Metal powder for 3D printers, modeling materials and methods for manufacturing modeling materials

Abstract

The metal powder used in 3D printers contains multiple metal particles. The particle size distribution of these particles exhibits a maximum peak within a diameter range of 1 μm to 200 μm. The cumulative proportion of the particle size distribution, by volume, is 90% of the particle size D. 90 Particle size D, with a cumulative proportion of 10% by volume. 10 The difference D 90 -D 10 It is above 10μm.

Description

[0001] This application is a divisional application of application number "201980035725.5", filed on May 29, 2019, entitled "Metal powder for 3D printer, model and method for manufacturing model". Technical Field

[0002] The implementation method involves metal powder for 3D printers and molded objects. Background Technology

[0003] As a novel forming technology, 3D printing is being developed using 3D printers. 3D printing is a technology that directly shapes three-dimensional objects using a three-dimensional model. In 3D printing, lasers are used, for example, to process resin molded bodies. Resin is a material that is easily formed into three-dimensional structures because it is melted by the laser.

[0004] In recent years, there have been attempts to create shapes from metal materials using 3D printing. For example, 3D printing using metal powder for 3D printers can be cited. This method involves spreading the metal powder and then solidifying it by irradiating it with a laser or electron beam.

[0005] Stainless steel can be used as a metal powder for 3D printers. The average particle size of stainless steel powder can be adjusted. Stainless steel has a melting point above 1400°C and below 1500°C. As long as the melting point is within this range, 3D printing can be used to create shapes. On the other hand, the shape-making methods using metal materials with higher melting points than stainless steel may not necessarily produce good results.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2015 / 041236 Summary of the Invention

[0009] The 3D printer metal powder involved in the embodiment comprises multiple metal particles. The particle size distribution of these multiple metal particles exhibits a maximum peak within a particle size range of 1 μm to 200 μm. The cumulative proportion of the particle size distribution, by volume, is 90% of the particle size D. 90 Particle size D, with a cumulative proportion of 10% by volume. 10 The difference D 90 -D 10 It is above 10μm. Attached Figure Description

[0010] Figure 1 This is a diagram showing an example of the particle size distribution of metal powder.

[0011] Figure 2 This is a diagram representing an example of a highly spherical metal particle.

[0012] Figure 3 This is a schematic diagram used to illustrate sphericity.

[0013] Figure 4 This is a schematic diagram used to illustrate the angle of repose. Detailed Implementation

[0014] The 3D printer metal powder involved in the implementation method is a metal powder used to manufacture shaped objects using a 3D printer. The metal powder contains multiple metal particles.

[0015] The metal powder (metal particles) preferably contains at least one element selected from tungsten (W), molybdenum (Mo), rhenium (Re), niobium (Nb), tantalum (Ta), chromium (Cr), and vanadium (V) as its main component. The main component is the element that constitutes the most abundant element in the metal powder, and for example, the main component element contains more than 50 atomic percent of the total composition.

[0016] Generally speaking, tungsten has a melting point of 3400℃, molybdenum 2620℃, rhenium 3180℃, niobium 2470℃, tantalum 2990℃, chromium 1905℃, and vanadium 1890℃. Metals with melting points above 1800℃ are thus called high-melting-point metals.

[0017] Due to their high melting points, high-melting-point metals require uniform molten state of the metal particles irradiated by lasers. Therefore, it is preferable to control the maximum peak of the particle size distribution and the deviation in particle size. In particular, the higher the melting point (above 1800°C, and further above 2400°C), the more crucial these controls become.

[0018] Figure 1 An example of particle size distribution of metal powder (metal particles) is shown. Figure 1 The horizontal axis represents the volume average diameter (μm), the left vertical axis represents the frequency (%), and the right vertical axis represents the cumulative percentage (%). Furthermore, the horizontal axis is logarithmically scaled. A graph where the vertical axis represents frequency is called a frequency graph. A graph where the vertical axis represents cumulative percentage is called a cumulative graph.

[0019] Particle size distribution can be measured using laser diffraction. The amount of metal powder used in a single measurement is the amount recommended by the measuring device. Generally, 0.02 g is recommended. Furthermore, the minimum amount is set to 0.01 g, and the maximum amount is set to 0.03 g. Additionally, the sample is thoroughly stirred before measurement.

[0020] The metal powder of the embodiment has a maximum peak in the particle size range of 1 μm to 200 μm, and the cumulative proportion of particle size D in the particle size distribution is 90% by volume. 90 Particle size D, with a cumulative proportion of 10% by volume. 10 The difference D 90 -D 10 It is above 10μm.

[0021] The flowability of metal powder can be improved by setting the maximum peak of the particle size distribution within the range of 1 μm to 200 μm. When the maximum peak of the particle size distribution is below 1 μm, the metal particles are too small and become prone to agglomeration. If the metal particles agglomerate, the flowability of the metal powder will be compromised. If the maximum peak of the particle size distribution is in the range of particle size exceeding 200 μm, it is difficult to create shapes using 3D printing. More preferably, the maximum peak of the particle size distribution is in the range of 10 μm to 150 μm.

[0022] The particle size distribution preferably has one peak in the particle size range of 1 μm to 200 μm. There may also be two or more peaks, but with D... 90 -D 10 There are concerns that adjustments become difficult. A peak, in this context, refers to the highest point in the particle size distribution. The particle size distribution value rises to its peak and then gradually declines. In other words, a peak is formed through a rise followed by a decline. A peak is not formed when the particle size distribution rises continuously without declining and when the slope changes midway.

[0023] The particle size distribution is preferably within the range of 0.1 μm to 300 μm. This means that, when the particle size distribution is required, there are no metal particles with a diameter smaller than 0.1 μm or larger than 300 μm. If the particle size is too small or too large, there are concerns about deviations in the shaping capabilities of 3D printing. 3D printing is a technology that shapes metal powder while simultaneously irradiating it with a laser. Therefore, if the size of the metal powder varies, the degree to which the surface of the metal powder is melted by the laser will also vary.

[0024] Particle size D 90 Particle size D 10 Cumulative charts can be used to determine the particle size distribution. The maximum peak of the particle size distribution can be determined using a frequency chart. A frequency of 0% for the particle size distribution indicates the absence of metal particles of comparable size.

[0025] If D is expressed as a formula 90 -D 10 If it is above 10μm, then it is D. 90 -D 10 ≥10μm. The overall particle size distribution can be controlled by using a cumulative proportion. To obtain high-density shapes, it is necessary to insert small metal particles into the gaps between large metal particles. By satisfying D... 90 -D10 ≥10μm, it can form both large and small metal particles.

[0026] D 90 -D 10 A particle size below 10 μm indicates a sharp peak in the particle size distribution. If the particle size is too uniform, gaps can easily form between particles, thus reducing the shapeability of 3D printing. By making the D... 90 -D 10 By inserting smaller metal particles into the gaps between larger metal particles (above 10 μm), the modeling capabilities of 3D printing are improved. This allows for the formation of dense models. Specifically, models with a density of over 90% can be obtained. The density can be measured using the Archimedes method.

[0027] D 90 -D 10 There is no specific upper limit, but it is preferably below 150 μm. If D 90 -D 10 Beyond 150 μm, adjusting the particle size distribution becomes difficult. Therefore, D 90 -D 10 Preferably, the micrometer size is 10 μm or more and 150 μm or less, more preferably 10 μm or more and 100 μm or less. Furthermore, it is even more preferably 70 μm ≥ D. 90 -D 10 ≥10μm.

[0028] The metal powder (multiple metal particles) preferably contains metal particles with a sphericity of 90% or higher. Figure 2 This is a diagram representing an example of a highly spherical metal particle. Figure 2 The diagram shows metal powder 1, high-sphericity metal particles 2, and low-sphericity metal particles 3 for 3D printers. Figure 3 This is a schematic diagram used to illustrate sphericity. Figure 3 The diagram shows a highly spherical metal particle 2, an imaginary circle 4, and a maximum diameter 5.

[0029] Sphericity can be determined using magnified photographs. These magnified photographs are obtained using a scanning electron microscope (SEM) at magnification between 100x and 1000x. Metal particles 2 with high sphericity appear as circular outlines in the SEM photographs. Therefore, the higher the sphericity, the closer the shape will be to a perfect circle; that is, it will appear as a sphere. Metal particles 3 with low sphericity show angular surfaces in the SEM photographs. Therefore, metal particles 3 with low sphericity appear as polygonal outlines.

[0030] The method for determining sphericity is as follows. Calculate the area of ​​an imaginary circle 4, using the largest diameter 5 of the metal particle 2 with high sphericity reflected in the SEM image as its diameter. Treat the imaginary circle 4 as a perfect circle. Calculate the area of ​​the metal particle 2 with high sphericity reflected in the SEM image. This can be calculated using the formula: Sphericity (%) = (Measured area in a grain of metal powder / Area of ​​the imaginary circle using the largest diameter as its diameter) × 100.

[0031] The preferred metal particles contain metal particles with a sphericity of 90% or higher. The 3D printer metal powder contains high-sphericity metal particles 2 (90% or higher) and low-sphericity metal particles 3 (less than 90%). The high-sphericity metal particles improve the flowability of the metal powder. Improved flowability allows for constant control of the metal powder supply in the 3D printed model. Constant supply reduces deviations in modeling. The upper limit for sphericity is 100%. As long as the sphericity is 90% or higher, the outline can also be angular. The outline of the high-sphericity metal particles 2 is preferably circular. High-sphericity metal particles are less likely to form aggregates.

[0032] Among the metal particles, those that are primary particles and have a maximum diameter of 1 μm or more preferably have an aspect ratio in the range of 1.0 or more and 1.5 or less. The SEM image shows unaggregated primary particles. In other words, a primary particle with a maximum diameter of 1 μm or more means an unaggregated metal particle with a maximum diameter of 1 μm or more. The aspect ratio of such metal particles is preferably in the range of 1.0 or more and 1.5 or less. By controlling the aspect ratio of large metal particles with a maximum diameter of 1 μm or more to 1.5 or less, the gaps generated around the large metal particles can be reduced. Since a structure can be formed that can accommodate small metal particles within these gaps, the manufacturability is improved.

[0033] The aspect ratio was determined using SEM images taken when sphericity was calculated. The largest diameter of a primary particle reflected in the SEM image was taken as the major axis. The length of the metal particle perpendicular to the major axis from its center was taken as the minor axis. The ratio of major axis to minor axis was taken as the aspect ratio. This process was performed on 50 particles, and the average value was taken as the mean aspect ratio.

[0034] The proportion of metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more is preferably in the range of 0.5 g or more per 10 g. By mixing highly spherical metal particles at a rate of 0.5 g or more per 10 g, flowability is improved. The improvement in flowability is minimal when the proportion is less than 0.5 g per 10 g. Average particle size D 90Preferably, the particle size is 60 μm or less. Even with high sphericity, if the particle size is too large, there is a concern that the gaps around the large metal particles will increase, leading to a decrease in shapeability. The upper limit of the proportion of metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more is preferably 5 g or less per 10 g. It is also possible to form only metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more. On the other hand, if there are too many spherical metal particles, there is a concern that the gaps between the metal particles will increase. Therefore, the proportion of metal particles with a maximum diameter of 1 μm or more and 60 μm or less and a sphericity of 90% or more and 100% or less is preferably in the range of 0.5 g or more and 5 g or less per 10 g. If the proportion of metal particles with high sphericity increases, it becomes a major cause of increased cost.

[0035] One method for adjusting the proportion of metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more is to separately manufacture metal powder containing highly spherical metal particles and metal powder containing poorly spherical metal particles, and then mix them. Another effective method is to randomly sample 10g of the mixed powder and observe it using SEM. The area ratio of the powder with high sphericity to that with low sphericity can be determined by SEM observation. This ratio can then be converted to a mass ratio by multiplying by the specific gravity of the metal particles. Alternatively, the mass ratio can be determined by classifying the powder with high sphericity and that with low sphericity. Furthermore, when mixing metal powder containing highly spherical metal particles and metal powder containing poorly spherical metal particles, if they are of the same material, the area ratio and mass ratio will be approximately the same.

[0036] In the embodiments of the 3D printer, the metal powder used preferably has a false density to true density ratio of 15% or more. The ratio of false density to true density is also called relative density. Relative density can represent the filling density of the metal powder. Relative density can be calculated by the formula (false density / true density) × 100 (%).

[0037] True density is the value obtained by dividing the mass of a metal powder by the volume of the powder itself after removing surface and internal pores. For a single metal, true density is the same as specific gravity. For example, the true density of tungsten is 19.3 g / cm³. 3 The molybdenum content is 10.2 g / cm³. 3 Rhenium content is 21.0 g / cm³. 3 Niobium content is 8.6 g / cm³. 3 Tantalum content is 16.7 g / cm³. 3 Furthermore, the true density of an alloy can also be calculated from the specific gravity of its individual components.

[0038] Apparent density, also known as false density, is the density measured by filling the gaps in a container with metal powder and treating them as part of the volume. It is also called apparent density. Tapped density, on the other hand, is the density measured after refilling the gaps created by vibrating a container with metal powder, and then tapping the powder into them. Tapped density is also a type of apparent density.

[0039] Apparent density is used as the pseudo-density. Apparent density can be determined according to ASTM-B329-98 (Apparent Density of Metal Powder and Compounds Using the Scott Volumeter), one of the standards of the American Society for Testing and Materials (ASTM). Furthermore, a container with a diameter of 28 mm and a height of 20 mm is used as the container for the test to hold the metal powder.

[0040] A relative density of 15% or higher indicates that the metal powder used in 3D printing has a specified infill density even without vibration. Having a specified infill density allows for a stable proportion of the metal powder used in 3D printing. There is no particular upper limit to the relative density, but it is preferably 80% or lower. If the relative density exceeds 80%, there is a possibility of excessive density and decreased flowability. A relative density of 15% or higher and 80% or lower is preferred, and more preferably 30% or higher and 80% or lower.

[0041] The metal powder used in the above-mentioned 3D printers has excellent flowability and molding properties. Therefore, it is suitable for shaping objects using 3D printing.

[0042] Flowability can be evaluated by measuring the angle of repose. The angle of repose is preferably below 65 degrees. The angle of repose can be measured using a Scott volumetric meter according to TMIAS0101 (Test Method for Powder Properties: 2010). Figure 4 An example of a Scott volumetric meter is shown. TMIAS0101 is an industry standard issued by the Tungsten & Molybdenum Industries Association. The Scott volumetric meter can also be used, based on the aforementioned ASTM-B329-98 standard.

[0043] Figure 4 This is a schematic diagram used to illustrate the angle of repose. Figure 4The diagram shows 3D printer powder 1, a cup 6, and an angle of repose 7. The angle of repose 7 can be measured using a Scott volumetric meter. Pour 3D printer powder 1 into the large funnel of the Scott volumetric meter. Pour the powder 1 into cup 6 until it reaches the cup and overflows outwards. Measure the angle of repose 7 formed by the upper surface of the cup and the two ends of the powder 1, and take the average angle as the angle of repose. If the powder 1 cannot fall naturally into cup 6, gently agitate the metal mesh with a brush to allow it to flow in. Cup 6 is a cup with a diameter of 28 mm and a height of 20 mm. The same sample can be used for the angle of repose measurement, or new samples can be used separately.

[0044] An angle of repose of 65 degrees or less indicates good flowability. Good flowability allows for the uniform supply of powder to the 3D printer stage. Therefore, an angle of repose of 65 degrees or less is preferred, more preferably 60 degrees or less, and even more preferably 50 degrees or less.

[0045] When preparing any powder for flowability testing, the deviation of the angle of repose is preferably less than 5 degrees. This can be calculated as: Dependence of angle of repose = (Average of 5 calculated angles of repose - Farthest value). For example, when the angles of repose are 45 degrees, 44 degrees, 42 degrees, 39 degrees, and 40 degrees, the average is 42 degrees. The values ​​furthest from 42 degrees are 45 degrees and 39 degrees. Therefore, the flowability deviation is (42 - 45) = 3 degrees or (42 - 39) = 3 degrees. By suppressing the flowability deviation, the uniformity of the powder on the test bench can be stabilized.

[0046] There is no specific lower limit for the angle of repose, but it should be above 30 degrees. If it is less than 30 degrees, the fluidity will be too high, and the deviation of the angle of repose will easily increase.

[0047] Next, the manufacturing method of metal powder for 3D printers will be described. The manufacturing method is not particularly limited as long as the metal powder for 3D printers described in the embodiments has the above-described structure; however, the following methods can be listed as methods for obtaining a good yield.

[0048] First, prepare the target metal powder. The metal powder is preferably composed of at least one element selected from tungsten, molybdenum, rhenium, niobium, tantalum, chromium, and vanadium.

[0049] Next, in order to control the particle size distribution and particle size D 90 Particle size D 10For particle size range, grading is preferred. During grading, multiple sieves with different mesh sizes (μm) are prepared. It is preferable to remove both small and large particles. The particle size is adjusted by changing the mesh size of the sieves, with intervals between 10 μm and 50 μm. Other methods include controlling particle size distribution by mixing metal particles with a specified particle size range. Airflow grading is also used to control particle size distribution. A combination of sieve grading and airflow grading can also be used.

[0050] For example, methods can be described that prepare metal particles with particle sizes of 10 μm or larger but less than 50 μm, 51 μm or larger but less than 100 μm, 101 μm or larger but less than 150 μm, 151 μm or larger but less than 200 μm, and 201 μm or larger but less than 250 μm, and mix them in the required amounts. Thus, a method that controls particle size distribution by mixing metal powders with particle sizes adjusted at intervals of 10 μm or larger but less than 50 μm is preferred.

[0051] Pre-crushing the agglomerated powder using a pulverizer is also effective. By crushing the agglomerated powder, it is easy to control the particle size distribution according to the primary particle size. Examples of pulverizers include ball mills, rod mills, semi-autogenous grinding (SAG) mills, and jet mills.

[0052] Prepare metal powder with a sphericity of 90% or higher, and add the necessary amount. Alternatively, 3D printer powder can be formed solely from metal powder with a sphericity of 90% or higher. Grading the metal powder with a sphericity of 90% or higher and adding the necessary amount is also an effective method.

[0053] Methods for manufacturing metal powder with a sphericity of 90% or higher include spraying, crushing, and granulation.

[0054] The so-called spraying process involves injecting molten metal into a hole and then spraying high-pressure water or gas onto the outflowing molten stream, causing it to disperse and solidify. Because the molten metal is simultaneously dispersed and solidified, it is possible to produce metal particles with smooth surfaces and high sphericity. Another spraying process involves injecting metal particles and then melting and solidifying them through high-frequency heating. Examples of spraying methods include gas spraying, water spraying, and centrifugal spraying.

[0055] As a pulverizing process, methods for pulverizing metal ingots can be listed. One method for pulverizing metal ingots is to use a pulverizer such as a ball mill. When metal ingots are pulverized, angular powder is formed. By using a pulverizer, the angles are removed, resulting in a powder with high sphericity. Using a pulverizer also has the effect of pulverizing agglomerated powder.

[0056] For pulverization, the Rotating Electrode Process (REP) is also effective. The REP process involves melting a rotating electrode using high-temperature plasma, then using centrifugal force to pulverize it into droplets. These droplets are then pulverized using a gas jet to achieve micronization.

[0057] One method to improve sphericity is granulation. Granulation refers to the process of agglomerating fine powder into spherical shapes. One method is to spherize metal powder by mixing a resin binder into it. When the metal powder is a high-melting-point metal, a low-melting-point metal can also be used as a binder. Preferably, the low-melting-point metal has a melting point below 1500°C. Examples of such metals include copper (melting point 1085°C), aluminum (melting point 660°C), and nickel (melting point 1455°C). Since granulated powder uses a binder, it can be distinguished from simply agglomerated powder.

[0058] If the method described above is used, it is possible to produce particles with a particle size distribution ranging from 1 μm to 200 μm, exhibiting a maximum peak and D... 90 -D 10 Metal powder for 3D printers with a particle size of 10μm or larger.

[0059] By using 3D printing with 3D printer powder according to the embodiment, it is possible to manufacture shaped objects having 3D printer powder. These shaped objects can be made of various structures, such as finned structures, lattice structures, plate structures, rod structures, column structures, honeycomb structures, hollow structures, and spring structures.

[0060] By using the metal powder for 3D printers according to the embodiments, even high-melting-point metals can be 3D printed with excellent flowability and shapeability. Previously, high-melting-point metals were difficult to sinter, requiring heating the molded body at high temperatures to form a sintered body. Forming complex shapes by machining the sintered body was difficult. In contrast, the shapes described in the embodiments can be easily formed into complex shapes because they can be shaped by 3D printing.

[0061] 3D printing methods, such as those using lasers or electron beams, can be exemplified. Laser-based 3D printing is known as Selective Laser Sintering (SLS). One type of SLS is Direct Metal Laser Sintering (DMLS). SLS involves spreading powder material on a molding table and irradiating it with a laser beam. The laser beam melts the powder material, which is then cooled to create the desired shape. The process involves resupplying powder material after each shaping and repeating the laser irradiation process.

[0062] DMLS is a laser sintering method with increased laser power. SLS uses a carbon dioxide laser. DMLS uses a ytterbium laser.

[0063] SLS and DMLS are methods of sintering powder materials using lasers. Another method using lasers is selective laser melting (SLM). SLM is a method of shaping powder materials by irradiating them with a laser.

[0064] 3D printing using electron beams is called electron beam melting (EBM). An electron beam is a beam of electrons emitted by heating a filament in a vacuum. Compared to laser beams, electron beams are characterized by high power and high speed. EBM is a technique that melts powdered material to create shapes. There are also methods in EBM that use metal filaments for shaping. When shaping high-melting-point metals using a 3D printer, SLM or EBM is preferred. SLM or EBM involves melting metal particles, which facilitates the production of high-density shapes.

[0065] For SLS (including DMLS), the preferred laser power is 100W or higher. For SLM, the preferred laser power is 100W or higher. For EBM, the preferred electron beam power is 2000W or higher.

[0066] The molding speed for SLS, SLM, or EBM is preferably 100 mm / s or higher. Molding speed refers to the speed of the scanning laser or electron beam. If the molding speed is lower than 100 mm / s, the molding speed is slow, resulting in reduced mass production capability. There is no specific upper limit to the molding speed, but it is preferably below 5000 mm / s. When using high-melting-point metals, if the speed exceeds 5000 mm / s, deviations in the sintering or molten state will occur, making it difficult to obtain high-density molded parts.

[0067] The 3D printing process involves spreading metal powder and solidifying it by laser irradiation, repeating this process multiple times. By improving flowability, the metal powder can be supplied uniformly. By using metal powder with a pseudo-density within a specified range, the amount of metal powder present can be stabilized. This allows for spreading in a way that reduces the gaps between the metal powder particles, thus improving shapeability. Therefore, even high-melting-point metals can be manufactured with high yield through 3D printing. Furthermore, it is possible to obtain molded objects with high density. The relative density or average density of the molded object is preferably 90% or higher. By containing metal particles with high sphericity, the adhesion between the metal particles can be improved. Based on this, high-density molded objects can also be obtained. Additionally, 3D printing can reduce the density deviation of the molded object.

[0068] When creating a 3D printed model by covering it with metal powder, it is preferable that the particle size of all metal particles is smaller than the coverage thickness. One method for creating a 3D printed model by covering it with metal powder is called the powder bed method. In the powder bed method, a coater (a flat tool) is used to flatten the surface of the covered metal powder. If the particle size of the metal particles is larger than the coverage thickness, the metal particles will get stuck on the coater. This causes an change in the distribution of the metal particles where they are stuck. Therefore, it is preferable that the particle size of all metal particles is smaller than the coverage thickness.

[0069] Example

[0070] (Examples 1-20, Comparative Examples 1-2)

[0071] The metal powders shown in Tables 1 and 2 were prepared as metal powders for 3D printers. The tungsten powder used in Examples 1-8 and Comparative Example 1 had a purity of 99% by mass or higher. The molybdenum powder used in Examples 9-15 and Comparative Example 2 had a purity of 99% by mass or higher. Furthermore, Rhenium powder with a purity of 99% by mass or higher was used in Example 16. Niobium powder with a purity of 99% by mass or higher was used in Example 17. Tantalum powder with a purity of 99% by mass or higher was used in Example 18. In Example 19, 0.7% by mass of hafnium carbide (HfC) powder and 99.3% by mass of tungsten powder were mixed. In Example 20, 0.5% by mass of titanium (Ti) powder and 99.5% by mass of molybdenum powder were mixed.

[0072] Prepare metal particles with a maximum diameter of 1 μm or more and 30 μm or less, and a sphericity of 90% or more and 100% or less. Mix them in a proportion shown in Table 1 or Table 2, where the proportion of metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more per 10 g is equal to the values ​​shown in Table 1 or Table 2. The aspect ratio of the metal particles with a maximum diameter of 1 μm or more and 30 μm or less, and a sphericity of 90% or more and 100% or less, is all in the range of 1.0 or more and 1.5 or less.

[0073] The particle size distribution was adjusted by mixing pre-sieved metal particles. Metal particles with a sphericity of 90% to 100% were produced through a spraying process. The metal powders involved in the examples and comparative examples all had particle size distributions adjusted to a range of 0.1 μm to 300 μm. Figure 1 The particle size distribution of the metal powder involved in Example 1 is shown.

[0074] The observation area was 100μm × 100μm using SEM photography (1000x magnification). The proportion of metal particles with a maximum diameter of 1μm or more and a sphericity of 90% or more per unit observation area is shown as an area ratio. This operation was performed at any three locations, and the average value is shown. An area ratio of 100% for the proportion of metal particles with a maximum diameter of 1μm or more and a sphericity of 90% or more indicates that all metal particles have a maximum diameter of 1μm or more and a sphericity of 90% or more. The smaller the area ratio, the lower the proportion of metal particles with a maximum diameter of 1μm or more and a sphericity of 90% or more.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] The flowability of the metal powder used in the 3D printers described in the examples and comparative examples was investigated. Flowability was evaluated by measuring the angle of repose. A Scott volumetric meter was prepared, and the sample was poured into a large funnel, flowing into a cup until it reached the top and overflowed. When it could not fall naturally, the metal mesh was gently agitated with a brush to allow it to flow. After the powder had flowed to the point of overflowing, the angle formed between the top of the cup and the powder was measured. This operation was performed five times with randomly selected powder samples, and the average value was taken as the angle of repose. The deviation was calculated as the angle of repose offset from the average angle of repose. The Scott volumetric meter used was a volumetric meter conforming to ASTM-B329-98.

[0080] The apparent density was also investigated. The apparent density was determined according to the ASTM B-329-98 standard. The angle of repose and apparent density were measured using a container with a diameter of 28 mm and a height of 20 mm. The ratio of apparent density to true density (relative density) was then calculated as (apparent density / true density) × 100 (%). The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] The table shows that the higher the proportion of metal particles with a maximum diameter of 1 μm or more and a sphericity of 90% or more, the better the fluidity.

[0084] Next, using the 3D printer described in the embodiments and comparative examples, a shaped object with a finned form was manufactured by 3D printing with metal powder. The shaped object has a finned structure or a hollow structure. The finned structure has five protrusions with a height of 2 mm and a diameter of 2 mm on a metal plate. The hollow structure has an outer diameter of 10 mm, an inner diameter of 8 mm, and a height of 5 mm.

[0085] For the 3D printer, two methods are prepared: SLM and EBM. In SLM mode, 3D printing is performed with a laser power of 400W and a modeling speed of 300mm / s. In powder bed 3D printing, the metal particles are made smaller than the thickness of the powder layer. In EBM mode, the electron beam power is 3500W and the modeling speed is 1000mm / s.

[0086] The density of the obtained sculptures was measured. The density was determined using the Archimedes method. Ten sculptures were created at a time. The average density of the ten sculptures was taken as the mean density. The deviation from the mean density was taken as the density deviation. The results are shown in Table 4.

[0087] Table 4

[0088]

[0089] As shown in the table, the malleability of the metal powder involved in the embodiments is improved. In particular, the malleability of the metal powder containing metal particles with a maximum diameter of 1 μm and a sphericity of 90% to 100% is improved. High density is obtained regardless of whether SLM or EBM is used for molding. Therefore, the metal powder involved in the embodiments is suitable for molding using a 3D printer.

[0090] The above description illustrates several embodiments of the present invention, but these embodiments are merely examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, with various omissions, substitutions, and modifications possible without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. The described embodiments can be implemented by combining with each other.

Claims

1. A metal powder for 3D printers, comprising multiple metal particles, The plurality of metal particles each contain more than 50 atomic percent of at least one element selected from tungsten, molybdenum, rhenium, niobium, tantalum, chromium, and vanadium. The particle size distribution of the plurality of metal particles has a maximum peak in the particle size range of 1 μm to 200 μm. The cumulative proportion of particle size D in the particle size distribution, calculated by volume, is 90%. 90 Particle size D, which accounts for 10% of the cumulative proportion by volume, 10 The difference D 90 -D 10 10μm or larger The plurality of metal particles includes a plurality of first metal particles and a plurality of second metal particles. Each of the plurality of first metal particles has a sphericity of 90% or higher. The sphericity of each of the plurality of second metal particles is less than 90%. The ratio of false density to true density is above 15% and below 80%. Angle of repose greater than 40 degrees and less than 60 degrees Among the plurality of metal particles, the aspect ratio of the primary metal particles with a maximum diameter of 1 μm or more is 1.0 or more and 1.5 or less.

2. The metal powder according to claim 1, wherein, The particle size distribution ranges from 0.1 μm to 300 μm.

3. The metal powder according to claim 1, wherein, The maximum diameter is greater than 1 μm and less than 60 μm.

4. The metal powder according to claim 1, wherein, The deviation of the angle of repose is less than 5 degrees.

5. A shaped object having the metal powder of claim 1.

6. The shape according to claim 5, wherein, The shaped article has at least one structure selected from finned structure, lattice structure, plate structure, column structure, honeycomb structure, hollow structure and spring structure.

7. The shaped object according to claim 5, wherein, The density of the molded product is above 90%.

8. A method for manufacturing a shaped object, comprising a step of forming the object using the metal powder described in claim 1 via a 3D printer.

9. The method according to claim 8, wherein, The average density of the molded article is above 90%.

Images