Copper alloy powder and method for producing additively-manufactured article using copper alloy powder

Abstract

To provide a copper alloy powder for additive manufacturing capable of obtaining an additive manufactured article having excellent conductivity and high relative density.MEANS: A copper alloy powder for additive manufacturing, comprising Cr, the balance being Cu and inevitable impurities, wherein A f represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and A b represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure in the XANES analysis of the copper alloy powder, wherein A b and A f are obtained by decomposing the obtained spectrum into a linear combination of an X-ray absorption spectrum derived from Cr2O3, an X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and an X-ray absorption spectrum derived from Cr having a body-centered cubic structure based on a spectrum of a standard sample. In the copper alloy powder for additive manufacturing, the ratio R is 0.1 to 10.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper alloy powder, and more particularly to a copper alloy powder that can be suitably used for additive manufacturing such as three-dimensional additive manufacturing, and a method for producing an additive manufactured product using the copper alloy powder. [Background technology]

[0002] Three-dimensional additive manufacturing (3D) machines, known as 3D printers, are rapidly becoming popular. Among the additive manufacturing methods using these machines, powder bed fusion (PBF) is a well-known method for producing metal objects. In PBF, a powder bed is irradiated with high-energy energy beams, such as a laser or electron beam, 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 additive manufacturing objects. The L-PBF method, which uses a laser as a heat source and metal-based powders, is also becoming more practical. L-PBF, which uses metal-based powders such as Co-Cr alloys, titanium alloys, maraging steels, stainless steels, and nickel-based superalloys, produces additive manufacturing objects with high processing precision and a high level of finish. This has led to the practical application of additive manufacturing objects suitable for heat-resistant and high-temperature applications.

[0003] However, the current L-PBF method is limited to only a limited number of usable metal-based powders, and the resulting metal products are limited to a certain range. For example, copper, a metal with high thermal and electrical conductivity and excellent workability, is considered difficult to apply to the L-PBF method. This is primarily due to its extremely low energy absorption rate of laser light, which prevents it from reaching its melting point, and even if it does reach its melting point, its high thermal conductivity causes rapid heat diffusion, preventing sufficient melting. To address this issue, Patent Document 1 reports that adding chromium (Cr) to copper alloy powder reduces thermal conductivity, facilitating additive manufacturing. Furthermore, heat treatment of the resulting additive manufactured product improves its electrical and thermal conductivity, as well as its mechanical strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-070169 Summary of the Invention

[0005] The above-mentioned Patent Document 1 describes that by subjecting an additive manufacturing product obtained using a copper alloy powder containing Cr to a heat treatment at a predetermined temperature for a predetermined time, a Cr phase contained in a supersaturated state is precipitated in the Cu matrix, thereby improving the mechanical strength, electrical conductivity, and thermal conductivity. However, the mechanical strength, electrical conductivity, etc. of the obtained additive manufacturing product itself are not necessarily superior, and additive manufacturing products using a copper alloy powder containing Cr are currently inferior to copper in terms of the electrical conductivity and relative density inherent to copper.

[0006] Therefore, an object of the present invention is to provide a copper alloy powder for additive manufacturing that can produce additively manufactured articles that have excellent electrical conductivity and a high relative density.

[0007] The inventors of the present invention have discovered that, in a copper alloy powder containing Cr, by controlling the proportion of Cr dissolved in copper or the proportion of a Cr-enriched phase having a face-centered cubic structure in the copper alloy, and the proportion of a Cr phase having a body-centered cubic structure precipitated from the Cr-enriched phase within a predetermined range, the Cr solid solubility and elastic strain of the copper matrix can be suppressed, resulting in a copper alloy powder that can realize an additive manufacturing product with excellent electrical conductivity and a high relative density. The present invention is based on this discovery. The gist of the present invention is as follows.

[0008] [1] Copper alloy powder for additive manufacturing, Contains Cr, with the balance being Cu and unavoidable impurities, The following formula: R=A f / A b (In the formula, A frepresents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, A b represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder, However, A b and A f is the standardized linear coefficient of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, based on the linear coefficient of each spectrum when the spectrum obtained based on the spectrum of a standard sample is decomposed into a linear combination of the X-ray absorption spectrum derived from Cr2O3, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure. The copper alloy powder for additive manufacturing has a ratio R of 0.1 to 10. [2] The copper alloy powder for additive manufacturing according to [1], having an oxygen concentration of 500 ppm or less by mass. [3] The copper alloy powder for additive manufacturing according to [1] or [2], having an angle of repose of 30° or more. [4] The copper alloy powder for additive manufacturing according to any one of [1] to [3], having an a* value of 15 or more in the L*a*b* color system. [5] The copper alloy powder for additive manufacturing according to any one of [1] to [4], which has an average particle size (D50) of 10 μm or more and 50 μm or less. [6] The copper alloy powder for additive manufacturing according to any one of [1] to [5], further containing Zr. [7] A method for manufacturing an additive manufacturing object using the copper alloy powder according to any one of [1] to [6], a first step of forming a powder layer containing the copper alloy powder; a second step of solidifying the copper alloy powder at a predetermined position in the powder layer to form a modeling layer; A method for manufacturing a layered object, which comprises sequentially repeating the first step and the second step to stack the modeling layers to manufacture a layered object. [8] The method according to [7], wherein the solidification of the copper alloy powder in the second step is carried out by an energy irradiation means selected from the group consisting of a laser, an electron beam, and plasma. [9] A method for producing a copper alloy product from an additive manufacturing product obtained by the method described in [7], the method comprising heat treating the additive manufacturing product.

[10] The method according to [9], wherein the heat treatment is carried out at a temperature of 400°C or higher and lower than the melting point of the copper alloy.

[0009] According to the copper alloy powder for additive manufacturing of the present invention, additive manufacturing products having excellent electrical conductivity and high relative density can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Copper alloy powder] The copper alloy powder according to the present invention is used as a raw material powder in an additive manufacturing method. In the additive manufacturing method, the raw material powder is irradiated with an energy beam, whereby the raw material powder melts and is rapidly cooled and solidified. That is, the raw material powder is solidified by irradiation with the energy beam. Details of the additive manufacturing method will be described later in the section "Method for manufacturing an additive manufactured product."

[0011] A copper alloy powder according to one embodiment of the present invention contains Cr, with the balance being Cu and unavoidable impurities, and has a composition represented by the following formula: R=A f / A b The ratio R is 0.1 to 10. Here, A f represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and A b represents the X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder. b and A fis a standard sample spectrum, and the obtained spectrum is decomposed into a linear combination of the X-ray absorption spectrum derived from Cr2O3, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure. Based on the linear coefficients of each spectrum, the linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure are normalized. The standard samples used are copper foil made of copper with a face-centered cubic structure (standard sample owned by the High Energy Accelerator Research Organization Photon Factory BL-12C), chromium foil made of chromium with a body-centered cubic structure (same as above), and α-Cr2O3 (US National Institute of Standards and Technology SRM674a). For α-Cr2O3, boron nitride (manufactured by Kojundo Chemical Co., Ltd., purity 99%, BBI03PB) is used as a molding agent to form the sample. f represents the X-ray absorption spectrum of Cr with a face-centered cubic structure, while A f The reason why copper foil was used instead of chromium foil as the standard sample for determining the XANES spectrum is that chromium does not have a stable face-centered cubic crystal phase, so the XANES spectrum of copper was used instead. The linear coefficients of each spectrum were calculated using XANES analysis software (Athena) under the following fitting conditions: <Fitting conditions> Standards: α-Cr2O3, copper foil (energy axis adjusted), chromium foil Fitting Space: norm μ(E) Energy range: -10 to 60 eV Fit E0:False Required: False All weights between 0 and 1:yes Force weights sum to 1:yes Overall e0 shift used:no Noise added to data:0

[0012] The copper alloy powder of the present invention can improve the electrical conductivity and relative density of an additive manufacturing product obtained by the L-PBF method using the copper alloy powder by adjusting the ratio of Cr dissolved in copper or the ratio of the Cr-enriched phase having a face-centered cubic structure in the copper alloy and the ratio of the Cr phase having a body-centered cubic structure precipitated from the Cr-enriched phase (i.e., the ratio R) within a predetermined range. If the ratio R is less than 0.1, the additive manufacturing product obtained will have excellent electrical conductivity but will not have a high relative density. On the other hand, if the ratio R exceeds 10, an additive manufacturing product will have a high relative density but will not have a high electrical conductivity. The reason for this is unclear, but is thought to be as follows. Specifically, as described below, Cr-containing copper alloy powders prepared by atomization or other methods contain Cr dissolved in copper or a Cr-enriched phase with a face-centered cubic structure immediately after preparation. The elastic strain introduced by the dissolved Cr atoms and the elastically constrained Cr-enriched phase with a face-centered cubic structure acts as a scattering factor for free electrons, reducing the electronic and thermal conductivity of the copper alloy powder. Therefore, the L-PBF method efficiently transfers heat energy from the energy beam to the copper alloy powder and suppresses heat diffusion from the molten raw powder to the surroundings, resulting in an additive manufacturing product with a high relative density. Subsequent heat treatment reduces the Cr solid solubility and elastic strain in the copper matrix by precipitating Cr with a body-centered cubic structure, thereby improving the electronic conductivity of the copper matrix. As a result, additive manufacturing products with excellent electrical conductivity and high relative density are obtained. The above ratio R(A f / A b ) is preferably 0.2 to 7, and more preferably 0.4 to 4.

[0013] The oxygen concentration of the copper alloy powder is preferably 500 ppm or less by mass, more preferably 400 ppm or less. When the oxygen concentration in the copper alloy powder is high, the proportion of copper oxide in the copper alloy increases, and the properties inherent to copper (high electrical and thermal conductivity, etc.) tend to decrease. The oxygen concentration can be calculated by oxygen gas analysis or the like. A method for adjusting the oxygen concentration of the copper alloy powder will be described later.

[0014] Furthermore, the copper alloy powder preferably has an angle of repose of 25° or more, more preferably 30° or more. When the copper alloy powder has an angle of repose of 25° or more, copper alloy powder particles contact each other over a large area, and also over a very small area. This allows the fluidity of the copper alloy powder to be appropriately suppressed when forming a powder bed using a coater or the like, thereby improving the packing properties of the powder bed. As a result, the relative density of the additive manufacturing product can be improved. The angle of repose can be adjusted by adjusting the physical properties (e.g., oxygen concentration) and shape (particle size and particle shape) of the copper alloy powder. The angle of repose refers to the angle between the floor and the slope of the mound formed by the copper alloy powder on a pedestal when the copper alloy powder is allowed to fall freely from a funnel. The angle of repose is an index of the fluidity of the copper alloy powder, and a smaller angle indicates better fluidity. However, if the fluidity is too high, the ease of forming a powder bed tends to decrease.

[0015] Furthermore, from the viewpoint of obtaining a fine and dense additive manufacturing product and from the viewpoint of the fluidity of the copper alloy powder, the average particle size of the copper alloy powder used is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 200 μm or less, and particularly preferably 10 μm or more and 50 μm or less. By using a copper alloy powder having an average particle size within the above range, it is possible to form a powder bed with a high packing density in a metal additive manufacturing method such as the L-PBF method, and it is also possible to increase the relative density of the product obtained by sintering or melt-solidifying the copper alloy powder. In this specification, the average particle size refers to the particle size (D 50 ) is shown.

[0016] Furthermore, the shape of each particle constituting the copper alloy powder is not particularly limited, but when used in a metal additive manufacturing method such as the L-PBF method, from the viewpoint of forming a powder bed with a high packing density of the copper alloy powder by squeegeeing, it is preferable that each particle has a shape close to spherical. A method for obtaining such a copper alloy powder with a predetermined particle size close to spherical will be described later.

[0017] The Cr content of the copper alloy powder is preferably 0.5% by mass or more and 5.0% by mass or less, more preferably 0.5% by mass or more and 3.1% by mass or less, and even more preferably 0.5% by mass or more and 2.5% by mass or less. The Cr content of the copper alloy powder can be measured by inductively coupled plasma (ICP) atomic emission spectrometry (AES) in accordance with JIS H 1071 (Method for Determination of Chromium in Copper and Copper Alloys). Specifically, a copper alloy is first melted in an alkali solution, and then the melt is dissolved in an acid solution to prepare a solution. The solution is then diluted to prepare a measurement sample. Alternatively, a solution may be prepared directly by dissolving the copper alloy in an acid solution. The measurement sample can be prepared by diluting the solution.

[0018] The copper alloy powder of the present invention may contain inevitable impurity elements other than the above-mentioned components, or may contain elements intentionally added during the production of the copper alloy powder. For example, inevitable impurity elements such as oxygen, phosphorus, and iron, as well as elements such as nickel, zinc, tin, silver, beryllium, zirconium, aluminum, silicon, cobalt, titanium, magnesium, and tellurium may be contained. Among these, zirconium (Zr) is preferably contained. When the copper alloy powder contains Zr, its content is not particularly limited, but is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 1% by mass or less. The Zr content in the copper alloy powder can be measured in the same manner as the Cr content described above.

[0019] Furthermore, the copper alloy powder of the present invention preferably has an a* value of 15 or more in the L*a*b* color system (CIE 1976 L*a*b* color space). The L*a*b* value can be measured using a spectrophotometer. The a* value is an index representing hue and saturation, with a positive a* value indicating a reddish color and a negative a* value indicating a greenish color. The further the value is from the center (a* = 0), the more vivid the color, and the closer it is to the center, the duller the color. In the present invention, by using a copper alloy powder having an a* value of 15 or more, the laser light absorption efficiency of the copper alloy powder can be improved when manufacturing an additive manufacturing product using the L-PBF method, resulting in an additive manufacturing product with a higher relative density. The L*a*b* value of the copper alloy powder can be measured using a commercially available colorimeter in accordance with JIS Z 8722.

[0020] [Method of manufacturing copper alloy powder] Next, a method for producing the above-mentioned copper alloy powder will be described. Copper alloy powder is generally produced by, for example, gas atomization, water atomization, disk atomization, plasma atomization, rotating electrode atomization, etc. However, in an embodiment of the present invention, copper alloy powder is produced by gas atomization from a molten copper alloy (i.e., a molten raw material in which copper is mixed with a predetermined Cr, etc.). The gas atomization method is a method in which a molten raw material prepared to have a desired composition is heated to or above its melting point by high-frequency induction heating, and the molten metal flows out through fine holes. An inert gas such as argon gas or nitrogen gas is sprayed onto the molten metal to finely pulverize it, and the molten metal is rapidly cooled and solidified to obtain powder.

[0021] Next, the copper alloy powder obtained by gas atomization is classified to adjust it to a predetermined aspect ratio and a predetermined uniformity. The classification of the copper alloy powder is preferably carried out in two stages, with the large diameter side and the small diameter side being removed separately. When the classification of the copper alloy powder is carried out in two stages, the order of classification is not particularly limited, and either the large diameter side particles or the small diameter side particles can be removed in the first stage, and the other can be removed in the second stage. In a preferred embodiment of the present invention, from the viewpoint of performing classification more efficiently, it is preferable to first remove the large diameter side particles in the first stage and then remove the small diameter side particles in the second stage.

[0022] Subsequently, the copper alloy powder whose particle size has been adjusted as described above is preferably dried at a temperature of about 50 to 100°C. By carrying out such a drying process, the properties of the copper alloy powder are stabilized. Note that drying in an air atmosphere may cause oxidation of the copper alloy powder, so it is preferable to carry out the drying in an inert atmosphere such as nitrogen or argon. For example, the copper alloy powder can be dried at 60°C for about 3 hours.

[0023] In the present invention, the copper alloy powder dried as described above can be used as it is as a copper alloy powder for an additive manufacturing product, but it may also be subjected to a heat treatment. The ratio of Cr having a face-centered cubic structure to Cr having a body-centered cubic structure in the copper alloy powder can also be adjusted by the heat treatment. That is, the ratio R(A f / A b ) can be adjusted.

[0024] When the copper alloy powder is heat-treated, it is preferably carried out at a temperature below 500°C. If the heat treatment is carried out at a temperature of 500°C or higher, the proportion of Cr having a body-centered cubic structure becomes too high, making it difficult to achieve a ratio R of 0.1 or more. The heat treatment time may also be adjusted as appropriate, but is preferably about 1 to 10 hours, and more preferably 2 to 5 hours. If the heat treatment time is too long, the proportion of Cr having a body-centered cubic structure becomes too high, as described above, making it difficult to achieve a ratio R of 0.1 or more. For example, the heat treatment can be carried out at a temperature of 100°C to 400°C for about 2 to 4 hours.

[0025] [Layered manufacturing method] Next, a method for manufacturing an additive manufacturing object using the metal powder described above will be described. The additive manufacturing object can be manufactured by forming a powder layer containing metal powder (first step), solidifying the metal powder at a predetermined position in the powder layer to form a modeling layer (second step), and sequentially repeating the first and second steps to stack the modeling layers. Specific embodiments will be described below. This description will be given of an embodiment in which a laser is used in powder bed fusion as a means for solidifying the metal powder. However, this means is not limited to a laser as long as it is capable of solidifying the metal powder. The means may also be, for example, an electron beam or plasma. In this embodiment, additive manufacturing (AM) methods other than powder bed fusion may also be used. In this embodiment, for example, directed energy deposition, binder jetting, fused deposition modeling, cold spraying, etc. may also be used. Furthermore, in this embodiment, cutting may be performed during the manufacturing process.

[0026] An additive manufacturing object can be manufactured by an additive manufacturing device. For example, three-dimensional shape data is created by a 3D scanner or the like. The three-dimensional shape data is, so to speak, a blueprint of the additive manufacturing object. The three-dimensional shape data is sliced ​​at predetermined intervals to create slice data. The slice interval is also referred to as the slice thickness. The slice data is, so to speak, a blueprint of the manufacturing layers.

[0027] Additive manufacturing devices are also called "3D printers" and generally comprise a piston, a table, and an output unit. The piston supports the table. The piston can move up and down.

[0028] The piston lowers the table. The amount of lowering corresponds to one layer of the slice data. Metal powder is laid on the table using a coater (blade, spatula, brush, roller, etc.). This forms a powder bed. When the powder bed is laid, the coater smooths the surface and removes excess metal powder. The powder bed contains metal powder. For example, the powder bed may consist essentially of metal powder. The coater's movement speed when forming the powder bed is preferably 10 mm / sec or more and 800 mm / sec or less, more preferably 10 mm / sec or more and 500 mm / sec or less, and particularly preferably 10 mm / sec or more and 150 mm / sec or less. The metal powder of the present invention has high fluidity and packing ability, so a powder bed of uniform thickness can be formed even when the coater's movement speed is relatively high. The thickness of the powder bed to be formed is preferably 0.01 mm or more and 0.5 mm or less, more preferably 0.01 mm or more and 0.2 mm or less, and particularly preferably 0.01 mm or more and 0.07 mm or less, from the viewpoint of being able to form a powder bed of uniform thickness with a coater.

[0029] The output unit of the additive manufacturing device irradiates an energy beam onto the powder bed (metal powder). The energy beam scans the powder bed in a predetermined pattern. The scanning pattern follows the slice data. The metal powder irradiated with the energy beam melts and then rapidly cools and solidifies or sinters. In other words, the metal powder irradiated with the energy beam solidifies. A modeling layer is formed according to the scanning pattern of the energy beam. The modeling layer is also called a solidified layer, solidified layer, sintered layer, unit layer, etc. Note that "solidification" refers to the loss of fluidity of the metal particle group as the metal particle group fuses and becomes one.

[0030] The energy beam may include, for example, at least one selected from the group consisting of a laser, an electron beam, and plasma. The energy beam may include, for example, at least one selected from the group consisting of a Yb fiber laser, a YAG laser, a CO2 laser, a semiconductor laser, a blue laser, and a green laser. The output of the energy beam may be, for example, 20 to 10,000 W. The scanning speed of the energy beam may be, for example, 50 to 10,000 mm / s. The energy density of the energy beam may be, for example, 40 to 1,000 J / mm 3 and preferably 60 to 800 J / mm 3 , more preferably 80 to 600 J / mm 3 The metal powder of the present invention has high fluidity and packing properties, so that a powder bed of high density and uniform thickness can be formed by squeegeeing (i.e., a powder bed with excellent thermal conductivity can be formed). Therefore, when irradiating the powder bed with an energy beam, even if the pitch interval when scanning the energy beam is widened or the scanning speed is increased, the powder bed can be properly solidified, and as a result, the energy density can be reduced.

[0031] After forming the first modeling layer in this manner, the piston lowers the table again. The amount of lowering corresponds to one layer of slice data. As described above, a second modeling layer is further formed, and the formation of the modeling layer is repeated to construct a layered object. In other words, a layered object can be manufactured by stacking multiple modeling layers.

[0032] For example, the additively manufactured object may be manufactured in an inert gas atmosphere. By manufacturing the additively manufactured object in an inert gas atmosphere, it is expected that oxidation of the additively manufactured object can be suppressed. The inert gas may contain, for example, at least one gas selected from the group consisting of argon (Ar), nitrogen (N2), and helium (He). For example, the additively manufactured object may be manufactured in a reducing gas atmosphere. The reducing gas may contain, for example, hydrogen (H2). For example, the additively manufactured object may be manufactured in a reduced pressure atmosphere.

[0033] The additively manufactured object may have any shape. For example, it may have a seamless and complex internal structure. For example, it is considered difficult to form a seamless and complex internal structure by machining.

[0034] [Copper alloy molded product] The additively manufactured product obtained as described above has improved electrical conductivity when subjected to heat treatment. In the present invention, the additively manufactured product is made using a copper alloy powder containing a predetermined amount of chromium and a specific element in a predetermined ratio. Therefore, the copper alloy molded product obtained by heat treatment at 400°C or higher has excellent electrical conductivity while maintaining mechanical strength. Heat treatment can be performed using a heat treatment furnace or the like. The heat treatment temperature can be measured using a temperature sensor or the like attached to the heat treatment furnace. For example, if the set temperature of the heat treatment furnace is 300°C, the heat treatment temperature can be considered to be 300°C.

[0035] The heat treatment must be performed at a temperature below the melting point of the copper alloy, but may be, for example, 900°C or lower. By setting the heat treatment temperature to 900°C or lower, it is expected that the electrical conductivity will be improved while preventing excessive softening. The heat treatment temperature is preferably 800°C or lower, and more preferably 700°C or lower. On the other hand, from the viewpoint of improving mechanical strength while maintaining good electrical conductivity, the lower limit of the heat treatment temperature is preferably 400°C or higher, and more preferably 550°C or higher. The heat treatment temperature may be changed during the heat treatment process. For example, the temperature may be increased from room temperature to 700°C, held at 700°C for 1 hour, decreased from 700°C to 500°C, held at 500°C for 5 hours, and then decreased from 500°C to room temperature.

[0036] For example, it may be 0.1 to 100 hours, 0.5 to 50 hours, or 1 to 40 hours. The atmosphere inside the heat treatment furnace may be, for example, a nitrogen atmosphere, an argon atmosphere, a hydrogen atmosphere, a reduced pressure atmosphere, or the like.

[0037] A copper alloy molded product obtained by heat-treating an additive manufacturing product may have, for example, an electrical conductivity of 50% IACS or more. It preferably has an electrical conductivity of 75% IACS or more, and more preferably 90% IACS or more. Note that "electrical conductivity" refers to IACS conductivity. In other words, the electrical conductivity of annealed standard soft copper (International Annealed Copper Standard, IACS) is defined as 100% IACS. Electrical conductivity is measured using an eddy current conductivity meter. The measurement temperature is room temperature (15 to 25°C).

[0038] The additively manufactured object and the copper alloy molded object are made of a copper alloy. The copper alloy may have high electrical conductivity and high thermal conductivity. The additively manufactured object may be used in applications where the properties of the copper alloy are utilized. The additively manufactured object may be used, for example, in induction heating coils, heat sinks, rocket engines, etc. In the additively manufactured object, complex water cooling paths (internal structures) can be realized without joints.

[0039] The laminated molded object and the copper alloy molded object according to an embodiment of the present invention may have a relative density of 99% or more, for example. Note that the relative density of the copper alloy molded object can be substantially the same as the relative density of the laminated molded object before heat treatment. The relative density is represented by the percentage of the measured density with respect to the theoretical density. Here, the "theoretical density" is defined as the density of a melted material having an alloy composition substantially the same as the alloy composition of the measurement target (laminated molded object). The measured density can be measured in accordance with "JIS Z 2501 Sintered Metal Materials - Test Methods for Density, Oil Content, and Open Porosity". Water is used as the displacement liquid in the measurement of the measured density.

Examples

[0040] Next, 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.

[0041] <Production of Copper Alloy Powder> A copper alloy composed of 1.0 mass% of Cr and the balance of copper was melted, and copper alloy powder was obtained by the gas atomization method. The obtained copper alloy powder was first classified with a 45 μm mesh using a vibrating sieve, and the particles on the larger diameter side were removed, and the powder on the smaller diameter side was recovered. Subsequently, it was dried at 60 °C for 30 minutes to obtain the target copper alloy powder. The copper alloy powder thus obtained is referred to as Cu-Cr. Also, a copper alloy composed of 0.88 mass% of Cr, 0.06 mass% of Zr, and the balance of copper was melted, and copper alloy powder was obtained by the gas atomization method. The obtained copper alloy powder was first classified with a 45 μm mesh using a vibrating sieve, and the particles on the larger diameter side were removed, and the powder on the smaller diameter side was recovered. Subsequently, it was dried at 60 °C for 30 minutes to obtain the target copper alloy powder. The copper alloy powder thus obtained is referred to as Cu-Cr-Zr.

[0042] Subsequently, each of the obtained copper alloy powders was heat-treated under the conditions (temperature, time) shown in Table 1 below.

[0043] <Obtaining XANES Spectrum> For each of the obtained copper alloy powders, the Cr-K edge X-ray absorption near-edge structure spectrum (hereinafter also referred to as the Cu-K edge XANES spectrum) was obtained by fluorescence method using the beamline BL-12C of Photon Factory (synchrotron energy: 2.5 GeV) and the beamline BL5S1 of Aichi SR (synchrotron energy: 1.2 GeV). Under atmospheric conditions, the spectroscopic crystal was Si(111), a silicon drift detector (SDD) was used, and the measurement was carried out in the energy range of 5690 eV to 6692 eV. Also, as standard samples, a copper foil made of copper having a face-centered cubic structure (a standard sample owned by the High Energy Accelerator Research Organization Photon Factory BL-12C), a chromium foil made of chromium having a body-centered cubic structure (the same above), and α-Cr2O3 (National Institute of Standards and Technology SRM674a) were used. Note that the α-Cr2O3 sample was prepared by the following procedure. First, α-Cr2O3 and boron nitride (purity 99%, BBI03PB, manufactured by High-Purity Chemical Co., Ltd.) were weighed so that the mass ratio was α-Cr2O3:boron nitride = 1:48, and mixed in a mortar for 20 minutes or more. Then, 120 mg of the mixed powder was packed into a die with a diameter of 10 mm and compressed with a hand press to form a pellet. The XANES spectra of these standard samples were obtained by the transmission method. The energy ranges of the Cr-K edge XANES spectra of the chromium foil and α-Cr2O3 are the same as those of each copper alloy powder. For the copper foil, the Cu-K edge XANES spectrum was obtained in the energy range of 8475 eV to 10117 eV.

[0044] <Analysis of XANES Spectrum> First, in order to use the Cu-K edge XANES spectrum obtained from the copper foil for the analysis of the Cr-K edge XANES spectrum, an operation was performed to align the energy axis of the spectrum with the Cr-K edge. Specifically, the Cu-K edge XANES spectrum of the copper foil read in Athena was saved as a.xmu file, and using a text editor software, the value of "# Element.symbol:" was changed from Cu to Cr, and the value of "# Athena.e0:" was changed to 5993.84 eV, and then the file was saved. Next, the Cu-K-edge XANES spectrum of the copper foil with the energy axis changed, as well as the Cr-K-edge XANES spectra of each copper powder alloy powder, chromium foil, and α-Cr2O3, created in the above manner, were normalized using the software Athena under the following conditions. Pre-edge range: -150 to -30 eV Normalization range: 105~605eV

[0045] Next, I opened the Linear combination fitting page of the software Athena and performed linear fitting with the following settings. The software used was Athena version 0.9.26. <Fitting conditions> Standards: α-Cr2O3, copper foil (energy axis adjusted), chromium foil Fitting Space: norm μ(E) Energy range: -10 to 60 eV Fit E0:False Required: False All weights between 0 and 1:yes Force weights sum to 1:yes Overall e0 shift used:no Noise added to data:0

[0046] From the fitting results, for each copper alloy powder, A b and A f The results are shown in Table 1. A b and A fis the standardized linear coefficient of the X-ray absorption spectrum of Cr having a body-centered cubic structure and the X-ray absorption spectrum of Cr having a face-centered cubic structure, based on the linear coefficient of each spectrum when the spectrum obtained based on the spectrum of a standard sample is decomposed into the X-ray absorption spectrum of Cr2O3, the X-ray absorption spectrum of Cr having a face-centered cubic structure, and the X-ray absorption spectrum of Cr having a body-centered cubic structure. Specifically, the linear coefficient of the X-ray absorption spectrum of Cr2O3 (the value of Cr2O3 in Table 1) and the linear coefficient of the X-ray absorption spectrum of Cr having a face-centered cubic structure (the value of A in Table 1) are normalized. f The linear coefficient of the X-ray absorption spectrum of Cr with a body-centered cubic structure (A in Table 1) b The values ​​were normalized so that the sum of the values ​​was 1.

[0047] <Particle size measurement of copper alloy powder> For each copper alloy powder obtained as described above, a laser diffraction particle size distribution analyzer (MT-3300EX-II, manufactured by Microtrac) was used to measure the particle diameter (dmin) corresponding to an integrated frequency of 0 volume %, the particle diameter (d10) corresponding to an integrated frequency of 10 volume %, the particle diameter (d50) corresponding to an integrated frequency of 50 volume %, and the particle diameter (d90) corresponding to an integrated frequency of 90 volume %. The measurement results are shown in Table 1 below.

[0048] <Oxygen concentration> The oxygen content of each copper alloy powder obtained as described above was measured using an oxygen / nitrogen analyzer (EMGA-620, Horiba, Ltd.). The oxygen content was determined from the amount of CO and CO2 generated when the metal powder was heated and melted in a He atmosphere. The measurement results are shown in Table 1 below.

[0049] <Angle of repose> For each of the copper alloy powders obtained as described above, the angle of repose was measured. The angle of repose was measured by pouring the copper alloy powder from above a sieve (JIS standard Z8801-1-2000, mesh size 75 μm) using a multi-functional powder physical property measuring instrument (MT-1001, manufactured by Seishin Enterprise Co., Ltd.). The measurement results were as shown in Table 1 below.

[0050] <Measurement of L* value, a* value, and b* value> The L* value, a* value, and b* value of each of the copper alloy powders obtained as described above were measured in accordance with JIS Z 8722 using a color difference meter (ZE 6000, manufactured by Nippon Denshoku Industries Co., Ltd.). The measurement results were as shown in Table 1 below.

[0051] <Fabrication of the laminated object> For each of the copper alloy powders, a laminated object was fabricated under the following manufacturing conditions using a laminated manufacturing apparatus (EOS M290, manufactured by EOS Electro Optical Systems Japan Co., Ltd.). As the laminated object, a prismatic test piece (bottom surface 10 mm square × height 15 mm) was fabricated. Manufacturing conditions: Laser type: Fiber laser, 370 W Spot diameter: Approximately 0.1 mm Laser irradiation speed: 600 mm / s Layer thickness: 0.03 mm

[0052] <Fabrication of the copper alloy object> The laminated object obtained as described above was placed in a heat treatment furnace and heat-treated at a temperature of 700 °C for 3 hours in a nitrogen atmosphere to obtain a copper alloy object.

[0053] <Measurement of conductivity> The conductivity of the copper alloy object obtained as described above was measured using an eddy current conductivity meter. The measurement results were as shown in Table 1 below.

[0054] <Measurement of relative density> The theoretical density of the copper alloy formed product obtained as described above was calculated, and the actual density was measured in accordance with JIS Z 2501 "Sintered metal materials - Test method for density, oil content, and open porosity." The relative density was calculated from the obtained theoretical density and the actual density. The theoretical density was calculated by multiplying the densities of common Cu, Cr, and Zr by their respective content ratios and adding them up. The calculation results are shown in Table 1 below.

[0055] [Table 1]

[0056] As is clear from Table 1, when the copper alloy powder has a ratio R of the X-ray absorption spectrum derived from Cr having a face-centered cubic structure to the X-ray absorption spectrum derived from Cr having a body-centered cubic structure in the copper alloy powder, which is in the range of 0.1 to 10, it is possible to obtain an additive manufacturing product (copper alloy product) having excellent electrical conductivity and high relative density. On the other hand, it is understood that when the copper alloy powder has a ratio R of less than 0.1, the resulting additive manufacturing product (copper alloy product) has excellent electrical conductivity but does not have a relative density of more than 99%.

Claims

1. A copper alloy powder for additive manufacturing, comprising: Contains Cr, with the balance being Cu and inevitable impurities; The following formula: R=A ｆ / A ｂ (In the formula, A ｆ represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, A ｂ represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder, However, A ｂ and A ｆ The spectrum obtained is based on the spectrum of the standard sample. ２ O ３ The linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure are normalized based on the linear coefficients of each spectrum when the X-ray absorption spectrum derived from Cr having a body-centered cubic structure is decomposed into a linear combination of the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure. The copper alloy powder for additive manufacturing, wherein the ratio R represented by the formula (I) is 0.1 to 10.

2. The copper alloy powder for additive manufacturing according to claim 1, wherein the oxygen concentration is 500 ppm or less by mass.

3. The copper alloy powder for additive manufacturing according to claim 2, having an angle of repose of 30° or more.

4. The copper alloy powder for additive manufacturing according to claim 1, wherein the a* value of the L*a*b* color system is 15 or more.

5. The copper alloy powder for additive manufacturing according to claim 1, wherein the average particle diameter (D50) is 10 μm or more and 50 μm or less.

6. The copper alloy powder for additive manufacturing according to claim 1, further containing Zr.

7. A method for manufacturing an additive manufacturing object using the copper alloy powder according to claim 1, a first step of forming a powder layer containing the copper alloy powder; a second step of solidifying the copper alloy powder at a predetermined position in the powder layer to form a modeling layer; A method for manufacturing a layered object, which manufactures a layered object by sequentially repeating the first step and the second step and stacking the modeling layers.

8. 8. The method according to claim 7, wherein the consolidation of the copper alloy powder in the second step is carried out by an energy irradiation means selected from the group consisting of a laser, an electron beam, and plasma.

9. A method for producing a copper alloy product from an additively shaped product obtained by the method according to claim 7, comprising heat treating the additively shaped product.

10. 10. The method of claim 9, wherein the heat treatment is carried out at a temperature of 400°C or higher and below the melting point of the copper alloy.

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