Cu-based alloy powder and additive fabricated bodies using the same

Abstract

This invention provides a means for stably and easily realizing additively manufactured bodies with high relative density. [Solution] Particle diameter D 10 A Cu-based alloy powder with a particle size of 13.0-23.0 μm and a tap density (TD) of 4.75-4.90 g / cc.

Description

[Technical Field]

[0001] The present invention relates to a Cu-based alloy powder and an additively fabricated body made of a Cu-based alloy fabricated by additive manufacturing using this Cu-based alloy powder. [Background technology]

[0002] Due to their high electrical and thermal conductivity, copper-based alloys are used in various coils, heat sinks, electrical contacts, and molds. Recently, in order to handle complex shapes, trials and studies are being conducted on manufacturing using additive manufacturing methods (also known as 3D printers, three-dimensional manufacturing, additive manufacturing, etc.).

[0003] Representative additive manufacturing methods include the powder bed method (powder bed fusion method) and the metal deposition method (directed energy deposition method). In the powder bed method, a laser beam or electron beam is irradiated, causing the irradiated areas of the spread-out powder to melt and solidify. The powder used in this powder bed method is generally sieved after powder manufacturing to remove excessively fine particles. This is because the presence of excessively fine particles worsens the fluidity, making it impossible to spread the powder evenly and thus impossible to perform additive manufacturing.

[0004] Now, when attempting to fabricate objects using copper-based powder by additive manufacturing, the copper-based powder reflects the laser beam, which is commonly used as a heat source in additive manufacturing. Therefore, even when attempting to use copper-based powder in additive manufacturing, it has been difficult to sufficiently raise the temperature of the copper-based powder, melt it, and obtain a fabricated object with high relative density and no residual pores.

[0005] Therefore, attempts have been made to obtain Cu-based alloy additive structures with high relative density by lowering the laser reflectivity (or increasing the laser absorptivity) of Cu-based alloy powder by adding various additive elements such as Cr, Zr, and Ni, thereby making it easier to melt (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-17639 [Patent Document 2] Japanese Patent Publication No. 2024-165108 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 discloses that an additively fabricated body with a relative density of approximately 95% can be obtained. However, with a relative density of 95%, many voids are observed inside the fabricated body, and it can be easily inferred that the hardness and electrical conductivity of the additively fabricated body will be significantly lower than that of the bulk material, indicating that there is room for further improvement.

[0008] To obtain a fabricated body with superior electrical and thermal conductivity and hardness, there is a need for a powder capable of producing a high-density additively fabricated body with a relative density of 99.0% or higher. Therefore, the object of the present invention is to provide a means for stably and easily realizing an additively fabricated body with an extremely high relative density. [Means for solving the problem]

[0009] In response to the above challenges, the inventors conducted thorough research and first focused on the fact that powders with small particle sizes have a small heat capacity per particle, and are easier to melt than powders with larger particle sizes even when irradiated with the same laser energy. However, simply miniaturizing the particles would result in poor powder fluidity for fabrication, which would not lead to an improvement in relative density. Therefore, the inventors found that by using powders with a higher proportion of particles smaller than those generally used for additive manufacturing, while maintaining fluidity, it is possible to obtain dense additive manufactured bodies with excellent relative density while maintaining practical fabrication capabilities.

[0010] In other words, the first means of solving the problems of the present invention is the particle size D 10is a Cu-based alloy powder having a particle diameter D of 13.0 to 23.0 μm and a tap density TD of 4.75 to 4.90 (g / cc).

[0011] The second means is the Cu-based alloy powder for additive manufacturing according to the first means, which has a fluidity of 18.0 (sec / 50g) or more.

[0012] The third means is the Cu-based alloy powder for additive manufacturing according to the first means or the second means, which contains, by mass%, one or more of Cr: 0.1 to 10.0%, Fe: 0.1 to 10.0%, Zr: 0.1 to 10.0%, Nb: 0.1 to 10.0%, Ni: 0.1 to 10.0%, and Si: 0.1 to 2.0% or less, with the balance being Cu and unavoidable impurities.

[0013] The fourth means is an additive molded article formed of the Cu-based alloy component according to the third means.

[0014] Another means is an additive molded article formed of a Cu-based alloy that is additively manufactured using only the Cu-based alloy powder according to any one of the first to third means. That is, the particle diameter D 10 is 13.0 to 23.0 μm, and the additive molded article is formed solely of a Cu-based alloy powder having a tap density TD of 4.75 to 4.90 (g / cc). Alternatively, the particle diameter D 10 is 13.0 to 23.0 μm, the tap density TD is 4.75 to 4.90 (g / cc), and the fluidity is 18.0 (sec / 50g) or more, and the additive molded article is formed solely of said Cu-based alloy powder. Alternatively, it contains, by mass%, one or more of Cr: 0.1 to 10.0%, Fe: 0.1 to 10.0%, Zr: 0.1 to 10.0%, Nb: 0.1 to 10.0%, Ni: 0.1 to 10.0%, and Si: 0.1 to 2.0% or less, the balance is Cu and unavoidable impurities, and the particle diameter D 10 is 13.0 to 23.0 μm, the tap density TD is 4.75 to 4.90 (g / cc), and the fluidity is 18.0 (sec / 50g) or more, and the additive molded article is formed solely of said Cu-based alloy powder. [Effects of the Invention]

[0015] By shaping the Cu-based alloy powder for additive manufacturing according to the present invention through a process involving rapid melting and rapid solidification, that is, an additive manufacturing method, a dense additive manufactured article having a relative density of 99.0% or more can be obtained. [Brief Description of the Drawings]

[0016] [Figure 1] Fig. 1 is an explanatory diagram modeling the state of particle size distribution by type. A is the particle size distribution model of the powder of the example of the present invention, and D10 is 17.2 µm. B is the particle size distribution model of the conventional normally distributed powder of the comparative example, and D10 is 26.1 µm. C is the particle size distribution model of the comparative powder biased to fine powder of the comparative example, and D10 is 11.0 µm. [Mode for Carrying Out the Invention]

[0017] Prior to the description of the mode for carrying out the present invention, first, D of the Cu-based alloy powder used in the present invention 10 , the reasons for defining tap density and fluidity will be described.

[0018] [D 10 : 13.0 to 23.0 µm] Particle diameter D of powder 10 is preferably 13.0 µm or more and 23.0 µm or less in view of the fluidity of the powder and the relative density of the shaped article. For Cu-based alloy powders used in additive manufacturing, if the powder supplied from the nozzle does not have fluidity, the shaping operation becomes difficult. A powder having a particle diameter D 10 of less than 13.0 µm tends to have difficulty flowing. If it does not flow properly, the spreading of powder in the powder bed method tends to be insufficient, leading to problems such as decreased relative density, nozzle clogging during supply resulting in poor shaping, and thus making the production of the additive manufactured article practically difficult. In this regard, if the powder has a particle diameter D 10 of 13.0 µm or more, practical fluidity can be ensured in combination with other conditions. Therefore, the particle diameter D 10The particle size is preferably 13.0 μm or larger. More preferably, particle size D 10 The particle size is 14.0 μm or larger, and more preferably 15.0 μm or larger.

[0019] On the other hand, if the particle size is excessively large, the relative density of the additively manufactured body will decrease. Particle size D 10 From powders with a particle size of 23.0 μm or less, additively fabricated bodies with high relative density can be obtained, while the particle size D 10 Powders with particle size D exceeding 23.0 μm will result in a relative density of the additively manufactured body falling below 99.0%. Therefore, from these perspectives, 10 The particle size is preferably 23.0 μm or less, more preferably 21.0 μm or less, and particularly preferably 19.0 μm or less.

[0020] [TD: 4.75~4.90 (g / cc)] The tap density TD of the powder is preferably 4.75 to 4.90 (g / cc). If the tap density TD is less than 4.75 (g / cc), the relative density of the resulting additively manufactured body will be insufficient, falling below 99.0%. On the other hand, if the tap density TD exceeds 4.90 (g / cc), the powder becomes difficult to flow, making it difficult to manufacture the additively manufactured body.

[0021] Particle size D 10 By defining this, while ensuring that a certain amount of fine powder is included, the tap density TD value does not become excessively large, thereby excluding powders that consist solely of fine powder. 10 If only the material is sufficient and the whole is a fine powder, the fluidity will be low and prone to clogging, causing problems when used in additive manufacturing. If the TD is too low, the filling rate will be low, and if it is excessively high, fluidity will not be obtained. Therefore, D 10 By comprehensively balancing TD, the present invention makes it possible to select powders with excellent moldability suitable for additive manufacturing, in which fine powder is appropriately contained within the powder.

[0022] Average particle diameter D 50 : 30.0~40.0 μm Average particle diameter D50 From the viewpoint of powder fluidity and relative density of the fabricated object, an average particle size of 30.0 to 40.0 μm is preferred. In Cu-based alloy powders used in additive manufacturing, if the powder supplied from the nozzle lacks fluidity, the fabrication process becomes difficult. If the powder does not flow properly, the powder bed will not be adequately packed, resulting in a low relative density or nozzle blockage during supply, leading to poor fabrication and making the production of additively manufactured objects practically difficult. From these viewpoints, the average particle size D of the powder is preferable. 50 The average particle diameter D is preferably 30.0 μm or larger, more preferably 32.0 μm or larger, even more preferably 33.0 μm or larger, and particularly preferably 34.0 μm or larger. If the particles are too coarse, the relative density will not be good, and the nozzle will become clogged, hindering fluidity. 50 The particle size is preferably 40.0 μm or less, more preferably 38.5 μm or less, even more preferably 37.5 μm or less, and particularly preferably 36.5 μm or less.

[0023] [Flow rate: 18.0 s / 50g or more] Furthermore, the fluidity of the powder is preferably 18.0 s / 50 g or higher. With powders that have a fluidity below 18.0 s / 50 g, the powder bed may not be adequately packed, making it difficult to obtain a dense additive body.

[0024] The Cu-based alloy powder of the present invention can be broadly used as long as it is a Cu-based alloy powder suitable for additive manufacturing. Examples of such Cu-based alloy powders for additive manufacturing include, but are not limited to, Cu-Zr, Cu-Cr-Zr, and Cu-Ni-Si based Cu-based alloys. The reasons for adding components that are suitably added to the Cu-based alloy powder in the present invention are explained below.

[0025] [Cr, Fe, Zr, Nb, Ni: preferably 0.1-10.0% or less] Cr (chromium), Fe (iron), Ni (nickel), Zr (zirconium), and Nb (niobium) have small solid solubility limits when added to Cu in the equilibrium phase diagrams of Cu-Cr, Cu-Fe, Cu-Zr, Cu-Nb, and Cu-Ni alloys. However, if the Cu-based alloy powder is produced by a method involving rapid solidification, such as atomization, these elements will not be in equilibrium but will be supersaturatedly dissolved in Cu. In such Cu-based alloy powders with a low solid solubility limit and supersaturated solid solution, the laser reflectivity is suppressed compared to pure Cu powder, allowing for more efficient heat input. Therefore, it is possible to obtain additively fabricated bodies with relatively fewer internal voids compared to pure Cu powder. However, adding less than 0.1% has little effect on improving moldability, and adding more than 10.0% significantly reduces conductivity. Therefore, when adding one or more of Cr, Fe, Ni, Zr, and Nb, the lower limit for each component is 0.1% or more, preferably 0.4% or more, preferably 0.6% or more, and the upper limit is 10.0% or less, preferably 8.0% or less, and more preferably 6.0% or less.

[0026] [Si: 0.1~2.0%] Silicon (Si) dissolves in Cu along with Cr, Fe, and Ni, and through heat treatment, it forms compounds that are swept out of the Cu matrix, thus maintaining the electrical and thermal conductivity of the Cu-based alloy. On the other hand, excessive addition will remain in the matrix and inhibit electrical and thermal conductivity. Therefore, from these viewpoints, the Si content should be 0.1% or more, preferably 0.5% or more, and more preferably 0.8% or more. The Si content should be 2.0% or less, preferably 1.8% or less, and more preferably 1.5% or less.

[0027] [Manufacturing of raw material powders] The Cu-based alloy powder of the present invention can generally be produced by water atomization or centrifugal atomization, but it is preferable to produce it with excellent roundness. Therefore, the following explanation will use gas atomization as an example.

[0028] Under vacuum and argon atmosphere, the raw materials to be melted in an alumina crucible are melted by high-frequency heating. This molten alloy is dispensed from a 5 mm diameter nozzle at the bottom of the crucible and immediately sprayed with high-pressure argon gas. This spray breaks the molten alloy into fine droplets, which cool and solidify as they fall through the tower of the atomizing apparatus, yielding atomized alloy powder. The resulting powder is classified using a sieve press with a predetermined mesh size.

[0029] For the examples and comparative examples of the present invention, alloy powders corresponding to three types of particle size distribution types, A, B, and C, shown in Figure 1, were prepared. A is the particle size distribution model of the powder in the example of the present invention, and D 10 It is 17.2 μm. B is the conventional normal distribution particle size distribution model for powders in the comparative example, and D 10 It is 26.1 μm. C is a particle size distribution model of a comparative powder biased towards the fine powder of the comparative example, and D 10 The particle size is 11.0 μm. Furthermore, the average circularity of all powder types was in the range of 0.70 or higher.

[0030] In the gas atomization example of the present invention shown as Type A in Figure 1, the gas pressure used for spraying during gas atomization is increased by approximately 2-3% compared to normal. By classifying the powder to remove coarse particles larger than 53 μm, while not cutting off the fine particles, the distribution in Figure 1A shows a slightly higher content of fine particles. In other words, by classifying the powder to remove coarse particles larger than 53 μm, while deliberately not actively removing fine particles, the distribution in Figure 1A shows a slightly higher content of fine particles.

[0031] Comparative Example Type B powder was prepared by gas atomization using a normal gas pressure, lower than that of Type A, and classified using gaps of 53 μm and 20 μm. This resulted in a powder with a particle size distribution close to a normal distribution, with irregular shapes such as fine powder and coarse particles removed.

[0032] Comparative Example C type powder was made finer by increasing the gas pressure used for spraying during gas atomization by about 15% compared to normal, and was classified into fine powders with mesh sizes of 32 μm and 20 μm.

[0033] [Particle size D 10 [About] The particle diameter is defined as the diameter of a sphere having the same volume as the powder particles, and the particle diameter D 10 This refers to the particle size of the powder that falls within the bottom 10% in terms of particle count when all measurable powders with a particle size of 0.02 μm or larger are arranged in order from smallest to largest particle size.

[0034] The particle size of the powder can be measured by laser diffraction scattering. From the obtained measurement results, D 10 The particle size of a powder of a certain size is determined. A suitable device for this measurement is, for example, Nikkiso's laser diffraction / scattering particle size distribution analyzer "Microtrac MT3000".

[0035] [Tap density: TD] Tap density is measured in accordance with JIS (Japanese Industrial Standards) Z2512. Specifically, approximately 50g of powder is measured in a volume of 100cm³. 3 The material was filled into a cylinder and its density was measured. The measurement conditions were a drop height of 10 mm and 200 taps. A tap density (TD) of 4.75 to 4.90 (g / cc) indicates a high relative density, and is therefore considered to be excellent in terms of TD value.

[0036] [Fluidity] Fluidity is measured in accordance with JIS Z2502. The evaluation method involves supplying 50g of powder to a funnel and measuring the passage time through the orifice. Fluidity of 18.0 s / 50g or better is considered excellent.

[0037] [Additive manufacturing] For additive manufacturing, a laser-heated powder bed system (EOS-M290, manufactured by EOS Corporation) was used. The manufacturing conditions were appropriately selected depending on the properties and composition of the Cu-based alloy powder, but the preferred energy density (ED) was 100-350 J / mm². 3 The base material for the fabrication was made of Cu, and a 12mm x 12mm x 12mm layered object was fabricated as a density sample. After separating these objects from the plate using wire cutting, the density of the objects was measured.

[0038] [Evaluation of the relative density of additively manufactured objects] The density of the additively fabricated object was determined by the Archimedes method. First, the weight of the test specimen was measured in air and water, respectively. The volume of the object was derived from the difference in the measured values, and the density was calculated by dividing the air weight by the obtained volume. The density of the raw material powder used was measured by the gas displacement method. In this method, the powder is placed in a container of a predetermined volume, a fixed amount of gas is introduced into it, the volume of the powder is derived from the gas pressure, and the density is calculated by dividing the weight of the powder by this volume. The density of the powder was taken as the true density of the alloy, and the relative density of the object was evaluated as "density of object / density of powder × 100 (%)". Objects with a relative density of 99.0% or higher were evaluated as superior from the viewpoint of excellent electrical conductivity, thermal conductivity, and hardness.

[0039] (Specific evaluation using examples and comparative examples) As Examples 1-5 and Comparative Examples 1-10, raw materials having the powder characteristics shown in Table 1 were prepared, and additive manufacturing was attempted. To prepare the powders, Cu-based alloy powders were obtained by spraying each raw material from a molten state using the gas atomization method in a vacuum or argon atmosphere. Examples 1-5 correspond to flow distribution type A in Figure 1, and are powders prepared by removing coarse powder particles larger than 150 μm through classification, while not actively removing fine powder particles. Comparative Examples 1, 3, 5, 7, and 9 correspond to flow distribution type B in Figure 1 and are powders produced by a general manufacturing method that removes both coarse and fine powder by classifying atomized powder using coarse and fine mesh sizes. Comparative Examples 2, 4, 6, 8, and 10 are powders that have been atomized with a higher pressure gas, and are extremely fine powders corresponding to flow distribution type C in Figure 1.

[0040] Next, the powders of Examples 1-5 and Comparative Examples 1-10 were subjected to the above procedure, and the particle size D 10 Tap density and fluidity were measured and evaluated. The results are shown in Table 1. Note that the underlined part in Table 1 represents the particle size D as defined by this invention. 10 This indicates that the tap density and fluidity are outside the specified range. Regarding relative density, if the molding results from using these powders are insufficient or the relative density falls below 99.0%, it will be underlined.

[0041] [Table 1]

[0042] For reference, Table 2 shows the component composition of the powders used in Examples 1-5 and Comparative Examples 1-10. Each powder contains one or more of the following elements: Cr, Fe, Ni, Zr, Nb, and Si, with the remainder being Cu and unavoidable impurities. Of course, Examples 1-5 in Table 2 are just examples of embodiments of the present invention, and it should be noted that the scope of the present invention is not limited to these components alone.

[0043] [Table 2]

[0044] The powders in Examples 1-5 are all of type A in terms of particle size distribution, therefore, D 10The powder has a particle size in the range of 13.0 to 23.0 μm and a tap density in the range of 4.75 to 4.90 (g / cc). It also has excellent fluidity of 18.0 s / 50g or more, making it suitable for additive manufacturing. Because it is manufactured by a rapid melting and rapid solidification method using gas atomization, these powders differ from equilibrium states in that the added components are supersaturated and solidified in Cu. Therefore, they absorb lasers more easily than pure Cu, and furthermore, the powder distribution is A type and D type. 10 Since the particle size range is 13.0 to 23.0 μm, the presence of a slightly larger amount of fine powder results in an appropriate tap density, D 10 A powder is selected that balances both parameters, D and TD. 10 By satisfying the numerical ranges of both and TD, fluidity is not lost, unlike when the powder is unilaterally biased towards fine powder. Therefore, it is a powder suitable for additive manufacturing with efficient filling efficiency and excellent filling rate. When used in additive manufacturing, the powders of Examples 1 to 5 satisfy a relative density of 99.3% or more for the manufactured body, resulting in a dense additive manufactured body with excellent electrical and thermal conductivity.

[0045] Comparative Examples 1, 3, 5, 7, and 9 are Type B, where the particle size distribution of the powder is a normal distribution, and D 10 Although fine powder particles larger than 23.5 μm have been removed, its fluidity is somewhat low, and its tap density is 4.72 g / cc or less. As a result, the relative density of the molded body remains in the 98% range, and its electrical and thermal conductivity is somewhat inferior.

[0046] Comparative Examples 2, 4, 6, 8, and 10 have a powder particle size distribution of type C, and D 10 Because the particle size is low, ranging from 12.5 to 12.9 μm, and the material is predominantly fine powder, the tap density (TD) becomes excessively high at 4.92 to 4.93 g / cc. However, the powder is difficult to flow, making it challenging to fabricate additively manufactured objects.

Claims

1. Particle size D 10 A Cu-based alloy powder having a particle size of 13.0 to 23.0 μm and a tap density TD of 4.75 to 4.90 (g / cc).

2. The Cu-based alloy powder for additive manufacturing according to claim 1, wherein the fluidity is 18.0 (sec / 50g) or higher.

3. Cu-based alloy powder for additive manufacturing according to claims 1 and 2, comprising, by mass%, one or more of the following: Cr: 0.1-10.0%, Fe: 0.1-10.0%, Zr: 0.1-10.0%, Nb: 0.1-10.0%, Ni: 0.1-10.0%, and Si: 0.1-2.0%, with the remainder being Cu and unavoidable impurities.

4. A laminated body consisting solely of a Cu-based alloy having the components described in claim 3.

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