JP2023024164A - Copper alloy molding having excellent electrical conductivity - Google Patents

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

The present invention relates to a copper alloy shaped article formed using a copper alloy powder suitable for processes involving rapid melting, rapid cooling and solidification, such as three-dimensional additive manufacturing, thermal spraying, laser coating, and build-up. In particular, the present invention relates to a copper alloy molded article having excellent electrical conductivity, which is formed using a copper alloy powder suitable for lamination molding by a powder bed method (powder bed fusion bonding method).

3D printers are beginning to be used to create objects made of metal. This 3D printer is a device that manufactures a modeled object by the additive manufacturing method. Typical methods of the metal additive manufacturing method include the powder bed method (powder bed fusion method) and the metal deposition method (directed energy deposition). method), etc. In the powder bed method, irradiated portions of the spread powder are melted and solidified by irradiation with a laser beam or an electron beam. This melting and solidification binds the powder particles together. The irradiation is selectively applied to a portion of the metal powder, the non-irradiated portion does not melt, and a bonding layer is formed only on the irradiated portion.

New metal powder is spread over the formed bonding layer, and the metal powder is irradiated with a laser beam or an electron beam. The irradiation then melts and solidifies the metal particles to form a new bonding layer. The new tie layer is also bonded to the existing tie layer.

By successively repeating melting and solidification by irradiation, an aggregate of the bonding layer gradually grows. Through this growth, a model having a three-dimensional shape is obtained. Using such a layered manufacturing method makes it possible to easily obtain a modeled object having a complicated shape.

As a powder bed type additive manufacturing method, a mixture of "iron-based powder" and "one or more powders selected from the group consisting of nickel, nickel-based alloys, copper, copper-based alloys, and graphite" is used. Used as a metal powder for metal stereolithography, a powder layer forming step of spreading these metal powders, a sintered layer forming step of irradiating the powder layer with a beam to form a sintered layer, and a removal by cutting the surface of the modeled object A procedure of forming a sintered layer by repeating steps to manufacture a three-dimensional shaped product is disclosed (see Patent Document 1).

High conductivity is required for alloys such as high-frequency induction heating devices and heat sinks for cooling motors. Cu-based alloys are suitable for such applications. Since the parts used for these applications have complicated shapes, methods using the additive manufacturing method are attracting attention, and the merits of the additive manufacturing method can be utilized.

However, since copper has a low light absorptivity at a laser wavelength of 1064 nm, which is used for general-purpose laser lamination molding, sufficient energy required for melting and solidification cannot be obtained, making it difficult to produce a modeled object. Therefore, development of copper alloys with improved light absorptance and excellent formability is underway.
For example, a copper alloy containing copper as a main component and having a solid solution amount in copper of less than 0.2 at % has been proposed (see Patent Document 2). This proposal is intended to obtain mechanical strength while reducing the decrease in electrical conductivity due to solid solubility in copper by using an additive element with a low solid solubility in copper. In this method, an element that is difficult to form a solid solution with copper is added in a non-solubilized form.

JP-A-2008-81840 International Publication No. 2019/039058

Laminated manufacturing is a process of forming a modeled object by irradiating it with an electron beam or laser, and energy absorption with respect to metal powder is an important factor in modeling. For example, in the case of the laser lamination molding method, the lower the laser light reflectance with respect to the laser wavelength to be irradiated, the easier the energy absorption becomes, and the more efficient the molding can be performed.

However, since copper has a high reflectance of laser light, it is difficult to absorb energy and it is difficult to improve the efficiency, so high-density modeling is difficult. Addition of additional elements makes it easier to absorb laser light and facilitate high-density modeling, but the amount of solid solution in the copper alloy matrix increases, so the electrical conductivity decreases.

The object of the present invention is to use a copper alloy powder that is suitable for processes involving rapid melting and rapid solidification such as additive manufacturing, enables the production of high-density molded objects, and provides molded objects with high electrical conductivity. To provide a shaped article having excellent electrical conductivity, formed by

As a result of intensive studies, the present inventors focused on carbon (including carbon black, activated carbon, and graphite) with excellent light absorption rate, and used a copper alloy powder in which this carbon layer was non-chemically fixed to the powder surface. The inventors have invented a copper alloy molded article having excellent electrical conductivity produced by A carbon layer is fixed to the surface layer of the copper alloy powder to increase the laser light absorption rate, so that a high-density model can be obtained.

The C component of the powder surface carbonized layer reacts with the element M component dissolved in the copper alloy powder to form a carbide during the production of the molded product. can be obtained, it becomes a modeled article that is also excellent in electrical conductivity. That is, by discharging the additive element to the grain boundary as a carbide, the amount of solid solution in the matrix becomes small, so that electrical conductivity close to that of pure Cu can be obtained. Furthermore, since these carbides are fine, they contribute to the improvement of strength, realizing a copper alloy shaped article excellent in formability, electrical conductivity, and strength.

Therefore, the first means for solving the problems of the present invention is mass %, C: 0.01 to 3.00%, element M as an optional additive component: 0.0 to 5.0% or less (However, the element M is one or more of Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, and Al.), and copper with the balance being Cu and unavoidable impurities It is an alloy molding.

A second means is the copper alloy shaped article according to the first means, wherein the copper alloy shaped article contains at least one of a carbide precipitate of the element M and a simple substance of carbon.

The third means is the copper alloy shaped article according to the second means, characterized in that the grain size of the precipitates and simple carbon is 1000 nm or less.

These copper alloy shaped objects contain 0.0 to 5.0% by mass of element M (M: Zr, Hf, Ti, Nb, V, Mo, Mn, Cr, W, Al from 1, or 2 or more), the surface of the Cu-based powder, the balance of which consists of Cu and unavoidable impurities, is further coated with 0.01 to 3.00% carbon, which is a carbon layer that is a non-chemical reaction layer It may be a copper alloy shaped article formed using a Cu-based powder with a powder.

These copper alloy shaped articles may be copper alloy shaped articles that are layered and formed by a layered manufacturing method using these Cu-based powders.
When a carbon layer is adhered to the surface of the powder used for layered manufacturing, the energy efficiency during layered manufacturing is excellent, so a high-density copper alloy shaped article can be obtained. Moreover, it is excellent also in electrical conductivity.

Preferably, it is a copper alloy shaped article having a relative density of 97% or more.

Preferably, it is a copper alloy shaped article that satisfies an electrical conductivity of 70% IACS or higher.

The copper alloy shaped article of the present invention contains precipitates of carbide of the element M and carbon, so that the copper alloy shaped article has excellent electrical conductivity. This is because the aging heat treatment causes the elemental components and compounds of the element group M to precipitate at the grain boundaries, thereby increasing the purity of Cu in the matrix phase of the copper alloy shaped product.
A copper alloy shaped article produced using a powder in which a carbon layer, which is a non-chemically reactive layer, is adhered to the powder surface of the Cu-based powder has additive elements dissolved in the matrix of the Cu-based powder. Since the copper alloy shaped article is discharged as carbides of 1000 nm or less, the copper alloy shaped article has a matrix structure close to that of pure Cu and has excellent electrical conductivity.
In addition, when the grain size of the precipitates or simple carbon of the copper alloy model is 1000 nm or less, the element M dissolved in the matrix is discharged from the matrix as a carbide, and the electrical conductivity of the model is reduced. will be excellent.

Prior to the description of the embodiments of the shaped article of the present invention, the reasons for defining the components of the copper alloy shaped article, the components used in the carbon-adhered Cu-based powder, the shape, and the characteristics will be described below.

[About carbon]
C: 0.01-3.00%
The carbon-adhered Cu-based powder suitable for obtaining the copper alloy shaped article of the present invention is obtained by adhering a carbon layer, which is a non-chemical reaction layer, to the surface of the Cu-based powder. This is for facilitating absorption of laser light during modeling of a copper alloy modeled object. C is difficult to dissolve in a solid state and can be said to be an impurity in copper alloys. Therefore, 0.01% or more of C is contained in the copper alloy shaped article. On the other hand, if it exceeds 3.00%, the demerit as an impurity exceeds. Therefore, C should be 0.01 to 3.00% by mass.
In addition, the time required for carbon adhesion can be shortened by physically fixing the carbon instead of chemically fixing it. From these points of view, it is preferable to use a physical method to fix the carbon to the Cu-based powder.
As used herein, "carbon" refers to carbon black, activated carbon, graphite, and combinations thereof. Carbon black is preferable for the present invention because it is excellent in laser light energy absorption, and in the description of the following examples, carbon black will be described as a representative example, but of course other carbon materials are excluded. isn't it.

[About the components of the model]
[Element M]
Elements M as optional components are Zr (zirconium), Hf (hafnium), Ti (titanium), Nb (niobium), V (vanadium), Mo (molybdenum), Mn (manganese), Cr (chromium), W (tungsten) and Al (aluminum). Two or more kinds can also be selected.
These elements M are elements that form carbides with C from the equilibrium diagram. Until the laser is irradiated during molding, the element M is dissolved in the mother phase and the carbon layer adheres to the powder surface. A dense model is obtained. When the melting and solidification is completed, the element M solid-dissolved in the matrix is discharged from the matrix as carbide, resulting in a structure close to that of pure Cu and a model having high electrical conductivity.
[Content of element M]
The element M dissolves in the Cu component of the mother phase of the Cu-based powder, thereby improving the laser light absorptance. Therefore, it is preferable to add the element M to the Cu-based powder.
However, if the addition amount is increased more than necessary, even if the solid-solution element M is discharged from the matrix as carbides when the copper alloy shaped article is formed, the element M will be in a state of being partially solid-dissolved in the matrix. This leads to a decrease in electrical conductivity. Therefore, the content of the selectively added element M in the copper alloy shaped article is preferably 5.0% by mass or less.

In addition to the element M, the following elements may be included 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 the copper alloy. Furthermore, since it is an element sensitive to crack generation during molding, it is necessary not to contain it in a large amount.

[Si (silicon)]
Si dissolves in Cu and inhibits the electrical and thermal conductivity of the copper alloy. From this point of view, the Si content is preferably 0.10% by mass or less, more preferably 0.05% by mass or less.

[P (phosphorus)]
P dissolves in Cu and inhibits electrical and thermal conduction of the copper alloy. From this point of view, the P content is preferably 0.10% by mass or less, more preferably 0.05% by mass or less.

[S (sulfur)]
S dissolves in Cu and inhibits the electrical and thermal conduction of the copper alloy. From this point of view, the S content is preferably 0.10% by mass or less, more preferably 0.05% by mass or less.

[Oxygen content]
Of the unavoidable impurities, when the oxygen content increases, oxides are formed in the copper alloy shaped article, resulting in lower electrical conductivity. Therefore, the oxygen content is preferably 500 ppm or less. In addition, since lamination modeling is usually carried out in an inert gas atmosphere, the oxygen content after modeling is approximately the same as the oxygen content of the powder before modeling.

[Laser light absorption rate of powder at wavelength 1064 nm]
If the absorptivity of the laser at a wavelength of 1064 nm is high, the alloy powder will be completely melted, but if the absorptivity is low, it will be partially melted and unmelted powder will remain. If this unmelted powder is left behind inside the model, a model with low density and poor strength is formed. Note that the wavelength of 1064 nm is the wavelength of Yb fiber laser light, which is a general-purpose energy source for laser lamination molding apparatuses. The laser light absorptance is preferably 50% or more.

[Particle size of Cu-based powder]
The average particle diameter D ₅₀ of the Cu-based powder used for molding the copper alloy molded article of the present invention is preferably 10 μm to 100 μm. Since fine particles tend to agglomerate, it becomes impossible to spread the powder smoothly as in layered manufacturing. Therefore, when the average particle size of the Cu-based powder of the present invention is 10 μm or more, the fluidity is excellent. On the other hand, if it exceeds 100 μm, the relative density of the resulting shaped article will decrease. Therefore, the average particle diameter D ₅₀ of the Cu-based powder is preferably 10 μm to 100 μm. More preferably, the lower limit of the average particle diameter _D50 is 20 µm or more, and still more preferably 30 µm or more. Also, the upper limit of the average particle diameter _D50 is more preferably 80 μm or less, and still more preferably 60 μm or less.

In the measurement of the average particle size _D50 , the total volume of the powder is taken as 100% and the cumulative curve is obtained. The particle size at the point on this curve where the cumulative volume is 50% is the average particle _D50 . The average particle size _D50 can be measured by a laser diffraction scattering method. For example, as an apparatus suitable for this measurement, Nikkiso Co., Ltd.'s laser diffraction/scattering particle size distribution measuring apparatus "Microtrac MT3000" can be mentioned. 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.

[Powder tap density]
The tap density TD of the powder is preferably 0.10 Mg/m3 or more and 0.40 Mg/m3 or less, and particularly preferably 0.15 Mg/m3 or more and 0.35 Mg/m3 or less, from the viewpoint of facilitating the production of shaped objects.

The tap density is measured in accordance with "JIS Z 2512". For the measurements, about 50 g of powder are packed into a cylinder with a volume of 100 cm 3 and the density is measured. The measurement conditions are as follows.
Drop height: 10mm
Number of taps: 200

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

In the measurement of sphericity, a specimen with powder embedded in resin is prepared. This test piece is subjected to mirror polishing, and the polished surface is observed with an optical microscope. The magnification of the microscope is 100x. Image analysis is performed on 20 randomly selected particles to measure the sphericity of the particles. The average of 20 measurements is the sphericity of the powder. The sphericity means the maximum length of one powder particle and the ratio of the length in the direction perpendicular to the maximum length.

[About Cu-based powder]
The production of the Cu-based powder of the present invention is described below.
Examples of methods for producing Cu-based powder include water atomization, single roll quenching, twin roll quenching, gas atomization, disk atomization and centrifugal atomization. Among these, preferred methods for producing a Cu-based powder are the single roll cooling method, the gas atomization method and the disc atomization method.
Further, in order to prepare the Cu-based powder, mechanical milling or the like can be performed to pulverize the powder to obtain powder. Examples of milling methods include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method and a vibrating ball mill method.
The gas atomization method is particularly preferable for the Cu-based powder used for layered manufacturing in the present invention, from the viewpoint of supersaturated solid solution of additive components and spheroidization. Therefore, in the following embodiments, a Cu-based powder obtained by gas atomization will be used for explanation.

[Carbon particle size: average particle size D ₅₀ is 0.25 μm or more and 10 μm or less in volume average]
Powdered carbon is suitable as the carbon to be adhered to the surface of the Cu-based alloy powder, and the average particle diameter D ₅₀ of the carbon is preferably 0.25 μm to 10 μm. A powder having an average particle diameter D ₅₀ of 0.25 μm or more is less likely to agglomerate, so that it can be uniformly adhered to the surface of the Cu-based alloy powder. Therefore, the average particle diameter _D50 is more preferably 0.30 μm or more. On the other hand, if a carbon powder having an average particle diameter _D50 exceeding 10 μm is used for bonding, the relative density and electrical conductivity of a model formed using this powder will decrease. Therefore, from the viewpoint of obtaining a shaped article having a high relative density and excellent electrical conductivity, the average particle diameter _D50 of carbon is more preferably 7 μm or less, and particularly preferably 5 μm or less.

[Laser light absorption rate of carbon black]
Carbon, particularly carbon black, exhibits a laser beam reflectance of 5% or less at a wavelength of 1064 nm, and can be said to be a substance that efficiently absorbs laser beams. Therefore, the laser light reflectance at a wavelength of 1064 nm can be reduced by adhering to the surface of the Cu-based powder. Therefore, as the carbon to be adhered to the surface of the Cu-based powder, activated carbon and graphite can be used in addition to carbon black.
Regardless of the type of carbon, the laser light reflectance of the carbon-fixed powder is preferably 50% or less at a laser wavelength of 1064 nm. Carbon black can be suitably applied as the carbon used in the Cu-based powder for the copper alloy molded article of the present invention.

[Amount of carbon adhered]
The amount of carbon adhered to the surface of the Cu-based alloy powder is preferably 3.00% by mass or less with respect to the Cu-based powder. If the amount of carbon adhered exceeds 3.00% by mass, the relative density of the modeled object rather decreases. Furthermore, electrical conductivity is reduced. Therefore, the amount of carbon adhering to the Cu-based powder is preferably 3.00% by mass or less, more preferably 2.00% by mass or less.

In addition, the carbon adhered to the Cu-based alloy powder may be adhered uniformly to the surface of the Cu-based alloy powder or not uniformly adhered to the surface of the Cu-based alloy powder.
When carbon is uniformly adhered to the Cu-based alloy powder, laser light is absorbed over the entire surface area where the carbon is adhered, so even when the object is formed with a low energy density, a high-density model can be obtained.

On the other hand, in the case of the powder that is partially adhered to the surface of the Cu-based alloy powder, the scattered and adhered portions are preferentially melted, but the non-fixed portions are quickly melted by the heat of fusion. I can let you. Therefore, a high-density modeled object can be obtained even when it is modeled with a low energy density. Therefore, the carbon does not need to cover the surface of the Cu-based alloy powder uniformly, and may adhere to the surface in a scattered manner.

[Production of Cu-based alloy powder]
Examples of the method for producing the Cu-based powder, which is one of the raw materials before carbon is fixed, include water atomization, single roll quenching, twin roll quenching, gas atomization, disc atomization, and centrifugal atomization. Among these, preferred methods for producing a Cu-based powder are the single roll cooling method, the gas atomization method and the disc atomization method. Further, in order to prepare the Cu-based powder, mechanical milling or the like can be performed to pulverize the powder to obtain powder. Examples of milling methods include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method and a vibrating ball mill method.

From the viewpoint of spheroidizing the Cu-based alloy powder used for additive manufacturing in the present invention, the gas atomization method is particularly preferable. Therefore, in the following embodiments, Cu-based alloy powder obtained by gas atomization will be used for explanation.

[Procedure for fixing carbon to the surface of Cu-based alloy powder]
Examples of methods for fixing carbon to the surface of the Cu-based alloy powder include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, and a vibrating ball mill method. Since fine carbon tends to aggregate, a fixing method capable of imparting convection, shear, and diffusion with a strong force is preferable. Moreover, in order to prevent oxidation, it is preferable to use a dry treatment when fixing. The Cu-based alloy powder and carbon black are added and milled for a predetermined time, whereby the carbon adheres to the surface of the Cu-based alloy powder. By fixing C in this manner, a Cu-based powder coated with C can be obtained.

By physically fixing the carbon instead of chemically fixing it, the time required for the carbon fixing can be shortened. Therefore, in the embodiments, a physical method is used to fix the carbon to the Cu-based alloy powder.

[About production of modeled objects]
As a method for producing the shaped article of the present invention using the carbon-adhered Cu-based alloy powder, there is a rapid melting, rapid cooling and solidification process, which is a process of melting and solidifying the metal powder. Specific examples of this process include three-dimensional additive manufacturing, thermal spraying, laser coating and overlaying. In particular, the carbon-adhered Cu-based alloy powder is suitable for melting and solidifying at a low energy density by absorbing laser light. It is suitable for making while laminating.

In the powder bed method, irradiated portions of the spread powder are melted and solidified by irradiation with a laser beam or an electron beam. This melting and solidification binds the powder particles together. The irradiation is selectively applied to a portion of the metal powder, the non-irradiated portion does not melt, and a bonding layer is formed only on the irradiated portion.

New metal powder is spread over the formed bonding layer, and the metal powder is irradiated with a laser beam or an electron beam. The irradiation then melts and solidifies the metal particles to form a new bonding layer. The new tie layer is also bonded to the existing tie layer.

By successively repeating melting and solidification by irradiation, an aggregate of the bonding layer gradually grows. Through this growth, a model having a three-dimensional shape is obtained. Using such an additive manufacturing method, a copper alloy shaped article having a complicated shape can be easily obtained.

The energy density for sintering in a rapid melting, rapid cooling and solidification process such as the additive manufacturing method is preferably 80 to 320 J/mm ³ . When the energy density is 80 J/mm ³ or more, sufficient heat is applied to the powder, so that unmelted powder is suppressed from remaining inside the model, and a model with a high relative density can be easily obtained. More preferably, the energy density is 100 J/mm ³ or higher. On the other hand, when the energy density is 320 J/mm ³ or less, the thermal stress associated with heating and cooling can be reduced. Furthermore, in order to prevent excessive heat more than necessary for melting, bumping of the molten metal is suppressed, and defects inside the model are suppressed. Therefore, more preferably, the energy density is 280 J/mm ³ or less.

[Relative Density of Molded Object]
The relative density of the copper alloy shaped article obtained by the rapid melting, rapid cooling and solidification process is preferably 97% or more. If the relative density of the copper alloy shaped article by additive manufacturing is 97% or more, the copper alloy shaped article having few defects inside the shaped article and excellent electrical conductivity can be obtained. Relative density is more preferably 98% or more.

The relative density is calculated based on the ratio between the density of a 10 mm square test piece prepared by lamination molding or the like and 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 powder can be measured by a dry density measuring instrument. For example, the bulk density can be measured by a constant volume expansion method using He gas replacement. An apparatus suitable for this measurement includes a dry automatic density meter "AccuPyc1330" manufactured by Shimadzu Corporation. The powder is filled into the cell of this device and the density is measured.

[Heat treatment]
In the heat treatment of the copper alloy shaped article, a step of subjecting the unheated shaped article to aging heat treatment is performed. Due to the aging heat treatment, a single phase of the elemental component of the element group M and/or a compound of Cu and the elemental component of the element group M are precipitated at the grain boundary. This precipitation can increase the purity of Cu in the parent phase of the copper alloy shaped article. This matrix contributes to the electrical conductivity of the copper alloy shape as well as to carbide formation.

When the temperature of the aging heat treatment is 350° C. or higher, a structure in which a single phase of elemental components of element group M and/or compounds of Cu and elemental components of element group M are sufficiently precipitated is obtained. Therefore, the temperature of the aging heat treatment is more preferably 400° C. or higher. When the temperature of the aging heat treatment is 1000° C. or less, solid solution of the element group M in the mother phase in the copper alloy shaped article is suppressed. Therefore, the temperature of the aging heat treatment is more preferably 900° C. or less.

When the time of the aging heat treatment is 1 hour or longer, a structure in which a single phase of elemental components of the element group M and/or a compound of Cu and the elemental components of the element group M are sufficiently precipitated is obtained. On the other hand, when the aging heat treatment time is 10 hours or less, it is possible to suppress the reduction in electrical conductivity and strength due to the coarsening of precipitates due to overaging. Therefore, the time for the aging heat treatment is preferably 1 hour or more and 10 hours or less.

[Precipitates (carbides)]
Carbides containing the element M are present inside the copper alloy shaped article. Precipitation of this carbide means that the element M solid-dissolved in the Cu matrix is discharged, and contributes to the improvement of electrical conductivity. If the size of the precipitate exceeds 1000 nm, it will hinder the conductive path and reduce the strength. From this point of view, the size of the carbide containing the element M is preferably 1000 nm or less.

[Electrical conductivity of copper alloy model]
The electrical conductivity of the copper alloy shaped article after heat treatment is preferably 70% IACS or more. A model having an electrical conductivity of 70% IACS or more has excellent electrical conductivity. More preferably, the electrical conductivity is 80% IACS or higher.

[Measurement of electrical conductivity]
A test piece (3×2×60 mm) was prepared, and the electric resistance value (Ω) was measured by the four-probe method based on "JIS C 2525". For the measurement, an apparatus "TER-2000RH" manufactured by ULVAC-RIKO was used. The measurement conditions are as follows.
Temperature: 25°C
Current: 4A
Distance between voltage drops: 40mm
The electric 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 piece, I is the current (A), and S is the cross-sectional area (m 2 ) of the test piece. The electrical conductivity (S/m) was calculated from the reciprocal of the electrical resistivity ρ. Also, the electrical conductivity (%IACS) of each test piece was calculated with 5.9×10 7 (S/m) as 100%IACS.

[Example]
Examples show that the effects of the present invention are confirmed. In the following, an example in which the copper alloy modeled article of the present invention is produced by an additive manufacturing method using a Cu-based powder whose particle surfaces are coated with C will be described. It should be noted that the present invention is not limitedly interpreted based on the description of this example.

First, the powder used for modeling is roughly gas-atomized to obtain a Cu-based powder, and then the surface thereof is coated with C using a dry stirrer to obtain a C-coated Cu-based powder. Table 1 shows the composition of the C-coated Cu-based powder before shaping. The remainder of the components in Table 1 are 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 fixed to the surface of the Cu-based powder is 0.10%. The Cu-based powder portion on the side to be coated is copper and unavoidable impurities, the amount of which is 99.90%.
In addition, before and after molding, there is no change in the composition shown in Table 1, and the composition shown in Table 1 matches the composition of the copper alloy shaped article.

Gas atomization in the examples was carried out by heating a raw material having a predetermined composition excluding C from the components shown in Table 1 by high-frequency induction heating in a vacuum in an alumina crucible, melting it, and then dissolving the material under the crucible with a diameter of 5 mm. The molten metal was dropped from the nozzle of. Next, argon gas was sprayed toward this molten metal to obtain a large number of particles. These particles were classified to remove particles with a diameter greater than 63 μm to obtain a Cu-based powder.

These Cu-based powders and carbon powder (thermal black) were placed in a dry stirrer (manufactured by Hosokawa Micron Corporation) and stirred to obtain C-coated Cu-based powders described in Table 1.

[Measurement of laser light absorption rate]
The resulting C-coated Cu-based powder was measured for laser light reflectance at a laser wavelength of 1064 nm using a spectrophotometer. The laser light absorptivity was calculated as 100-“laser light reflectance (%)”%. Results are shown in Table 1.

[molding]
Using the obtained C-coated Cu-based powder as a raw material, the additive manufacturing method was carried out using a three-dimensional additive manufacturing apparatus (EOS-M280) to obtain a copper alloy model (unheat-treated model).

[Heat treatment]
A heat treatment (aging treatment) was applied to the non-heat-treated molded article at 350 to 1000° C. for 1 to 10 hours. These heat treatment conditions are heat treatments that are considered appropriate according to each composition.

[Relative density measurement]
A test piece (10×10×10 mm) was prepared for each shaped article after the heat treatment, and the relative density (%) was measured. Table 2 shows the results.

[Electrical conductivity measurement]
A test piece (3×2×60 mm) was prepared for each of the heat-treated copper alloy shaped objects, and the electrical conductivity (%IACS) was measured by the four-probe method according to "JIS C 2525". Table 2 shows the results.

[Measurement of precipitate size]
A thin-film test piece was prepared by FIB (focused ion beam) processing from each copper alloy model obtained using the Cu-based powder of the example as a raw material. Each test piece was observed with a transmission electron microscope (TEM) to confirm the size (maximum diameter) of precipitates and simple carbon. The grain size of the precipitates and simple carbon particles was observed with a TEM at 100 μm ² , and the maximum diameter among the particles of inclusions and simple carbon particles observed was determined. Since the carbon alone has a smaller diameter than the precipitates of carbides, when both are present, the diameter of the precipitates of carbides is the maximum diameter referred to herein.
Table 3 shows the results. Since Example 10 contains only carbon alone, Example 10 in Table 3 is the maximum diameter (nm) of carbon alone.

[Rating]
Table 3 shows the results of three-level grading based on the following criteria regarding the properties of copper alloy shaped articles.
Evaluation ⊚: Relative density of 98% or more and electric conductivity of 80% IACS or more.
Evaluation ◯: Relative density of 97% or more and electric conductivity of 70% IACS or more.
Evaluation x: Relative density less than 97% or electrical conductivity less than 70% IACS.

From Table 2, the copper alloy molded article of the present invention has a high density, and even when the additive element M is added, a molded article having sufficiently excellent electrical conductivity can be obtained.

[Comparative example]
Comparative examples are shown in Tables 4-6. In both cases, a copper alloy modeled product obtained by laminate-molding a Cu-based powder was evaluated in the same manner.
Comparative Examples 2 and 3 were examples in which the amount of C was excessive, and the electric conductivity was lowered. In Comparative Examples 4 to 13, the elemental component M was excessive and the electric conductivity was lowered. Comparative Example 1 did not contain C and had poor laser light absorptance, resulting in a low relative density.

Claims (3)

% by mass, C: 0.01 to 3.00%, element M as an optional additive component: 0.0 to 5.0% or less (where element M is Zr, Hf, Ti, Nb, V, Mo , Mn, Cr, W, and Al), and the balance is Cu and unavoidable impurities. 2. The copper alloy shaped article according to claim 1, containing at least one of carbide precipitates of the element M and elemental carbon. 3. The shaped article according to claim 2, wherein the particle size of the precipitates and the simple carbon is 1000 nm or less.