Powder for additive manufacturing, method for manufacturing powder for additive manufacturing, and additive manufacturing method

Abstract

Provided are a powder for additive manufacturing that can be obtained efficiently and that can be prevented from scattering, a method for manufacturing the powder for additive manufacturing, and an additive manufacturing method that uses the powder for additive manufacturing. [Solution] One form of the present disclosure is a powder PM for additive manufacturing, which comprises a first powder P1 that can be melted and solidified when irradiated with an electron beam EB, and a second powder P2 that can be melted and solidified when irradiated with an electron beam EB and has a time constant calculated as the product of the capacitive component of the impedance and the resistive component of the impedance of 3.5 microseconds or less, and the weight ratio of the second powder P2 to the total weight of the first powder P1 and the second powder P2 is at least 30% or more.

Description

[Technical Field]

[0001] The present disclosure relates to a powder for additive manufacturing, a method for producing the powder for additive manufacturing, and an additive manufacturing method. [Background technology]

[0002] Additive manufacturing technology involves repeating the steps of spreading powder evenly and irradiating the spread powder with an electron beam to obtain a three-dimensional object. When the powder is irradiated with an electron beam, the powder becomes negatively charged. It is known that when the powder becomes highly charged, the powder scatters due to electrical repulsion. Patent Document 1 discloses a technique for performing mechanical treatments, including a collision treatment, on metal powder. The mechanical treatment changes the electrical properties of the powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 059183 Summary of the Invention [Problem to be solved by the invention]

[0004] In the mechanical processing using a jet mill, a ball mill, or the like described in Patent Document 1, the amount of powder processed per hour may be small depending on the jet mill, ball mill, or the like. Furthermore, several hundred kilograms of powder may be used to produce one additive manufacturing object. For these reasons, when additive manufacturing objects are produced using only the mechanically processed powder described above, there is a possibility that the capital investment cost or the overall processing time will increase.

[0005] The present disclosure provides a powder for additive manufacturing that can be obtained efficiently and that can suppress scattering, a method for manufacturing the powder for additive manufacturing, and an additive manufacturing method using the powder for additive manufacturing. [Means for solving the problem]

[0006] A powder for additive manufacturing that is one form of the present disclosure comprises a first powder that can be melted and solidified when irradiated with an electron beam, and a second powder that can be melted and solidified when irradiated with the electron beam and has a time constant calculated as the product of the capacitive component of the impedance and the resistive component of the impedance of 3.5 microseconds or less, and the ratio of the weight of the second powder to the total weight of the first powder and the second powder is at least 30% or more.

[0007] This powder for additive manufacturing is mixed with a second powder having a time constant of 3.5 microseconds or less, calculated by the product of the capacitance component of the impedance and the resistance component of the impedance, so that the weight ratio of the second powder to the total weight of the first and second powders is at least 30%. This reduces the time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance of the entire powder for additive manufacturing. This reduces the charge amount of the entire powder for additive manufacturing, thereby preventing powder scattering due to electrical repulsion. Furthermore, by preparing a second powder with a weight that is smaller than the weight of the entire powder for additive manufacturing, the above-mentioned effects can be achieved. Therefore, the cost of preparing the second powder is lower than, for example, when the entire powder for additive manufacturing is the second powder, or when, for example, the majority of the weight of the powder for additive manufacturing is the second powder. Therefore, this powder for additive manufacturing can be obtained efficiently and prevents scattering.

[0008] In some embodiments, the imaginary part of the impedance of the first powder may be less than 0. In this case, even if the imaginary part of the impedance of the first powder is less than 0, by including the second powder in the powder for additive manufacturing in the above-mentioned ratio, the amount of charge in the entire powder for additive manufacturing can be kept low, and scattering of the powder due to electrical repulsion can be suppressed.

[0009] In some embodiments, the powder for additive manufacturing may have a resistance component of the impedance of the entire powder including the first powder and the second powder that is greater than 0. Even if the resistance component of the impedance is greater than 0, the inclusion of the second powder can keep the amount of charge of the entire powder for additive manufacturing low, and can prevent the powder from scattering due to electrical repulsion.

[0010] In some embodiments, the capacitance component of the impedance of the second powder may be zero. In this case, the capacitance component of the impedance, which is an index of powder charge, is considered to be zero for the entire powder for additive manufacturing. This allows the charge amount of the entire powder for additive manufacturing to be kept small, and powder scattering due to electrical repulsion can be suppressed. Furthermore, even in this case, the powder for additive manufacturing can be efficiently obtained and scattering can be suppressed.

[0011] In some embodiments, the first powder and the second powder have solidified structures formed therein, and the solidified structure of the second powder may be more crushed than the solidified structure of the first powder. In this case, for example, the solidified structure may be formed on the surface of the powder by atomization or the like. By subjecting the second powder to mechanical processing or the like, the solidified structure of the second powder is more crushed than the solidified structure of the first powder. In this way, the surface of the second powder is distorted (deformed) compared to the surface of the first powder. A second powder having such characteristics can appropriately suppress scattering.

[0012] In some embodiments, the particle size of the second powder may be 40 μm or more and 300 μm or less. In this case, too, the powder for additive manufacturing can be obtained efficiently and scattering can be suppressed.

[0013] In some embodiments, the first powder and the second powder may be the same type of metal powder. Even in this case, the inclusion of the second powder can reduce the charge amount of the entire powder for additive manufacturing, thereby preventing the powder from scattering due to electrical repulsion.

[0014] A method for manufacturing powder for additive manufacturing according to one embodiment of the present disclosure includes the steps of preparing a first powder that can be melted and solidified by irradiating it with an electron beam, acquiring a portion of the first powder, processing the acquired portion of the first powder to produce a second powder having a time constant calculated as the product of the capacitive component of the impedance and the resistive component of the impedance of 3.5 microseconds or less, and mixing the second powder with the first powder so that the ratio of the weight of the second powder to the total weight of the first powder and the second powder is at least 30%.

[0015] In this method for producing powder for additive manufacturing, a second powder having a time constant of 3.5 microseconds or less, calculated by the product of the capacitance component of the impedance and the resistance component of the impedance, is mixed with the first powder so that the weight ratio of the second powder to the total weight of the first and second powders is at least 30%. This reduces the time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance of the entire powder for additive manufacturing. This reduces the charge amount of the entire powder for additive manufacturing, thereby preventing powder scattering due to electrical repulsion. Furthermore, by preparing a second powder with a weight that is smaller than the weight of the powder for additive manufacturing, the above-mentioned effects can be achieved. Therefore, the production cost of the second powder production step is reduced compared to, for example, when all the powder for additive manufacturing is the second powder, or when, for example, the majority of the weight of the powder for additive manufacturing is the second powder. Therefore, this method for producing powder for additive manufacturing can efficiently obtain powder for additive manufacturing and prevent powder scattering.

[0016] An additive manufacturing method according to one embodiment of the present disclosure includes the steps of: preparing a first powder that can be melted and solidified when irradiated with an electron beam; and a second powder that can be melted and solidified when irradiated with the electron beam, and that has a time constant of 3.5 microseconds or less, calculated as the product of the capacitive component of the impedance and the resistive component of the impedance; producing powder for additive manufacturing by mixing the second powder with the first powder so that the weight ratio of the second powder to the total weight of the first powder and the second powder is at least 30%; supplying the powder to a modeling table that supports the powder for additive manufacturing and the model; and irradiating the powder on the modeling table with an electron beam.

[0017] In this additive manufacturing method, a second powder having a time constant of 3.5 microseconds or less, calculated by the product of the capacitance component of the impedance and the resistance component of the impedance, is mixed with the first powder so that the weight ratio of the second powder to the total weight of the first and second powders is at least 30%. This reduces the time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance of the entire additive manufacturing powder. Therefore, in the irradiating step, the charge amount of the entire additive manufacturing powder can be reduced, and powder scattering due to electrical repulsion can be suppressed. Furthermore, by preparing a second powder with a weight smaller than the total weight of the additive manufacturing powder, the above-mentioned effects can be obtained. Therefore, the preparation cost in the step of preparing the second powder is lower than, for example, when all the additive manufacturing powder is the second powder, or when, for example, the second powder accounts for a majority of the weight of the additive manufacturing powder. Therefore, this additive manufacturing method uses efficiently obtainable additive manufacturing powder to suppress scattering of the additive manufacturing powder. [Effects of the Invention]

[0018] According to the present invention, there are provided a powder for additive manufacturing that can be obtained efficiently and that can be prevented from scattering, a method for manufacturing a powder for additive manufacturing, and an additive manufacturing method. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an additive manufacturing system. [Figure 2] FIG. 2 is a perspective view showing the main components of the layered manufacturing apparatus of FIG. [Figure 3] FIG. 3 is a diagram showing the configuration of the storage system. [Figure 4] FIG. 4 is a schematic diagram showing an equivalent circuit when measuring the impedance of the first powder, the second powder, and the powder for additive manufacturing. [Figure 5] FIG. 5 is a flowchart showing the main steps of the additive manufacturing method using the additive manufacturing system. [Figure 6] FIG. 6 is a graph showing the frequency distribution of particle sizes of the first powder and the second powder according to the example. [Figure 7] 7(a) and 7(b) are images showing an example of the surface state of the first powder according to the example. [Figure 8] Fig. 8(a) is a graph showing changes in impedance of the first powder and the second powder according to the example. Fig. 8(b) is a graph showing changes in impedance of the second powder, the first sample, and the second sample according to the example. Fig. 8(c) is a graph showing changes in impedance of the second powder and the third sample according to the example. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0021] The additive manufacturing system 200 shown in FIG. 1 is a system that stores, mixes, and supplies powders used in additive manufacturing, and manufactures additively manufactured objects. The additive manufacturing system 200 includes an additive manufacturing apparatus 1 and a storage system 100. The storage system 100 stores a first powder and a second powder used in additive manufacturing, mixes the first powder and the second powder to generate powder PM for additive manufacturing, and supplies the powder PM for additive manufacturing to the additive manufacturing apparatus 1. The additive manufacturing apparatus 1 manufactures additively manufactured objects using the powder for additive manufacturing. Hereinafter, the powder PM for additive manufacturing may be simply referred to as the "powder PM," and the additively manufactured object may be simply referred to as the "manufactured object."

[0022] First, the additive manufacturing apparatus 1 will be described. The additive manufacturing apparatus 1 shown in FIG. 1 is, for example, a three-dimensional rotational additive manufacturing apparatus. The additive manufacturing apparatus 1 is a so-called 3D printer. The additive manufacturing apparatus 1 uses an electron beam as an energy beam. In other words, the additive manufacturing apparatus 1 uses a so-called electron gun powder bed fusion method. The additive manufacturing apparatus 1 applies an electron beam EB to powder PM for additive manufacturing. Note that the additive manufacturing apparatus 1 is not limited to a three-dimensional rotational additive manufacturing apparatus, but may be an apparatus capable of manufacturing an object using an electron beam EB.

[0023] The additive manufacturing apparatus 1 applies an electron beam EB to a region of the powder PM to be molded, thereby applying energy to the powder PM. In other words, the additive manufacturing apparatus 1 increases the temperature of the powder PM. As a result, the powder PM melts or sinters. When the additive manufacturing apparatus 1 stops applying energy, the temperature of the powder PM drops, causing it to solidify. In other words, the additive manufacturing apparatus 1 manufactures an additively manufactured object PA by repeatedly applying and stopping energy application multiple times. Hereinafter, the additively manufactured object PA will be simply referred to as a "manufactured object PA." Note that in this embodiment, "solidifying the powder PM" includes both a case in which the powder PM is heated to a temperature higher than its melting point and becomes liquid, thereby solidifying, and a case in which the powder PM is heated to a temperature lower than its melting point and thereby sintered. The manufactured object PA is, for example, a mechanical part. The manufactured object PA may also be another structure.

[0024] The layered manufacturing apparatus 1 has a drive unit 2, a manufacturing processing unit 3A, a controller 4 (controller), and a housing 5. The drive unit 2 realizes various operations required for manufacturing. The manufacturing processing unit 3A processes powder PM to obtain a manufactured object PA. Specifically, the processing of the powder PM includes a supply process of the powder PM, a preheating process of the powder PM, and a manufacturing process of the powder PM. The housing 5 is supported by a plurality of columns. The housing 5 forms a manufacturing space S. The manufacturing space S is an airtight space that can be decompressed for processing the powder PM by the manufacturing processing unit 3.

[0025] A start plate 51 and a modeling tank 52 are arranged in the modeling space S. The start plate 51 is an example of a processing table on which the modeling process is performed. The start plate 51 has, for example, a circular plate shape, and powder PM, which is the raw material of the model PA, is arranged on the start plate 51. The start plate 51 may be arranged so that its central axis overlaps with the central axis of the housing 5. A drive unit 2 is connected to the start plate 51. Therefore, the start plate 51 rotates and moves linearly along the rotation axis by the drive unit 2.

[0026] The drive unit 2 rotates and elevates the start plate 51. The drive unit 2 has a rotation drive mechanism 21 and an elevation drive mechanism 22. The rotation drive mechanism 21 rotates the start plate 51. The upper end of the rotation drive mechanism 21 is connected to the start plate 51. The lower end of the rotation drive mechanism 21 is attached to a drive source. The elevation drive mechanism 22 elevates and lowers the start plate 51 relative to the modeling tank 52. This elevation is along the rotation axis of the rotation drive mechanism 21. Note that the drive unit 2 may be any mechanism that can rotate and elevate the start plate 51, and the drive unit 2 is not limited to the above mechanism.

[0027] FIG. 2 shows an enlarged view of the main components used in the forming process. Forming process units 3A and 3B are arranged on a start plate 51. That is, the forming process units 3A and 3B face the plate main surface 51a of the start plate 51. The forming process units 3A and 3B are arranged at equal intervals (180 degrees) around the rotation axis. In other words, the forming process units 3A and 3B are arranged, for example, at equal intervals in the circumferential direction. This arrangement makes it possible to make the layer thickness of the powder PM uniform depending on the rotation angle to the next processing area. Note that the arrangement of the forming process units 3A and 3B described above is an example and is not limited to this configuration. For example, the forming process units 3A and 3B may be arranged at different angles in the circumferential direction.

[0028] The formation processing units 3A and 3B are different from each other only in their positions, but have the same specific components. Note that the components of the formation processing units 3A and 3B may be different from each other. For example, the formation processing units 3A and 3B may be formed by omitting some of the components of one of them. The formation processing unit 3A will be described below.

[0029] The modeling processing unit 3A includes a powder bed formation section 30 (powder bed formation section, powder bed formation device), a heater 3a, and a beam source 3b (irradiation section). The powder bed formation section 30 forms a layer of powder PM (powder bed PB). The heater 3a performs a preheating process for the powder bed PB. The beam source 3b performs a modeling process by irradiating the powder bed PB with an energy beam.

[0030] The powder bed formation unit 30 forms a powder bed PB on the start plate 51. The powder bed formation unit 30 has a supply unit 31, an application unit 32, and a measuring instrument 33. The supply unit 31 stores powder PM and supplies the powder PM onto the start plate 51. The application unit 32 levels the surface of the powder PM on the start plate 51. The measuring instrument 33 measures the amount of powder PM before it is spread and leveled by the application unit 32. The powder bed formation unit 30 will be described in detail later.

[0031] The heater 3a raises the temperature of the powder PM by radiating heat. The heater 3a may be, for example, an infrared heater or a gas heater. The heater 3a may preheat the powder PM. Preheating here refers to a process of heating the powder PM so that its temperature in the preheating region is higher than that in the supply region. This heating process may also be, for example, a process of pre-sintering the powder PM. Pre-sintering is a state in which powder PM particles are diffused and bonded together at their minimum points by a diffusion phenomenon. For example, the heater 3a heats the powder PM to a temperature equal to or greater than half the melting point of the powder PM. This is because the diffusion phenomenon of sintering generally becomes active at a temperature equal to or greater than half the melting point. For example, if the powder PM is titanium, the pre-sintering temperature is 700°C to 800°C. The melting point of titanium alloys is approximately 1500°C to 1600°C. If the powder PM is aluminum, the pre-sintering temperature is 300°C. The melting point of aluminum is approximately 660°C.

[0032] The beam source 3b generates an electron beam EB. The electron beam EB is irradiated onto the powder PM. The beam source 3b is, for example, an electron gun. The electron gun generates the electron beam EB according to the potential difference generated between the cathode and the anode. The region on the plate main surface 51a irradiated with the electron beam EB is the region that increases the temperature of the powder PM. This temperature is higher than the temperature at which the heater 3a can preheat the powder PM. In other words, the temperature of the powder PM irradiated with the electron beam EB is a temperature (sintering temperature or melting temperature) at which a molded object PA can be formed. The beam source 3b scans and irradiates the electron beam EB onto the desired portion.

[0033] The powder bed forming section 30, heater 3a, and beam source 3b are arranged in this order along the rotation direction (clockwise CW) of the start plate 51. In the following description, "upstream" and "downstream" are based on the rotation direction of the start plate 51.

[0034] The start plate 51 rotates clockwise (CW). As a result, when a certain point is assumed on the start plate 51, the point passes through the powder bed formation section 30, the heater 3a, and the beam source 3b in this order as the start plate 51 rotates.

[0035] The controller 4 controls the rotation drive mechanism 21. As a result, the start plate 51 rotates clockwise (CW) at a constant rotation speed. This rotation speed may be determined based on the temperature rise in the preheating zone and the modeling zone. For example, the amount of energy required to raise the temperature of the powder PM from preheating to a predetermined temperature after preheating is obtained. Next, the time required to impart this amount of energy to the powder PM is determined. The rotation speed is then obtained based on this required time and the length of the path traveled when passing through the preheating zone. The controller 4 controls the lift drive mechanism 22. As a result, the start plate 51 moves continuously downward over time (separating operation). The movement speed of the start plate 51 may be determined based on the thickness of the layer formed per rotation of the start plate 51 (i.e., the thickness of the powder bed PB). The controller 4 controls the powder bed formation unit 30.

[0036] The supply unit 31 shown in FIGS. 2 and 3 stores powder PM and supplies the powder PM onto the start plate 51. The supply unit 31 includes a roller 311, a hopper 312, and a casing 313. The supply unit 31 is called a roller feeder. Note that the supply unit 31 may have a configuration other than a roller feeder. For example, the supply unit 31 may be a screw feeder. In the case of a screw feeder, multiple powder discharge ports are provided along the radial direction of the start plate 51. This arrangement of the discharge ports allows for a uniform supply of the powder PM in a quasi-linear manner.

[0037] Hopper 312 is a container that stores powder PM. Hopper 312 supplies powder PM to casing 313. An outlet of hopper 312 is connected to an inlet of casing 313. In the example shown in FIG. 3, hopper 312 and casing 313 form an integrated container. Casing 313 supplies the powder PM provided from hopper 312 to roller 311. Casing 313 may also include a support unit that rotatably supports roller 311 and a drive unit that rotates roller 311.

[0038] The roller 311 is housed in a casing 313, with a portion of its circumferential surface exposed. The roller 311 is driven to rotate by a drive motor, which serves as a drive unit, and rotates around a rotation axis. A gap G is formed between the circumferential surface 311a of the roller 311 and the lower end of the casing 313. The circumferential surface 311a of the roller 311 is preferably rough. The roller 311 has a shape and size (i.e., diameter) that allows the powder PM to be maintained in a deposited state on the circumferential surface 311a. As the roller 311 rotates, the circumferential surface 311a moves in the circumferential direction. In this case, the conveying direction is an arc. The amount of movement of the conveying surface is the amount of movement of the circumferential surface 311a of the roller 311, and is determined by the radius and rotation angle of the roller 311. The controller 4 controls the drive motor to rotate the roller 311 by a predetermined rotation angle. This rotation causes the circumferential surface 311a to reverse at the front end. At this time, the powder PM deposited on the peripheral surface 311a with a thickness corresponding to the gap falls from the front end portion.

[0039] The coating unit 32 shown in Fig. 2 spreads and evens out the surface of the powder PM on the start plate 51. The coating unit 32 spreads and evens out the powder PM that has dropped from the supply unit 31 onto the plate main surface 51a. Here, "spreading and evens out" means forming a layer of powder PM with a predetermined thickness on the building surface. This layer of powder PM is called a powder bed PB.

[0040] The coating unit 32 has a rake blade 321. A blade tip 321e of the rake blade 321 is spaced a predetermined height from the surface to be processed. The surface to be processed refers to, for example, the surface of the powder bed PB after being partially irradiated with an energy beam in the modeling processing unit 3A and before receiving the supply of powder PM from the supply unit 31 in the downstream modeling processing unit 3B. Of the powder PM supplied to the opposite side of the rake blade 321 in the clockwise direction CW, the powder PM present above the blade tip 321e is blocked by the rake blade 321 and cannot move toward the clockwise direction CW of the rake blade 321. Therefore, a powder bed PB is formed, which is a layer of powder PM having the same thickness as the gap between the surface to be processed and the blade tip 321e.

[0041] Next, the storage system 100 will be described. The storage system 100 shown in Figures 1 and 3 includes a first storage unit 70, a mechanical processing unit 71, a second storage unit 72, and a mixing unit 80. The storage system 100 may further include a hopper 312 of the supply unit 31 of the additive manufacturing apparatus 1.

[0042] The first storage section 70 is a container that stores the first powder P1. The first storage section 70 may be a hopper. The first storage section 70 is connected to the mechanical processing section 71 and the mixing section 80. A weighing scale (not shown) capable of measuring the weight of the first powder P1 may be provided in a conduit that supplies the first powder P1 from the first storage section 70 to the mixing section 80. A control valve that controls opening and closing of the conduit based on the amount measured by the weighing scale may be provided in the conduit.

[0043] The first powder P1 is a powder that can be melted and solidified by irradiation with an electron beam EB. In the first powder P1, the capacitive component of the impedance is less than zero. In the first powder P1, for example, the capacitive component of the impedance measured at room temperature is less than zero.

[0044] 4 is a schematic diagram showing an equivalent circuit when measuring the impedance of the first powder P1, the second powder P2, and the powder PM. As shown in FIG. 4, the first powder P1, the second powder P2, and the powder PM are represented by a resistance component R of the impedance indicating the real part of the impedance Z in an equivalent circuit model 300. metal and the reactance component of impedance Z, which indicates the imaginary part of impedance Z, are connected in series. The reactance component of impedance Z is the component R of impedance Z. oxide and the capacitance component C of the impedance Z oxide and are connected in parallel. The impedance Z of the first powder P1, the second powder P2, and the powder PM is expressed by the equation shown in FIG. 4, where p is a coefficient. p is set, for example, depending on the temperature. p is approximately 1.00. It is known from Patent Document 1 and other documents that when the first powder P1 is charged, the imaginary part of the impedance of the first powder takes a value smaller than zero (a negative value).

[0045] The first powder P1 is, for example, a metal powder. The first powder P1 is, for example, a nickel-based alloy, a cobalt-chromium alloy, an iron-based alloy, an aluminum alloy, a titanium alloy, a copper alloy, a tungsten alloy, or the like. The first powder P1 may also be a powder containing carbon fiber and resin, such as CFRP (Carbon Fiber Reinforced Plastics). The first powder P1 is produced, for example, by an atomization method. A solidified structure is formed in the first powder P1. The solidified structure includes, for example, a dendritic structure (dendrite crystals).

[0046] Referring again to FIG. 3 , the mechanical treatment unit 71 generates the second powder P2 by performing a mechanical treatment, including a collision treatment, on the first powder P1. In the example shown in FIG. 3 , the mechanical treatment unit 71 is a ball mill. The mechanical treatment unit 71 may also be, for example, a jet mill. The mechanical treatment unit 71 acquires a portion of the first powder P1 stored in the first storage unit 70 and applies a mechanical stimulus to the solidified structure on the surface of the acquired first powder P1. The mechanical treatment unit 71 rotates around the rotation axis L1 in a rotation direction R1. The mechanical treatment unit 71 deforms the first powder P1 by rotating with the first powder P1 and balls BA stored therein. The mechanical treatment unit 71 generates the second powder P2 by crushing the solidified structure on the surface of the first powder P1. The crushing of the solidified structure includes a state in which the solidified structure is deformed, including a state in which the degree of protrusion of the solidified structure on the surface of the first powder P1 is reduced, or a state in which the solidified structure has disappeared. As the powder particles constituting the first powder P1 are deformed in this way, the electrical properties of the powder particles change.

[0047] The second powder P2 is a powder that can be melted and solidified by irradiation with an electron beam EB. The particle size of the second powder P2 may be 40 μm or more and 300 μm or less. In the second powder P2, the time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance is 3.5 microseconds or less. This time constant is a value for a titanium-aluminum alloy TiAl, an example of the second powder, and is a value cited from the paper "Ball-milling treatment of gas-atomized Ti-48Al-2Cr-2Nb powder and its effect on preventing smoking during electron beam powder bed fusion building process" (Seungkyun Yim et al., Tohoku University, 2022). For example, in the second powder P2, the capacitive component of the impedance is zero. In the second powder P2, for example, the capacitive component of the impedance measured at room temperature is zero. In the equivalent circuit model 300 shown in FIG. 4, the capacitive component C of the impedance Z of the second powder P2 is oxideThe phrase "the capacitance component of the impedance becomes zero" includes the case where the capacitance component of the impedance of the second powder P2 after the mechanical treatment becomes smaller by an order of magnitude than the capacitance component of the impedance of the first powder P1, and becomes very close to zero or becomes zero.

[0048] The solidification structure on the surface of the second powder P2 is more crushed than the solidification structure on the surface of the first powder P1. That is, the solidification structure on the surface of the second powder P2 is flatter than the solidification structure on the surface of the first powder P1. The surface roughness of the second powder P2 is greater than that of the first powder P1. The surface roughness is, for example, the arithmetic mean roughness Ra or maximum height Rz calculated based on JIS-B0601:2013. Because the solidification structure, including the dendrite structure, of the first powder P1 is flattened, the capacitive component of the impedance of the second powder P2 is smaller than that of the first powder P1 and disappears at low temperatures. Furthermore, impedance measurement of the second powder P2 after mechanical processing showed that the capacitive component of the impedance approached or became zero even at room temperature (RT).

[0049] The second storage section 72 is a container that stores the second powder P2. The second storage section 72 may be a hopper. The second storage section 72 stores the second powder P2 produced by the mechanical processing section 71. The second storage section 72 is connected to the mechanical processing section 71 and the mixing section 80. A weigh scale (not shown) that can measure the weight of the second powder P2 may be provided in a pipeline that supplies the second powder P2 from the second storage section 72 to the mixing section 80. A control valve that controls the opening and closing of the pipeline based on the amount measured by the weigh scale may be provided in the pipeline.

[0050] The mixing unit 80 mixes the second powder with the first powder. The mixing unit 80 is, for example, a rocking mixer. The mixing unit 80 is not limited to a rocking mixer and may be any other mixer as long as it is configured to mix the first powder P1 and the second powder P2. The mixing unit 80 mixes the second powder P2 with the first powder P1 so that the weight ratio of the second powder P2 to the total weight of the powder PM including the first powder P1 and the second powder P2 is at least 30% or more. The mixing unit 80 mixes the second powder P2 with the first powder P1 so that the weight ratio of the second powder P2 to the total weight of the powder PM including the first powder P1 and the second powder P2 is less than 100%. By controlling the above-mentioned control valves, the weight of the first powder P1 supplied from the first storage unit 70 to the mixing unit 80 and the weight of the second powder P2 supplied from the second storage unit 72 to the mixing unit 80 are controlled. This control may be performed by a controller (not shown) provided in the mixer 80, or may be performed by the controller 4 of the additive manufacturing apparatus 1.

[0051] The mixer 80 rotates around the rotation axis L2 in a rotation direction R2 and tilts in a tilt direction SW along a plane passing through the rotation axis L2. The mixer 80 mixes the first powder P1 and the second powder P2 by rotating and tilting with the first powder P1 and the second powder P2 fed into it in the above-mentioned ratio. This results in the first powder P1 and the second powder P2 being mixed uniformly. "Uniformly mixed" means that there is no bias in the location of each powder in the second powder P2. The powder PM is a powder in which the first powder P1 and the second powder P2 are mixed uniformly. The mixer 80 supplies the powder PM to the hopper 312 of the supply unit 31 of the additive manufacturing apparatus 1.

[0052] The time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance of the powder PM supplied to the hopper 312 is kept small (at least compared to the first powder P1). The capacitance component of the impedance of the powder PM is zero. For example, the capacitance component of the impedance of the powder PM measured at room temperature is zero. Even if the capacitance component of the impedance of the first powder P1 is greater than zero, the capacitance component of the impedance of the powder PM as a whole is considered to be a value below zero or very close to zero. This is thought to be because, as the weight of the second powder P2 contained in the powder PM increases, the powder particles constituting the second powder P2, whose capacitance component of the impedance is zero, come into contact with each other, increasing the likelihood of forming a conductive path (conductive path), or the number of such conductive paths increases. As a result, even if the powder PM contains the first powder P1 whose capacitance component of the impedance is greater than zero, the capacitance component of the impedance of the powder PM as a whole is zero. This allows the charge amount of the entire powder for additive manufacturing to be kept small. The higher the ratio of the weight of the second powder P2 to the total weight of the powder PM, the smaller the resistive component of the impedance. This is because the probability that particles of the second powder P2, which do not exhibit a capacitive component of the impedance, will come into contact with each other and form a conductive path to the electrode increases, and the number of conductive paths also increases. In this case, the resistive component of the impedance of the powder PM may be greater than zero.

[0053] Next, we will explain the additive manufacturing method executed in the additive manufacturing system 200. The flowchart shown in Fig. 5 shows an example of the additive manufacturing method MT. As shown in Fig. 5, the additive manufacturing method MT includes a manufacturing method MTA for powder PM.

[0054] In the manufacturing method MTA of the powder PM, first, in step S11, a first powder P1 is prepared. As an example of the preparation, the first powder P1 is supplied from an external supply source (not shown) into the first storage section 70, and the first powder P1 is stored in the first storage section 70. The first powder P1 is stored in the first storage section 70 in an amount by weight that is sufficient to form at least one object.

[0055] Next, in step S12, the mechanical processing unit 71 acquires a portion of the first powder P1 from the first storage unit 70. The mechanical processing unit 71 acquires the first powder P1 so that the weight of the second powder P2 is at least 30% or more of the total weight of the powder PM in step S14 described below.

[0056] Next, in step S13, the mechanical processing unit 71 generates a second powder P2 from a portion of the acquired first powder P1. The mechanical processing unit 71 rotates the first powder P1 and the ball BA stored therein, applying a mechanical stimulus to the first powder P1 to generate the second powder P2. The rotation speed and rotation time are predetermined based on the weight of the first powder P1 (or the weight of the second powder P2 to be generated). The mechanical processing unit 71 generates a powder (second powder) having a time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance of 3.5 microseconds or less. The mechanical processing unit 71 supplies the generated second powder P2 to the second storage unit 72. The second storage unit 72 stores the second powder P2.

[0057] Next, in step S14, the mixer 80 mixes the first powder P1 and the second powder P2 to produce a powder PM for additive manufacturing (powder PM). The mixer 80 acquires the first powder P1 from the first storage unit 70 and acquires the second powder P2 from the second storage unit 72 so that the weight ratio of the second powder P2 to the total weight of the first powder P1 and the second powder P2 is at least 30%. The mixer 80 rotates and tilts the first powder P1 and the second powder P2 stored in the mixer 80 for a predetermined time to mix the first powder P1 and the second powder P2 uniformly. The rotation speed, rotation time, number of tilts, and tilt angle are predetermined based on the weight of the powder PM. In this way, the powder PM is formed. Completion of step S14 completes the manufacturing method MTA for powder PM.

[0058] In the additive manufacturing method MT, a model is manufactured using powder PM produced by the powder PM manufacturing method MTA. In the additive manufacturing method MT of this embodiment, following the powder PM manufacturing method MTA, in step S15, the mixer 80 supplies the powder PM to the supply unit 31. The supply unit 31 stores the powder PM in a hopper 312.

[0059] Subsequently, in step S16, supply unit 31 supplies powder PM to start plate 51. Supply unit 31 supplies powder PM onto start plate 51. Coating unit 32 smoothes the surface of the powder PM on start plate 51 that has been supplied to supply unit 31. The coated powder PM may be preheated.

[0060] Next, in step S17, the beam source 3b irradiates the powder PM on the start plate 51 with the electron beam EB. This increases the temperature of the powder PM, causing it to melt. The molten powder PM solidifies, thereby forming an object. Completion of step S17 completes the additive manufacturing method MT.

[0061] Next, the effects achieved by the additive manufacturing powder PM, the manufacturing method MTA for the additive manufacturing powder PM, and the additive manufacturing method MT according to this embodiment will be described, along with the problems associated with the prior art. In additive manufacturing methods using electron beams, the metal powder is charged by the irradiation of the electron beam, causing a phenomenon in which the powder particles repel each other (hereinafter, sometimes referred to as "smoke"). When smoke is generated, there is a possibility that the powder to be melted will scatter outside the area irradiated by the electron beam.

[0062] Conventional technology addresses this issue by irradiating metal powder with an electron beam under conditions where the irradiation energy is reduced and smoke is not generated (hereinafter, sometimes referred to as the preheating process). In the preheating process, the powder surfaces are weakly bonded. This ensures electrical conductivity between the powder particles and physically fixes them, suppressing the generation of smoke. It has also been reported that the higher the temperature of metal powder, the smaller the capacitance component of its impedance. By preheating the powder to reduce the capacitance component of its impedance and then applying more energy than in the preheating process using the electron beam EB, smoke generation is suppressed.

[0063] In the preheating process described above, the metal powder is preheated to a temperature between 50% and 80% of its melting point. Because the preheating temperature must be maintained until the electron beam EB, which requires a high amount of energy to melt the powder, is irradiated, the preheating temperature may need to be set very high depending on the type of metal powder. However, after preheating, the temperature drops due to radiation from the top surface of the powder bed and heat transfer to the surrounding powder layers, making it difficult to maintain a high temperature over a wide area until the electron beam EB is irradiated. For this reason, a low preheating temperature is desirable. However, if the preheating temperature is set too low, smoke may be generated, potentially resulting in failure in the fabrication of the molded object.

[0064] In response to the above-mentioned problems, the aforementioned Patent Document 1 discloses that mechanical processing that applies mechanical stimuli to the powder changes the electrical properties of the metal powder, preventing the metal powder from charging and lowering the preheating temperature. Patent Document 1 discloses a method for producing metal powder using mechanical processing equipment such as a jet mill and a ball mill. However, some factories that perform this processing method may not be equipped with mechanical processing equipment with sufficient capacity. That is, the mechanical processing using a jet mill, a ball mill, or the like described in Patent Document 1 may result in a small amount of powder processed per hour. In particular, a ball mill requires media and space with a volume similar to that of the powder, so a device with a volume three times the desired volume of powder to be processed is required. Therefore, increasing the size of the equipment that performs the mechanical processing is costly. Furthermore, several hundred kilograms of powder may be used to produce a single model. For these reasons, when additive manufacturing objects are produced using only mechanically processed powder, the capital investment cost or overall processing time may increase. Alternatively, when additive manufacturing objects are produced using only mechanically processed powder, the number of times (number of cycles, number of batches) that the method for producing the mechanically processed powder must be performed may be increased.

[0065] In contrast, in the powder PM (powder PM for additive manufacturing) of this embodiment, the second powder P2 is mixed so that the weight ratio of the second powder P2 to the total weight of the first powder P1 and the second powder P2 is at least 30% or more, and the time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance is 3.5 microseconds or less. This reduces the time constant calculated by the product of the capacitance component of the impedance and the resistance component of the impedance of the entire powder PM. This is thought to be because, as the weight of the second powder P2 contained in the powder PM increases, the likelihood that powder particles constituting the second powder P2 with a time constant of 3.5 microseconds or less will come into contact with each other and form a conductive path (conductive path), or the number of such conductive paths increases. This reduces the amount of charge on the entire powder PM for additive manufacturing, thereby preventing the powder PM from scattering (producing smoke) due to electrical repulsion.

[0066] Furthermore, by preparing the second powder P2 with a weight smaller than the total weight of the powder PM for additive manufacturing, the above-mentioned effects can be obtained, and therefore the cost of preparing the second powder P2 is lower than when, for example, all of the powder PM is the second powder P2, or when the majority of the weight of the powder PM is the second powder P2. Therefore, this powder PM can be obtained efficiently and scattering can be suppressed.

[0067] In this embodiment, the imaginary part of the impedance of the first powder P1 is less than zero. In this case, even if the imaginary part of the impedance of the first powder P1 is less than zero, by including the second powder P2 in the powder PM at the above-mentioned ratio or more, the charge amount of the entire powder PM can be kept low, and the powder PM can be prevented from scattering due to electrical repulsion. In other words, by mixing the second powder P2, which is not likely to cause powder scattering (smoke generation), with the first powder P1, which is likely to cause powder scattering (smoke generation), at the above-mentioned ratio or more, the powder PM as a whole can be prevented from scattering powder (smoke generation).

[0068] In this embodiment, the resistance component of the impedance of the entire powder PM including the first powder P1 and the second powder P2 (powder PM) may be greater than zero. In the equivalent circuit model 300 of the powder PM, the resistance component R of the impedance Z metal Even if is greater than zero, the capacitive component of the impedance, C oxide When the charge amount of the powder as a whole is zero, the powder PM can be kept small, and therefore the scattering of the powder PM due to the electrical repulsive force can be suppressed.

[0069] In this embodiment, the capacitance component of the impedance of the second powder may be zero. In this case, the capacitance component of the impedance, which is an index of the charge of the powder, is considered to be zero for the entire powder for additive manufacturing (powder PM). Therefore, the charge amount of the entire powder for additive manufacturing can be kept small, and scattering of the powder due to electrical repulsion can be suppressed. Furthermore, even in this case, the powder PM can be efficiently obtained and scattering can be suppressed.

[0070] In this embodiment, solidified structures are formed in the first powder P1 and the second powder P2, and the solidified structure of the second powder P2 is more crushed than the solidified structure of the first powder P1. In this case, for example, the solidified structures can be formed on the surfaces of the first powder P1 and the second powder P2 by an atomization method or the like. The first powder P1 is subjected to a mechanical treatment or the like to generate the second powder P2, and the solidified structure of the second powder P2 is more crushed than the solidified structure of the first powder P1. In this way, the surface of the second powder is distorted (deformed) compared to the surface of the first powder. The second powder P2 having such characteristics can appropriately suppress scattering.

[0071] In this embodiment, the particle size of the second powder P2 is 40 μm or more and 300 μm or less. In this case, too, the powder PM can be efficiently collected and scattering can be suppressed.

[0072] In this embodiment, the first powder and the second powder may be the same type of metal powder. Even in this case, the powder PM contains the second powder, which can reduce the charge amount of the entire powder PM and prevent the powder from scattering due to electrical repulsion.

[0073] In the manufacturing method MTA for powder PM for additive manufacturing according to this embodiment, the second powder P2 is mixed with the first powder P1 so that the weight ratio of the second powder P2 to the total weight of the first powder P1 and the second powder P2 is at least 30%. This allows the time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance of the entire powder PM to be kept small. This reduces the charge amount of the entire powder and prevents the powder PM from scattering due to electrical repulsion. Furthermore, by preparing a second powder P2 with a weight smaller than the weight of the entire powder PM, the above-mentioned effects can be achieved. Therefore, the production cost in the step of generating the second powder P2 (step S14) is reduced compared to, for example, when all the powder for additive manufacturing is the second powder P2 or when the majority of the weight of the powder for additive manufacturing is the second powder P2. Therefore, this manufacturing method MTA for powder PM for additive manufacturing can efficiently obtain the powder PM and prevent the powder PM from scattering.

[0074] In the additive manufacturing method MT of this embodiment, the second powder P2, whose time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance is 3.5 microseconds or less, is mixed with the first powder P1 so that the weight ratio of the second powder P2 to the total weight of the first powder P1 and the second powder P2 is at least 30%. This reduces the time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance for the entire powder PM. This reduces the charge on the entire powder PM in the irradiating step (step S17), thereby preventing the powder PM from scattering due to electrical repulsion. Furthermore, like the powder PM manufacturing method MTA described above, this additive manufacturing method MT can reduce the production cost in the step of generating the second powder P2 (step S14). Therefore, this additive manufacturing method MT can efficiently obtain the powder PM and prevent the powder PM from scattering.

[0075] The powder PM for additive manufacturing, the manufacturing method MTA for powder PM for additive manufacturing, and the additive manufacturing method MT of the present disclosure are not limited to the above-described embodiments. The specific aspects of the powder PM for additive manufacturing, the manufacturing method MTA for powder PM for additive manufacturing, and the additive manufacturing method MT of the present disclosure may be modified as appropriate within the scope of the claims.

[0076] For example, the second powder P2 is exemplified as a powder obtained by mechanically processing the first powder P1 using the mechanical processing unit 71. However, the second powder P2 is not limited to the above-described form as long as the powder has a capacitance component of zero impedance. For example, the second powder P2 may be a powder that has been preheated to a temperature that is 50% to 80% of the melting point of the first powder P1 using a heater 3a or the like. In this case, the manufacturing method MTA for powder PM and the additive manufacturing method MT may generate the second powder P2 by preheating in step S13. Furthermore, the second powder P2 does not have to be stored in the second storage unit 72. In this case, the mixing unit 80 may directly obtain the second powder P2 from the mechanical processing unit 71.

[0077] [Example] First, to compare the particle size of the first powder with that of the second powder produced from a portion of the first powder, the first powder was mechanically treated. Nickel-based alloy IN718 was used as the first powder. The first powder was produced by plasma atomization. To produce the second powder, the first powder was mechanically treated using a ball mill. A planetary ball mill, model pulverisette 7, manufactured by FRITSCH, was used as the ball mill. For each batch, 15 ml of the first powder and 5 mm diameter media were added to a 45 ml processing vessel, with a bulk volume of 15 ml, and the mixture was stirred for 10 minutes. Air or argon (Ar) was introduced into the processing vessel as a gas. No pressure or heat was applied during stirring, and the rotation speed was 500 rpm. After stirring, the powder removed from the ball mill was designated the second powder.

[0078] First, the surface shape and microstructure of the first and second powders prepared under the above conditions were confirmed using a JEOL JCM-6000 scanning electron microscope (SEM). Figure 7(a) is an image showing an example of the surface condition of the first powder according to the example. Figure 7(b) is an image showing an example of the surface condition of the first powder according to the example. As shown in Figures 7(a) and 7(b), the surface of the second powder is deformed compared to the surface of the first powder. The solidified structure is more difficult to visualize on the surface of the second powder than on the surface of the first powder. For example, it was confirmed that a dendritic pattern, which is characteristic of a solidified structure, was formed on the surface of the first powder. On the other hand, it was confirmed that a dendritic pattern was not formed on the surface of the second powder. The presence or absence of a dendritic pattern revealed that the solidified structure of the second powder was more crushed than that of the first powder. In addition, the phrase "the solidified structure of the second powder is more crushed than the solidified structure of the first powder" includes at least one of the following states: the surface of the second powder has fewer dendritic patterns than the surface of the first powder, the dendritic patterns are smaller in size, and no dendritic patterns are formed.

[0079] The particle size frequency distributions of the first and second powders were obtained using a laser diffraction evaluation method. A Microtrac-Bell MT3300EXII was used as the evaluation device for the laser diffraction evaluation method. Figure 6 is a graph showing the particle size frequency distributions of the first and second powders according to the example. The horizontal axis of the graph in Figure 6 represents particle size (μm), and the vertical axis represents the frequency (%) of the number of particles detected at the corresponding particle size relative to the total number. The graph for the first powder was confirmed to show a steep peak in the particle size range of 70 μm to 80 μm. The graph for the second powder also showed a peak in the particle size range of 70 μm to 80 μm, but the peak was confirmed to have a gentler shape than the graph for the first powder. Furthermore, it was confirmed that the frequency of the second powder was higher than that of the first powder in the particle size range of 90 μm or more. These results suggest that mechanical processing using a ball mill device transforms the spherical first powder into a flattened second powder.

[0080] Next, impedance measurements were performed on the first and second powders obtained by the mechanical processing described above, as well as on powders with varying mixing ratios of the first and second powders. The impedance measurement method employed was similar to the method described in paragraph

[0047] of Patent Document 1 (WO 2020 / 059183). Specifically, the devices used to measure the impedance of each of the powders described above were the Powder AC Resistivity Measurement System 29710 (Toei Scientific Industry Co., Ltd.) and the High-Temperature Powder Resistivity Measurement Vacuum Furnace TG26667 (Toei Scientific Industry Co., Ltd.). In the powder AC resistance measurement system, the powder to be measured is placed in the high-temperature powder resistance measurement vacuum furnace and its electrical resistance is measured. Measurement conditions include, for example, an ambient pressure of less than 0.01 Pa, a powder filling cylinder inner diameter of φ10 mm, and a powder height of 10 mm. Figure 4 shows an example of a circuit diagram for measuring powders in the powder AC resistance measurement system. As powders with different mixing ratios of the first powder and the second powder, the following samples were prepared: a first sample in which 90% of the total weight of the powder was the first powder and 10% of the total weight of the powder was the second powder; a second sample in which 80% of the total weight of the powder was the first powder and 20% of the total weight of the powder was the second powder; and a third sample in which 70% of the total weight of the powder was the first powder and 30% of the total weight of the powder was the second powder.

[0081] 8(a) to 8(c) are graphs showing the change in impedance of the first powder and the second powder according to the example, and of powders in which the mixing ratio of the first powder and the second powder is changed. Each of the graphs of FIG. 7(a) to 8(c) is a so-called Cole-Cole plot. The horizontal axis of the graphs shown in each of FIG. 8(a) to 8(c) represents the real part of the impedance (Ω), and the vertical axis of the graph represents the imaginary part of the impedance (Ω). FIG. 8(a) is a graph showing the change in impedance of the first powder and the second powder according to the example. In the imaginary part of the impedance, when only the first powder is used, the change is 10 6 In the case of the second powder alone, the impedance is a negative value of the order of 10. In the case of the first sample, the impedance is 0 or more. FIG. 8(b) is a graph showing the change in impedance of the second powder, the first sample, and the second sample according to the example. In the imaginary part of the impedance, in the case of the first sample, the 2In the case of the second sample, the negative values ​​are on the order of 10 1 ~10 2 (c) of FIG. 8 is a graph showing the change in impedance of the second powder and the third sample according to the example. In the imaginary part of the impedance, in the case of the third sample, -1 indicates a positive value of the order of .

[0082] When the capacitance component of the impedance was calculated based on the imaginary part of these impedances, it was confirmed that the capacitance component of the impedance was zero only for the second powder and the third sample. Furthermore, as shown in Figure 8(c), it was confirmed that the real part, which represents the resistive component of the impedance, was larger and positive for the third sample compared to the second powder. As described in Patent Document 1 (WO 2020 / 059183), it has been shown that powder scattering (smoke generation) due to electron beam irradiation is suppressed when the capacitance component of the impedance approaches zero in the equivalent circuit model. Therefore, it is suggested that powder scattering (smoke generation) due to electron beam irradiation is also suppressed for the third sample, in which the capacitance component of the impedance approaches zero in the equivalent circuit model 300. Therefore, it was revealed that powder scattering (smoke generation) due to electron beam irradiation is suppressed for the powder (third sample) in which the weight ratio of the second powder to the total weight of the first and second powders is at least 30%.

[0083] Furthermore, the time constant calculated by multiplying the capacitance component of the impedance of the second powder by the resistance component of the impedance was found to be 1 nanosecond or less. This time constant is a value for a nickel-based alloy, IN718, an example of the second powder, and is a value derived based on the method disclosed in the paper "Ball-milling treatment of gas-atomized Ti-48Al-2Cr-2Nb powder and its effect on preventing smoking during electron beam powder bed fusion building process" (Seungkyun Yim et al., Tohoku University, 2022). Note that for the second powder produced using a titanium-aluminum-based alloy, TiAl, under the same conditions as above, the time constant calculated by multiplying the capacitance component of the impedance by the resistance component of the impedance was found to be 3.5 microseconds or less, although this is not shown in the figure.

[0084] [Note] The powder for additive manufacturing, the method for manufacturing the powder for additive manufacturing, and the additive manufacturing method include the following configurations.

[0085] The present disclosure relates to [1] "a first powder that can be melted and solidified by being irradiated with an electron beam; and a second powder that can be melted and solidified by irradiation with the electron beam, and that has a time constant of 3.5 microseconds or less, calculated as the product of the capacitive component of impedance and the resistive component of impedance, wherein the ratio of the weight of the second powder to the total weight of the first powder and the second powder is at least 30% or more.

[0086] The present disclosure is [2] "The powder for additive manufacturing according to [1] above, wherein the first powder has an imaginary part of impedance that is less than zero."

[0087] The present disclosure is [3] "The powder for additive manufacturing according to [1] or [2] above, wherein the resistance component of the impedance of the entire powder including the first powder and the second powder is greater than zero."

[0088] The present disclosure is [4] "the powder for additive manufacturing according to any one of the above [1] to [3], wherein the capacitance component of the impedance of the second powder is zero."

[0089] The present disclosure is [5] "A powder for additive manufacturing according to any one of [1] to [4] above, wherein a solidified structure is formed in the first powder and the second powder, and the solidified structure of the second powder is crushed compared to the solidified structure of the first powder."

[0090] The present disclosure is [6] "The powder for layered manufacturing according to any one of the above [1] to [5], wherein the particle size of the second powder is 40 μm or more and 300 μm or less."

[0091] The present disclosure is [7] "The powder for additive manufacturing according to any one of the above [1] to [6], wherein the first powder and the second powder are metal powders of the same type."

[0092] The present disclosure is [8] "A method for producing powder for additive manufacturing, comprising the steps of: preparing a first powder that can be melted and solidified by irradiating it with an electron beam; acquiring a portion of the first powder; generating a second powder by processing the acquired portion of the first powder so that the time constant calculated by the product of the capacitive component of the impedance and the resistive component of the impedance is 3.5 microseconds or less; and mixing the second powder with the first powder so that the ratio of the weight of the second powder to the total weight of the first powder and the second powder is at least 30%."

[0093] The present disclosure is [9] "an additive manufacturing method comprising the steps of: preparing a first powder that can be melted and solidified by irradiating it with an electron beam; and a second powder that can be melted and solidified by irradiating it with an electron beam, and that has a time constant of 3.5 microseconds or less, calculated as the product of the capacitive component of impedance and the resistive component of impedance; producing powder for additive manufacturing by mixing the second powder with the first powder so that the weight ratio of the second powder to the total weight of the first powder and the second powder is at least 30%; supplying the powder to a processing stage that supports the powder for additive manufacturing; and irradiating the powder on the processing stage with an electron beam." [Explanation of symbols]

[0094] 1. Additive manufacturing equipment 3b Beam source 4 Controller 30 Powder bed forming section 31 Supply section 32 Application section 51 Start plate (an example of a processing table) 70 First Reservoir 71 Mechanical Processing Unit 72 Second storage section 80 Mixing section 100 Storage System 200 Additive Manufacturing System 300 Equivalent Circuit Model 312 Hopper 313 Casing EB electron beam MT additive manufacturing method MTA manufacturing method P1 1st powder P2 2nd powder PA sculpture PB powder bed PM powder (an example of powder for additive manufacturing)

Claims

1. a first powder that can be melted and solidified by being irradiated with an electron beam; a second powder that can be melted and solidified by being irradiated with the electron beam, and that has a time constant calculated by the product of a capacitive component of impedance and a resistive component of impedance of 3.5 microseconds or less; Equipped with a ratio of the weight of the second powder to the total weight of the first powder and the second powder is at least 30% or more; Powder for additive manufacturing.

2. The powder for additive manufacturing according to claim 1 , wherein the first powder has an imaginary part of impedance that is less than zero.

3. The powder for additive manufacturing according to claim 1 or 2, wherein a resistance component of the impedance of the entire powder including the first powder and the second powder is greater than zero.

4. The powder for additive manufacturing according to claim 1 or 2, wherein a capacitive component of impedance of the second powder is zero.

5. a solidified structure is formed in the first powder and the second powder, The solidified structure of the second powder is crushed compared to the solidified structure of the first powder. The powder for layered manufacturing according to claim 1 or 2.

6. The powder for additive manufacturing according to claim 1 or 2, wherein the particle size of the second powder is 40 μm or more and 300 μm or less.

7. The powder for additive manufacturing according to claim 1 or 2, wherein the first powder and the second powder are metal powders of the same type.

8. preparing a first powder that can be melted and solidified by being irradiated with an electron beam; obtaining a portion of the first powder; generating a second powder by processing a portion of the obtained first powder so that a time constant calculated by the product of a capacitive component of impedance and a resistive component of impedance is 3.5 microseconds or less; mixing the second powder with the first powder so that a weight ratio of the second powder to a total weight of the first powder and the second powder is at least 30%; A method for producing a powder for additive manufacturing, comprising:

9. preparing a first powder that can be melted and solidified by being irradiated with an electron beam, and a second powder that can be melted and solidified by being irradiated with the electron beam, and has a time constant calculated by the product of a capacitive component of impedance and a resistive component of impedance of 3.5 microseconds or less; generating a powder for additive manufacturing by mixing the second powder with the first powder so that a ratio of a weight of the second powder to a total weight of the first powder and the second powder is at least 30%; supplying the powder to a processing stage that supports the powder for additive manufacturing; irradiating the powder on the treatment table with an electron beam; An additive manufacturing method comprising:

Images