Copper-based powder, its manufacturing method, and manufacturing method of optically modeled object using copper-based powder

Abstract

To provide a copper-based powder that has laser light absorptivity and flowability suitable for metal stereolithography such as powder bed fusion (PBF), and can give a molding having high hardness.SOLUTION: A copper-based powder comprises particles with an average particle size of 1 μm or more and 100 μm or less, the particles comprising copper particles, and carbides deposited on at least part of the copper particle surfaces, with a reflectance of 60% or less at the wavelength 1070 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper-based powder, and more particularly to a copper-based powder used in metal laser sintering, which produces a three-dimensionally shaped object by irradiation with an energy beam such as a laser beam. [Background technology]

[0002] Three-dimensional (3D) printing, a type of machine that can easily produce three-dimensional (3D) objects, is becoming increasingly popular. Among the methods for producing objects using these 3D printing machines, powder bed fusion (L-PBF) is one well-known method for producing metal objects. In L-PBF, a high-energy laser beam is irradiated onto the surface of a powder layer to sinter or melt and solidify the powder particles. These layers, each several tens of microns thick, are then stacked and repeatedly bonded to produce three-dimensional objects. L-PBF using metal-based powders is also becoming more practical. L-PBF using metal-based powders such as Co-Cr alloys, maraging steels, stainless steels, and nickel-based superalloys has achieved high processing accuracy and high product quality, and is beginning to be put into practical use. However, the current L-PBF method is limited to certain metal-based powders, and the resulting metal products are also limited to a certain range.

[0003] The main reason for this is the light absorption of the metal-based powder used as the raw material. Specifically, the L-PBF method utilizes the phenomenon in which metal-based powder particles absorb the optical energy of a laser beam and heat up, causing sintering or melting and solidifying. Therefore, the metal-based powder must be able to efficiently absorb optical energy. The wavelength of the laser beam typically used in the L-PBF method is in the near-infrared or far-infrared range. Metals with low optical absorption in this wavelength range (e.g., aluminum, gold, silver, copper, etc.) cannot absorb sufficient heat from the laser beam, resulting in low sintered densities of the resulting metal laser-sintered objects. Furthermore, metals with high thermal conductivity quickly dissipate the heat from the laser beam even after absorbing it as heat, before sufficient sintering or melting and solidification occurs, making it difficult to obtain high-density metal laser-sintered objects. Furthermore, copper's relatively high melting point of approximately 1084°C also makes sintering difficult. Therefore, even though copper is a metal with high thermal and electrical conductivity and excellent workability, it has been considered difficult to apply the L-PBF method.

[0004] Therefore, various studies have been attempted to apply copper-based powder to the L-PBF method. For example, it has been proposed to form a specific metal coating such as gadolinium (Gd) on the surface of copper particles to increase the laser light absorption rate (Patent Document 1), to form a copper oxide coating (Patent Documents 2 and 3), and even to form a carbon coating derived from an organic compound on the surface of copper or aluminum particles (Patent Document 4).

[0005] As described above, metal laser-sintered products obtained using copper-based powders in which the surfaces of copper powders are coated with metals or metal oxides with high laser beam absorptivity contain substances other than copper (coatings) and can therefore be endowed with properties not found in pure copper, in addition to the various properties inherent to copper (e.g., thermal conductivity, electrical conductivity, and processability). For example, Patent Document 5 proposes that by using copper alloy-based powders containing a predetermined amount of chromium in copper, copper alloy-sintered products can be obtained that have excellent thermal conductivity, electrical conductivity, and strength while increasing the laser beam absorptivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 064745 Brochure [Patent Document 2] International Publication No. 2019 / 017467 Brochure [Patent Document 3] Japanese Patent Publication No. 2020-94271 [Patent Document 4] Japanese Patent Application Publication No. 2018-199862 [Patent Document 5] Japanese Patent Application Publication No. 2019-70169 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, copper is a metal with excellent thermal conductivity, electrical conductivity, and workability, and is used in a variety of industrial applications. Among these, there are industrial applications that require hardness, such as electrodes for resistance welding and injection molding dies, and there is a potential demand for applying copper objects manufactured by the L-PBF method to such applications.

[0008] Therefore, an object of the present invention is to provide a copper-based powder that has laser light absorbency and flowability suitable for the L-PBF method, and that can be used to obtain shaped articles with high hardness. [Means for solving the problem]

[0009] The inventors of the present invention have found that by adhering carbide to the surfaces of the copper particles (primary particles) that make up the copper powder, it is possible to obtain a shaped product that has laser light absorbency and flowability suitable for the L-PBF method, as well as high hardness. The present invention is based on this finding.

[0010] The copper-based powder according to the present invention comprises: A copper-based powder consisting of particles having an average particle size of 1 μm or more and 100 μm or less, The particles are Copper particles, carbide attached to at least a portion of the surface of the copper particles; Including, The reflectance at a wavelength of 1070 nm is 60% or less. [Effects of the Invention]

[0011] According to the present invention, by adhering carbide to the surfaces of copper particles constituting the copper-based powder to an extent that the reflectivity of laser light is 60% or less, not only is the powder provided with laser light absorption properties suitable for the L-PBF method, but it is also possible to obtain a highly hard shaped object while improving the fluidity of the copper-based powder, which is necessary when carrying out the L-PBF method. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Definition] In this specification, "copper particles" refers to particles made of copper or a copper alloy, "copper powder" refers to a collection of multiple copper particles, and "copper-based powder" refers to a collection of multiple copper particles having carbides attached to at least a portion of their surfaces. In addition, "adhesion" refers not only to a state in which the carbide is physically in contact with or adhered to the surface of the copper particle, but also to a state in which the carbide is chemically bonded to the surface, or a state in which part of the carbide is embedded in the copper particle and integrated (alloyed).

[0013] [Copper-based powder of the present invention] The copper-based powder of the present invention comprises copper particles and carbides adhered to at least a portion of the surfaces of the copper particles. The particles have an average particle size of 1 μm or more and 100 μm or less, and a reflectance of 60% or less at a wavelength of 1070 nm. In the present invention, carbides are adhered to the surfaces of the particles constituting the copper-based powder so that the reflectance of the copper-based powder at a wavelength of 1070 nm is 60% or less, thereby providing laser light absorption suitable for the L-PBF method. Specifically, copper has a light absorption rate of only a few percent in the wavelength range (1030 nm or more and 1070 nm or less) of the Yb fiber laser light typically used in metal laser sintering, making it a metal that does not readily absorb laser light. Furthermore, its thermal conductivity is significantly higher than that of titanium, iron, nickel, etc., making it difficult to heat by laser irradiation without modification. In contrast, in the present invention, carbides are adhered to the surfaces of the copper particles so that the reflectance at a wavelength of 1070 nm is 60% or less, thereby improving laser light absorption. In the present invention, the upper limit of the reflectance is 60%, preferably 55% or less, more preferably 50% or less, and even more preferably 45% or less. On the other hand, the lower limit of the reflectance is not particularly determined, and a lower value is preferable from the viewpoint of laser light absorption, but from the viewpoint of the feasibility of producing a copper-based powder to which carbide is attached, the lower limit is typically 10% or more, more typically 15% or more, and even more typically 20% or more.

[0014] In this specification, "reflectance" refers to the spectral reflectance measured using a spectrophotometer equipped with an integrating sphere unit, and refers to the ratio calculated based on the amount of total reflected light in a specific wavelength range of a standard reflector (e.g., a barium sulfate standard reflector) with known spectral reflectance, based on the amount of total reflected light on the measured surface (copper-based powder) measured for light of a specific wavelength. Commonly used base powders made of copper particles have a reflectance of about 70% to 80% at a wavelength of 1070 nm.

[0015] Furthermore, with the copper-based powder of the present invention, carbides are attached to the surfaces of the copper particles, which allows for the production of shaped articles with higher hardness than those produced using copper particles. Furthermore, because the copper shaped articles contain trace amounts of carbides, it is believed that the decrease in strength of the shaped articles when placed in a high-temperature environment can be suppressed. Therefore, shaped articles that are particularly suitable for applications such as electrode materials for resistance welding and injection molding dies can be obtained.

[0016] Furthermore, according to the present invention, the fluidity of the powder is improved by attaching carbide to the surfaces of the copper particles. While the reason for this is unclear, it is believed that the attachment of carbide to the surfaces of the copper particles results in the formation of minute irregularities on the particle surfaces, improving fluidity. The excellent fluidity of the copper-based powder facilitates squeegeeing during stereolithography using the L-PBF method, enabling the preparation of a uniform, flat powder bed. While base powders suitable for the L-PBF method are required to have a fluidity of 5 s / 50 g or more and 30 s / 50 g or less, the copper-based powder of the present invention can achieve a fluidity of 30 s / 50 g or less. The fluidity refers to a value measured in accordance with JIS Z 2502.

[0017] The copper particles constituting the copper-based powder can be used without particular limitation as long as the average primary particle size is 1 μm or more and 100 μm or less. For example, copper particles can be obtained by wet reduction of copper compounds such as copper acetate or copper sulfate using various reducing agents such as hydrazine. Copper particles can also be obtained by atomization using molten copper.

[0018] The shape of the copper particles is not particularly limited, but when used in metal laser sintering processes such as the L-PBF process, a nearly spherical shape is preferred from the viewpoint of forming a base powder bed with a high powder packing density by squeegeeing. Therefore, it is preferable to use copper particles obtained by atomization. Examples of atomization methods include gas atomization and water atomization, but gas atomization is preferred from the viewpoint of easily obtaining copper particles that are more nearly spherical. High-pressure gas atomization can produce copper particles with a uniform particle shape that is even more nearly spherical.

[0019] The copper particles obtained as described above can be classified as necessary to make the copper particles uniform in size. This classification can be easily carried out by separating coarse particles and fine particles from the obtained copper powder using an appropriate classifier so as to obtain copper particles of a target average particle size.

[0020] In the present invention, by using copper particles having an average primary particle size of 1 μm or more and 100 μm or less as described above, a copper-based powder having an average primary particle size of 1 μm or more and 100 μm or less can be obtained. By using a copper-based powder having an average primary particle size within the above range, a powder bed with a high packing density can be formed in a metal laser sintering method such as the L-PBF method, and the sintered density of a shaped product obtained by sintering or melt-solidifying the copper-based powder can also be increased. In this specification, the average particle size is the volume-cumulative particle size (D ) at 50% cumulative volume as determined by a laser diffraction / scattering particle size distribution measurement method. 50 From the viewpoint of obtaining a fine and dense stereolithographic object and from the viewpoint of the fluidity of the copper-based powder, the average particle size of the copper particles used is preferably 2 μm or more and 80 μm or less, and particularly preferably 3 μm or more and 64 μm or less.

[0021] Next, a method for adhering a carbide to the surface of the copper particles will be described. The carbide used in the copper-based powder of the present invention can be any metal carbide with high light absorption at a wavelength of 1070 nm, but among these, from the viewpoint of the effects of the present invention, boron carbide, titanium carbide, vanadium carbide, chromium carbide, manganese carbide, cobalt carbide, nickel carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, tantalum carbide, and tungsten carbide are preferred. In particular, from the viewpoint of obtaining the effects of the present invention while maintaining the electrical conductivity of copper, chromium carbide is more preferred.

[0022] Carbide deposition is achieved by contacting copper particles with carbide. Specifically, carbide can be deposited on the surfaces of copper particles by various methods, including chemical vapor deposition methods such as plasma CVD and atomic layer deposition (ALD), physical deposition methods such as sputtering, coating methods in which a carbide-containing paste is applied to the surfaces of copper particles and then fired, and hybridization methods. Among these methods, hybridization is preferred for depositing carbide, as it allows for the production of copper-based powders with high sphericity and excellent fluidity. The hybridization method, also known as high-velocity airflow impact deposition, is a technique in which multiple types of powders are dry-dispersed in a high-velocity airflow, and the particle surfaces are modified or composited with other types of particles by a force primarily consisting of impact force. In the present invention, carbide can be deposited on at least a portion of the surfaces of copper particles by mixing copper particles and carbide particles using the high-velocity airflow impact deposition method.

[0023] When using the high-velocity airflow impact method, the carbide preferably has a particulate form. From the viewpoint of carbide adhesion and obtaining a copper-based powder with high sphericity, the average particle size of the carbide particles is preferably 1 nm or more and 300 nm or less, and more preferably 50 nm or more and 150 nm or less. When carbide particles having such an average particle size are attached to the surface of copper particles using the high-velocity airflow impact method, it is believed that the presence of the carbide particles will form minute irregularities on the copper surface. Furthermore, the high-velocity airflow impact method also improves the sphericity of the copper particles themselves. As a result, it is believed that the fluidity of the resulting copper-based powder is improved. The carbide particles described above can be obtained by conventional methods, such as static synthesis, dynamic synthesis, and vapor-phase synthesis. In this specification, the average particle size of the carbide particles is defined as the average value of particle sizes measured for 20 randomly selected particles using a transmission electron microscope.

[0024] From the viewpoint of improving the fluidity of the copper-based powder, the particle size ratio between the copper particles and the carbide particles used (the ratio of the average particle size of the copper particles to the average particle size of the carbide particles) is preferably 100 to 5000, and more preferably 200 to 3000.

[0025] The carbide is attached to the surface of the copper particles so that the reflectance of the copper-based powder at a wavelength of 1070 nm is 60% or less. The greater the amount of carbide attached, the more the reflectance can be reduced. However, from the viewpoint of improving the hardness of the molded product while maintaining the inherent properties of copper, the proportion of carbide relative to the total copper-based powder is preferably 0.2% by mass or more and 5.0% by mass or less, and more preferably 0.4% by mass or more and 2.0% by mass or less. The amount of carbide attached can be adjusted by the ratio of copper particles and carbide particles when mixed and the hybridization time. The presence or absence of carbide attachment can be confirmed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM / EDX) or X-ray diffraction (XRD), and depending on the particle size and amount of carbide attached, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), etc. may be used. The amount of carbide attached can be quantitatively measured using known means such as an X-ray photoelectron spectrometer (XPS), an inductively coupled plasma (ICP) emission spectrometer, or a carbon analyzer.

[0026] Furthermore, in the present invention, the adhesion of carbide to the surface of the copper particles can improve the stability of the copper particles over time. It is known that metallic copper is highly susceptible to oxidation by air and moisture, and that the powder properties are prone to change during storage. Even when copper powder from the same lot is used, the properties of the copper powder change over time during storage, which may result in changes in the properties of the stereolithography product. According to the present invention, the adhesion of carbide to the surface of the copper particles is thought to suppress the progression of oxidation reactions with air and moisture, and as a result, it is expected that stereolithography products can be obtained more stably.

[0027] [Method of manufacturing a stereolithography object using copper-based powder] A method for producing a stereolithography object using the copper-based powder described above will now be described. First, copper base powder is supplied to a modeling stage, and a squeegee blade is used to squeeze the powder surface to form a powder bed of a predetermined thickness (Step 1). Note that squeegeeing in the present invention refers to the metal laser sintering method in which a blade, spatula, roller, or the like is brought into contact with and moved against the surface of a powder bed made of base powder to smooth the surface of the powder bed and remove excess base powder.

[0028] Next, a light beam, such as a laser beam, is irradiated at a desired position on the surface of the powder bed. This irradiation position can be determined from a cross-sectional plan view created based on 3D CAD data of the product to be manufactured. The copper particles at the irradiated position are sintered or melted and solidified, forming the first layer (Step 2).

[0029] Next, the position of the modeling stage is moved by a depth equivalent to the thickness of the first layer (Step 3). Steps 1 to 3 are repeated to sequentially stack multiple layers on the first layer, such as the second layer and the third layer, to produce a copper stereolithography object.

[0030] Such metal laser sintering devices are typically equipped with an infrared laser as the light beam. Examples include solid-state lasers with wavelengths in a wavelength band that includes infrared light at 1064 nm, fiber lasers with wavelengths in the range of 950 nm to 1900 nm, and CO₂ lasers with wavelengths in the range of 10.6 μm. Rare earth elements such as Yb (1030 nm to 1070 nm), Nd (approximately 950 nm), Tm (approximately 1900 nm), and Er (approximately 1550 nm) are commonly used as amplification media for the glass core of fiber lasers. Because the copper-based powder of the present invention has a reflectance of 60% or less at a wavelength of 1070 nm, it is preferable to use a Yb-doped fiber laser with a central wavelength of 1070 nm. The laser irradiation mode may be either single-mode or multimode, although differences in beam quality and focusing ability exist. Furthermore, the above-described sintering method is merely an example of a case in which sintering is used, and is not limited thereto.

[0031] A stereolithography object obtained from a copper-based powder as described above has electrical and thermal conductivity similar to that of a stereolithography object made of copper powder, but is dense and has excellent mechanical strength due to sufficient sintering or melt-solidification caused by laser light absorption. Furthermore, the stereolithography object has high hardness due to the inclusion of carbides. Specifically, a stereolithography object obtained using the copper-based powder of the present invention can have a Vickers hardness (Hv) of 40 Hv or more as measured in accordance with JIS Z 2244. Furthermore, a stereolithography object obtained in this manner can be used in a variety of applications, but is particularly suitable for applications in high-temperature environments (e.g., electrodes for resistance welding, injection molding dies, etc.). It is known that the hardness of a pure copper object decreases due to the growth of copper crystal grains during heat treatment. However, in the present invention, the inclusion of carbides in the copper inhibits crystal grain growth, which is believed to result in a reduction in the hardness of the object even in applications involving high-temperature environments. [Example]

[0032] Next, the embodiments of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0033] <Preparing copper powder> The following two types of gas atomized copper powder were prepared. Copper powder 1: MA-CH-S, manufactured by Mitsui Mining & Smelting Co., Ltd. (pure copper, average particle size of primary particles D 50 :33μm) Copper powder 2: MA-CCR25L, manufactured by Mitsui Mining & Smelting Co., Ltd. (copper containing 1.2 wt% Cr, average particle size of primary particles D 50 :28μm)

[0034] <Preparation of carbide> The following four types of carbides were prepared. Carbide 1: NP-SIC-8, manufactured by EM Japan Co., Ltd. (silicon carbide (SiC) 99% or more, particle size: <80 nm) Carbide 2: NP-CR3C2, manufactured by EM Japan Co., Ltd. (chromium carbide (Cr3C2) 99.7% or more, particle size: 30 to 120 nm) Carbide 3: NP-ZRC-3, manufactured by EM Japan Co., Ltd. (zirconium carbide (ZrC) 99% or more, particle size: 80 nm) Carbide 4: NP-WC-1, manufactured by EM Japan Co., Ltd. (tungsten carbide (WC) 99.9% or more, particle size: 55 nm)

[0035] <Preparation of copper-based powder> The copper powder and carbide were weighed out so that the total weight was 1.5 kg, and the two were stirred at 1000 rpm for 10 minutes using a mixer (OMO-3, manufactured by Nara Machinery Works, Ltd.). Next, 150 g of the mixed and stirred product was weighed out and circulated at 6000 rpm for 5 minutes using a hybridizer (HYB-1, manufactured by Nara Machinery Works, Ltd.) to obtain a copper-based powder. Furthermore, since no carbide was visually observed remaining on the mixer and hybridizer after the copper-based powder was removed, it can be assumed that almost all of the added carbide adhered to the copper powder.

[0036] <Measurement of average particle size> The average particle size (D50) of the obtained copper-based powder was measured using a laser diffraction / scattering particle size distribution measuring device (Microtrac Bell Co., Ltd., MT3300EXII). The measurement results are shown in Table 1 below.

[0037] <Reflectance measurement> The reflectance of copper powder and each copper-based powder was measured using a spectrophotometer (U-4100, Hitachi High-Technologies Corporation) by filling the copper powder into a concave holder, sealing it with a quartz cover glass, and using the integrating sphere method at a wavelength of 1070 nm. The measurement results are shown in Table 1 below.

[0038] <Measurement of liquidity> Using a flowability measuring device (Tsutsui Scientific Instruments Co., Ltd.), 50 g of each copper powder and copper-based powder was placed in a funnel, and the powder flowability (seconds) was measured according to a method in accordance with JIS Z 2502. The measurement results are shown in Table 1 below. Note that "NG" in Table 1 indicates that the powder got stuck when falling from the funnel, and not all of the powder (copper powder or copper-based powder) placed in the funnel fell. Furthermore, with the copper-based powders of Examples 5 and 6, the powder sometimes got stuck in the funnel and stopped midway.

[0039] [Table 1]

[0040] As is clear from Table 1 above, the copper-based powder in which carbide is adhered to copper powder has improved fluidity compared to copper powder.

[0041] <Creating optically modeled objects> The copper powder and copper-based powder were each subjected to laser lithography using a metal laser lithography machine (Concept Laser M2, manufactured by GE Additive) at an output of 370 W and a layer pitch of 0.03 mm to produce a 15 mm x 15 mm x 10 mm object. The energy density per unit volume of the laser beam was 600 J / mm when copper powder 1 (pure copper) was used. 3 When copper powder 2 (copper chromium alloy) is used, it is 160 J / mm 3 It was decided. The resulting shaped object was then heat treated in a nitrogen stream at 700°C for 3 hours.

[0042] <Evaluation of characteristics of stereolithography objects> (1) Vickers hardness The Vickers hardness (Hv) of the stereolithography objects before and after heat treatment was measured in accordance with JIS Z 2244. In addition, the degree to which the hardness of the stereolithography objects (after heat treatment) made using each copper-based powder increased compared to the stereolithography object (after heat treatment) made using copper powder without carbide attached was calculated using the following formula. Hardness increase rate (%) = (hardness of stereolithography object using copper-based powder - hardness of stereolithography object using copper powder) / hardness of stereolithography object using copper powder × 100 The measurement results are shown in the following Table 2. For Example 5 and Comparative Example 2, only the Vickers hardness (Hv) after the heat treatment was measured.

[0043] (2) Relative density For each of the heat-treated stereolithography products, the theoretical density was calculated from the densities of the copper powder and carbide, the bulk density was calculated using the Archimedes method in accordance with JIS-R1634, and the relative density was calculated from the ratio of the bulk density to the theoretical density. The results are shown in Table 2 below.

[0044] (3) Conductivity The electrical conductivity (100% IACS) of each of the heat-treated stereolithography objects was measured using an eddy current phase displacement sensitive measuring device (SIGMASCOPE SMP350, manufactured by Fischer Instruments Inc.) The results are shown in Table 2 below.

[0045] [Table 2]

[0046] As is clear from Table 2, the hardness of the resulting stereolithography product increases when carbide is attached to the copper powder. Furthermore, although the hardness of the stereolithography product decreases upon heat treatment, the stereolithography product obtained from copper powder with carbide attached (i.e., copper-based powder) has a higher hardness retention rate than the stereolithography product obtained from copper powder without carbide attached (Comparative Examples 1 and 2). Furthermore, it can be seen that even stereolithography objects obtained from copper powder with carbide attached (i.e., copper-based powder) have electrical conductivity equivalent to that of stereolithography objects obtained from copper powder without carbide attached.

Claims

1. A copper-based powder consisting of particles having an average particle size of 1 μm or more and 100 μm or less, The particles are Copper particles, a metal carbide attached to at least a portion of the surface of the copper particles; Including, A copper-based powder having a reflectance of 60% or less at a wavelength of 1070 nm.

2. 2. The copper-based powder according to claim 1, wherein the proportion of the metal carbide relative to the total copper-based powder is 0.2 mass % or more and 5.0 mass % or less.

3. A copper-based powder as described in claim 1 or 2, wherein the metal carbide is at least one selected from the group consisting of boron carbide, titanium carbide, vanadium carbide, chromium carbide, manganese carbide, cobalt carbide, nickel carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, tantalum carbide, and tungsten carbide.

4. 4. The copper-based powder according to claim 1, wherein particles made of the metal carbide adhere to the surfaces of the copper particles, so that at least a portion of the surfaces are coated with the metal carbide.

5. 5. The copper-based powder according to claim 4, wherein the metal carbide particles have an average particle size of 1 nm or more and 300 nm or less.

6. A method for producing the copper-based powder according to any one of claims 1 to 5, comprising: bringing a metal carbide into contact with copper particles to cause the metal carbide to adhere to the surfaces of the copper particles; A method comprising:

7. The contact of the metal carbide with the copper particles is mixing the copper particles and the metal carbide particles by impacting them in a high-velocity air stream; sputtering the metal carbide onto the copper particles; or applying the metal carbide-containing paste to the surfaces of the copper particles; The method of claim 6, which is carried out by

8. The method according to claim 6 or 7, wherein the copper particles have an average particle size of 1 μm or more and 100 μm or less.

9. A method for producing a stereolithography product using copper-based powder, comprising a step of sintering or melting and solidifying the copper-based powder according to any one of claims 1 to 5 with laser light.

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