Method of manufacturing formed body and method of manufacturing metal sintered body

Abstract

To provide a method of manufacturing a formed body allowing for efficiently manufacturing a formed body having high surface accuracy and a method of manufacturing a metal sintered body allowing for efficiently manufacturing a metal sintered body having high surface accuracy.SOLUTION: A method of manufacturing a formed body includes: a powder-layer forming step that forms a powder layer by laying a metal powder having an average particle size of 1 μm or greater and 10 μm or smaller and an average circularity of 0.70 or greater and 1.00 or smaller; a binder-solution supply step that supplies drips of binder solution having a volume of 1 pL or greater and 10 pL or smaller at an ejection interval of 90 μm or smaller from an ink-jet head, while moving the ink-jet head at a moving speed of 0.1 mm / s or higher and 20 mm / s or lower, to a predetermined area of the powder layer, thereby forming a fixed layer in the predetermined area; and a take-out step that takes out the fixed layer from the powder layer and obtains a formed body.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a shaped body and a method for producing a metal sintered body. [Background technology]

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

[0003] Patent Document 1 discloses a solid freeform manufacturing system that uses inkjet printing technology to eject droplets of different volumes as binder droplets onto a powder layer, solidifying the powder and producing an object. A method for manufacturing an object using such a system can be considered a type of binder jet method since it includes a step of ejecting binder droplets. According to such a system, an object with a smooth surface can be manufactured by ejecting droplets of different volumes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2006-515813 Summary of the Invention [Problem to be solved by the invention]

[0005] The solid freeform fabrication system described in Patent Document 1 attempts to solve the problem of finishing to a smooth surface by using large and small volume droplets in combination. However, when large volume droplets are ejected, craters with high walls are formed in the powder layer. These walls tend to remain in the powder layer, causing the surface roughness of the final object to deteriorate.

[0006] On the other hand, it is believed that reducing the volume of the droplets will improve the surface roughness of the resulting object. However, since the amount of droplets supplied per unit area is reduced, it is expected that the amount of binder supplied will be insufficient, which may worsen the surface roughness or reduce the manufacturing efficiency of the shaped body. For this reason, the conditions for efficiently manufacturing objects with good surface roughness have not been optimized and there is room for further study. [Means for solving the problem]

[0007] A method for manufacturing a shaped body according to an application example of the present invention includes the steps of: a powder layer forming step of forming a powder layer in which metal powder having an average particle size of 1 μm or more and 10 μm or less and an average circularity of 0.70 or more and 1.00 or less is spread; a binder solution supplying step of supplying droplets of a binder solution having a volume of 1 pL to 10 pL from the inkjet head at a discharge interval of 90 μm or less to a predetermined region of the powder layer while moving the inkjet head at a moving speed of 0.1 mm / s to 20 mm / s, thereby forming a binder layer in the predetermined region; a removing step of removing the binder layer from the powder layer to obtain a shaped body; has.

[0008] A method for producing a metal sintered body according to an embodiment of the present invention includes the steps of: a shaping step for obtaining a shaped body by a manufacturing method of a shaped body according to an application example of the present invention; a sintering step of sintering the shaped body to obtain a metal sintered body; has. [Brief description of the drawings]

[0009] [Figure 1] 1A to 1C are process diagrams illustrating a method for manufacturing a shaped body according to an embodiment. [Diagram 2] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Diagram 3] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 4] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Diagram 5] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 6] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 7] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 8] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 9] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 10] 2A to 2C are diagrams for explaining a method for producing the shaped body shown in FIG. [Figure 11] 1A to 1C are process diagrams illustrating a method for manufacturing a metal sintered body according to an embodiment. [Figure 12] Photographs of the surfaces of shaped bodies produced using the metal powders of Sample No. 1 and Sample No. 4 observed with a scanning electron microscope, and a table showing the measured values ​​of the arithmetic mean roughness Ra of the surfaces. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for producing a shaped body and the method for producing a metal sintered body of the present invention will be described in detail below with reference to the accompanying drawings.

[0011] 1. Manufacturing method of the model First, a method for manufacturing a shaped body according to the embodiment will be described.

[0012] FIG. 1 is a process diagram for explaining a method for manufacturing a shaped body according to an embodiment. FIGS. 2 to 10 are diagrams for explaining a method for manufacturing a shaped body shown in FIG. 1. In FIGS. 2 to 10, an X-axis, a Y-axis, and a Z-axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip side being the "plus side" and the base side being the "minus side". In the following description, the plus side of the Z-axis is particularly referred to as "up" and the minus side of the Z-axis is particularly referred to as "down". In addition, both directions parallel to the X-axis are referred to as X-axis directions, both directions parallel to the Y-axis are referred to as Y-axis directions, and both directions parallel to the Z-axis are referred to as Z-axis directions.

[0013] 1 to 10 is a method called the binder jet method, and includes a powder layer forming step S102, a binder solution supplying step S104, a repeating step S106, and a removal step S108, as shown in Fig. 1. The binder jet method has the advantage that it is possible to produce objects with complex shapes because it does not require a support structure to support the object.

[0014] In the powder layer forming step S102, metal powder 1 is spread to form a powder layer 31. In the binder solution supplying step S104, a binder solution 4 is supplied from an inkjet head 26 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 stack the bonded layers 41. In the removing step S108, the bonded layer 41 is removed from the powder layer 31, and a shaped body 6 is obtained. Each step will be described in order below.

[0015] 1.1.Additive manufacturing equipment First, prior to describing the powder layer forming step S102, the layered manufacturing apparatus 2 will be described.

[0016] The additive manufacturing device 2 comprises an apparatus main body 21 having a powder storage section 211 and a modeling section 212, a powder supply elevator 22 provided in the powder storage section 211, a modeling stage 23 provided in the modeling section 212, and a coater 24, a roller 25 and an inkjet head 26 movably arranged on the apparatus main body 21.

[0017] The powder storage unit 211 is a recess that is provided in the device body 21 and is open at the top. The metal powder 1 is stored in the powder storage unit 211. An appropriate amount of the metal powder 1 stored in the powder storage unit 211 is supplied to the modeling unit 212 by the coater 24.

[0018] A powder supply elevator 22 is disposed at the bottom of the powder storage section 211. The powder supply elevator 22 is capable of moving up and down with the metal powder 1 loaded thereon. By moving the powder supply elevator 22 upward, the metal powder 1 loaded on the powder supply elevator 22 is pushed up and caused to overflow from the powder storage section 211. This allows the overflowing amount of metal powder 1 to be moved toward the modeling section 212.

[0019] The modeling section 212 is provided in the device body 21, and is a recess with an open top. A modeling stage 23 is disposed inside the modeling section 212. Metal powder 1 is laid in layers on the modeling stage 23 by a coater 24. The modeling stage 23 is movable in the vertical direction with the metal powder 1 laid on it. The amount of metal powder 1 laid on the modeling stage 23 can be adjusted by appropriately setting the height of the modeling stage 23.

[0020] The coater 24 and the roller 25 each extend in the Y-axis direction and are movable in the X-axis direction from the powder storage unit 211 to the modeling unit 212. The coater 24 drags the metal powder 1 to level it and spread it in a layer. The roller 25 rolls on the leveled metal powder 1 to compress the metal powder 1 from above.

[0021] The inkjet head 26 is movable in the X-axis direction and the Y-axis direction in the modeling unit 212. The inkjet head 26 supplies a desired amount of the binder solution 4 to a desired position. The inkjet head 26 may include a plurality of discharge nozzles. The binder solution 4 may be discharged from the plurality of discharge nozzles simultaneously or with a time lag.

[0022] 1.2. Powder layer formation process Next, the powder layer forming step S102 using the above-mentioned additive manufacturing apparatus 2 will be described. In the powder layer forming step S102, the metal powder 1 is spread on the modeling stage 23 to form a powder layer 31. Specifically, as shown in Figs. 2 and 3, the coater 24 is used to drag the metal powder 1 stored in the powder storage section 211 onto the modeling stage 23 and smooth it to a uniform thickness. This results in the powder layer 31 shown in Fig. 4. At this time, the upper surface of the modeling stage 23 is lowered below the upper end of the modeling section 212, and the thickness of the powder layer 31 can be adjusted by adjusting the amount of lowering.

[0023] 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 makes it possible to increase the filling rate of the metal powder 1 in the powder layer 31. Note that the compression with the roller 25 may be performed as necessary and may be omitted. Also, the powder layer 31 may be compressed by a means other than the roller 25, such as a pressing plate.

[0024] 1.3. Binder solution supply process Next, a description will be given of the binder solution supplying step S104 using the above-mentioned layered modeling apparatus 2. In the binder solution supplying step S104, as shown in Fig. 5, droplets of the binder solution 4 are supplied from the inkjet head 26 to a formation region 60 of the powder layer 31 that corresponds to the modeled body 6 to be formed. The binder solution 4 is a liquid containing a binder and a solvent or dispersion medium.

[0025] The inkjet head 26 ejects droplets of the binder solution 4 at ejection intervals of 90 μm or less toward the formation region 60 while moving at a speed of 0.1 mm / s to 20 mm / s. In the formation region 60 where the binder solution 4 is ejected, the particles of the metal powder 1 are bonded together, and an adhesive layer 41 as shown in Fig. 6 is obtained. In the adhesive layer 41, the particles of the metal powder 1 are bonded together by the binder, and the adhesive layer 41 has enough shape retention to prevent the particles from breaking under their own weight.

[0026] The moving speed of the inkjet head 26 may be within the above range, but is preferably 1 mm / s to 15 mm / s, more preferably 3 mm / s to 10 mm / s. By setting the moving speed of the inkjet head 26 within the above range, the accuracy of the ejection position of the droplets of the binder solution 4 can be improved. This can improve the shape accuracy of the binder layer 41, and the surface accuracy of the finally obtained shaped body 6 can be improved. If the moving speed of the inkjet head 26 is below the lower limit, the manufacturing efficiency of the shaped body 6 decreases. On the other hand, if the moving speed of the inkjet head 26 exceeds the upper limit, the accuracy of the ejection position of the droplets decreases, and therefore the shape accuracy of the binder layer 41 decreases.

[0027] The moving speed of the inkjet head 26 is the average speed of the inkjet head 26 measured at the timing when droplets of the binder solution 4 are discharged toward the formation region 60. The average speed is calculated by measuring the speed of the inkjet head 26 10 or more times at the timing when droplets are discharged, and averaging the measured values.

[0028] The interval between the droplets of the binder solution 4 may be within the above range, but is preferably 5 μm to 80 μm, more preferably 10 μm to 70 μm, and even more preferably 20 μm to 60 μm. By setting the interval between the droplets of the binder solution 4 within the above range, the binder solution 4 can be supplied uniformly and in sufficient amount. The interval between the droplets of the binder solution 4 may be below the lower limit, but in that case, the improvement in the surface accuracy of the molded body 6 cannot be expected, and it becomes difficult to increase the moving speed of the inkjet head 26, which may reduce the manufacturing efficiency of the molded body 6. On the other hand, if the interval between the droplets of the binder solution 4 exceeds the upper limit, the droplets of the binder solution 4 that land on the powder layer 31 are too far apart from each other, and a continuous coating film is not formed. As a result, the probability of particles that cannot be bound increases, and the surface accuracy of the molded body 6 decreases.

[0029] The interval between droplets of the binder solution 4 is determined by measuring the distance between droplets of the binder solution 4 within a 5 mm x 5 mm area under the same conditions as when the binder solution 4 is discharged onto a smooth surface that does not absorb the binder solution 4, and then taking the average value. The distance between droplets is the center-to-center distance between adjacent droplets. The average value is determined by measuring the distance between each of 10 or more pairs of droplets randomly selected.

[0030] In addition, the inkjet head 26 sets the volume of the droplets of the binder solution 4 to 1 pL or more and 10 pL or less. In addition, the volume of the droplets of the binder solution 4 is preferably 1 pL or more and 8 pL or less, and more preferably 2 pL or more and 6 pL or less. By setting the volume of the droplets of the binder solution 4 within the above range, the accuracy of the droplet ejection position can be improved, particularly at the outer edge of the binder layer 41. This can improve the surface accuracy of the part of the shaped body 6 that corresponds to the outer edge of the binder layer 41. If the volume of the droplets of the binder solution 4 falls below the lower limit, it becomes difficult to increase the moving speed of the inkjet head 26, and the manufacturing efficiency of the shaped body 6 decreases. On the other hand, if the volume of the droplets of the binder solution 4 exceeds the upper limit, the mass of the droplets increases. Therefore, the impact when the droplets land on the powder layer 31 becomes large, and the surface accuracy of the binder layer 41 decreases, leading to a decrease in the surface accuracy of the shaped body 6.

[0031] The volume of the droplets of the binder solution 4 is the average value of the volumes determined by observing the plan view and cross section of the droplets after discharging the binder solution 4 onto a smooth surface that does not absorb the binder solution 4 under the same conditions as when it is discharged onto the formation region 60. The average value is the average value of the volumes determined from 10 or more droplets randomly selected.

[0032] The binder layer 41 may be heated simultaneously with or after the supply of the binder solution 4. This promotes the evaporation of the solvent or dispersion medium contained in the binder solution 4, and promotes the binding of particles together due to the 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.

[0033] The heating temperature in the case of heating is not particularly limited, but is preferably from 50° C. to 250° C., and more preferably from 70° C. to 200° C. 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.

[0034] The binder solution 4 is not particularly limited as long as it is a liquid having a component capable of binding the particles of the metal powder 1 together. As an example, the solvent or dispersion medium contained in the binder solution 4 may be, for example, water, alcohols, ketones, carboxylates, etc., and may be a mixed liquid containing at least one of these. In addition, as the binder contained in the binder solution 4, for example, fatty acid, paraffin wax, microwax, polyethylene, polypropylene, polystyrene, acrylic resin, polyamide resin, polyester, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), urethane resin, epoxy resin, vinyl resin, unsaturated polyester resin, phenol resin, etc. may be mentioned.

[0035] A solution containing polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) and water is particularly preferably used as the binder solution 4. This allows the binder solution 4 to have appropriate affinity and viscosity for the metal powder 1, as well as good binding properties. For this reason, such a binder solution 4 contributes to the production of a shaped body 6 with particularly good surface precision.

[0036] The concentration of the binder in the binder solution 4 is preferably 0.1 mass % or more and 20.0 mass % or less, more preferably 1.0 mass % or more and 15.0 mass % or less, and even more preferably 5.0 mass % or more and 12.0 mass % or less, which optimizes the viscosity of the binder solution 4 and ensures sufficient binding strength between the particles of the metal powder 1.

[0037] In addition to the above components, additives may be included in the binder solution 4. Examples of additives include surfactants, stabilizers, thickeners, antifoaming agents, and moisturizing agents.

[0038] The total content of the 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.

[0039] 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. In other words, these steps are performed a total of two or more times. As a result, a plurality of binder layers 41 are laminated. By laminating the binder layers 41 in this manner, a shaped body 6 having a desired three-dimensional shape as shown in FIG. 10 is obtained.

[0040] Specifically, first, a new powder layer 31 shown in Fig. 7 is formed on the binder layer 41 shown in Fig. 6. Next, as shown in Fig. 8, the 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 shown in Fig. 9. The two binder layers 41 may have the same shape or different shapes.

[0041] 1.5.Removal process In the removal step S108, the binder layer 41 is removed from the powder layer 31. In this way, a shaped body 6 shown in FIG.

[0042] The smaller the arithmetic mean roughness Ra of the surface of the obtained shaped body 6, the better, but it is preferably 7.0 μm or less, more preferably 0.5 μm to 5.0 μm, and even more preferably 1.0 μm to 4.0 μm. This allows the shaped body 6 to have sufficient surface accuracy. By sintering such a shaped body 6, a metal sintered body having a surface accuracy to the extent that secondary processing is not required can be manufactured. The arithmetic mean roughness Ra may be below the lower limit, but in that case, depending on the individual difference of the shaped body 6, it may exceed the lower limit, which may reduce the manufacturing yield of the shaped body 6. On the other hand, if the arithmetic mean roughness Ra exceeds the upper limit, the surface accuracy of the shaped body 6 decreases, which may lead to a decrease in the surface accuracy of the metal sintered body obtained by sintering the shaped body 6.

[0043] The arithmetic mean roughness Ra of the surface of the shaped body 6 is measured using a non-contact surface roughness measuring device. An example of such a surface roughness measuring device is a digital microscope VHX-6000 manufactured by Keyence Corporation. The imaging magnification when calculating the arithmetic mean roughness Ra is 500 times.

[0044] In addition, the metal powder 1 in the powder layer 31 that does not form the binder layer 41 is collected and reused as necessary, that is, it is provided again for manufacturing the shaped body 6.

[0045] 2. Manufacturing method of metal sintered body A metal sintered body is obtained by subjecting the shaped body 6 to a sintering treatment. In the sintering treatment, the shaped body 6 is heated to cause a sintering reaction.

[0046] FIG. 11 is a process diagram for explaining the method for producing a metal sintered body according to the embodiment. The manufacturing method for a metal sintered body shown in FIG. 11 includes a shaping step S202 for obtaining a shaped body 6 by the above-described manufacturing method for a shaped body, and a sintering step S204 for sintering the shaped body 6 to obtain a metal sintered body.

[0047] 2.1. Molding process In the modeling step S202, a modeled body 6 is obtained by the above-described method for manufacturing a modeled body.

[0048] 2.2.Sintering process In the sintering step S204, the shaped body 6 is sintered to obtain a metal sintered body.

[0049] The sintering temperature varies depending on the constituent material and particle size of the metal powder 1, but is preferably 980° C. to 1330° C., and more preferably 1050° C. to 1260° C., for example. The sintering time is preferably 0.2 hours to 7 hours, and more preferably 1 hour to 6 hours.

[0050] 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, etc. 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.

[0051] When the sintering process performed under the above conditions is referred to as "main sintering", at least one of "preliminary sintering" and "debinding" corresponding to pretreatment for the main sintering may be performed on the shaped body 6 as necessary. This makes it possible to remove at least a part of the binder contained in the shaped body 6, or to sinter a part of the shaped body 6. This makes it possible to suppress unintended deformation during the main sintering.

[0052] The temperature for the preliminary sintering and degreasing is not particularly limited as long as it is a temperature that does not complete sintering of the metal powder 1, but is preferably 100° C. or higher and 500° C. or lower, and more preferably 150° C. or higher and 300° C. or lower. The time for the preliminary sintering and degreasing 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, within the above temperature range. Examples of the atmosphere for the preliminary 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.

[0053] The metal sintered body obtained as described above can be used as a material for constituting the whole or part of, for example, automobile parts, bicycle parts, railroad vehicle parts, ship parts, aircraft parts, and space transport parts, electronic device parts such as personal computer parts, mobile phone terminal parts, tablet terminal parts, and wearable terminal parts, electrical device 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, metal tableware, jewelry, and decorative items such as eyeglass frames.

[0054] 3. Metal powder Next, the metal powder 1 will be described.

[0055] 3.1.Constituent Materials The metal powder 1 contains a metal material. The metal material contained in the metal powder 1 is not particularly limited, but when a metal sintered body is produced from the shaped body 6, the metal material is a sinterable material. Examples of the sinterable metal material include simple elements such as Fe, Ni, Co, Ti, Al, and Mg, as well as alloys and intermetallic compounds mainly composed of these elements. Of these, an Fe-based metal material is preferably used as the metal material. An Fe-based metal material refers to a metal material in which the content of Fe exceeds 50% in terms of atomic ratio. An Fe-based metal material is easy to obtain and can be used to produce a metal sintered body with excellent mechanical properties.

[0056] Examples of Fe-based metallic materials include stainless steels such as ferritic stainless steel, austenitic 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.

[0057] Among these, stainless steel is preferably used as the Fe-based metallic material. Stainless steel is a type of steel that is excellent in mechanical strength and corrosion resistance. Therefore, by using the metal powder 1 made of stainless steel, it is possible to efficiently manufacture a metal sintered body that is excellent in mechanical strength and corrosion resistance and has high shape accuracy.

[0058] 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, and SUSXM15J1.

[0059] Examples of ferritic stainless steels include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.

[0060] Examples of martensitic stainless steel include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.

[0061] Examples of precipitation hardening stainless steel include SUS630 and SUS631.

[0062] Examples of austenitic-ferritic (duplex) stainless steels include SUS329J1, SUS329J3L, and SUS329J4L.

[0063] The above symbols are material symbols based on the JIS standard. In this specification, the types of stainless steel are distinguished by the above material symbols.

[0064] The shaped body 6 may be manufactured using metal powders 1 containing different types of stainless steel. For example, when the shaped body 6 is composed of two or more bonding layers 41, one bonding layer 41 may be manufactured using metal powder 1 containing a first stainless steel, and another bonding layer 41 may be manufactured using metal powder 1 containing a second stainless steel.

[0065] The metal powder 1 may also be provided with a coating that covers the surface of the core particle made of a metal material. This coating is provided for the purpose of, for example, increasing the fluidity and packing ability of the metal powder 1, and increasing the affinity between the metal powder 1 and a binder. Examples of materials that can be used for the coating include organic materials such as resins, inorganic materials such as ceramics and glass, and compounds derived from coupling agents.

[0066] 3.2.Various characteristics of metal powders Next, there will be described various characteristics of the metal powder 1. Note that all of the following characteristics are measured in a state where the metal powder 1 is not provided with the above-mentioned coating.

[0067] 3.2.1. Particle size distribution For the metal powder 1 according to this embodiment, when the particle size distribution is obtained on a volume basis by a laser diffraction particle size distribution measuring device, the particle size when the cumulative frequency is 10% from the small diameter side is defined as D10. Similarly, the particle sizes when the cumulative frequency is 50% and 90% from the small diameter side are defined as D50 and D90. Examples of the particle size distribution measuring device include Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0068] The particle size D50 (average particle size D50) of the metal powder 1 is set to 1.0 μm or more and 10.0 μm or less, preferably 2.0 μm or more and 9.0 μm or less, and more preferably 3.0 μm or more and 8.0 μm or less. This allows the metal powder 1 to have both good filling properties and good flowability. As a result, a dense shaped body 6 with high surface accuracy can be obtained, and by using this, a metal sintered body with high density and high surface accuracy can be finally manufactured.

[0069] If the particle size D50 is below the lower limit, the particles of the metal powder 1 tend to aggregate. This reduces the fluidity of the metal powder 1, and the filling ability and surface precision of the shaped body 6 deteriorate. On the other hand, if the particle size D50 exceeds the upper limit, the particles of the metal powder 1 themselves become large. This makes it easier for the particle shape to be reflected on the surface of the shaped body 6, and reduces the surface precision.

[0070] The ratio D10 / D50 of the particle diameter D10 to the particle diameter 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 makes the particle diameter of the metal powder 1 relatively uniform, making it easier to increase the fluidity and ensuring the sinterability. If the ratio D10 / D50 is below the lower limit, the particle size distribution will be broadened, and the fluidity may decrease. 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 decreasing the sinterability.

[0071] The ratio D90 / D50 of the particle diameter D90 to the particle diameter 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 makes the particle diameter of the metal powder 1 relatively uniform, making it easier to increase the fluidity and ensuring the 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 there is a risk of the sinterability decreasing. On the other hand, if the ratio D90 / D50 exceeds the upper limit, the particle size distribution widens, and there is a risk of the fluidity decreasing.

[0072] The particle size difference D90-D10 between the particle size D90 and the particle size D10 is preferably 5.0 μm or more and 18.0 μm or less, more preferably 8.0 μm or more and 15.0 μm or less, and even more preferably 9.0 μm or more and 13.0 μm or less. This optimizes the particle size distribution of the metal powder 1, and provides high fluidity. As a result, the filling property of the metal powder 1 is improved, and a shaped body 6 that is dense and has high surface accuracy can be obtained.

[0073] If the particle size difference D90-D10 is below the lower limit, the particle size distribution of the metal powder 1 becomes too narrow, making it difficult to increase the filling rate and possibly reducing the surface precision of the molded body 6. On the other hand, if the particle size difference D90-D10 exceeds the upper limit, the particle size distribution of the metal powder 1 becomes broader and the flowability decreases. As a result, the surface precision of the molded body 6 to be manufactured may decrease.

[0074] 3.2.2.Average circularity The average circularity of the metal powder 1 is set to 0.70 or more and 1.00 or less, preferably 0.80 or more and 0.98 or less, and more preferably 0.85 or more and 0.97 or less. This makes it possible for the particles of the metal powder 1 to roll easily even if the particle size of the metal powder 1 is small, and allows the packed state to approach close packing. As a result, it is possible to achieve both the packing property and the fluidity of the metal powder 1. This makes it possible to obtain a dense shaped body 6 with high surface accuracy, and by using this, it is possible to finally manufacture a metal sintered body with high density and high surface accuracy.

[0075] If the average circularity is below the lower limit, the fluidity and filling rate of the metal powder 1 decrease. On the other hand, if the average circularity is above the upper limit, the manufacturing difficulty increases and the manufacturing efficiency of the metal powder 1 decreases.

[0076] The average circularity of the metal powder 1 is measured as follows. First, an image (secondary electron image) of the metal powder 1 is taken 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. 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.

[0077] Next, image processing software is used to calculate the circularity of 300 or more particle images and obtain the average value. The obtained average value is the average circularity of metal powder 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 obtained by the following formula. e=4πS / L 2

[0078] 3.2.3.Oxygen content The oxygen content of the metal powder 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. If the oxygen content is within the above range, it is possible to suppress the adsorption of moisture and to suppress the change in characteristics over time. In other words, the metal powder 1 having high storage stability can be obtained.

[0079] If the oxygen content falls below the lower limit, the oxide film present on the particle surface of the metal powder 1 may become thin and may be easily deteriorated over time. On the other hand, if the oxygen content exceeds the upper limit, moisture may be easily adsorbed, the moisture content may increase, and the flowability of the metal powder 1 may decrease.

[0080] The oxygen content of the metal powder 1 is measured, for example, in accordance with the general rules for determining oxygen content of metallic materials as defined 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.

[0081] 4.Metal powder manufacturing method Next, an example of a method for producing the metal powder 1 will be described.

[0082] The metal powder 1 may be produced by any method, for example, the atomization method. In the atomization method, molten metal is made 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 collided with the fluid falls by inertia, and the droplets are made spherical at that time. As a result, it is possible to produce metal powder 1 that has a relatively small diameter but a high average circularity and a relatively small specific surface area.

[0083] The atomization method includes water atomization, gas atomization, and rotating water flow atomization, depending on the type of coolant and the configuration of the device. Of these, metal powder 1 produced by water atomization is preferably used. In the water atomization method, a fluid with a high specific gravity, i.e., water, is used to atomize molten metal, so metal powder 1 with a small diameter and narrow particle size distribution can be obtained. Despite its small diameter, such metal powder 1 has excellent fluidity, and ultimately contributes to the production of a shaped body 6 with high surface precision.

[0084] The flow rate of the molten metal varies depending on the size of the device, but is preferably more than 1.0 kg / min and not more than 20.0 kg / min, and more preferably 2.0 kg / min or more and not more than 10.0 kg / min. This allows the amount of molten metal flowing down in a certain period of time to be optimized, making it possible to efficiently produce metal powder 1 with a narrow particle size distribution and sufficient sphericity. As a result, it is possible to produce metal powder 1 with a relatively small diameter but a high average circularity and a relatively small specific surface area.

[0085] The temperature of the molten metal in the crucible (casting temperature) is preferably set to Tm+100°C or more and Tm+350°C or less, more preferably Tm+180°C or more and Tm+320°C or less, and even more preferably Tm+250°C or more and Tm+300°C or less, relative to the melting point Tm [°C] of the constituent material of the metal powder 1. This ensures that the time during which the metal exists as molten metal when it is refined by various atomization methods and solidifies is longer than in the past. As a result, it is possible to manufacture metal powder 1 that has a high average circularity and a relatively small specific surface area even with a small diameter.

[0086] In addition, in various atomization methods, the outer diameter of the thin stream when the molten metal is allowed to flow 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 to the molten metal uniformly, so that metal powder 1 having the above-mentioned average particle size and good average circularity can be produced.

[0087] Furthermore, the produced metal powder 1 may be classified as necessary. Examples of classification methods include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0088] 5. Advantages of the above embodiment As described above, the manufacturing method of the shaped body according to the embodiment includes the powder layer forming step S102, the binder solution supplying step S104, and the removal step S108. In the powder layer forming step S102, the powder layer 31 is formed by spreading the metal powder 1 having an average particle size of 1 μm to 10 μm and an average circularity of 0.70 to 1.00. In the binder solution supplying step S104, the inkjet head 26 is moved at a moving speed of 0.1 mm / s to 20 mm / s to the formation region 60 (predetermined region) of the powder layer 31, and droplets of the binder solution 4 having a volume of 1 pL to 10 pL are supplied from the inkjet head 26 at a discharge interval of 90 μm or less. As a result, the binder layer 41 is formed in the formation region 60. In the removal step S108, the binder layer 41 is removed from the powder layer 31 to obtain the shaped body 6.

[0089] With this configuration, the average particle size D50 and average circularity of the metal powder 1, as well as the movement conditions of the inkjet head 26 and the ejection conditions of the binder solution 4 are each optimized, so that when manufacturing a shaped body 6 using the binder jet method, a shaped body 6 with high surface precision can be efficiently manufactured.

[0090] The binder solution 4 may also contain polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), and water.

[0091] According to this configuration, the binder solution 4 has an appropriate affinity and viscosity for the metal powder 1, and also has good binding properties. Therefore, such a binder solution 4 contributes to the production of a shaped body 6 with particularly good surface precision.

[0092] The metal powder 1 may be a powder produced by a water atomization method. In the water atomization method, a fluid with a high specific gravity, i.e., water, is used to atomize the molten metal, resulting in metal powder 1 with a small diameter and narrow particle size distribution. Despite its small diameter, such metal powder 1 has excellent fluidity, which ultimately contributes to the production of a shaped body 6 with high surface precision.

[0093] The method for manufacturing a shaped body according to the embodiment may include a repeating step S106. In the repeating step S106, a plurality of stacked binder layers 41 are obtained as the shaped body 6 by repeating the powder layer forming step S102 and the binder solution supplying step S104. According to this configuration, it is possible to manufacture a shaped body 6 having a desired three-dimensional shape.

[0094] The arithmetic mean roughness Ra of the surface of the shaped body 6 is preferably 7.0 μm or less. According to this configuration, a shaped body 6 having sufficient surface precision can be obtained. Then, by sintering the shaped body 6 that satisfies this surface roughness, a metal sintered body having a surface precision that does not require secondary processing can be manufactured.

[0095] Moreover, the above-mentioned ejection interval is preferably 20 μm or more. According to this configuration, the moving speed of the inkjet head 26 can be prevented from becoming too slow, and the efficiency of manufacturing the shaped body 6 can be improved.

[0096] The manufacturing method of a metal sintered body according to the embodiment includes a shaping step S202 and a sintering step S204. In the shaping step S202, a shaped body 6 is obtained by the manufacturing method of a shaped body according to the embodiment. In the sintering step S204, the shaped body 6 is sintered to obtain a metal sintered body.

[0097] According to this configuration, a metal sintered body having high surface accuracy can be efficiently manufactured.

[0098] The above describes the method for manufacturing a shaped body and the method for manufacturing a metal sintered body of the present invention based on the illustrated embodiment, but the present invention is not limited to this, and for example, any purposed process may be added to the above embodiment. EXAMPLES

[0099] Next, specific examples of the present invention will be described. 6. Metal powder manufacturing First, metal powders with different particle sizes were produced by water atomization under different manufacturing conditions. The material of the metal powder was precipitation hardening stainless steel SUS630 (17-4PH).

[0100] Next, the average particle size D50, average circularity and oxygen content of the produced metal powder were measured. The measurement results are shown in Table 1.

[0101] 7. Manufacturing of the model Next, a rectangular parallelepiped shaped object was fabricated by the binder jet method using the metal powder of each sample number. The size of the fabricated object was 40 mm in length, 20 mm in width, and 5 mm in thickness. For the binder solution, an aqueous solution containing PVP at a concentration of 10% by mass and a humectant at a concentration of 12% was used. Table 1 shows the volume of the binder solution droplets, the moving speed of the inkjet head, and the ejection interval of the binder solution droplets in the binder jet method. In Table 1, among the shaped objects of each sample number, those corresponding to the present invention are designated as "Examples" and those not corresponding to the present invention are designated as "Comparative Examples."

[0102] 8. Evaluation of the sculpture 8.1. Relative density of the structure The mass and volume of the molded bodies manufactured using the metal powder of each sample number were measured, and the density was calculated. The measured density was then divided by the true density of the metal powder to calculate the relative density. The calculated relative density was then evaluated relatively in accordance with the following evaluation criteria. The evaluation results are shown in Table 1.

[0103] A: Relatively high relative density B: Relatively medium density C: Relatively low relative density

[0104] 8.2. Surface roughness of the object The surface of the obtained molded body was observed using a digital microscope that functions as a non-contact surface roughness measuring device. The arithmetic mean roughness Ra of the surface of the molded body was then measured. The measurement results were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.

[0105] A: The arithmetic mean roughness Ra is 4.0 μm or less B: The arithmetic mean roughness Ra is more than 4.0 μm and 7.0 μm or less. C: The arithmetic mean roughness Ra is more than 7.0 μm

[0106] [Table 1]

[0107] As shown in Table 1, in each example, a molded object with small surface roughness was manufactured without excessively slowing down the moving speed of the inkjet head or excessively narrowing the interval between droplets. From the above results, it was found that the present invention can efficiently manufacture a molded object with high surface precision.

[0108] FIG. 12 is a table showing photographs obtained by observing the surfaces of the bodies produced using the metal powders of Sample No. 1 and Sample No. 4 with a scanning electron microscope, and the measured values ​​of the arithmetic mean roughness Ra of the surfaces.

[0109] 12, the photograph shows that the object manufactured by the manufacturing method of the example has a small arithmetic mean roughness Ra and is relatively smooth. In contrast, the photograph shows that the object manufactured by the manufacturing method of the comparative example has a large arithmetic mean roughness Ra and is relatively rough. [Explanation of symbols]

[0110] Reference Signs List 1...metal powder, 2...layered manufacturing device, 4...binder solution, 6...modeled body, 21...device body, 22...powder supply elevator, 23...modeling stage, 24...coater, 25...roller, 26...inkjet head, 31...powder layer, 41...binding layer, 60...forming area, 211...powder storage section, 212...modeling section, S102...powder layer forming process, S104...binder solution supply process, S106...repeating process, S108...removal process, S202...modeling process, S204...sintering process

Claims

1. a powder layer forming step of forming a powder layer in which metal powder having an average particle size of 1 μm or more and 10 μm or less and an average circularity of 0.70 or more and 1.00 or less is spread; a binder solution supplying step of supplying droplets of a binder solution having a volume of 1 pL to 10 pL from the inkjet head at a discharge interval of 90 μm or less to a predetermined region of the powder layer while moving the inkjet head at a moving speed of 0.1 mm / s to 20 mm / s, thereby forming a binder layer in the predetermined region; a removing step of removing the binder layer from the powder layer to obtain a shaped body; A method for producing a shaped body, comprising the steps of:

2. The method for producing a shaped body according to claim 1 , wherein the binder solution contains polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), and water.

3. The method for producing a shaped body according to claim 1 or 2, wherein the metal powder is produced by a water atomization method.

4. The method for manufacturing a shaped body according to claim 1 , further comprising a repeating step of obtaining a plurality of stacked binder layers as the shaped body by repeating the powder layer forming step and the binder solution supplying step.

5. The method for manufacturing a shaped body according to claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the shaped body is 7.0 μm or less.

6. The method for manufacturing a shaped body according to claim 1 , wherein the discharge interval is 20 μm or more.

7. a shaping step for obtaining the shaped body by the manufacturing method of the shaped body according to claim 1 or 2; a sintering step of sintering the shaped body to obtain a metal sintered body; A method for producing a metal sintered body, comprising the steps of:

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