for specifying the components of the copper alloy shaped product and the components, shape, and properties used in the carbon-bonded Cu-based powder will be explained below.

[0023] [About carbon] C: 0.01 to 3.00% The carbon-bonded Cu-based powder suitable for producing the copper alloy shaped product of the present invention has a non-chemically reactive carbon layer bonded to the surface of the Cu-based powder. This is to facilitate the absorption of laser light during the fabrication of the copper alloy shaped product. C is difficult to dissolve and can be considered an impurity in copper alloys. However, by intentionally bonding C to the powder surface and then fabricating the copper alloy, the benefits of improved laser light absorption during fabrication outweigh the drawbacks. Therefore, the copper alloy shaped product contains 0.01% or more C. On the other hand, if the C content exceeds 3.00%, the disadvantages of C as an impurity outweigh the drawbacks. Therefore, the C content is set to 0.01 to 3.00% by mass. Furthermore, by physically fixing the carbon instead of chemically fixing it, the time required for fixing the carbon can be reduced. From these viewpoints, it is preferable to fix the carbon to the Cu-based powder using a physical method. The term "carbon" as used herein refers to carbon black, activated carbon, graphite, and combinations thereof. Carbon black is preferred in the present invention because it has excellent laser beam energy absorption properties. In the following description of the examples, carbon black will be used as a representative example, but other carbon materials are not excluded.

[0024] [About the components of the sculpture] [Element M] The optional element M is selected from the group consisting of Zr (zirconium), Hf (hafnium), Ti (titanium), Nb (niobium), V (vanadium), Mo (molybdenum), Mn (manganese), Cr (chromium), W (tungsten), and Al (aluminum), and two or more elements may be selected. According to the equilibrium phase diagram, these elements M are elements that form carbides with C. Until the laser is irradiated during molding, element M is in solid solution in the matrix, and a carbon layer is adhered to the powder surface, which increases the laser light absorption rate and results in a high-density molded product with few defects. Once melting and solidification is complete, element M, which was in solid solution in the matrix, is expelled from the matrix as carbides, resulting in a structure close to pure Cu, and a molded product with high electrical conductivity is obtained. [Content of element M] The element M is preferably added to the Cu-based powder because the element M improves the laser light absorption rate by forming a solid solution in the Cu component of the matrix phase of the Cu-based powder. However, if the amount of element M added is increased more than necessary, even if the solute element M is expelled from the matrix as carbides when the copper alloy shaped product is formed, the element M will remain partially dissolved in the matrix, leading to a decrease in electrical conductivity. Therefore, the content of the selectively added element M in the copper alloy shaped product is preferably 5.0 mass% or less.

[0025] In addition to element M, the following elements may be contained as inevitable impurities. Si: 0.10% by mass or less P: 0.10% by mass or less S: 0.10% by mass or less Among the unavoidable impurities, Si, P, and S inhibit the electrical and thermal conduction of copper alloys. Furthermore, they are elements that are sensitive to cracking during molding, so their content must be kept to a minimum.

[0026] [Si (Silicon)] Si dissolves in Cu and inhibits the electrical and thermal conduction of the copper alloy, so the Si content is preferably 0.10% by mass or less, and more preferably 0.05% by mass or less.

[0027] [P (Rin)] P dissolves in Cu and inhibits the electrical and thermal conduction of the copper alloy, so the P content is preferably 0.10% by mass or less, and more preferably 0.05% by mass or less.

[0028] [S (Sulfur)] S forms a solid solution in Cu and inhibits the electrical and thermal conduction of the copper alloy, so the S content is preferably 0.10 mass % or less, and more preferably 0.05 mass % or less.

[0029] [Oxygen content] Among the unavoidable impurities, if the oxygen content is high, oxides will form in the copper alloy molded product, resulting in low conductivity. Therefore, it is preferable that the oxygen content be 500 ppm or less. Note that, since additive manufacturing is usually performed in an inert gas atmosphere, the oxygen content after molding is roughly the same as the oxygen content of the powder before molding.

[0030] [Laser light absorption rate of powder at a wavelength of 1064 nm] If the laser's absorption rate at a wavelength of 1064 nm is high, the alloy powder will melt completely, but if the absorption rate is low, the powder will melt partially and unmelted. If this unmelted powder is left inside the molded object, the molded object will have low density and poor strength. The wavelength of 1064 nm is the wavelength of Yb fiber laser light, which is a general-purpose energy source for laser additive manufacturing devices. Laser light absorption rate of 50% or more is preferable.

[0031] [Particle size of Cu-based powder] The average particle diameter D of the Cu-based powder used to form the copper alloy shaped product of the present invention 50 is preferably 10 μm to 100 μm. Fine particles tend to aggregate, making it difficult to spread the powder smoothly when spreading it as in additive manufacturing. Therefore, if the average particle diameter of the Cu-based powder of the present invention is 10 μm or more, it will have excellent fluidity. On the other hand, if it exceeds 100 μm, the relative density of the resulting molded product will decrease. Therefore, the average particle diameter D of the Cu-based powder 50 The average particle diameter D is preferably 10 μm to 100 μm. 50 The lower limit of the average particle diameter D is 20 μm or more, and more preferably 30 μm or more. 50 The upper limit is more preferably 80 μm or less, and even more preferably 60 μm or less.

[0032] Average particle diameter D 50 In the measurement, the total volume of the powder is taken as 100% and a cumulative curve is obtained. The particle diameter at the point on this curve where the cumulative volume is 50% is the average particle diameter D 50 Average particle diameter D 50can be measured by the laser diffraction scattering method. For example, a suitable device for this measurement is the Microtrac MT3000 laser diffraction and scattering particle size distribution analyzer from Nikkiso Co., Ltd. Powder is poured into the cell of this device together with pure water, and the particle size is detected based on the light scattering information of the particles.

[0033] [Tap density of powder] From the standpoint of ease of production of a shaped product, the tap density TD of this powder is preferably 0.10 Mg / m 3 or more and 0.40 Mg / m 3 or less, and particularly preferably 0.15 Mg / m 3 or more and 0.35 Mg / m 3 or less.

[0034] Tap density is measured in accordance with the provisions of "JIS Z 2512." In the measurement, approximately 50 g of powder is filled into a cylinder with a volume of 100 cm3, and the density is measured. The measurement conditions are as follows: Drop height: 10mm Number of taps: 200

[0035] [Sphericity of powder] The sphericity of the powder is preferably 0.80 or more and 0.95 or less. A powder with a sphericity of 0.80 or more has excellent fluidity. From this viewpoint, the sphericity is more preferably 0.83 or more, and particularly preferably 0.85 or more. A powder with a sphericity of 0.95 or less can suppress laser reflection. From this viewpoint, the sphericity is more preferably 0.93 or less, and particularly preferably 0.90 or less.

[0036] To measure sphericity, a test piece is prepared by embedding powder in resin. This test piece is mirror-polished, and the polished surface is observed under an optical microscope. The magnification of the microscope is 100x. Image analysis is performed on 20 randomly selected particles, and the sphericity of these particles is measured. The average of the 20 measurements is the sphericity of the powder. Sphericity refers to the ratio of the maximum length of a single powder particle to the length perpendicular to the maximum length.

[0037] [About Cu-based powder] The production of the Cu-based powder of the present invention will be described below. Examples of methods for producing Cu-based powders include water atomization, single-roll quenching, twin-roll quenching, gas atomization, disk atomization, and centrifugal atomization. Of these, the preferred methods for producing Cu-based powders are single-roll quenching, gas atomization, and disk atomization. Alternatively, the Cu-based powder may be prepared by pulverizing the material using mechanical milling, etc. Examples of milling methods include ball milling, bead milling, planetary ball milling, attritor milling, and vibration ball milling. The Cu-based powder used in the additive manufacturing of the present invention is preferably produced by gas atomization, from the viewpoint of supersaturation of the added components and spheroidization. Therefore, the following embodiments will be described using a Cu-based powder produced by gas atomization.

[0038] [Carbon particle size: average particle size D 50 is between 0.25 μm and 10 μm on a volume average. As the carbon to be adhered to the surface of the Cu-based alloy powder, powder carbon is suitable, and the average particle diameter D 50 The average particle diameter D is preferably 0.25 μm to 10 μm. 50 Powders having an average particle diameter D of 0.25 μm or more are less likely to aggregate, and can be adhered to the surface of the Cu-based alloy powder without being uneven. 50 On the other hand, the average particle size D 50 If carbon powder having an average particle diameter D of more than 10 μm is used for adhesion, the relative density and electrical conductivity of the molded product formed using this powder will decrease. Therefore, from the viewpoint of obtaining a molded product with high relative density and excellent electrical conductivity, it is more preferable that the average particle diameter D of the carbon is more than 10 μm. 50 is 7 μm or less, more preferably 5 μm or less.

[0039] [Laser light absorption rate of carbon black] Carbon, especially carbon black, exhibits a laser light reflectance of 5% or less at a wavelength of 1064 nm, making it a substance that efficiently absorbs laser light. By adhering carbon to the surface of Cu-based powder, the reflectance of laser light at a wavelength of 1064 nm can be reduced. Therefore, activated carbon and graphite can also be used as carbon to be adhered to the surface of Cu-based powder, in addition to carbon black. Regardless of the carbon, it is preferable that the powder to which the carbon is adhered has a laser light reflectance of 50% or less at a laser wavelength of 1064 nm. Carbon black is preferably used as the carbon for the Cu-based powder for the copper alloy shaped product of the present invention.

[0040] [Amount of carbon adhesion] The amount of carbon adhered to the surface of the Cu-based alloy powder is preferably 3.00% by mass or less relative to the Cu-based powder. If the amount of carbon adhered exceeds 3.00% by mass, the relative density of the molded object will decrease. Furthermore, the electrical conductivity will decrease. Therefore, the amount of carbon adhered is preferably 3.00% by mass or less relative to the Cu-based powder, and more preferably 2.00% by mass or less.

[0041] The state of adhesion of carbon to the Cu-based alloy powder may be either uniformly adhered to the surface of the Cu-based alloy powder or not uniformly adhered. When carbon is uniformly adhered to the Cu-based alloy powder, the laser light is absorbed over the entire adhered surface area, resulting in a high-density object even when fabricated at a low energy density.

[0042] On the other hand, when carbon is partially adhered to the surface of the Cu-based alloy powder, the scattered adhered areas melt preferentially, but the heat of fusion also quickly melts the unadhered areas. Therefore, even when molding is performed at a low energy density, a high-density molded product can be obtained. Therefore, the carbon does not need to uniformly cover the surface of the Cu-based alloy powder; it can be adhered in a scattered manner.

[0043] [Production of Cu-based alloy powder] Examples of methods for producing Cu-based powder, which is one of the raw materials before carbon is adhered, include water atomization, single-roll quenching, twin-roll quenching, gas atomization, disk atomization, and centrifugal atomization. Of these, preferred methods for producing Cu-based powder are single-roll quenching, gas atomization, and disk atomization. Furthermore, to produce Cu-based powder, powder can also be obtained by pulverization using mechanical milling or the like. Examples of milling methods include ball milling, bead milling, planetary ball milling, attritor milling, and vibration ball milling.

[0044] From the viewpoint of spheroidization, the Cu-based alloy powder used in the additive manufacturing of the present invention is preferably produced by gas atomization, and therefore, the following embodiments will be described using Cu-based alloy powder produced by gas atomization.

[0045] [Procedure for adhering carbon to the surface of Cu-based alloy powder] Examples of methods for adhering carbon to the surface of Cu-based alloy powder include ball milling, bead milling, planetary ball milling, attritor milling, and vibrating ball milling. Because fine carbon particles tend to aggregate, adhering methods that can impart strong forces such as convection, shear, and diffusion are preferred. Furthermore, to prevent oxidation, dry treatment is preferred for adhering. By adding Cu-based alloy powder and carbon black and milling for a predetermined period of time, carbon is adhered to the surface of the Cu-based alloy powder. By adhering carbon in this manner, a Cu-based powder coated with carbon can be obtained.

[0046] By physically fixing carbon instead of chemically fixing carbon, the time required for carbon fixing can be reduced, and therefore, in the examples, carbon is fixed to the Cu-based alloy powder using a physical method.

[0047] [About the creation of sculptures] A method for producing the shaped object of the present invention using carbon-bonded Cu-based alloy powder includes a rapid melting and solidification process, which involves melting and solidifying a metal powder. Specific examples of this process include three-dimensional additive manufacturing, thermal spraying, laser coating, and build-up welding. Carbon-bonded Cu-based alloy powder is particularly well-suited for absorbing laser light and melting and solidifying at low energy densities, making it suitable for layering and producing shaped objects using a powder bed fusion three-dimensional additive manufacturing method.

[0048] In the powder bed method, the irradiated areas of the spread powder are melted and solidified by irradiation with a laser beam or electron beam. This melting and solidification causes the powder particles to bond together. Irradiation is selectively applied to parts of the metal powder, and the unirradiated areas do not melt, forming a bonded layer only in the irradiated areas.

[0049] New metal powder is then laid on top of the bonded layer, and the powder is irradiated with a laser or electron beam. The irradiation melts and solidifies the metal particles, forming a new bonded layer. The new bonded layer also bonds with the existing bonded layer.

[0050] The repeated melting and solidification caused by irradiation gradually grows the aggregate of bonding layers. This growth results in a three-dimensional object. Using this additive manufacturing method, copper alloy objects with complex shapes can be easily produced.

[0051] The energy density when sintering in a rapid melting and rapid solidification process such as additive manufacturing is 80 to 320 J / mm 3 It is preferable that the energy density is 80 J / mm 3 If the energy density is 100 J / mm or more, sufficient heat is applied to the powder, which prevents unmelted powder from remaining inside the molded object, making it easier to obtain a molded object with a high relative density. 3On the other hand, the energy density is 320 J / mm 3 If the energy density is 280 J / mm or less, the thermal stress caused by heating and cooling can be reduced. Furthermore, by preventing excess heat beyond that required for melting, bumping of the molten metal is suppressed, and defects inside the molded object are suppressed. Therefore, it is more preferable that the energy density is 280 J / mm 3 The following is the result.

[0052] [Relative density of the object] The relative density of the copper alloy shaped product obtained by the rapid melting and rapid solidification process is preferably 97% or more. If the relative density of the copper alloy shaped product obtained by additive manufacturing is 97% or more, the copper alloy shaped product will have few internal defects and excellent electrical conductivity. The relative density is more preferably 98% or more.

[0053] The relative density is calculated based on the ratio of the density of a 10 mm square test piece produced by additive manufacturing or other methods to the bulk density of the raw material powder. First, the density of a 10 mm square test piece can be measured by the Archimedes method. The bulk density of a powder can be measured using a dry density measuring instrument. For example, bulk density can be measured using the constant volume expansion method, which utilizes He gas substitution. An example of a suitable instrument for this measurement is Shimadzu's AccuPyc1330 dry automatic density meter. The powder is filled into the cell of this instrument, and the density is measured.

[0054] [Heat treatment] In the heat treatment of the copper alloy shaped product, an aging heat treatment is performed on the unheat-treated shaped product. The aging heat treatment causes a single phase of elemental components of element group M and / or a compound of Cu and elemental components of element group M to precipitate at the grain boundaries. This precipitation can increase the purity of Cu in the matrix of the copper alloy shaped product. This matrix contributes to the electrical conductivity of the copper alloy shaped product, similar to the formation of carbides.

[0055] When the aging heat treatment temperature is 350°C or higher, a structure in which a single phase of the element group M and / or a compound of Cu and the element group M is sufficiently precipitated is obtained. Therefore, the aging heat treatment temperature is more preferably 400°C or higher. When the aging heat treatment temperature is 1000°C or lower, the solid solution of the element group M in the matrix phase of the copper alloy shaped product is suppressed. Therefore, the aging heat treatment temperature is more preferably 900°C or lower.

[0056] When the aging heat treatment time is 1 hour or longer, a structure in which a single phase of the element component of element group M and / or a compound of Cu and the element component of element group M are sufficiently precipitated is obtained. On the other hand, when the aging heat treatment time is 10 hours or shorter, a decrease in electrical conductivity and strength due to coarsening of precipitates caused by overaging can be suppressed. Therefore, the aging heat treatment time is preferably 1 hour or longer and 10 hours or shorter.

[0057] [Precipitates (carbides)] Carbide containing element M exists inside the copper alloy shaped product. The precipitation of this carbide means that element M, which was dissolved in the Cu matrix, is expelled, contributing to improved electrical conductivity. If the size of the precipitate exceeds 1000 nm, it will obstruct the conductive path and reduce strength. From this perspective, it is preferable that the size of the carbide containing element M be 1000 nm or less.

[0058] [Electrical conductivity of copper alloy molded objects] The copper alloy shaped product after the heat treatment preferably has an electrical conductivity of 70% IACS or more. A shaped product with an electrical conductivity of 70% IACS or more has excellent electrical conductivity. More preferably, the electrical conductivity is 80% IACS or more.

[0059] [Measurement of electrical conductivity] Test pieces (3 x 2 x 60 mm) were prepared and the electrical resistance (Ω) was measured using the four-terminal method in accordance with JIS C 2525. The measurement was performed using an ULVAC-RIKO TER-2000RH model device. The measurement conditions were as follows: Temperature: 25℃ Current: 4A Voltage drop distance: 40mm The electrical resistivity ρ (Ωm) was calculated based on the following formula. ρ=R / I×S In this formula, R is the electrical resistance value (Ω) of the test specimen, I is the current (A), and S is the cross-sectional area of ​​the test specimen (m2). The electrical conductivity (S / m) was calculated from the reciprocal of the electrical resistivity ρ. In addition, the electrical conductivity (%IACS) of each test specimen was calculated, assuming that 5.9 x 107 (S / m) is 100% IACS.

[0060] [Example] The effects of the present invention will be confirmed by examples. In the following, an example will be described in which a copper alloy shaped article of the present invention is produced by an additive manufacturing method using a Cu-based powder whose particle surfaces are coated with C. Note that the present invention should not be construed as being limited by the description of these examples.

[0061] The powder used for shaping is generally obtained by gas atomizing a Cu-based powder, and then coating the surface of the powder with C using a dry mixer to obtain a C-coated Cu-based powder. The composition of the C-coated Cu-based powder before shaping is shown in Table 1. The remainder of the components in Table 1 is Cu and unavoidable impurities. That is, the chemical components in Table 1 are the components of the C-coated Cu-based powder before shaping. For example, in Example 1, the amount of C adhered to the surface of the Cu-based powder is 0.10%, so the portion of the Cu-based powder that is coated is copper and unavoidable impurities, and the amount thereof is 99.90%. Furthermore, there was no change in the component composition shown in Table 1 before and after molding, and the components shown in Table 1 match the component composition of the copper alloy molded object.

[0062] In the gas atomization process in the examples, raw materials having a predetermined composition, excluding C from the components in Table 1, were heated by high-frequency induction heating in an alumina crucible in a vacuum, and then melted. The molten metal was then dropped from a nozzle with a diameter of 5 mm located below the crucible. Argon gas was then sprayed onto the molten metal to obtain a large number of particles. These particles were then classified to remove particles with a diameter exceeding 63 μm, and a Cu-based powder was obtained.

[0063] These Cu-based powders and carbon powder (thermal black) were placed in a dry mixer (manufactured by Hosokawa Micron Corporation) and stirred to obtain C-coated Cu-based powders as shown in the examples in Table 1.

[0064] [Laser light absorption rate measurement] The laser light reflectance of the obtained C-coated Cu-based powder at a laser wavelength of 1064 nm was measured using a spectrophotometer. The laser light absorptance was calculated as 100 - "laser light reflectance (%)". The results are shown in Table 1.

[0065] [Table 1]

[0066] [molding] Using the obtained C-coated Cu-based powders as raw materials, additive manufacturing was carried out using a three-dimensional additive manufacturing device (EOS-M280) to obtain copper alloy objects (unheat-treated objects).

[0067] [Heat treatment] The unheat-treated shaped objects were subjected to heat treatment (aging treatment) at 350 to 1000°C for 1 to 10 hours. These heat treatment conditions were determined based on the composition of each material.

[0068] [Relative density measurement] Test pieces (10 x 10 x 10 mm) were prepared from the heat-treated molded products, and the relative density (%) was measured. The results are shown in Table 2.

[0069] [Electrical conductivity measurement] Test pieces (3 x 2 x 60 mm) were prepared from each of the heat-treated copper alloy molded products, and the electrical conductivity (%IACS) was measured using the four-terminal method in accordance with JIS C 2525. The results are shown in Table 2.

[0070] [Table 2]

[0071] [Precipitate size measurement] Thin film test pieces were fabricated from copper alloy shaped articles obtained using the Cu-based powders of the examples as raw materials by FIB (focused ion beam) processing. Each test piece was observed with a transmission electron microscope (TEM) to confirm the size (maximum diameter) of the precipitates and carbon elemental particles. The particle diameter of the precipitates and carbon elemental particles was measured by TEM at 100 μm. 2 The maximum diameter of the inclusions and particles of pure carbon was determined. Note that pure carbon has a smaller diameter than carbide precipitates, so when both particles are present, the diameter of the carbide precipitates is the maximum diameter. The results are shown in Table 3. Since Example 10 is made of only simple carbon, Example 10 in Table 3 is the maximum diameter (nm) of simple carbon.

[0072] [Evaluation Rating] The properties of the copper alloy molded products were rated on a three-level scale based on the following criteria, and the results are shown in Table 3. ◎: Relative density 98% or more and electrical conductivity 80% IACS or more. Rating: Relative density 97% or more and electrical conductivity 70% IACS or more. Rating ×: Relative density less than 97% or electrical conductivity less than 70% IACS.

[0073] [Table 3]

[0074] As can be seen from Table 2, the copper alloy shaped article of the present invention has a high density, and even when the additive element M is added, the shaped article has sufficiently excellent electrical conductivity.

[0075] [Comparative Example] Comparative examples are shown in Tables 4 to 6. In all cases, copper alloy shaped articles obtained by additive manufacturing of Cu-based powders were evaluated in the same manner. Comparative Examples 2 and 3 were examples in which the amount of C was excessive, resulting in reduced electrical conductivity. Comparative Examples 4 to 13 were examples in which the amount of element component M was excessive, resulting in reduced electrical conductivity. Comparative Example 1 did not contain C, resulting in poor laser light absorption and therefore a low relative density.

[0076] [Table 4]

[0077] [Table 5]

[0078] [Table 6]

Claims

1. An additive manufacturing product having a relative density of 97% or more, made from copper alloy powder containing, by mass%, 0.01 to 3.00% C, 0.1 to 5.0% element M (wherein element M is one or more components selected from Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, and Al), with the remainder being Cu and unavoidable impurities.

2. 2. The copper alloy shaped article according to claim 1, which contains at least one of precipitates of carbide of element M and elemental carbon.

3. 3. The shaped object according to claim 2, wherein the precipitates and the carbon element have a particle size of 1000 nm or less.

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