Method for manufacturing metal molded bodies and metal molded bodies

Abstract

To provide a metal molded body with high density and dimensional accuracy and homogeneity, and a method for manufacturing such a metal molded body. [Solution] A method for manufacturing a metal molded body by bonding together metal powder particles contained in a powder layer, wherein the average circularity is 0.80 or more and less than 1.00, and the specific surface area is 0.30 m². 2 A method for manufacturing a metal molded body, comprising: a powder layer formation step of leveling a metal powder with a squeegee roller to form a powder layer, wherein the metal powder has a particle size D50 of 1.0 μm or more and a particle size D90 of 11.0 μm or more, where the cumulative frequency of particles in the cumulative particle size distribution is 50% from the smallest diameter side, and the particle size D90 is 11.0 μm or more and the particle size D90 is 25.0 μm or less; and a particle bonding step of bonding particles in the powder layer, wherein the rotation speed of the squeegee roller is 0 rpm or more and 50 rpm or less, and the movement speed of the squeegee roller is 1 mm / s or more and 25 mm / s or less.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a metal molded object and to a metal molded object. [Background technology]

[0002] In recent years, additive manufacturing methods using metal powders have become increasingly popular as a technique for creating three-dimensional objects. Among these, powder bed fusion and binder jetting include the steps of forming a powder layer and forming a three-dimensional powder-based object by melting or bonding particles together in a portion of the powder layer. The powder-based object formed by bonding the particles together is then subjected to a sintering process to become a metal object (metal sintered object).

[0003] For example, Patent Document 1 discloses a method for manufacturing a powder-molded body that repeatedly includes the steps of forming a powder layer, applying liquid to the powder layer based on the shape data of a three-dimensional model, and drying the powder layer to which the liquid has been applied. Furthermore, Patent Document 1 discloses that the quality of the powder-molded body can be stabilized by controlling the operation of applying the liquid according to the drying state of the powder layer. By stabilizing the quality of the powder-molded body in this way, the quality of the metal body formed by sintering the powder-molded body can ultimately be stabilized. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-142420 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In the metal fabrication method described above, the packing efficiency of the metal powder in the powder layer affects the density and dimensional accuracy of the final metal fabrication. However, Patent Document 1 does not adequately disclose methods for improving the packing efficiency of the powder layer.

[0006] For example, Patent Document 1 discloses a method for increasing the space-filling ratio of a powder layer by using multiple types of powders with different average particle sizes. However, even when using multiple types of powders, it is difficult to sufficiently increase the space-filling ratio of the powder layer depending on the method of forming the powder layer. If there are areas with low space-filling ratio, the density and dimensional accuracy of the final metal molded body will decrease, and its homogeneity will be compromised.

[0007] Therefore, there is a need for metal molded bodies with high density and dimensional accuracy and uniformity, as well as a method for efficiently manufacturing such metal molded bodies. [Means for solving the problem]

[0008] The method for manufacturing a metal molded body according to an application example of the present invention is: A method for manufacturing a metal object by bonding together metal powder particles contained in a powder layer, The average circularity is between 0.80 and 1.00, and the specific surface area is 0.30 m². 2 A powder layer formation step in which the metal powder is less than or equal to / g, and in the cumulative particle size distribution on a volume basis obtained using a laser diffraction particle size distribution analyzer, the particle size D50 at which the cumulative frequency from the smallest diameter side is 50% is between 1.0 μm and 10.0 μm, and the particle size D90 at which the cumulative frequency from the smallest diameter side is 90% is between 11.0 μm and 25.0 μm is leveled with a squeegee roller to form the powder layer, A particle bonding step for bonding the particles in the powder layer together, It has, The rotation speed of the squeegee roller is set to be between 0 rpm and 50 rpm. The movement speed of the squeegee roller shall be between 1 mm / s and 25 mm / s.

[0009] The metal formed body according to the application example of the present invention is a metal formed body formed by laminating melts or sintered products between particles in a powder layer containing metal powder in the stacking direction, which is cut by a plane including the normal line of the powder layer, and in the obtained cross section, a region having a width of 10 μm in the extending direction of the normal line and a length of 700 μm in the direction orthogonal to the normal line is defined as one analysis range, while shifting the region by 10 μm in the depth direction, a total of 10 such analysis ranges are set, in each of the analysis ranges, the occupied area and the occupied area ratio of the melt or the sintered product are calculated, when the calculation is performed by the calculation formula |(the ratio of the occupied areas in the adjacent analysis ranges) - 1| in the adjacent analysis ranges to obtain a calculation result, the occupied area ratios in the 10 analysis ranges are all 90.0% or more, and the average value of the calculation results obtained from the 10 analysis ranges is 0.050 or less.

Brief Description of Drawings

[0010] [Figure 1] It is a process diagram for explaining a method of manufacturing a metal formed body according to the first embodiment. [Figure 2] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 3] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 4] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 5] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 6] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 7] It is a diagram for explaining the method of manufacturing the metal formed body shown in FIG. 1. [Figure 8]This figure illustrates the manufacturing method for the metal molded object shown in Figure 1. [Figure 9] This figure illustrates the manufacturing method for the metal molded object shown in Figure 1. [Figure 10] This figure illustrates the manufacturing method for the metal molded object shown in Figure 1. [Figure 11] This figure illustrates the manufacturing method for the metal molded object shown in Figure 1. [Figure 12] This is a schematic diagram showing 10 analysis ranges AN1 to AN10 set on a cross-section obtained by cutting a metal fabricated body according to the embodiment along a plane containing the normal to the powder layer. [Figure 13] This is a process diagram illustrating the manufacturing method of a metal molded body according to the second embodiment. [Figure 14] Table 1 shows the steel grade of the additive manufacturing powder for each sample number. [Figure 15] Table 2 shows the composition of the additive manufacturing powder for each sample number, the composition of the manufacturing method for the metal object, and the evaluation results. [Figure 16] Table 3 shows the composition of the additive manufacturing powder for each sample number, the composition of the manufacturing method for the metal object, and the evaluation results. [Figure 17] Table 4 shows the composition of the additive manufacturing powder for each sample number, the composition of the manufacturing method for the metal object, and the evaluation results. [Figure 18] Table 5 shows the composition of the additive manufacturing powder for each sample number, the composition of the manufacturing method for the metal object, and the evaluation results. [Figure 19] Table 6 shows the sample numbers of the additive manufacturing powders used in the production of the metal objects, the composition of the metal objects, and the evaluation results of the metal objects. [Modes for carrying out the invention]

[0011] The method for manufacturing a metal molded body according to the present invention and the metal molded body will be described in detail below based on the embodiments shown in the attached drawings.

[0012] 1. First Embodiment First, a description will be given of the method for manufacturing a metal molded body according to the first embodiment.

[0013] 1.1. Method for manufacturing metal molded objects Figure 1 is a process diagram illustrating the manufacturing method of a metal molded body according to the first embodiment. Figures 2 to 11 are diagrams illustrating the manufacturing method of the metal molded body shown in Figure 1. In Figures 2 to 11 of this application, the X-axis, Y-axis, and Z-axis are defined as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip side being the "positive side" and the base side being the "negative side". In the following description, the positive side of the Z-axis will be referred to as "up" and the negative side of the Z-axis as "down". Furthermore, both directions parallel to the X-axis will be referred to as the X-axis direction, both directions parallel to the Y-axis as the Y-axis direction, and both directions parallel to the Z-axis as the Z-axis direction.

[0014] The manufacturing method for metal structures shown in Figures 1 to 11 includes the binder jet method, a type of additive manufacturing method, and comprises a powder layer formation step S102 and a particle bonding step S104. The binder jet method has the advantage that it does not require a support structure to support the structure, making it possible to manufacture additively manufactured structures with complex shapes.

[0015] In the powder layer formation process S102, the additive manufacturing powder 1 (metal powder) is leveled with a squeegee roller 24 to form a powder layer 31. The additive manufacturing powder 1 has an average circularity of 0.80 or more and less than 1.00, and a specific surface area of ​​0.30 m². 2 Metal powder is used that is less than or equal to / g, has a particle size D50 of 1.0 μm to 10.0 μm, and a particle size D90 of 11.0 μm to 25.0 μm. Particle size D50 refers to the particle size at which the cumulative frequency from the smallest diameter side accounts for 50% of the volume-based cumulative particle size distribution of the additive manufacturing powder 1 obtained using a laser diffraction particle size distribution analyzer. Particle size D90 refers to the particle size at which the cumulative frequency from the smallest diameter side accounts for 90% of the cumulative particle size distribution. In addition, the rotation speed of the squeegee roller 24 is set to 0 rpm to 50 rpm, and the movement speed of the squeegee roller 24 is set to 1 mm / s to 25 mm / s.

[0016] Furthermore, the particle bonding step S104 includes a binder solution supply step S112 and a sintering step S114. In the binder solution supply step S112, the binder solution 4 is supplied to a predetermined area of ​​the powder layer 31 to bond the particles in the powder layer 31 together and obtain a bonding layer 41. By repeating the powder layer formation step S102 and the binder solution supply step S112 one or more times, the powder-molded body 6 shown in Figure 10 is obtained. In the sintering step S114, the particles of the additive manufacturing powder 1 contained in the powder-molded body 6 are sintered (bonded) together.

[0017] With this configuration, the powder layer 31 can be sufficiently densified, thereby increasing the density and homogenization of the powder-formed body 6. As a result, when sintering the powder-formed body 6 using the sintering of particles in the powder layer 31, the shrinkage rate can be suppressed and the amount of shrinkage can be made uniform. As a result, a metal-formed body 10 is obtained that consists of a sintered layer with high density and dimensional accuracy and homogeneity. The following describes each process in order.

[0018] In the method for manufacturing a metal molded body according to the first embodiment, the powder molded body 6 is produced by the binder jet method. However, the method for manufacturing a metal molded body according to the present invention may include a step for producing the powder molded body 6 by a method other than the binder jet method. An example of a method other than the binder jet method is fused deposition modeling (FDM). In this case, since a filament containing metal powder and binder is used, the powder layer formation step S102 and the binder solution supply step S112 described above can be performed in a single step.

[0019] 1.1.1. Additive Manufacturing Equipment First, we will describe the additive manufacturing apparatus 2 used in the production of the powder-based molded body 6 by the binder jet method.

[0020] As shown in Figures 2 to 10, the additive manufacturing apparatus 2 comprises a main body 21 having a powder storage section 211 and a molding section 212, a powder supply elevator 22 provided in the powder storage section 211, a molding stage 23 provided in the molding section 212, and a squeegee roller 24 and a liquid supply section 26 that are movably provided on the main body 21.

[0021] The powder storage section 211 is a recess provided in the main body 21 of the apparatus, with an open top. The additive manufacturing powder 1 is stored in this powder storage section 211. 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 squeegee roller 24. The additive manufacturing powder 1 is a metal powder whose average circularity, specific surface area, particle size D50, and particle size D90 are within the aforementioned ranges.

[0022] A powder supply elevator 22 is located at the bottom of the powder storage section 211. The powder supply elevator 22 is movable vertically while loaded with additive manufacturing powder 1. By moving the powder supply elevator 22 upward, the additive manufacturing powder 1 placed on the powder supply elevator 22 is pushed up and spills out of the powder storage section 211. This allows the spilled additive manufacturing powder 1 to be moved towards the manufacturing section 212.

[0023] The molding section 212 is a recess provided in the main body 21 of the apparatus, with an open top. A molding stage 23 is located inside the molding section 212. Layers of additive manufacturing powder 1 are laid on the molding stage 23 by a squeegee roller 24. The molding stage 23 is also movable vertically while the additive manufacturing powder 1 is laid on it. The amount of additive manufacturing powder 1 laid on the molding stage 23 can be adjusted by setting the height of the molding stage 23 as appropriate.

[0024] As shown in Figures 3 and 4, the squeegee roller 24 is movable in the X-axis direction from the powder storage section 211 to the molding section 212. The squeegee roller 24 can level, layer, and compress the additive manufacturing powder 1 by dragging it.

[0025] The liquid supply unit 26 is composed of, for example, an inkjet head or a dispenser, and is movable in the X-axis and Y-axis directions within the molding unit 212. The liquid supply unit 26 can supply a desired amount of binder solution 4 to the desired position. The liquid supply unit 26 may have multiple discharge nozzles on a single head. The binder solution 4 may be discharged simultaneously or with a time delay from the multiple discharge nozzles.

[0026] 1.1.2. Powder layer formation process Next, the powder layer formation process S102 using the additive manufacturing apparatus 2 will be described. In the powder layer formation process S102, the additive manufacturing powder 1 is laid on the manufacturing stage 23 to form a powder layer 31. Specifically, as shown in Figures 2 and 3, a squeegee roller 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 Figure 4. At this time, the thickness of the powder layer 31 can be adjusted by lowering the upper surface of the manufacturing stage 23 below the upper end of the manufacturing section 212 and by adjusting the amount of lowering. The additive manufacturing powder 1 is a powder with excellent packing properties when leveled, as will be described later. Therefore, a powder layer 31 with a high packing rate can be obtained.

[0027] The rotation speed of the squeegee roller 24 is set to 0 rpm or more and 50 rpm or less, and the movement speed of the squeegee roller 24 is set to 1 mm / s or more and 25 mm / s or less. By using a metal powder having the aforementioned characteristics as the additive manufacturing powder 1, and by setting the rotation speed and movement speed of the squeegee roller 24 within the above range, the formed powder layer 31 can be sufficiently densified. As a result, the powder-formed body 6 formed in the particle bonding step S104 described later can be made higher in density and more homogenized.

[0028] Furthermore, if the rotation speed of the squeegee roller 24 exceeds the upper limit, when the additive manufacturing powder 1 separates from the squeegee roller 24 after being crushed by the rotating squeegee roller 24, the additive manufacturing powder 1 will fall from a higher position. As a result, the density of the formed powder layer 31 is more likely to vary, and the uniformity of the density and thickness of the powder layer 31 decreases.

[0029] Furthermore, the rotational speed of the squeegee roller 24 is preferably 0 rpm or more and 40 rpm or less, and more preferably 0 rpm or more and 20 rpm or less.

[0030] Furthermore, if the movement speed of the squeegee roller 24 falls below the lower limit, the efficiency of powder layer 31 formation decreases. On the other hand, if the movement speed of the squeegee roller 24 exceeds the upper limit, the squeegee roller 24 is more likely to ride up onto the accumulated additive manufacturing powder 1. As a result, the effect of leveling the additive manufacturing powder 1 by the squeegee roller 24 is reduced. This reduces the uniformity of the density and thickness of the powder layer 31.

[0031] Furthermore, the travel speed of the squeegee roller 24 is preferably 5 mm / s or more and 25 mm / s or less, and more preferably 10 mm / s or more and 20 mm / s or less.

[0032] The outer diameter of the squeegee roller 24 is not particularly limited, but is preferably 10 mm or more and 100 mm or less, and more preferably 20 mm or more and 80 mm or less.

[0033] Furthermore, in forming the powder layer 31, other powders may be used in combination with the additive manufacturing powder 1. This allows for a higher density of the powder layer 31. Examples of other powders include ceramic powders. Examples of constituent materials for ceramic powders include oxide-based ceramics such as aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, iron oxide, potassium oxide, sodium oxide, calcium oxide, chromium oxide, and niobium oxide, as well as nitride-based ceramics such as boron nitride and silicon nitride, and silicon carbide. One or more of these may be used.

[0034] Next, the powder layer 31 is compressed in the thickness direction by the squeegee roller 24, and the squeegee roller 24 is moved in the X-axis direction as shown in Figure 3. This increases the filling density of the additive manufacturing powder 1 in the powder layer 31. The compression by the squeegee roller 24 may be performed as needed and may be omitted. Alternatively, the powder layer 31 may be compressed by means other than the squeegee roller 24, such as a pressing plate.

[0035] 1.1.3.Particle bonding process The particle bonding step S104 includes the binder solution supply step S112 and the sintering step S114.

[0036] 1.1.3.1. Binder Solution Supply Process In the binder solution supply step S112, as shown in Figure 5, the liquid supply unit 26 supplies the binder solution 4 to the formation region 60 of the powder layer 31 that corresponds to the powder body 6 to be fabricated. The binder solution 4 contains a binder and a solvent. In the formation region 60 to which the binder solution 4 is supplied, the particles of the additive manufacturing powder 1 bind together, and a binding layer 41 is obtained as shown in Figure 6. In the binding layer 41, the particles of the additive manufacturing powder 1 are bound together by the binder and have enough shape retention to prevent them from breaking under their own weight.

[0037] Furthermore, the binding layer 41 may be heated simultaneously with or after the supply of the binder solution 4. This promotes the volatilization of the solvent and dispersion medium contained in the binder solution 4, and also promotes the binding of particles by solidification or hardening of the binder. If the binder contains a photocurable resin or an ultraviolet curable resin, light irradiation or ultraviolet irradiation may be performed instead of heating, or in conjunction with heating.

[0038] The heating temperature is not particularly limited, but is preferably between 50°C and 250°C, and more preferably between 70°C and 200°C. This allows sufficient heat to be supplied to the binder layer 41, and the volatilization of the solvent and dispersion medium can be sufficiently promoted.

[0039] Binder solution 4 may contain other solvents along with the solvent. Examples of solvents include alcohols, ketones, carboxylic acid esters, etc., and at least one of these is used. Examples of binders contained in binder solution 4 include fatty acids, paraffin wax, microwax, 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, phenolic resins, etc.

[0040] The binder solution 4 preferably contains polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) and water. This gives the binder solution 4 appropriate affinity and viscosity to the additive manufacturing powder 1, as well as good binding properties. For this reason, such a binder solution 4 contributes to the production of powder-molded bodies 6 with particularly good density and surface accuracy.

[0041] The binder concentration in the binder solution 4 is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 1.0% by mass or more and 15.0% by mass or less, and even more preferably 5.0% by mass or more and 12.0% by mass or less. This optimizes the viscosity of the binder solution 4 and ensures sufficient binding force between the particles of the additive manufacturing powder 1.

[0042] In addition to the components listed above, the binder solution 4 may also contain additives. Examples of additives include surfactants, stabilizers, thickeners, defoamers, and humectants. The total content of additives in the binder solution 4 is preferably 20.0% by mass or less, and more preferably 1.0% by mass or more and 15.0% by mass or less.

[0043] If it is necessary to stack multiple binding layers 41, the powder layer formation step S102 and the binder solution supply step S112 are repeated one or more times until the desired shape is achieved. In other words, these steps are performed a total of two or more times. This makes it possible to form a three-dimensional powder-molded body 6 as shown in Figure 10 without using a support structure.

[0044] Specifically, as shown in Figure 7, a new powder layer 31 is formed on top of the binding layer 41. Next, as shown in Figure 8, a binder solution 4 is supplied to the formation region 60 of the newly formed powder layer 31. This yields the second binding layer 41 shown in Figure 9. By repeating these operations, a three-dimensional powder molded body 6 can be formed.

[0045] Furthermore, any additive manufacturing powder 1 from the powder layer 31 that did not form the binding layer 41 is recovered and reused as needed, i.e., used again to form the powder-molded body 6.

[0046] 1.1.3.2. Sintering Process In the sintering process S114, the binding layer 41 is removed from the powder layer 31 to obtain the powder-formed body 6 shown in Figure 10. Next, the powder-formed body 6 is subjected to a sintering process to obtain the metal-formed body 10 shown in Figure 11. In the sintering process, the powder-formed body 6 is heated to induce a sintering reaction.

[0047] The sintering temperature varies depending on the constituent materials and particle size of the additive manufacturing powder 1, but as an example, it is preferably 980°C to 1330°C, and more preferably 1050°C to 1260°C. The sintering time is preferably 0.2 hours to 7 hours, and more preferably 1 hour to 6 hours.

[0048] The atmosphere used for the sintering process can 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 atmospheric pressure (100 kPa), but it is preferably 10 kPa or less, and more preferably 1 kPa or less.

[0049] Furthermore, when the sintering process performed under the above conditions is referred to as "main sintering," the powder-molded body 6 may be subjected to a pre-treatment equivalent to main sintering, such as "pre-sintering" or "degreasing," as needed. This makes it possible to remove at least a portion of the binder contained in the powder-molded body 6 or to induce a sintering reaction in a portion of it. This makes it possible to suppress unintended deformations, etc., when performing main sintering.

[0050] The temperature for pre-sintering and degreasing is not particularly limited as long as it is a temperature that does not cause the metal powder to complete sintering, but it is preferably between 100°C and 500°C, and more preferably between 150°C and 300°C. The time for pre-sintering and degreasing is preferably 5 minutes or more, more preferably between 10 minutes and 120 minutes, and even more preferably between 20 minutes and 60 minutes, within the aforementioned temperature range. Examples of the atmosphere for pre-sintering and degreasing include an air atmosphere, an inert atmosphere such as nitrogen or argon, or a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres.

[0051] The metal molded body 10 obtained as described above can be used as a material to constitute all or part of, for example, parts for transportation equipment such as automobile parts, bicycle parts, railway vehicle parts, ship parts, aircraft parts, and space transport vehicle parts; parts for electronic equipment such as personal computer parts, mobile phone terminal parts, tablet terminal parts, and wearable terminal parts; parts for electrical equipment such as refrigerators, washing machines, and air conditioners; parts for machinery such as machine tools and semiconductor manufacturing equipment; parts for plants such as nuclear power plants, thermal power plants, hydroelectric power plants, oil refineries, and chemical complexes; parts for watches; and decorative items such as metal tableware, jewelry, and eyeglass frames.

[0052] 1.1.4. Characteristics of powder-based and metal-based fabricated bodies From the viewpoint of shape accuracy, it is preferable that the powder-formed body 6 and the metal-formed body 10 described above satisfy the following characteristics.

[0053] First, in the binder solution supply step S112, a powder-formed body 6 having a rectangular parallelepiped shape with a length of 35 mm, a width of 25 mm, and a thickness of 2 mm is formed.

[0054] Next, in the sintering process S114, the powder-formed body 6 is subjected to a sintering treatment to obtain a metal-formed body 10.

[0055] Next, the length, width, and thickness of the metal molded body 10 are measured. Subsequently, the shrinkage rate of the length of the metal molded body 10 relative to the length of the powder molded body 6 is calculated. Similarly, the shrinkage rates of the width and thickness of the metal molded body 10 are calculated.

[0056] In the manufacturing method of the metal molded body according to this embodiment, it is preferable that the shrinkage rate of length αL, the shrinkage rate of width αW, and the shrinkage rate of thickness αt calculated as described above are all 20% or less.

[0057] Furthermore, ALW is defined as the average value of the length shrinkage rate αL and the width shrinkage rate αW. In this case, the ratio of the average value ALW to the thickness shrinkage rate αt, ALW / αt, is preferably 0.85 or more and 1.00 or less.

[0058] By satisfying this range for the ratio ALW / αt, a manufacturing method can be realized that exhibits low shrinkage and isotropic shrinkage. This enables the production of a highly dimensionally accurate and homogeneous metal molded body 10.

[0059] 1.2. Powder for additive manufacturing Next, we will describe the additive manufacturing powder 1.

[0060] 1.2.1. Constituent Materials The additive manufacturing powder 1 contains an Fe-based metal material. The Fe-based metal material refers to a metal material in which the Fe content exceeds 50% by atomic ratio. By using the Fe-based metal material, a powder-molded body 6 with a high Fe content can be obtained. Such a powder-molded body 6 can be, for example, sintered to become a metal-molded body 10 with excellent mechanical strength and corrosion resistance derived from Fe.

[0061] Examples of Fe-based metal materials include stainless steels such as austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation-hardening 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.

[0062] Of these, stainless steel is preferably used as the Fe-based metal material. Stainless steel is a type of steel with excellent mechanical strength and corrosion resistance. Therefore, by using additive manufacturing powder 1 made of stainless steel, it is possible to efficiently manufacture metal molded bodies 10 with excellent mechanical strength and corrosion resistance and high shape accuracy.

[0063] Furthermore, among stainless steels, precipitation-hardening stainless steel is particularly preferred. Precipitation-hardening stainless steel has excellent mechanical strength and toughness due to the formation of precipitates.

[0064] Examples of austenitic stainless steels 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, SUSXM15J1, and others.

[0065] Examples of ferritic stainless steels include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.

[0066] Examples of martensitic stainless steels include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.

[0067] Examples of precipitation-hardening stainless steels include SUS630 (17-4PH) and SUS631 (17-7PH).

[0068] Examples of austenitic-ferritic (duplex) stainless steels include SUS329J1, SUS329J3L, and SUS329J4L.

[0069] The symbols above are material symbols based on JIS standards. In this specification, types of stainless steel are distinguished by these material symbols.

[0070] Furthermore, the additive manufacturing powder 1 may be provided with a coating that covers the surface of core particles made of Fe-based metal material. This coating is provided for purposes such as improving the fluidity and packing properties of the additive manufacturing powder 1, or improving the affinity between the additive manufacturing powder 1 and the binder. Examples of materials that make up the coating include organic materials such as resins, inorganic materials such as ceramics and glass, and compounds derived from coupling agents.

[0071] 1.2.2. Various properties of powders for additive manufacturing Next, we will describe the various properties of the additive manufacturing powder 1. Note that all of the following properties are measured with the additive manufacturing powder 1 without the aforementioned coating.

[0072] 1.2.2.1. Particle size distribution In this embodiment, when the particle size distribution is obtained on a volume basis using a laser diffraction particle size distribution analyzer for the additive manufacturing powder 1, the particle size when the cumulative frequency is 10% from the smallest diameter side is defined as D10. Similarly, the particle sizes when the cumulative frequency is 50% and 90% from the smallest diameter side are defined as D50 and D90, respectively. An example of a particle size distribution analyzer is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0073] The particle size D50 of the additive manufacturing powder 1 is 1.0 μm or more and 10.0 μm or less, preferably 3.0 μm or more and 10.0 μm or less, and more preferably 4.0 μm or more and 9.0 μm or less. This improves both the fluidity and packing properties of the additive manufacturing powder 1. As a result, a dense powder layer 31 can be formed, making it possible to obtain a dense powder-molded body 6 with high molding accuracy. Finally, a high-density metal molded body 10 with high surface accuracy can be manufactured using this.

[0074] Furthermore, if the particle size D50 falls below the lower limit, the particles of the additive manufacturing powder 1 tend to aggregate. As a result, the fluidity and packing properties of the additive manufacturing powder 1 decrease, and the density of the powder layer 31 decreases. On the other hand, if the particle size D50 exceeds the upper limit, the gaps between the particles of the additive manufacturing powder 1 become larger, and the density of the powder layer 31 decreases.

[0075] The particle size D90 of the additive manufacturing powder 1 is 11.0 μm or more and 25.0 μm or less, preferably 13.0 μm or more and 24.0 μm or less, and more preferably 15.0 μm or more and 23.0 μm or less. This improves both the fluidity and packing properties of the additive manufacturing powder 1. As a result, a dense powder-molded body 6 with high molding accuracy can be obtained. Then, using this, a high-density metal molded body with high surface accuracy can be manufactured.

[0076] Furthermore, if the particle size D90 falls below the lower limit, it becomes necessary to narrow the particle size distribution, which increases the difficulty of manufacturing the additive manufacturing powder 1 and leads to an increase in manufacturing costs. On the other hand, if the particle size D90 exceeds the upper limit, the gaps between particles in the additive manufacturing powder 1 become larger, and the density of the powder layer 31 decreases.

[0077] The ratio of particle size D10 to particle size D50, D10 / D50, is preferably 0.30 to 0.70, more preferably 0.35 to 0.60, and even more preferably 0.40 to 0.55. This optimizes the particle size distribution of the additive manufacturing powder 1, making it easier to improve fluidity and packing efficiency. It also ensures the sinterability of the powder-molded body 6. If the ratio D10 / D50 falls below the lower limit, the particle size distribution will broaden, which may reduce fluidity. On the other hand, if the ratio D10 / D50 exceeds the upper limit, the particle size distribution will be too narrow, making it difficult to increase the packing efficiency, which may reduce sinterability.

[0078] The ratio of particle size D90 to particle size D50, D90 / D50, is preferably 1.70 to 3.00, more preferably 2.10 to 2.90, and even more preferably 2.30 to 2.80. This optimizes the particle size distribution of the additive manufacturing powder 1, making it easier to improve fluidity and packing efficiency. It also ensures the sinterability of the powder-formed body 6. If the ratio D90 / D50 falls below the lower limit, the particle size distribution will narrow, making it difficult to increase the packing efficiency and potentially reducing sinterability. On the other hand, if the ratio D90 / D50 exceeds the upper limit, the particle size distribution will widen, potentially reducing fluidity.

[0079] The particle size difference D90-D10 between particle size D90 and particle size D10 is preferably 8.0 μm to 24.0 μm, more preferably 12.0 μm to 22.0 μm, and even more preferably 14.0 μm to 20.0 μm. This results in a sufficiently narrow particle size distribution of the additive manufacturing powder 1, providing high fluidity. As a result, the packing efficiency of the additive manufacturing powder 1 is improved, making it possible to obtain a dense powder-molded body 6 with high molding accuracy.

[0080] Furthermore, 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 packing density and potentially reducing sinterability. This may result in a decrease in the density and surface accuracy of the manufactured metal object 10. 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 becomes wider, potentially reducing fluidity. This may also result in a decrease in the density and surface accuracy of the manufactured metal object 10.

[0081] 1.2.2.2.Specific surface area The specific surface area of ​​additive manufacturing powder 1 is 0.30 m². 2 It is less than or equal to / g, preferably 0.10[m 2 / g] or more 0.25[m 2 [g] or less, more preferably 0.15[m 2 / g] or more 0.22[m 2The specific surface area is less than or equal to [ / g]. If the specific surface area is within the above range, the fluidity and packing properties of the additive manufacturing powder 1 can be improved, and a dense powder layer 31 can be obtained. This results in a dense powder-molded body 6 with high molding accuracy. Furthermore, the sinterability of the powder-molded body 6 can also be ensured.

[0082] Furthermore, if the specific surface area falls below the lower limit, the manufacturing difficulty of the additive manufacturing powder 1 may increase. On the other hand, if the specific surface area exceeds the upper limit, the fluidity and packing properties of the additive manufacturing powder 1 will decrease.

[0083] The specific surface area of ​​additive manufacturing powder 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 Mountec Co., Ltd., with a sample quantity of 5g.

[0084] 1.2.2.3. Mean Circularity The average circularity of the additive manufacturing powder 1 is 0.80 or more and less than 1.00, preferably 0.82 or more and 0.95 or less, and more preferably 0.84 or more and 0.92 or less. This allows the particles to roll easily even if the particle size of the additive manufacturing powder 1 is small, and the packing state can be brought closer to close packing. As a result, the fluidity and packing properties of the additive manufacturing powder 1 can be particularly improved. In addition, since the surface energy is optimized, it is possible to manufacture metal molded bodies with high density and high surface accuracy in the end.

[0085] Furthermore, if the average circularity falls below the lower limit, the fluidity and filling rate of the additive manufacturing powder 1 will decrease. On the other hand, if the average circularity exceeds the upper limit, the manufacturing difficulty will increase, and the manufacturing efficiency of the additive manufacturing powder 1 will decrease.

[0086] The average circularity of the additive manufacturing powder 1 is measured as follows: First, an image (secondary electron image) of the powder 1 for additive manufacturing is captured with 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. Note that the imaging magnification is adjusted so that 50 to 100 particles are captured in one image. Then, a plurality of images are acquired so that a total of 300 or more particle images can be obtained.

[0087] Next, using the software, the circularity of 300 or more particle images is calculated. 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 is obtained by the following formula. e = 4πS / L 2

[0088] Next, the average value of the calculated circularity is obtained. The obtained average value becomes the average circularity of the powder 1 for additive manufacturing.

[0089] 1.2.2.4. Bulk Density and Tap Density The bulk density of the powder 1 for additive manufacturing is preferably 2.50 g / cm 3 or more and 3.50 g / cm 3 or less, more preferably 2.70 g / cm 3 or more and 3.40 g / cm 3 or less, and even more preferably 2.90 g / cm 3 or more and 3.30 g / cm 3 or less. If the bulk density is within the above range, good filling properties can be ensured even in the natural state. As a result, when the powder layer 31 is formed using the powder 1 for additive manufacturing, a powder layer 31 with a high filling rate can be formed. As a result, a dense and highly shaped powder compact 6 can be obtained.

[0090] The bulk density of the additive manufacturing powder 1 is measured in accordance with the apparent density measurement method for metal powders specified in JIS Z 2504:2012. For measuring bulk density, the Powder Tester® PT-X powder property evaluation device manufactured by Hosokawa Micron Corporation is preferably used. Prior to measuring bulk density, it is preferable to leave the additive manufacturing powder 1 to be measured in an environment with a temperature of 25°C and a relative humidity of 50% for at least one hour.

[0091] The tap density of additive manufacturing powder 1 is 4.20 g / cm³. 3 More than 4.90g / cm 3 Preferably, it is 4.30 g / cm³ 3 More than 4.80g / cm 3 It is more preferable that it be 4.40 g / cm³ 3 More than 4.70g / cm 3 It is even more preferable that the following conditions are met: 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 molding stage 23 or compressed on the squeegee roller 24. This makes it possible to obtain a dense powder-molded body 6 with high molding accuracy.

[0092] The tap density of additive manufacturing powder 1 is measured using a powder property evaluation device, Powder Tester® PT-X, manufactured by Hosokawa Micron Corporation. Prior to measuring the tap density, it is preferable to leave the additive manufacturing powder 1 to be measured in an environment with a temperature of 25°C and a relative humidity of 50% for at least one hour.

[0093] Furthermore, the ratio of tap density to bulk density of the additive manufacturing powder 1 is preferably 1.20 or more and 1.75 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 density between the additive manufacturing powder 1 in its natural state and the additive manufacturing powder 1 after vibration, load, etc., has been applied can be reduced. As a result, the fluidity and packing properties of the additive manufacturing powder 1 can be improved, and deformation of the powder layer 31 and the powder-molded body 6 due to differences in packing density can be suppressed.

[0094] While this ratio may fall below the aforementioned lower limit, it may become more difficult to stably manufacture the additive manufacturing powder 1. On the other hand, if this ratio exceeds the aforementioned upper limit, the difference in filling density will increase, which may lead to deformation of the powder-molded body 6.

[0095] 1.3. Method for manufacturing powder for additive manufacturing Next, an example of a method for manufacturing additive manufacturing powder 1 will be described.

[0096] The additive manufacturing powder 1 may be manufactured by any method, for example, by atomization. In atomization, molten metal is allowed to flow from a crucible and collide with a fluid such as a liquid or gas that is ejected at high speed. As the molten metal collides with the fluid, it falls by inertia, and the droplets become spherical. As a result, it is possible to manufacture metal powders that have a relatively small diameter but a high average circularity and a relatively small specific surface area. Furthermore, by reducing the specific surface area, the water content can be reduced.

[0097] Atomization methods include water atomization, gas atomization, and rotary water flow atomization, depending on the type of coolant and the configuration of the equipment.

[0098] The flow rate of molten metal varies depending on the size of the apparatus, but it is preferably between 1.0 kg / min and 20.0 kg / min, and more preferably between 2.0 kg / min and 10.0 kg / min. This allows for the optimization of the amount of molten metal flowing in a given time, enabling the efficient production of metal powder with a narrow particle size distribution and sufficient spherical shape. As a result, it is possible to produce metal powder with a relatively small diameter, high average circularity, and a relatively small specific surface area. Furthermore, reducing the specific surface area reduces the moisture content.

[0099] The temperature of the molten metal in the crucible (casting temperature) is preferably set to Tm+100°C to Tm+350°C, more preferably to Tm+180°C to Tm+320°C, and even more preferably to Tm+250°C to Tm+300°C, relative to the melting point Tm[°C] of the constituent material of the additive manufacturing powder 1. This allows the molten metal to exist for a longer period than conventional methods when it is atomized and solidified by various atomization methods. As a result, it is possible to manufacture metal powders with a high average circularity and a relatively small specific surface area, even at small diameters.

[0100] Furthermore, in various atomization methods, the outer diameter of the narrow stream when molten metal is flowed 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, so that droplets of an appropriate size are easily dispersed uniformly. 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.

[0101] Furthermore, in the water atomization method, water is sprayed at high speed in an inverted cone shape, and molten metal is made to collide with the area near the apex. As a result, a negative pressure is created near the collision point by the water film, which makes the molten metal finer. In addition, oxidation of the molten metal is suppressed, and even if the metal powder produced is fine, it can be made spherical. For this reason, it is preferable to use water atomized powder (powder produced by the water atomization method) as the additive manufacturing powder 1. The negative pressure near the impact point is preferably between 10 kPa and 150 kPa, and more preferably between 30 kPa and 120 kPa. This allows for the efficient production of metal powder with optimized particle size and circularity. Furthermore, increasing the negative pressure within this range tends to promote finer and more spherical particles.

[0102] Furthermore, the apex angle of the injected water (the angle formed inside the apex of the inverted cone) can further reduce the pressure near the impact point formed by the water film, and also increase the time it takes for the flowing molten metal to reach the impact point. This allows for sufficient spheroidization even if the metal powder produced is fine. The apex angle of the injected water is preferably 3° to 15°, and more preferably 5° to 10°. Within this range, reducing the apex angle tends to promote finer particle size and spheroidization.

[0103] Furthermore, the manufactured additive manufacturing powder may be classified as needed. Examples of classification methods include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0104] Furthermore, the particle surface of the manufactured additive manufacturing powder may be subjected to a surface treatment. Examples of surface treatments include coupling agent treatment.

[0105] 1.4. Metal objects Next, a description of a metal molded body according to an embodiment will be given.

[0106] The metal molded body produced by the above-described method is formed by leveling metal powder that satisfies predetermined conditions under predetermined conditions, and in the powder layer, sintered material of the particles is stacked in the stacking direction, resulting in high density, dimensional accuracy, and homogeneity. Specifically, the metal molded body according to the embodiment satisfies the following characteristics.

[0107] Figure 12 is a schematic diagram showing 10 analysis ranges AN1 to AN10 set in the cross-section SE obtained when the metal molded body 10 according to the embodiment is cut by a plane containing the normal to the powder layer 31. In Figure 12, the cross-section SE of the metal molded body 10 extends from the surface SU toward the depth D. In Figure 12, voids PO that are inevitably formed in the sintered material, which occupies most of the area, are schematically illustrated.

[0108] The analysis range AN1 shown in Figure 12 is a rectangular region set in the cross-section SE, with a width of 10 μm in the direction of the normal extension and a length of 700 μm in the direction perpendicular to the normal, and is the region located closest to the surface SU. Note that analysis range AN1 is set in a position close to the surface SU. Analysis ranges AN2 to AN10 are the same size as analysis range AN1 and are regions arranged sequentially in the depth direction D, starting from a position adjacent to analysis range AN1.

[0109] Next, the area occupied by the sintered material is calculated for each of the analysis ranges AN1 to AN10. The area occupied ratio is then calculated from the calculated area. The area occupied by the sintered material is obtained by subtracting the area of ​​the voids PO from the area of ​​each of the analysis ranges AN1 to AN10. The area occupied ratio of the sintered material is the percentage [%] of the area occupied by the sintered material relative to the area of ​​the analysis ranges AN1 to AN10.

[0110] Next, the calculation R is obtained by performing the following calculation using the formula below for adjacent analysis ranges. Calculation result R = |(Ratio of the occupied area of ​​sintered material in adjacent analysis ranges) - 1|

[0111] In the above, "the ratio of the occupied area of ​​sintered material in adjacent analysis ranges" refers to the ratio obtained by dividing the occupied area of ​​sintered material in the analysis range closer to the surface SU by the occupied area of ​​sintered material in the analysis range further from the surface SU. For example, when calculating the result R for analysis ranges AN1 and AN2, it is the quotient obtained by dividing the occupied area of ​​sintered material in analysis range AN1 by the occupied area of ​​sintered material in analysis range AN2.

[0112] As described above, the area occupancy ratio of the sintered material in the analysis range AN1 to AN10, and the calculated result R obtained from the analysis range AN1 to AN10 can be obtained. There are 10 data points for the area occupancy ratio and 9 data points for the calculated result R.

[0113] The metal molded body 10 according to this embodiment satisfies the following two elements (a) and (b). (a) All 10 occupied areas have an area ratio of 90.0% or higher. (b) The average value of the nine calculation results R is 0.050 or less.

[0114] A metal molded body 10 that satisfies the above characteristics has high density and dimensional accuracy, and is homogeneous.

[0115] In particular, element (a) indicates that the occupancy rate of voids PO is sufficiently low and the density is high in all analytical ranges AN1 to AN10 set in cross-section SE. Since cross-section SE reflects the cross-section of the powder-formed object obtained by stacking powder layers 31 before the metal molded object 10 is sintered, element (a) can be said to be a characteristic that reflects the high density of the powder-formed object.

[0116] The numerical range of element (a) is preferably 91.0% or higher. Furthermore, if at least one of the area occupancy ratios falls below the lower limit of the numerical range of element (a), the density of the metal molded body 10 decreases. This leads to a decrease in the mechanical strength of the metal molded body 10, among other things.

[0117] Furthermore, element (b) indicates that the difference in the occupied area of ​​the sintered material between adjacent analysis ranges is sufficiently small across the entire cross-section SE. In other words, element (b) indicates that the metal molded body 10 is homogeneous and that the deformation due to the difference in shrinkage rate between analysis ranges is small, resulting in high dimensional accuracy.

[0118] The numerical range of element (b) is preferably 0.040 or less, and more preferably 0.030 or less.

[0119] Furthermore, if the average value of the calculation result R exceeds the upper limit of the numerical range of element (b), at least one of the dimensional accuracy and homogeneity of the metal molded body 10 will decrease. Furthermore, the metal molded body may be composed of molten material instead of sintered material.

[0120] 2. Second Embodiment Next, a method for manufacturing a metal molded body according to the second embodiment will be described. Figure 13 is a process diagram illustrating the manufacturing method of a metal molded body according to the second embodiment.

[0121] The second embodiment will be described below, focusing on the differences from the first embodiment, and similar matters will be omitted from the description. In Figure 13, components similar to those in Figure 1 are denoted by the same reference numerals.

[0122] The manufacturing method for a metal object shown in Figure 13 includes a powder bed fusion method, which is a type of additive manufacturing method, and comprises a powder layer formation step S102 and a particle bonding step S104. Of these, the particle bonding step S104 includes an energy ray irradiation step S116. In the energy ray irradiation step S116, an energy ray is irradiated onto a predetermined area of ​​the powder layer 31 to melt the particles of the additive manufacturing powder 1 (metal powder), thereby forming a molten layer in the predetermined area. After that, the molten layer is removed from the powder layer 31 to obtain a metal object 10. Examples of energy rays include laser light and electron beams.

[0123] With this configuration, a metal molded body 10 can be obtained by utilizing the melting of particles to obtain a molten layer that is homogeneous, has high density and dimensional accuracy. In the second embodiment described above, the same effects as in the first embodiment can be obtained.

[0124] 3. Effects achieved by the above embodiment As described above, the method for manufacturing a metal molded body according to the embodiment is a method for manufacturing a metal molded body 10 by bonding together the particles of additive manufacturing powder 1 (metal powder) contained in the powder layer 31, and comprises a powder layer formation step S102 and a particle bonding step S104.

[0125] In the powder layer formation process S102, the average circularity is 0.80 or more and less than 1.00, and the specific surface area is 0.30 m². 2A powder for additive manufacturing 1, which is less than or equal to / g, has a particle size D50 of 1.0 μm or more and a particle size D90 of 11.0 μm or more and 25.0 μm or less, is leveled with a squeegee roller 24 to form a powder layer 31. The rotation speed of the squeegee roller 24 is set to 0 rpm or more and 50 rpm or less, and the movement speed of the squeegee roller 24 is set to 1 mm / s or more and 25 mm / s or less. In the particle bonding step S104, the particles in the powder layer 31 are bonded together. Particle size D50 is the particle size at which the cumulative frequency from the smallest diameter side is 50% in the volume-based cumulative particle size distribution obtained using a laser diffraction particle size distribution analyzer. Particle size D90 is the particle size at which the cumulative frequency from the smallest diameter side is 90% in the cumulative particle size distribution.

[0126] With this configuration, a homogeneous metal molded body 10 with high density and dimensional accuracy can be manufactured efficiently.

[0127] In the method for manufacturing a metal molded body according to the above embodiment, the particle bonding step S104 preferably includes a binder solution supply step S112 and a sintering step S114. In the binder solution supply step S112, a binder layer 41 is formed in a formation region 60 (predetermined region) by supplying droplets of binder solution 4 from a liquid supply unit 26 to a predetermined region of the powder layer 31. In the sintering step S114, the binder layer 41 is removed from the powder layer 31 to obtain a powder molded body 6, and a metal molded body 10 is obtained by sintering the particles of additive manufacturing powder 1 (metal powder) contained in the powder molded body 6.

[0128] With this configuration, a metal molded body 10 consisting of a sintered layer can be obtained by utilizing the sintering of particles.

[0129] In the method for manufacturing a metal molded body according to the above embodiment, the powder layer formation step S102 and the binder solution supply step S112 may be repeated.

[0130] With this configuration, a three-dimensional powder-molded body 6 can be formed. Therefore, a three-dimensional metal molded body 10 can be manufactured.

[0131] In the method for manufacturing a metal molded body according to the above embodiment, the binder solution 4 preferably contains polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) and water.

[0132] With this configuration, the binder solution 4 has appropriate affinity and viscosity to the additive manufacturing powder 1, as well as good binding properties, resulting in a powder-molded body 6 with particularly good density and surface accuracy.

[0133] In the method for manufacturing a metal molded body according to the above embodiment, when the shape of the powder molded body 6 is a rectangular parallelepiped with a length of 35 mm, a width of 25 mm, and a thickness of 2 mm, it is preferable that the length shrinkage rate αL, the width shrinkage rate αW, and the thickness shrinkage rate αt of the metal molded body 10 relative to the powder molded body 6 are all 20% or less, and that the ratio ALW / αt of the average value ALW of the length shrinkage rate αL and the width shrinkage rate αW relative to the thickness shrinkage rate αt is 0.85 or more and 1.00 or less.

[0134] This configuration enables a manufacturing method that results in low shrinkage and isotropic shrinkage. This makes it possible to produce a metal molded body 10 with high dimensional accuracy and uniformity.

[0135] In the method for manufacturing a metal molded body according to the above embodiment, the particle bonding step S104 may include an energy ray irradiation step S116. In the energy ray irradiation step S116, an energy ray is irradiated onto a predetermined region of the powder layer 31 to melt the particles of the additive manufacturing powder 1 (metal powder), thereby forming a molten layer in the predetermined region. After that, the molten layer is removed from the powder layer 31 to obtain the metal molded body 10.

[0136] With this configuration, a metal molded body 10 consisting of a molten layer can be obtained by utilizing the melting of particles.

[0137] In the method for manufacturing a metal molded body according to the above embodiment, the additive manufacturing powder 1 (metal powder) may be water atomized powder.

[0138] In the water atomization method, water is sprayed at high speed in an inverted cone shape, and molten metal is impacted near the apex. This creates a negative pressure near the impact point due to the water film, which makes the molten metal finer. Furthermore, oxidation of the molten metal is suppressed, allowing the additive manufacturing powder 1 to be spherical even if it is fine. As a result, additive manufacturing powder 1 with optimized particle size and circularity can be efficiently produced.

[0139] The metal molded body according to the above embodiment is a metal molded body 10 formed by the layering of molten or sintered material between particles in a powder layer 31 containing metal powder in the layering direction. Furthermore, this metal molded body 10 is cut in a plane containing the normal to the powder layer 31, and in the resulting cross section SE, a region with a width of 10 μm in the direction of extension of the normal and a length of 700 μm in the direction perpendicular to the normal is set as one analysis range, and a total of 10 analysis ranges AN1 to AN10 are set by shifting this range by 10 μm in the depth direction D. Furthermore, the occupied area and occupied area ratio of the molten or sintered material are calculated for each of the analysis ranges AN1 to AN10. In addition, a calculation is performed using the formula |(ratio of occupied areas in adjacent analysis ranges)-1| for adjacent analysis ranges to obtain the calculation result R. In this case, in the metal molded body 10, the area occupancy rate in each of the 10 analysis ranges AN1 to AN10 is 90.0% or more, and the average value of the calculation result R obtained from the 10 analysis ranges AN1 to AN10 is 0.050 or less.

[0140] With this configuration, a homogeneous metal molded body 10 with high density and dimensional accuracy can be obtained.

[0141] The method for manufacturing a metal molded body and the metal molded body according to the present invention have been described above based on the illustrated embodiments, but the present invention is not limited thereto. For example, the method for manufacturing a metal molded body according to the present invention may have additional steps for any purpose added to the above embodiments. Also, the metal molded body according to the present invention may have additional configurations added to the above embodiments. [Examples]

[0142] Next, specific embodiments of the present invention will be described. 4. Manufacturing of powder for additive manufacturing Powder for additive manufacturing of samples No. 1 to 25 was prepared using the water atomization method. The various conditions for the water atomization method are as follows:

[0143] • Outer diameter of the molten metal flowing down: 3.0 mm • Molten metal flow rate: 5.0 kg / min • Casting temperature: Tm + 270℃ • Negative pressure near the point of water collision: 50-100 kPa • Water apex angle: 5-10°

[0144] The composition of the additive manufacturing powder for each sample No. is shown in Tables 1 (Figure 14) to 5 (Figure 18). Figure 14 is Table 1, showing the steel grade of the additive manufacturing powder for each sample No. Figure 15 is Table 2, showing the composition of the additive manufacturing powder, the manufacturing method of the metal object, and the evaluation results for each sample No. Figure 16 is Table 3, showing the composition of the additive manufacturing powder, the manufacturing method of the metal object, and the evaluation results for each sample No. Figure 17 is Table 4, showing the composition of the additive manufacturing powder, the manufacturing method of the metal object, and the evaluation results for each sample No. Figure 18 is Table 5, showing the composition of the additive manufacturing powder, the manufacturing method of the metal object, and the evaluation results for each sample No.

[0145] 5. Characteristics of powders for additive manufacturing Table 1 shows the steel grades used for each additive manufacturing powder.

[0146] For each additive manufacturing powder, the representative particle size, specific surface area, average circularity, and the ratio of tap density to bulk density were measured or calculated. The measurement and calculation results are shown in Tables 2 to 5.

[0147] In Tables 2 to 5, the manufacturing methods for the metal molded bodies of each sample No. and the additive manufacturing powders used therein are designated as "Examples" if they correspond to the present invention, and as "Comparative Examples" if they do not correspond to the present invention.

[0148] 6. Evaluation of the manufacturing method for metal molded objects 6.1. Relative density of the powder layer Powder layers were formed using additive manufacturing powder and silica powder according to each sample number in an additive manufacturing apparatus. The particle size D50 of the silica powder was 10 nm. The amount of silica powder added was 0.02 parts by mass per 100 parts by mass of additive manufacturing powder.

[0149] Next, the volume and mass of the obtained powder layer were measured, and the density of the powder layer was calculated. The calculated density was then evaluated against the following evaluation criteria. The evaluation results are shown in Tables 2 to 5.

[0150] A: The density of the powder layer is 4.30 [g / cm³] 3 That's all. B: The density of the powder layer is 4.10 [g / cm³] 3 ] or more than 4.30[g / cm 3 ] is less than C: The density of the powder layer is 3.90 [g / cm³] 3 ] or more than 4.10[g / cm 3 ] is less than D: The density of the powder layer is 3.90 [g / cm³] 3 ] is less than

[0151] 6.2. Relative density of powder-based molded bodies Using the additive manufacturing powders of each sample number, rectangular prism-shaped powder bodies were fabricated using the binder jet method. The dimensions of the fabricated powder bodies were 35 mm in length, 25 mm in width, and 2 mm in thickness. A PVP aqueous solution was used as the binder solution.

[0152] Next, the volume and mass of the fabricated powder-based 3D model, as well as the particle density of the additive manufacturing powder used, were measured. A dry-type automatic densimeter capable of gas displacement measurement was used to measure the particle density. Then, the density of the powder-based 3D model was calculated from the volume and mass, and the relative density of the powder-based 3D model was calculated from the obtained density and particle density. The calculation results are shown in Tables 2 to 5.

[0153] 6.3. Relative density of metal structures First, the powder-formed body created in 6.2 was degreased and then sintered in a firing furnace. For steel type 1, the sintering conditions were 1100°C for 3 hours in an argon atmosphere. This resulted in obtaining a metal form. For steel types 2 and 3, the sintering conditions were selected according to their composition.

[0154] Next, the relative density of the metal object was calculated based on its volume and mass, as well as the particle density of the additive manufacturing powder used. The calculation results are shown in Tables 2 to 5.

[0155] 6.4. Discussion of the Evaluation Results As shown in Tables 2 to 5, it was confirmed that high-density metal molded bodies can be formed by carrying out the metal molded body manufacturing method of each embodiment.

[0156] 7. Composition of Metal Forms For metal objects manufactured using additive manufacturing powder sample No. 9 and metal objects manufactured using additive manufacturing powder sample No. 16, the length shrinkage rate αL, width shrinkage rate αW, and thickness shrinkage rate αt were calculated. In addition, the ratio of the average value ALW to the thickness shrinkage rate αt, ALW / αt, was calculated.

[0157] Furthermore, the sintered material's area ratio and its minimum value were calculated for each metal molded object within the analysis ranges AN1 to AN10.

[0158] Furthermore, the calculation result R, obtained using the aforementioned formula from the adjacent analysis ranges of each metal molded object, and its average value were calculated.

[0159] These calculation results are shown in Table 6 (Figure 19). Figure 19 is Table 6, which shows the sample numbers of the additive manufacturing powders used in the production of the metal molded bodies, the composition of the metal molded bodies, and the evaluation results of the metal molded bodies.

[0160] In Table 6, the metal object manufactured using the additive manufacturing powder of Sample No. 9 is labeled as "Example," and the metal object manufactured using the additive manufacturing powder of Sample No. 16 is labeled as "Comparative Example."

[0161] 8. Evaluation results of metal sculptures The relative density and dimensional accuracy of the metal molded bodies of the examples and comparative examples shown in Table 6 were evaluated. Relative density was measured using the method described above. Dimensional accuracy was evaluated by calculating the ratio of the deviation of the metal molded body to the target value and applying it to the following evaluation criteria.

[0162] A: High dimensional accuracy (deviation from target value is less than 1%) B: Dimensional accuracy is moderately high (deviation from target value is between 1% and 2%) C: Low dimensional accuracy (deviation from target value is 2% or more)

[0163] The metal fabricated bodies of the examples shown in Table 6 satisfy both of the aforementioned elements (a) and (b). In other words, the metal fabricated bodies of the examples have low porosity across all analysis ranges, and the variation in porosity between analysis ranges is small. Therefore, the metal fabricated bodies of the examples are more homogeneous than the metal fabricated bodies of the comparative examples. Furthermore, the metal molded bodies of the examples were found to have higher relative density and higher dimensional accuracy compared to the metal molded bodies of the comparative examples.

[0164] From the above, it has become clear that the method for manufacturing metal molded bodies according to the present invention can produce metal molded bodies with high density and dimensional accuracy and uniformity. [Explanation of symbols]

[0165] 1...Additive manufacturing powder, 2...Additive manufacturing apparatus, 4...Binder solution, 6...Powder-formed body, 10...Metal-formed body, 21...Apparatus body, 22...Powder supply elevator, 23...Formation stage, 24...Squeegee roller, 26...Liquid supply section, 31...Powder layer, 41...Binding layer, 60...Formation area, 211...Powder storage section, 212...Formation section, AN1...Analysis range, AN2...Analysis range, AN3...Analysis range, AN4...Analysis range, AN5...Analysis range, AN6...Analysis range, AN7...Analysis range, AN8...Analysis range, AN9...Analysis range, AN10...Analysis range, D...Depth direction, PO...Vacuum, S102...Powder layer formation process, S104...Particle bonding process, S112...Binder solution supply process, S114...Sintering process, S116...Energy ray irradiation process, SE...Cross section, SU...Surface

Claims

1. A method for manufacturing a metal object by bonding together metal powder particles contained in a powder layer, The average circularity is 0.80 or higher and less than 1.00, and the specific surface area is 0.30 m². ２ A powder layer formation step in which the metal powder is leveled with a squeegee roller to form the powder layer, wherein the particle size D50, where the cumulative frequency from the smallest diameter side in the volume-based cumulative particle size distribution obtained using a laser diffraction particle size distribution analyzer is 50%, is between 1.0 μm and 10.0 μm, and the particle size D90, where the cumulative frequency from the smallest diameter side in the cumulative particle size distribution is 90%, is between 11.0 μm and 25.0 μm, and the metal powder is leveled with a squeegee roller to form the powder layer, A particle bonding step for bonding the particles in the powder layer together, It has, The rotational speed of the squeegee roller is set to 0 rpm or more and 50 rpm or less. A method for manufacturing a metal molded body, characterized in that the movement speed of the squeegee roller is 1 mm / s or more and 25 mm / s or less.

2. The particle bonding step is A binder solution supply step involves supplying droplets of the binder solution to a predetermined region of the powder layer from a liquid supply unit to form a binding layer in the predetermined region, A sintering step to obtain a metal body by removing the binding layer from the powder layer and sintering the metal powder particles contained in the powder body, A method for manufacturing a metal molded body according to claim 1, including the following:

3. The method for manufacturing a metal molded body according to claim 2, wherein the powder layer formation step and the binder solution supply step are repeated.

4. The method for producing a metal molded body according to claim 2 or 3, wherein the binder solution contains polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) and water.

5. When the shape of the powder-formed body is a rectangular parallelepiped with a length of 35 mm, a width of 25 mm, and a thickness of 2 mm, The shrinkage rates of the length, width, and thickness of the metal molded body relative to the powder molded body are all 20% or less. A method for manufacturing a metal molded body according to claim 2 or 3, wherein the ratio of the average value of the shrinkage rate of the length and the shrinkage rate of the width to the shrinkage rate of the thickness is 0.85 or more and 1.00 or less.

6. The particle bonding step is Energy ray irradiation process to obtain the metal molded body: After irradiating a predetermined region of the powder layer with energy rays to melt the particles of the metal powder together and form a molten layer in the predetermined region, the molten layer is removed from the powder layer. A method for manufacturing a metal molded body according to claim 1, including the following:

7. The method for manufacturing a metal molded body according to claim 1, wherein the metal powder is a water atomized powder.

8. A metal object formed by the layering of molten or sintered material between particles in a powder layer containing metal powder in the layering direction, The powder layer is cut along a plane containing the normal to the powder layer, and in the resulting cross-section, A region with a width of 10 μm in the direction of extension of the normal and a length of 700 μm in the direction perpendicular to the normal is defined as one analysis range. By shifting the aforementioned region by 10 μm in the depth direction, a total of 10 analysis ranges are set. In each of the aforementioned analysis ranges, the occupied area and occupied area ratio of the molten material or sintered material are calculated. When a calculation is performed using the formula |(ratio of the occupied area in the adjacent analysis ranges)-1| in the adjacent analysis ranges and a calculation result is obtained, A metal molded body characterized in that the area ratio in each of the ten analysis ranges is 90.0% or more, and the average value of the calculation results obtained from the ten analysis ranges is 0.050 or less.

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