Powder for additive manufacturing and additive manufactured body

Abstract

To provide additive manufacturing powder excellent in both sinterability and fluidity, and excellent in permeability of an aqueous binder solution, and an additive manufacturing having such additive manufacturing powder.SOLUTION: A powder for additive manufacturing containing Fe-based metal materials, used in the binder jetting method, wherein the particle diameter D50 is 1.0 μm or more and less than 15.0 μm, the particle diameter difference D90-D10 between the particle diameter D90 and the particle diameter D10 is 5.0 μm or more and 18.0 μm or less, the specific surface area is 0.05 [m2 / g] or more and 0.25 [m2 / g] or less, the average circularity is 0.85 or more and 0.99 or less, the relative density is 45% or more and 47% or less, and when the evaluation powder layer formed by compressing to a thickness of 10 mm is subjected to multiple droplets of an evaluation PVP aqueous solution totaling 1.36 mL dropping onto the same position, the depth to which the evaluation PVP aqueous solution penetrates is 110 μm or more and 250 μm or less.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a powder for additive manufacturing and an additive manufactured product. [Background technology]

[0002] In recent years, additive manufacturing using metal powder has become increasingly popular as a technology for creating three-dimensional objects. Depending on the bonding principle, additive manufacturing methods include fused deposition modeling (FDM), selective laser sintering (SLS), and binder jetting.

[0003] Patent Document 1 discloses a metal powder for molding that consists of a large number of particles, these particles containing at least one of Ni, Fe, and Co, and has a total content of Ni, Fe, and Co of 50 mass% or more, in which the ratio P1 of the number of particles having a circularity of less than 0.80 to the total number of particles is 10% or less, and the ratio P3 of the number of particles having a circularity of 0.95 or more to the total number of particles is 50% or more.

[0004] Such metal powder for molding contains a large number of particles with a high degree of circularity, making it easy to handle and enabling the production of high-strength molded articles.

[0005] Furthermore, by sintering the manufactured shaped body, a metal sintered body can be manufactured efficiently. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-102229 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the metal powder for molding described in Patent Document 1 has a relatively large particle diameter D50, which corresponds to the average particle diameter, of 15 μm or more. Therefore, the resulting molded object has a problem of low sinterability of the metal powder. Furthermore, the smaller the particle diameter, the lower the powder's fluidity and the lower its packing ability. Therefore, if the particle diameter is reduced to improve sinterability, it is necessary to improve the powder's fluidity. Furthermore, as the particle diameter decreases, the surface area of ​​the powder increases. This can lead to a decrease in the permeability of the aqueous binder solution depending on the surface condition of the particles that make up the powder. This decrease in permeability reduces the shape precision of the molded object.

[0008] Therefore, the realization of a powder for additive manufacturing that has both good sinterability and fluidity, and also has good permeability for aqueous binder solutions, is a challenge. [Means for solving the problem]

[0009] The powder for additive manufacturing according to the application example of the present invention is A powder for additive manufacturing containing an Fe-based metal material and used in a binder jet method, In a volume-based cumulative particle size distribution curve measured by a laser diffraction method, the particle size when the cumulative value from the small diameter side is 10% is defined as D10, the particle size when the cumulative value from the small diameter side is 50% is defined as D50, and the particle size when the cumulative value from the small diameter side is 90% is defined as D90, the particle size D50 is 1.0 μm or more and less than 15.0 μm, and the particle size difference D90-D10 between the particle size D90 and the particle size D10 is 5.0 μm or more and 18.0 μm or less, The specific surface area is 0.05 [m 2 / g] or more 0.25[m 2 / g] or less, The average circularity is 0.85 or more and 0.99 or less, When a powder layer for evaluation is formed by compacting powder to a relative density of 45% to 47% and a thickness of 10 mm, and multiple droplets of the PVP aqueous solution for evaluation are dropped onto the same position so that the total amount is 1.36 mL, the depth to which the PVP aqueous solution for evaluation penetrates is 110 μm to 250 μm.

[0010] The layered object according to the application example of the present invention is A powder for additive manufacturing according to an application example of the present invention; a binder that binds particles of the powder for additive manufacturing together; It has. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a process diagram illustrating a method for manufacturing a layered object. [Figure 2] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 3] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 4] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 5] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 6] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 7] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 8] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 9] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 10] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 11] FIG. 1 is a cross-sectional view illustrating a method for measuring the penetration depth of an evaluation powder layer with an evaluation PVP aqueous solution. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a powder for layered manufacturing and a layered manufactured body according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[0013] 1. Manufacturing method for additive manufacturing objects First, a method for manufacturing an additive manufacturing object using powder for additive manufacturing will be described.

[0014] FIG. 1 is a process diagram illustrating a method for manufacturing an additive manufacturing object. FIGS. 2 to 10 are diagrams illustrating the method for manufacturing the additive manufacturing object shown in FIG. 1. In FIGS. 2 to 10 of the present application, three mutually orthogonal axes are defined: an X-axis, a Y-axis, and a Z-axis. Each axis is represented by an arrow, with the tip end side being the "plus side" and the base end side being the "minus side." In the following description, the plus side of the Z-axis will be referred to as "up" and the minus side of the Z-axis will be referred to as "down." Furthermore, both directions parallel to the X-axis will be referred to as X-axis directions, both directions parallel to the Y-axis will be referred to as Y-axis directions, and both directions parallel to the Z-axis will be referred to as Z-axis directions.

[0015] 1 to 10 is a type of additive manufacturing method known as the binder jet method, and includes a powder layer forming step S102, a binder solution supplying step S104, and a repeating step S106, as shown in Fig. 1. The binder jet method has the advantage of being able to produce additive manufacturing objects with complex shapes because it does not require a support structure to support the object.

[0016] In the powder layer forming step S102, the additive manufacturing powder 1 is spread to form a powder layer 31. In the binder solution supplying step S104, a binder solution 4 is supplied to a predetermined region of the powder layer 31 to bond the particles in the powder layer 31 together, thereby obtaining a bonded layer 41. In the repeating step S106, the powder layer forming step S102 and the binder solution supplying step S104 are repeated one or more times to obtain an additive manufacturing body 6 shown in FIG. 10. Each step will be described in turn below.

[0017] The produced layered manufactured body 6 is subjected to a sintering process to become a metal sintered body, which makes it possible to efficiently manufacture metal sintered bodies with complex shapes.

[0018] 1.1. Additive manufacturing equipment First, the layered manufacturing apparatus 2 used to manufacture the layered manufactured body 6 will be described.

[0019] As shown in Figures 2 to 10, the additive manufacturing device 2 comprises an apparatus main body 21 having a powder storage section 211 and a manufacturing section 212, a powder supply elevator 22 provided in the powder storage section 211, a manufacturing stage 23 provided in the manufacturing section 212, and a coater 24, a roller 25, and a liquid supply section 26 movably provided on the apparatus main body 21.

[0020] The powder storage section 211 is a recessed section that is provided in the device main body 21 and is open at the top. The powder storage section 211 stores the additive manufacturing powder 1. An appropriate amount of the additive manufacturing powder 1 stored in the powder storage section 211 is supplied to the manufacturing section 212 by the coater 24.

[0021] A powder supply elevator 22 is disposed at the bottom of the powder storage unit 211. The powder supply elevator 22 is movable up and down with the additive manufacturing powder 1 loaded thereon. By moving the powder supply elevator 22 upward, the additive manufacturing powder 1 loaded on the powder supply elevator 22 is pushed up and overflows from the powder storage unit 211. This allows the overflowing additive manufacturing powder 1 to be moved toward the manufacturing unit 212.

[0022] The modeling unit 212 is provided in the device main body 21 and is a recessed portion that is open at the top. A modeling stage 23 is arranged inside the modeling unit 212. The powder 1 for additive manufacturing is spread in layers on the modeling stage 23 by a coater 24. The modeling stage 23 is also movable in the vertical direction while the powder 1 for additive manufacturing is spread on it. By appropriately setting the height of the modeling stage 23, the amount of powder 1 for additive manufacturing spread on the modeling stage 23 can be adjusted.

[0023] As shown in Figures 3 and 4, the coater 24 and roller 25 are movable in the X-axis direction from the powder storage unit 211 to the modeling unit 212. The coater 24 drags the powder 1 for additive manufacturing, thereby leveling the powder 1 for additive manufacturing and spreading it in layers. The roller 25 compresses the leveled powder 1 for additive manufacturing from above.

[0024] The liquid supply unit 26 is configured by, for example, an inkjet head or a dispenser, and is movable in the X-axis and Y-axis directions in the modeling unit 212. The liquid supply unit 26 can supply a desired amount of binder solution 4 to a desired position. Note that the liquid supply unit 26 may be provided with multiple discharge nozzles in one head. The binder solution 4 may be discharged from the multiple discharge nozzles simultaneously or with a time lag.

[0025] 1.2. Powder layer formation process Next, the powder layer forming step S102 using the additive manufacturing apparatus 2 will be described. In the powder layer forming step S102, the additive manufacturing powder 1 is spread on the manufacturing stage 23 to form a powder layer 31. Specifically, as shown in FIGS. 2 and 3, a coater 24 is used to drag the additive manufacturing powder 1 stored in the powder storage section 211 onto the manufacturing stage 23 and level it to a uniform thickness. This results in the powder layer 31 shown in FIG. 4. At this time, the upper surface of the manufacturing stage 23 is lowered below the upper end of the manufacturing section 212, and the thickness of the powder layer 31 can be adjusted by adjusting the amount of lowering. Note that the additive manufacturing powder 1 is a powder that has excellent packing properties when leveled, as will be described later. Therefore, a powder layer 31 with a high packing rate can be obtained.

[0026] Next, while compressing the powder layer 31 in the thickness direction with the roller 25, the roller 25 is moved in the X-axis direction as shown in FIG. 4. This increases the filling rate of the powder 1 for layered manufacturing in the powder layer 31. Note that compression with the roller 25 may be performed as needed and may be omitted. Alternatively, the powder layer 31 may be compressed by a means other than the roller 25, such as a pressure plate.

[0027] 1.3. Binder solution supply process In the binder solution supplying step S104, as shown in FIG. 5, the liquid supply unit 26 supplies the binder solution 4 to a formation region 60 of the powder layer 31 that corresponds to the layered manufacturing body 6 to be manufactured. The binder solution 4 is a liquid containing a binder and water (a water-based binder solution). In the formation region 60 to which the binder solution 4 is supplied, the particles of the powder 1 for layered manufacturing are bound together, resulting in a bonded layer 41 as shown in FIG. 6. In the bonded layer 41, the particles of the powder 1 for layered manufacturing are bound together by the binder, and the bonded layer 41 has enough shape retention to prevent it from breaking under its own weight.

[0028] The binder layer 41 may be heated simultaneously with or after the supply of the binder solution 4. This promotes evaporation of the solvent or dispersion medium contained in the binder solution 4 and promotes the bonding of particles together due to solidification or hardening of the binder. When the binder contains a photocurable resin or an ultraviolet-curable resin, light irradiation or ultraviolet irradiation may be performed instead of or in addition to heating.

[0029] The heating temperature when heating is not particularly limited, but is preferably 50° C. or higher and 250° C. or lower, and more preferably 70° C. or higher and 200° C. or lower. This allows a sufficient amount of heat to be applied to the binder layer 41, and can sufficiently promote the volatilization of the solvent or dispersion medium.

[0030] The binder solution 4 may contain other solvents in addition to water. Examples of the solvent include alcohols, ketones, and carboxylic acid esters, and at least one of these is used. Examples of the binder contained in the binder solution 4 include fatty acids, paraffin wax, microcrystalline wax, polyethylene, polypropylene, polystyrene, acrylic resins, polyamide resins, polyesters, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), urethane resins, epoxy resins, vinyl resins, unsaturated polyester resins, and phenolic resins.

[0031] 1.4.Repetitive process In the repeating step S106, the powder layer forming step S102 and the binder solution supplying step S104 are repeated one or more times until the laminate formed by laminating multiple binder layers 41 assumes a predetermined shape. In other words, these steps are performed two or more times in total. This results in a three-dimensional layered object 6 shown in FIG. 10.

[0032] Specifically, first, a new powder layer 31 is formed on the binder layer 41 shown in Fig. 6, as shown in Fig. 7. Next, as shown in Fig. 8, a binder solution 4 is supplied to a formation region 60 of the newly formed powder layer 31. This results in a second binder layer 41 as shown in Fig. 9. By repeating these operations, a layered object 6 as shown in Fig. 10 is obtained.

[0033] Of the powder layer 31, the powder for layered manufacturing 1 that did not form the binder layer 41 is collected and reused as necessary, that is, it is used again to manufacture the layered manufactured body 6. The layered product 6 obtained in this manner is subjected to a sintering process, which will be described later.

[0034] 1.5.Method for manufacturing sintered metal bodies A metal sintered body is obtained by sintering the layered manufactured body 6. In the sintering process, the layered manufactured body 6 is heated to cause a sintering reaction.

[0035] The sintering temperature varies depending on the constituent materials and particle size of the powder for additive manufacturing 1, but as an example, it is preferably 980°C or higher and 1330°C or lower, and more preferably 1050°C or higher and 1260°C or lower. The sintering time is preferably 0.2 hours or higher and 7 hours or lower, and more preferably 1 hour or higher and 6 hours or lower.

[0036] The atmosphere for the sintering treatment may be, for example, a reducing atmosphere such as hydrogen, an inert atmosphere such as nitrogen or argon, or a reduced pressure atmosphere obtained by reducing the pressure of these atmospheres. The pressure of the reduced pressure atmosphere is not particularly limited as long as it is less than normal pressure (100 kPa), but is preferably 10 kPa or less, and more preferably 1 kPa or less.

[0037] When the sintering process performed under the above conditions is referred to as "main sintering," the layered product 6 may be subjected to "pre-sintering" or "debinding," which are pre-treatments for the main sintering, as needed. This makes it possible to remove at least a portion of the binder contained in the layered product 6 or to induce a sintering reaction in a portion of the binder. This makes it possible to suppress unintended deformation during the main sintering process.

[0038] The temperature for the preliminary sintering and debinding is not particularly limited as long as it is a temperature that does not completely sinter the metal powder, but is preferably 100°C or higher and 500°C or lower, and more preferably 150°C or higher and 300°C or lower. Furthermore, the time for the preliminary sintering and debinding within the above temperature range is preferably 5 minutes or longer, more preferably 10 minutes or higher and 120 minutes or lower, and even more preferably 20 minutes or higher and 60 minutes or lower. Examples of the atmosphere for the preliminary sintering and debinding include air, an inert atmosphere such as nitrogen or argon, or a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres.

[0039] The metal sintered body obtained as described above can be used as a material for constituting all or part of transportation equipment parts such as automobile parts, bicycle parts, railway vehicle parts, ship parts, aircraft parts, and space transport vehicle parts; electronic equipment parts such as personal computer parts, mobile phone terminal parts, tablet terminal parts, and wearable terminal parts; electrical equipment parts such as refrigerators, washing machines, and air conditioners; machine parts such as machine tools and semiconductor manufacturing equipment; plant parts such as nuclear power plants, thermal power plants, hydroelectric power plants, refineries, and chemical complexes; watch parts; and decorative items such as metal tableware, jewelry, and eyeglass frames.

[0040] 2. Powder for additive manufacturing Next, the powder for additive manufacturing according to the embodiment will be described.

[0041] The powder for additive manufacturing 1 according to this embodiment is a powder used in a binder jet method.

[0042] 2.1.Constituent Materials The powder for additive manufacturing 1 contains an Fe-based metallic material. The Fe-based metallic material refers to a metallic material in which the content of Fe in terms of atomic ratio exceeds 50%.

[0043] Examples of Fe-based metallic materials include stainless steels such as austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardened stainless steel, and austenitic-ferritic (duplex) stainless steel, as well as low-carbon steel, carbon steel, heat-resistant steel, die steel, high-speed tool steel, Fe-Ni alloys, and Fe-Ni-Co alloys.

[0044] Among these, stainless steel is preferably used as the Fe-based metallic material. Stainless steel is a type of steel that has excellent mechanical strength and corrosion resistance. Therefore, by using powder 1 for additive manufacturing made of stainless steel, it is possible to efficiently manufacture a metal sintered body that has excellent mechanical strength and corrosion resistance and high shape accuracy.

[0045] Among stainless steels, precipitation hardening stainless steel is particularly preferred, as it has excellent mechanical strength and toughness due to the formation of precipitates.

[0046] Examples of austenitic stainless steel include SUS301, SUS301L, SUS301J1, SUS302B, SUS303, SUS304, SUS304Cu, SUS304L, SUS304N1, SUS304N2, SUS304LN, SUS304J1, SUS304J2, SUS305, SUS309S, SUS310S, SUS312L, SUS315J1, SUS315J2, SUS316, SUS316L, SUS316N, SUS316LN, SUS316Ti, SUS316J1, SUS316J1L, SUS317, SUS317L, SUS317LN, SUS317J1, SUS317J2, SUS836L, SUS890L, SUS321, SUS347, SUSXM7, and SUSXM15J1.

[0047] Examples of ferritic stainless steel include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.

[0048] Examples of martensitic stainless steel include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.

[0049] Examples of precipitation hardening stainless steel include SUS630 (17-4PH) and SUS631 (17-7PH).

[0050] Examples of austenitic-ferritic (duplex) stainless steel include SUS329J1, SUS329J3L, and SUS329J4L.

[0051] The above symbols are material symbols based on the JIS standard. The types of stainless steel in this specification are distinguished by the above material symbols.

[0052] The additive manufacturing powder 1 may also be provided with a coating that covers the surface of the core particles made of an Fe-based metal material. This coating is provided for purposes such as increasing the fluidity and packing ability of the additive manufacturing powder 1, or increasing the affinity between the additive manufacturing powder 1 and the binder. Examples of materials that can constitute the coating include organic materials such as resins, inorganic materials such as ceramics and glass, and compounds derived from coupling agents.

[0053] 2.2. Various properties of powders for additive manufacturing Next, we will explain various properties of the powder for layered manufacturing 1. Note that all of the following properties are measured in a state where the powder for layered manufacturing 1 is not provided with the above-mentioned coating.

[0054] 2.2.1. Penetration depth of PVP aqueous solution for evaluation When the evaluation powder layer 10 is formed using the additive manufacturing powder 1 according to this embodiment, the evaluation powder layer 10 has the property that the penetration depth of the evaluation PVP aqueous solution 40 falls within a predetermined range. The penetration depth of the evaluation PVP aqueous solution 40 in the evaluation powder layer 10 serves as an index that quantitatively represents the permeability of the binder solution 4 in the binder jet method described above. By optimizing this index, it is possible to realize an additive manufacturing powder 1 that can form a powder layer 31 that has excellent permeability for the binder solution 4, even when the particle size of the additive manufacturing powder 1 is small.

[0055] The PVP aqueous solution for evaluation 40 is used to quantitatively represent the permeability of the binder solution 4 used in the binder jet method. The PVP aqueous solution for evaluation 40 is an aqueous solution containing PVP and 2-butoxyethanol. The PVP (polyvinylpyrrolidone) content in the PVP aqueous solution for evaluation 40 is 8% by mass, the 2-butoxyethanol content is 2% by mass, and the remainder is ion-exchanged water. The viscosity of the PVP aqueous solution for evaluation 40 is 0.006 [Pa·s] (6 cP).

[0056] The penetration depth d of the PVP aqueous solution for evaluation 40 is measured as follows. FIG. 11 is a cross-sectional view illustrating a method for measuring the penetration depth of the evaluation powder layer 10 with the evaluation PVP aqueous solution 40. As shown in FIG.

[0057] When measuring the penetration depth d of the evaluation PVP aqueous solution 40, first, the powder for additive manufacturing 1 is placed in a container 20 and compressed to form the evaluation powder layer 10. The thickness of the evaluation powder layer 10 is 10 mm, and the relative density is 45% to 47%. The horizontal size of the evaluation powder layer 10 is set taking into account the spread of the evaluation PVP aqueous solution 40, and is, for example, 30 mm square or larger. The relative density is calculated by dividing the mass of the evaluation powder layer 10 by its volume to calculate the density, and then dividing this density by the true density of the evaluation powder 1.

[0058] Next, multiple droplets of the PVP aqueous solution for evaluation 40 are ejected from the inkjet head 30 toward one location on the powder layer for evaluation 10. The inkjet head 30 used has a resolution of 600 dpi, a droplet ejection speed of 7.17 m / sec, a total amount of the PVP aqueous solution for evaluation 40 ejected at one location of 1.36 mL, and an air temperature of 23°C.

[0059] Next, the powder layer 10 for evaluation is heated at 100° C. for 1 hour, whereby the water in the discharged aqueous PVP solution 40 for evaluation is removed, and the area into which the aqueous PVP solution 40 for evaluation has permeated is solidified.

[0060] Next, the solidified portion is removed from the evaluation powder layer 10. Then, the length from the surface to the deepest part of the evaluation powder layer 10 (the length of the solidified portion) is measured. The measurement result is defined as the penetration depth (penetration depth d) of the evaluation PVP aqueous solution 40.

[0061] In the evaluation powder layer 10 using the additive manufacturing powder 1 according to this embodiment, the penetration depth d of the evaluation PVP aqueous solution 40 is 110 μm or more and 250 μm or less. The additive manufacturing powder 1 having a penetration depth within this range can form a powder layer 31 that can be sufficiently penetrated by the aqueous binder solution 4, even when the particle size of the additive manufacturing powder 1 is small and the surface energy of the particles is high. Therefore, when used to manufacture an additive manufacturing object 6 by the binder jet method, an additive manufacturing powder 1 can be realized that can manufacture an additive manufacturing object 6 with high shape accuracy.

[0062] The penetration depth d is preferably 130 μm or more and 220 μm or less, and more preferably 150 μm or more and 200 μm or less.

[0063] If the penetration depth d is below the lower limit, the binder solution 4 cannot penetrate into the desired range in the binder solution supplying step S104, reducing the shape accuracy of the layered object 6. Furthermore, penetration takes time, reducing the molding speed of the layered object 6. On the other hand, if the penetration depth d is above the upper limit, the penetration distance of the binder solution 4 becomes too large in the binder solution supplying step S104, causing so-called bleeding, reducing the shape accuracy of the layered object 6.

[0064] Furthermore, it is preferable that all droplets of the discharged PVP aqueous solution for evaluation 40 penetrate into the powder layer for evaluation 10 within 3 seconds, and more preferably within 1 second, starting from the time when the last droplet was discharged. This makes it possible to particularly increase the manufacturing speed of the layered object 6.

[0065] 2.2.2.Particle size distribution When the particle size distribution of the powder for additive manufacturing 1 according to this embodiment is obtained on a volume basis using a laser diffraction particle size distribution analyzer, the particle size at which the cumulative frequency is 10% from the smallest diameter side is defined as D10. Similarly, the particle sizes at which the cumulative frequency is 50%, 90%, and 99% from the smallest diameter side are defined as D50, D90, and D99. An example of an apparatus for measuring particle size distribution is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0066] The particle size D50 of the additive manufacturing powder 1 is 1.0 μm or more and less than 15.0 μm, preferably 3.0 μm or more and 12.0 μm or less, and more preferably 4.0 μm or more and 10.0 μm or less. This allows the additive manufacturing powder 1 to achieve both sinterability and flowability. As a result, a dense additive manufacturing body 6 with high manufacturing accuracy can be obtained, and this can be used to ultimately manufacture a metal sintered body with high density and surface accuracy.

[0067] If the particle size D50 is below the lower limit, the particles of the additive manufacturing powder 1 tend to aggregate. This reduces the fluidity of the additive manufacturing powder 1, and the density of the metal sintered body decreases. On the other hand, if the particle size D50 is above the upper limit, the sinterability of the additive manufacturing powder 1 decreases, and the density of the metal sintered body decreases.

[0068] The ratio D10 / D50 of particle size D10 to particle size D50 is preferably 0.30 or more and 0.70 or less, more preferably 0.35 or more and 0.60 or less, and even more preferably 0.42 or more and 0.55 or less. This ensures that the particle size of the powder 1 for additive manufacturing is relatively uniform, making it easier to improve fluidity and ensuring sinterability. If the ratio D10 / D50 is below the lower limit, the particle size distribution will broaden, which may result in a decrease in fluidity. On the other hand, if the ratio D10 / D50 is above the upper limit, the particle size distribution will be too narrow, making it difficult to increase the filling rate and resulting in a decrease in sinterability.

[0069] The ratio D90 / D50 of particle size D90 to particle size D50 is preferably 1.50 or more and 2.70 or less, more preferably 1.70 or more and 2.60 or less, and even more preferably 1.90 or more and 2.50 or less. This ensures that the particle size of the powder 1 for additive manufacturing is relatively uniform, making it easier to improve fluidity and ensuring sinterability. If the ratio D90 / D50 is below the lower limit, the particle size distribution narrows, making it difficult to increase the filling rate and potentially reducing sinterability. On the other hand, if the ratio D90 / D50 exceeds the upper limit, the particle size distribution broadens, potentially reducing fluidity.

[0070] The particle size difference D90-D10 between particle size D90 and particle size D10 is set to 5.0 μm or more and 18.0 μm or less, preferably 8.0 μm or more and 15.0 μm or less, and more preferably 9.0 μm or more and 13.0 μm or less. This narrows the particle size distribution of the powder 1 for additive manufacturing sufficiently, resulting in high fluidity. As a result, the filling ability of the powder 1 for additive manufacturing is improved, allowing for the production of a dense additive manufacturing body 6 with high modeling accuracy.

[0071] If the particle size difference D90-D10 falls below the lower limit, the particle size distribution of the additive manufacturing powder 1 becomes extremely narrow, making it difficult to increase the filling rate and reducing sinterability. This reduces the density and surface precision of the resulting metal sintered body. On the other hand, if the particle size difference D90-D10 exceeds the upper limit, the particle size distribution of the additive manufacturing powder 1 broadens, reducing fluidity. This reduces the density and surface precision of the resulting sintered body.

[0072] 2.2.3. Specific surface area The specific surface area of ​​additive manufacturing powder 1 is 0.05 [m 2 / g] or more 0.25[m 2 / g] or less, preferably 0.10 [m 2 / g] or more 0.22[m 2 / g] or less, and more preferably 0.15 [m 2 / g] or more 0.20[m 2 / g] or less. If the specific surface area is within this range, both the sinterability and fluidity of the powder for additive manufacturing 1 can be achieved. Furthermore, because the surface energy is optimized, the penetration depth of the binder solution 4 is also optimized, allowing the binder solution 4 to quickly penetrate into the desired range. As a result, a dense additive manufacturing body 6 with high molding accuracy can be obtained, and this can be used to ultimately produce a metal sintered body with high density and surface accuracy.

[0073] If the specific surface area is below the lower limit, the sinterability of the powder for additive manufacturing 1 will decrease, and the density of the metal sintered body will decrease. Furthermore, the penetration distance of the binder solution 4 will become too long, which may result in a decrease in molding accuracy. On the other hand, if the specific surface area exceeds the upper limit, the sinterability of the powder for additive manufacturing 1 will increase, but the fluidity of the powder for additive manufacturing 1 will decrease, and the density and surface accuracy of the metal sintered body will decrease. Furthermore, the penetration depth of the binder solution 4 will be insufficient, which may result in the binder solution 4 not being able to penetrate the desired range.

[0074] The specific surface area of ​​the powder for layered manufacturing 1 is obtained by the BET method. An example of a specific surface area measuring device is the BET type specific surface area measuring device HM1201-010 manufactured by Mountech Co., Ltd., and the amount of sample is 5 g.

[0075] 2.2.4.Average circularity The average circularity of the additive manufacturing powder 1 is 0.85 or more and 0.99 or less, preferably 0.86 or more and 0.98 or less, and more preferably 0.87 or more and 0.97 or less. This allows the particles to roll easily even when the particle size of the additive manufacturing powder 1 is small, and the packed state can approach close packing. As a result, both the sinterability and fluidity of the additive manufacturing powder 1 can be achieved. Furthermore, because the surface energy is optimized, the penetration depth of the binder solution 4 is also optimized, allowing the binder solution 4 to quickly penetrate the desired range. This allows for a dense additive manufacturing body 6 with high molding accuracy to be obtained, which can then be used to ultimately produce a metal sintered body with high density and surface accuracy.

[0076] If the average circularity is below the lower limit, the average circularity decreases, resulting in a decrease in the fluidity of the powder for additive manufacturing 1 and a decrease in the filling rate. Furthermore, the penetration depth of the binder solution 4 becomes insufficient, and the binder solution 4 may not be able to penetrate the desired range. On the other hand, if the average circularity exceeds the upper limit, the difficulty of production increases, and the production efficiency of the powder for additive manufacturing 1 decreases. Furthermore, the penetration distance of the binder solution 4 becomes too long, and the modeling accuracy may decrease.

[0077] The average circularity of the powder for layered manufacturing 1 is measured as follows. First, an image (secondary electron image) of the powder for additive manufacturing 1 is taken using a scanning electron microscope (SEM). Next, the obtained image is loaded into image processing software. For example, image analysis type particle size distribution measurement software "Mac-View" manufactured by Mountech Co., Ltd. is used as the image processing software. The imaging magnification is adjusted so that 50 to 100 particles are captured in one image. Then, multiple images are acquired so that a total of 300 or more particle images are obtained.

[0078] Next, using software, the circularity of 300 or more particle images is calculated and the average value is obtained. The obtained average value is the average circularity of the powder for additive manufacturing 1. Note that when the circularity is e, the area of ​​the particle image is S, and the perimeter of the particle image is L, the circularity e can be calculated using the following formula. e=4πS / L 2

[0079] 2.2.5.Moisture content The moisture content of the powder for additive manufacturing 1 is preferably 200 ppm or less, more preferably 30 ppm to 200 ppm, even more preferably 40 ppm to 150 ppm, and particularly preferably 50 ppm to 100 ppm. If the moisture content is within this range, the decrease in fluidity due to moisture adsorption is suppressed. Therefore, the powder for additive manufacturing 1 has excellent fluidity. Furthermore, if the moisture content is within this range, the chargeability of the powder for additive manufacturing 1 can be controlled within an appropriate range, and the decrease in fluidity due to charging can be suppressed.

[0080] If the moisture content is below the lower limit, the powder for additive manufacturing 1 may be easily charged, which may reduce the flowability. On the other hand, if the moisture content is above the upper limit, the moisture content of the powder for additive manufacturing 1 may be too high, which may reduce the flowability.

[0081] The moisture content of the additive manufacturing powder 1 is measured by leaving the target additive manufacturing powder 1 in an environment at a temperature of 25°C and a relative humidity of 50% for at least one hour, and then measuring it at 250°C by the Karl Fischer method. For the measurement, for example, a moisture measuring device CA-310 manufactured by Nitto Seiko Analytech Co., Ltd. is used.

[0082] 2.2.6.Oxygen content The oxygen content of the powder for additive manufacturing 1 is preferably 1000 ppm or more and 4000 ppm or less by mass, more preferably 1500 ppm or more and 3500 ppm or less, and even more preferably 2000 ppm or more and 3000 ppm or less. When the oxygen content is within the above range, moisture adsorption can be suppressed while suppressing changes in properties over time. This results in a powder for additive manufacturing 1 with high fluidity and high storage stability. Furthermore, an oxide film of appropriate thickness is easily formed on the particle surface of the powder for additive manufacturing 1. This oxide film contributes to the penetration of the binder solution 4.

[0083] If the oxygen content falls below the lower limit, the oxide film present on the particle surfaces of the powder for additive manufacturing 1 may become thinner, which may lead to a risk of deterioration over time. Furthermore, when a powder layer 31 is formed using the powder for additive manufacturing 1, the permeability of the binder solution 4 in the powder layer 31 may decrease. On the other hand, if the oxygen content exceeds the upper limit, moisture may be easily adsorbed, increasing the moisture content and potentially reducing the fluidity of the powder for additive manufacturing 1. Furthermore, the sinterability of the powder for additive manufacturing 1 may decrease.

[0084] The oxygen content of the powder for additive manufacturing 1 is measured, for example, in accordance with the general rules for determining oxygen content in metallic materials specified in JIS Z 2613: 2006. Specifically, the oxygen content can be measured using a LECO oxygen / nitrogen analyzer, TC-300 / EF-300, a LECO oxygen / nitrogen / hydrogen analyzer, ONH836, or the like.

[0085] 2.2.7. Bulk and tapped density The bulk density of additive manufacturing powder 1 is 2.50 g / cm 3 More than 3.50g / cm 3 Preferably, it is 2.70 g / cm or less. 3 More than 3.40g / cm 3 More preferably, it is 3.00 g / cm or less. 3 More than 3.30g / cm 3 It is even more preferable that the bulk density is equal to or less than this range. If the bulk density is within this range, good packing properties can be ensured even in the natural state. This allows the powder layer 31 to be formed with a high packing rate when the powder for additive manufacturing 1 is used to form the powder layer 31. As a result, a dense additive manufacturing body 6 with high molding accuracy can be obtained, and this can be used to finally manufacture a metal sintered body with high density and surface accuracy.

[0086] The bulk density of the additive manufacturing powder 1 is measured in accordance with the method for measuring the apparent density of metal powders specified in JIS Z 2504:2012. A powder property evaluation device, Powder Tester (registered trademark) PT-X, manufactured by Hosokawa Micron Corporation, is preferably used to measure the bulk density. Prior to measuring the bulk density, the additive manufacturing powder 1 to be measured is preferably left in an environment at a temperature of 25°C and a relative humidity of 50% for at least one hour.

[0087] The tap density of additive manufacturing powder 1 is 4.20 g / cm 3 More than 4.90g / cm 3 Preferably, it is 4.40 g / cm or less. 3 More than 4.80g / cm 3 More preferably, it is 4.50 g / cm or less. 3 More than 4.70g / cm 3 If the tap density is within the above range, a high filling rate can be obtained when the powder layer 31 is leveled on the building stage 23 or compressed with the roller 25. This makes it possible to obtain a dense layered manufactured body 6 with high manufacturing accuracy, which can then be used to ultimately manufacture a metal sintered body with high density and surface accuracy.

[0088] The tap density of the powder for additive manufacturing 1 is measured using a powder property evaluation device, Powder Tester (registered trademark) PT-X, manufactured by Hosokawa Micron Corp. Before measuring the tap density, the powder for additive manufacturing 1 to be measured is preferably left in an environment at a temperature of 25°C and a relative humidity of 50% for at least one hour.

[0089] Furthermore, the ratio of tap density to bulk density of the additive manufacturing powder 1 is preferably 1.20 or more and 1.80 or less, more preferably 1.30 or more and 1.70 or less, and even more preferably 1.40 or more and 1.60 or less. If this ratio is within the above range, the difference in packing rate between the additive manufacturing powder 1 in its natural state and the additive manufacturing powder 1 after vibration, load, or the like has been applied can be reduced. This makes it possible to suppress deformation of the additive manufacturing body 6 due to the difference in packing rate. As a result, a metal sintered body with high surface precision can be obtained.

[0090] Although this ratio may be below the lower limit, it may be more difficult to stably produce the powder for additive manufacturing 1 having such properties. On the other hand, if this ratio exceeds the upper limit, the difference in filling rate becomes large, which may result in deformation of the additive manufacturing body 6.

[0091] Furthermore, the ratio of the tap density to the true density of the powder for additive manufacturing 1 is preferably 0.580 or more and 0.640 or less, more preferably 0.590 or more and 0.630 or less, and even more preferably 0.600 or more and 0.620 or less. If this ratio is within the above range, it is possible to realize a powder for additive manufacturing 1 that can particularly increase the density of the powder layer 31 even if the particle size is small. As a result, it is possible to manufacture a metal sintered body with high density and surface precision. Furthermore, it is possible to manufacture the additively manufactured body 6 while reducing the amount of binder solution 4 used.

[0092] If the ratio of the tap density to the true density is below the lower limit, the filling ability of the powder for additive manufacturing 1 may decrease, or a larger amount of binder solution 4 may be required. On the other hand, if the ratio of the tap density to the true density is above the upper limit, the difficulty of manufacturing the powder for additive manufacturing 1 may increase, which may result in higher costs and reduced manufacturing efficiency.

[0093] 3. Manufacturing method of powder for additive manufacturing Next, an example of a method for producing the powder 1 for layered manufacturing will be described.

[0094] The additive manufacturing powder 1 may be produced by any manufacturing method, for example, by atomization. In atomization, molten metal is allowed to flow down from a crucible and collide with a fluid, such as a liquid or gas, sprayed at high speed. The molten metal that collides with the fluid falls by inertia, causing the droplets to become spherical. As a result, it is possible to produce metal powder that has a high average circularity and a relatively small specific surface area, despite its relatively small diameter. Furthermore, by reducing the specific surface area, the water content can be reduced.

[0095] The atomization method includes water atomization, gas atomization, and rotary water jet atomization, depending on the type of coolant and the configuration of the device.

[0096] The flow rate of the molten metal varies depending on the size of the equipment, but is preferably greater than 1.0 kg / min and less than 20.0 kg / min, and more preferably between 2.0 kg / min and 10.0 kg / min. This allows the amount of molten metal flowing in a given period of time to be optimized, thereby efficiently producing metal powder with a narrow particle size distribution and sufficient spherical shape. As a result, metal powder with a relatively small diameter but a high average circularity and a relatively small specific surface area can be produced. Furthermore, reducing the specific surface area allows for a reduction in the water content.

[0097] The temperature of the molten metal in the crucible (pouring temperature) is preferably set to between Tm + 100°C and Tm + 350°C, where Tm [°C] is the melting point of the constituent material of the additive manufacturing powder 1, more preferably between Tm + 180°C and Tm + 320°C, and even more preferably between Tm + 250°C and Tm + 300°C. This ensures that the molten metal remains in existence for a longer period than conventional methods when it is refined and solidified by various atomization methods. As a result, it is possible to produce metal powder with a high average circularity and a relatively small specific surface area, even if it has a small diameter.

[0098] In addition, in various atomization methods, the outer diameter of the thin streams of molten metal when flowing down is not particularly limited, but is preferably 3.0 mm or less, more preferably 0.3 mm to 2.0 mm, and even more preferably 0.5 mm to 1.5 mm. This makes it easier to apply the fluid uniformly to the molten metal, making it easier to uniformly scatter droplets of appropriate size. As a result, metal powder with the above-mentioned average particle size and good average circularity can be produced with a narrow particle size distribution.

[0099] The produced metal powder may be classified as needed by methods such as dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0100] 4. Effects of the above embodiment As described above, the additive manufacturing powder 1 according to the embodiment contains an Fe-based metal material and is an additive manufacturing powder used in a binder jet method. In a volume-based cumulative particle size distribution curve measured by laser diffraction, the particle size D10 is the particle size at which the cumulative value from the small diameter side is 10%, the particle size D50 is the particle size at which the cumulative value from the small diameter side is 50%, and the particle size D90 is the particle size at which the cumulative value from the small diameter side is 90%. The additive manufacturing powder 1 has a particle size D50 of 1.0 μm or more and less than 15.0 μm, and the particle size difference D90-D10 between the particle size D90 and the particle size D10 is 5.0 μm or more and 18.0 μm or less. Furthermore, the additive manufacturing powder 1 has a specific surface area of ​​0.05 m 2 / g] or more 0.25[m 2 / g] or less, and an average circularity of 0.85 to 0.99. Furthermore, when a plurality of droplets of the aqueous PVP solution 40 for evaluation are dropped onto the same position on the powder layer 10 for evaluation, which has been formed by compacting powder to have a relative density of 45% to 47% and a thickness of 10 mm, so that the total amount of droplets is 1.36 mL, the penetration depth (penetration depth d) of the aqueous PVP solution 40 for evaluation is 110 μm to 250 μm.

[0101] According to this configuration, it is possible to obtain a powder for layered manufacturing 1 that has good sinterability and flowability, and that has good permeability for the binder solution 4 (aqueous binder solution).

[0102] Moreover, the powder for layered manufacturing 1 according to the embodiment has an oxygen content of 1000 ppm or more and 4000 ppm or less.

[0103] This configuration can suppress moisture adsorption while suppressing changes in properties over time. This results in a powder for additive manufacturing 1 with high fluidity and high storage stability. Furthermore, an oxide film of appropriate thickness is easily formed on the particle surfaces of the powder for additive manufacturing 1. This oxide film contributes to the penetration of the binder solution 4.

[0104] In addition, the powder for layered manufacturing 1 according to the embodiment has a particle size D50 of 4.0 μm or more and 10.0 μm or less, and a specific surface area of ​​0.10 [m 2 / g] or more 0.22[m 2 / g or less.

[0105] This configuration makes it possible to achieve both sinterability and fluidity of the layered manufacturing powder 1. As a result, a dense layered manufactured body 6 with high manufacturing accuracy can be obtained.

[0106] Furthermore, the powder for layered manufacturing 1 according to the embodiment has a moisture content of 200 ppm or less as measured at 250° C. by the Karl Fischer method.

[0107] This configuration suppresses the decrease in fluidity that accompanies moisture absorption. As a result, the powder for layered manufacturing 1 has excellent fluidity. Furthermore, if the moisture content is within the above range, the tendency for the powder for layered manufacturing 1 to become electrically charged can be controlled within an appropriate range, and the decrease in fluidity that accompanies charging can be suppressed.

[0108] Furthermore, in the powder for layered manufacturing 1 according to the embodiment, the ratio of tap density to bulk density is 1.20 or more and 1.80 or less.

[0109] This configuration reduces the difference in filling rate between the additive manufacturing powder 1 in its natural state and the additive manufacturing powder 1 after vibration, load, etc. are applied. This makes it possible to suppress deformation of the additive manufacturing body 6 due to the difference in filling rate. As a result, a metal sintered body with high surface precision can be obtained.

[0110] In addition, in the powder 1 for additive manufacturing according to the embodiment, the Fe-based metallic material is a precipitation hardening stainless steel.

[0111] According to this configuration, a metal powder for injection molding can be obtained that can be used to produce a metal sintered body that is excellent in mechanical strength and toughness.

[0112] Furthermore, in the powder for layered manufacturing 1 according to the embodiment, the ratio of the tap density to the true density is 0.580 or more and 0.640 or less.

[0113] This configuration makes it possible to realize a powder for additive manufacturing 1 that can particularly increase the density of the powder layer 31 even if the particle size is small. As a result, it is possible to manufacture a metal sintered body with high density and surface precision. In addition, it is possible to manufacture an additive manufacturing body 6 while reducing the amount of binder solution 4 used.

[0114] Moreover, the layered manufacturing body 6 according to the embodiment includes the powder for layered manufacturing 1 according to the embodiment, and a binder that binds the particles of the powder for layered manufacturing 1 together.

[0115] With this configuration, it is possible to obtain a dense, highly accurate layered object 6 by taking advantage of the high fluidity and packing properties of the layered object powder 1. Therefore, for example, by sintering this layered object 6, it is possible to obtain a metal sintered body with high density and high surface accuracy.

[0116] The powder for additive manufacturing and the additive manufacturing body of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to this. For example, the powder for additive manufacturing and the additive manufacturing body of the present invention may be those of the above embodiments to which any component has been added. [Example]

[0117] Next, specific examples of the present invention will be described. 5. Production of powder for additive manufacturing Powders for additive manufacturing were produced by water atomization for Samples Nos. 1 to 23. The composition of the powders for additive manufacturing for each Sample No. is as shown in Tables 1 to 4.

[0118] [Table 1]

[0119] 6. Obtaining the properties of powders for additive manufacturing For each powder for additive manufacturing, the representative particle size, specific surface area, average circularity, penetration depth of the PVP aqueous solution for evaluation, oxygen content, water content, ratio of tapped density to bulk density, and ratio of tapped density to true density were measured. The measurement results are shown in Tables 2 to 4. In Tables 2 to 4, among the powders for additive manufacturing of each sample number, those that correspond to the present invention are designated as "Examples," and those that do not correspond to the present invention are designated as "Comparative Examples."

[0120] 7. Evaluation of Powders for Additive Manufacturing 7.1. Relative Density of Sintered Metals Using the additive manufacturing powder of each sample number, an additive manufacturing object in the shape of a rectangular parallelepiped was fabricated by the binder jet method. The size of the manufactured additive manufacturing object was 40 mm in length, 20 mm in width, and 5 mm in thickness. The binder solution used was the same as the PVP aqueous solution for evaluation.

[0121] The resulting additively manufactured body was then degreased and sintered in a furnace. The sintering conditions for steel type 1 were 1100°C for 3 hours in an argon atmosphere. This resulted in a metal sintered body. For steel types 2 and 3, the sintering conditions were selected according to the composition.

[0122] Next, the density of the obtained metal sintered body was measured. Next, the relative value of the measured density to the true density of the used powder for additive manufacturing, i.e., the relative density of the sintered body, was calculated. The calculated relative density was then evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Tables 2 to 4.

[0123] A: Relative density is 99.0% or more B: Relative density is 98.5% or more and less than 99.0% C: Relative density is 98.0% or more and less than 98.5% D: Relative density is less than 98.0%

[0124] 7.2.Surface roughness of sintered metal bodies The surface roughness of the largest surface of each metal sintered compact was measured. This surface roughness, the arithmetic mean roughness Ra, was measured according to the method specified in JIS B 0671-1:2002. In Table 2, the surface roughness of each metal sintered compact was evaluated relative to the surface roughness of the metal sintered compact manufactured using the additive manufacturing powder of Sample No. 9. In Table 3, the surface roughness of the metal sintered compact manufactured using the additive manufacturing powder of Sample No. 19 was used as the standard, and in Table 4, the surface roughness of the metal sintered compact manufactured using the additive manufacturing powder of Sample No. 23 was used as the standard. The evaluation results are shown in Tables 2 to 4.

[0125] A: The relative value of the surface roughness is less than 80% of the standard value. B: The relative value of the surface roughness is 80% or more but less than 90% of the standard value. C: The relative value of the surface roughness is 90% or more but less than 100% of the reference value. D: The relative value of the surface roughness is 100% or more of the standard value.

[0126] [Table 2]

[0127] [Table 3]

[0128] [Table 4]

[0129] 7.3. Discussion of evaluation results As shown in Tables 2 to 4, it was confirmed that the metal sintered bodies manufactured using the powders for additive manufacturing of each example had high relative density and good surface roughness.

[0130] From the above, it has become clear that the powder for additive manufacturing of the present invention can produce metal sintered bodies with high density and surface precision. [Explanation of symbols]

[0131] 1... Powder for additive manufacturing, 2... Additive manufacturing apparatus, 4... Binder solution, 6... Additive manufacturing object, 10... Powder layer for evaluation, 20... Container, 21... Apparatus body, 22... Powder supply elevator, 23... Modeling stage, 24... Coater, 25... Roller, 26... Liquid supply unit, 30... Inkjet head, 31... Powder layer, 40... PVP aqueous solution for evaluation, 41... Binder layer, 60... Formation area, 211... Powder storage unit, 212... Modeling unit, S102... Powder layer formation process, S104... Binder solution supply process, S106... Repeating process, d... Penetration depth

Claims

1. A powder for additive manufacturing used in a binder jet method, containing an Fe-based metal material, In a volume-based cumulative particle size distribution curve measured by a laser diffraction method, the particle size when the cumulative value from the small diameter side is 10% is defined as D10, the particle size when the cumulative value from the small diameter side is 50% is defined as D50, and the particle size when the cumulative value from the small diameter side is 90% is defined as D90, the particle size D50 is 1.0 μm or more and less than 15.0 μm, and the particle size difference D90-D10 between the particle size D90 and the particle size D10 is 5.0 μm or more and 18.0 μm or less, The specific surface area is 0.05 [m ２ / g] or more 0.25 [m ２ / g] or less, an average circularity of 0.85 or more and 0.99 or less; A powder for additive manufacturing characterized in that when a powder layer for evaluation is formed by compacting powder to have a relative density of 45% or more and 47% or less and a thickness of 10 mm, and multiple droplets of an aqueous PVP solution for evaluation are dropped onto the same position so that the total amount is 1.36 mL, the depth to which the aqueous PVP solution for evaluation has penetrated is 110 μm or more and 250 μm or less.

2. The powder for layered manufacturing according to claim 1, wherein the oxygen content is 1000 ppm or more and 4000 ppm or less.

3. The particle size D50 is 4.0 μm or more and 10.0 μm or less, The specific surface area is 0.10 [m ２ / g] or more 0.22[m ２ 3. The powder for layered manufacturing according to claim 1 or 2, wherein the powder has a viscosity of 1 / g or less.

4. 3. The powder for layered manufacturing according to claim 1, wherein the moisture content measured at 250°C by the Karl Fischer method is 200 ppm or less.

5. The powder for layered manufacturing according to claim 1 or 2, wherein the ratio of tap density to bulk density is 1.20 or more and 1.80 or less.

6. The powder for additive manufacturing according to claim 1 or 2, wherein the Fe-based metallic material is a precipitation hardening stainless steel.

7. The powder for additive manufacturing according to claim 6, wherein the ratio of tap density to true density is 0.580 or more and 0.640 or less.

8. The powder for additive manufacturing according to claim 1 or 2, a binder that binds particles of the powder for additive manufacturing together; A layered object comprising:

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