Method for manufacturing laminate molding

Abstract

To provider a method for manufacturing a laminate molding, which can efficiently manufacture a laminate molding with high shape accuracy.SOLUTION: A method for manufacturing a laminate molding comprises: a powder layer forming step of forming a powder layer by layering metal particles and molding particles having a film provided on the surface of the metal particles and containing a compound derived from a coupling agent having a hydrophobic functional group; a filling degree adjustment step of compressing the powder layer so that a relative density is 40% or higher; and a binder solution supply step of supplying an aqueous binder solution having a surface tension of 20 mN / m or more and 40 mN / m or less to the powder layer subjected to the filling degree adjustment step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a layered object. [Background technology]

[0002] In recent years, additive manufacturing methods using metal powder have become increasingly popular as a technology for creating three-dimensional objects. One such additive manufacturing method is the binder jet method.

[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.

[0004] Patent Document 2 also discloses that, as a powder for additive manufacturing used in the binder jet method, a powder in which a ring-structure-containing group, a fluoroalkyl group, or a fluoroaryl group is introduced to the particle surface of a metal powder is used. By introducing such a functional group, a powder for additive manufacturing with high fluidity can be realized, and a powder layer with a high packing rate can be obtained. By increasing the packing rate of the powder layer, an additive manufacturing object with high shape accuracy can be finally obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2006-515813 [Patent Document 2] Patent Publication No. 2022-122503 Summary of the Invention [Problem to be solved by the invention]

[0006] In the binder jet method, a water-based liquid (water-based binder solution) is often used as the binder droplets. The water-based binder solution penetrates the powder layer, solidifying that area.

[0007] However, the powder for additive manufacturing described in Patent Document 2 has a highly hydrophobic particle surface, so the aqueous binder solution may not penetrate the powder layer quickly. In this case, it takes time for the aqueous binder solution to penetrate, so the supply rate of the aqueous binder solution decreases or the penetration range becomes uneven. This reduces the manufacturing speed of the object (modeled body) and reduces the shape accuracy of the manufactured object. [Means for solving the problem]

[0008] A method for producing a layered object according to an application example of the present invention includes the steps of: a powder layer forming step of laying a layer of shaping particles having metal particles and a coating film formed on the surface of the metal particles and containing a compound derived from a coupling agent having a hydrophobic functional group; a packing density adjusting step of compressing the powder layer so that the relative density is 40% or more; a binder solution supplying step of supplying an aqueous binder solution having a surface tension of 20 mN / m or more and 40 mN / m or less to the powder layer that has been subjected to the filling degree adjusting step; has. [Brief description of the drawings]

[0009] [Figure 1] 1A to 1C are process diagrams illustrating a configuration of a method for manufacturing a layered object according to an embodiment. [Diagram 2] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Diagram 3] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 4] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Diagram 5] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 6] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 7] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 8] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 9] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 10] FIG. 2 is a diagram for explaining a method for producing the layered object shown in FIG. [Figure 11] 1A to 1C are process diagrams illustrating a method for manufacturing a metal sintered body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the method for producing a layered object of the present invention will be described in detail with reference to the accompanying drawings.

[0011] 1. Manufacturing method for additive manufacturing First, a method for producing a layered object according to the embodiment will be described.

[0012] FIG. 1 is a process diagram showing the configuration of a method for manufacturing a layered object according to an embodiment. FIGS. 2 to 10 are diagrams for explaining the method for manufacturing the layered object 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 the X-axis directions, both directions parallel to the Y-axis are referred to as the Y-axis directions, and both directions parallel to the Z-axis are referred to as the Z-axis directions.

[0013] 1 to 10 is a method called the binder jet method, and includes a powder layer forming step S102, a filling degree adjusting step S104, a binder solution supplying step S106, a repeating step S108, and a removal step S110, 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, the modeling powder 1 is spread to form the powder layer 31. In the binder solution supplying step S106, the aqueous binder solution 4 is supplied from the 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 binder layer 41. In the repeating step S108, the powder layer forming step S102 and the binder solution supplying step S106 are repeated one or more times to stack the binder layers 41. In the removing step S110, the binder layer 41 is removed from the powder layer 31, thereby obtaining a layered model 6. 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, a coater 24 movably arranged on the apparatus main body 21, a roller 25 and an inkjet head 26.

[0017] The powder storage section 211 is a recess that is provided in the device body 21 and is open at the top. The powder storage section 211 stores the molding powder 1. An appropriate amount of the molding powder 1 stored in the powder storage section 211 is supplied to the molding section 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 powder 1 for shaping placed thereon. By moving the powder supply elevator 22 upward, the powder 1 for shaping placed on the powder supply elevator 22 is pushed up and made to overflow from the powder storage section 211. This allows the overflowing powder 1 for shaping to be moved toward the shaping 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. The modeling powder 1 is spread in layers on the modeling stage 23 by a coater 24. The modeling stage 23 is movable in the up and down direction with the modeling powder 1 spread thereon. The amount of the modeling powder 1 spread 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 section 211 to the modeling section 212. The coater 24 drags the powder 1 for modeling, thereby leveling the powder 1 for modeling and spreading it in a layer. The roller 25 rolls on the leveled powder 1 for modeling, thereby compressing the powder 1 for modeling 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 water-based binder solution 4 to a desired position. The inkjet head 26 may include a plurality of discharge nozzles. The water-based 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 In the powder layer forming process S102, the powder 1 for molding 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 powder 1 for molding 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] The thickness of the powder layer 31 in this step is not particularly limited, but is preferably 20 μm to 200 μm, more preferably 40 μm to 150 μm, and even more preferably 50 μm to 100 μm. If the thickness of the powder layer 31 is within the above range, the shape precision of the finally obtained layered object 6 can be sufficiently improved.

[0024] If the thickness of the powder layer 31 is below the lower limit, a larger number of powder layers 31 are required to manufacture the desired layered object 6. This may result in a longer time required to manufacture the layered object 6. On the other hand, if the thickness of the powder layer 31 exceeds the upper limit, the bonding layer 41 formed from the powder layer 31 also becomes thick, which may result in a decrease in the shape accuracy of the layered object 6.

[0025] 1.3.Filling degree adjustment process In the packing degree adjustment step S104, the packing degree is adjusted by compressing the powder layer 31 so that the relative density is 40% or more. Specifically, 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 uniformly increase the packing degree of the powder 1 for molding in the powder layer 31.

[0026] Note that, as long as the powder layer 31 can be compressed in the thickness direction, another method may be used instead of compression by the roller 25. As an example of the other method, a method of pressing a plate-shaped member or the like may be mentioned.

[0027] Furthermore, the coater 24 or the roller 25 may have both the function of forming the powder layer 31 and the function of compressing the powder layer 31. In that case, the powder layer forming step S102 and the filling degree adjusting step S104 can be performed simultaneously using a member having both functions. This can improve the manufacturing efficiency of the layered object 6.

[0028] Note that "simultaneously" refers to a state in which the time period during which the powder layer forming step S102 is performed and the time period during which the filling degree adjusting step S104 is performed at least partially overlap.

[0029] Here, the aqueous binder solution 4 is supplied to the powder layer 31 in a binder solution supplying step S106 described later. This causes the particles of the powder 1 for shaping to be bound together, and a binding layer 41 is obtained. At this time, in order to bind the particles together within a desired range, good permeability of the aqueous binder solution 4 is required in the powder layer 31. However, if the particle surfaces of the powder 1 for shaping are given hydrophobicity, the aqueous binder solution 4 is easily repelled by the particle surfaces of the powder 1 for shaping. For this reason, the permeability of the aqueous binder solution 4 to the powder layer 31 is reduced, and the shape accuracy of the binding layer 41 is reduced, which has been a problem.

[0030] In contrast, by increasing the relative density of the powder layer 31 in this step, the distance between the particles of the powder 1 for modeling can be reduced. When the distance between the particles is reduced, the gaps between the particles become smaller, and capillary action that draws the aqueous binder solution 4 into the gaps becomes more likely to occur. This is because the driving force for penetration by capillary action tends to be stronger as the gaps become smaller. This allows the aqueous binder solution 4 to penetrate into the desired range of the powder layer 31 in the binder solution supply step S106. As a result, it is possible to manufacture a layered object 6 having the desired shape.

[0031] If the relative density of the powder layer 31 is lower than the above range, the gaps between the particles are large, making it difficult for capillary action to occur. In this case, the driving force for drawing in the aqueous binder solution 4 is small, resulting in insufficient permeability.

[0032] The relative density of the powder layer 31 is the ratio of the density of the powder layer 31 to the true density of the material constituting the powder for molding 1. The density of the powder layer 31 can be calculated based on the volume calculated from the area and thickness of the powder layer 31, and the mass of the powder layer 31.

[0033] The relative density of the powder layer 31 after the filling degree adjustment step S104 may be 40% or more, but is preferably 45% to 70%, and more preferably 50% to 65%. If the relative density is below the lower limit, the gaps between the particles in the powder layer 31 become large, and the aqueous binder solution 4 cannot penetrate sufficiently. This tendency is particularly noticeable when the particle surfaces of the powder 1 for molding are given hydrophobicity. On the other hand, if the relative density is above the upper limit, the gaps between the particles in the powder layer 31 may become too small. In this case, the continuity of the gaps may be lost, and the permeability of the aqueous binder solution 4 may decrease.

[0034] 1.4. Binder solution supply process In the binder solution supplying process S106, as shown in Fig. 5, droplets of the aqueous binder solution 4 are supplied from the inkjet head 26 to a formation region 60 of the powder layer 31 whose filling density has been adjusted, which corresponds to the layered object 6 to be formed. In the formation region 60 to which the aqueous binder solution 4 has been supplied, the particles of the powder 1 for forming are bound to each other, and a bound layer 41 as shown in Fig. 6 is obtained.

[0035] The aqueous binder solution 4 is a liquid that contains water and a binder component capable of binding the particles of the powder for molding 1 together.

[0036] The surface tension of the aqueous binder solution 4 is set to 20 mN / m or more and 40 mN / m or less. The driving force of the permeation due to the capillary phenomenon tends to increase as the surface tension of the aqueous binder solution 4 increases. Therefore, if the surface tension of the aqueous binder solution 4 is within the above range, even if the particle surfaces of the powder for molding 1 are given hydrophobicity, the permeability of the aqueous binder solution 4 can be increased, and the shape accuracy of the binding layer 41 can be improved. In addition, the surface tension of the aqueous binder solution 4 is preferably 20 mN / m or more and 35 mN / m or less, and more preferably 20 mN / m or more and 30 mN / m or less.

[0037] If the surface tension of the aqueous binder solution 4 is below the lower limit, the driving force for the permeation of the aqueous binder solution 4 supplied to the powder layer 31 due to capillary action does not work sufficiently. As a result, the aqueous binder solution 4 does not permeate the powder layer 31 sufficiently, and the shape precision of the binding layer 41 decreases. On the other hand, if the surface tension of the aqueous binder solution 4 is above the upper limit, the surface tension becomes excessive, and the droplets of the aqueous binder solution 4 tend to become spherical. As a result, the aqueous binder solution 4 does not permeate the powder layer 31 easily.

[0038] The surface tension of the aqueous binder solution 4 is measured using a surface tensiometer. Examples of the surface tensiometer include the CBVP-Z surface tensiometer manufactured by Kyowa Interface Science Co., Ltd.

[0039] Examples of binder components contained in the aqueous 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, and phenolic resins. By adding these components to a solvent or dispersion medium containing water, the surface tension of the aqueous binder solution 4 tends to decrease. Therefore, the surface tension of the aqueous binder solution 4 can be adjusted depending on the amount of binder component added.

[0040] Of these, polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) is preferably used as the binder component. The aqueous binder solution 4 containing these binder components has an appropriate affinity and viscosity for the shaping powder 1, and also has good binding properties. Therefore, such an aqueous binder solution 4 contributes to the production of an additive manufacturing body 6 with particularly good shape accuracy.

[0041] The concentration of the binder component in the aqueous 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 aqueous binder solution 4 and ensures sufficient binding strength between the particles of the powder for molding 1. Furthermore, by setting the concentration of the binder component within the above range, the surface tension of the aqueous binder solution 4 can be optimized.

[0042] Furthermore, when the aqueous binder solution 4 contains a liquid other than water, the liquid may be, for example, alcohols, ketones, carboxylates, etc., and a mixture containing at least one of these may be used. By adding these components to water, the surface tension of the aqueous binder solution 4 tends to decrease. This allows the surface tension of the aqueous binder solution 4 to be adjusted.

[0043] The water content in the aqueous binder solution 4 is adjusted appropriately depending on the target value of the surface tension, but is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This allows the water ratio in the aqueous binder solution 4 to be sufficiently increased, and the environmental load when the aqueous binder solution 4 is dried or disposed of can be reduced.

[0044] In addition to the above components, the aqueous binder solution 4 may contain additives such as a viscosity adjuster, a surfactant, a moisturizing agent, a stabilizer, a defoaming agent, a crosslinking agent, and an antioxidant.

[0045] The total content of the additives in the aqueous 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.

[0046] The moving speed of the inkjet head 26 is not particularly limited, but is preferably 0.1 mm / s to 20 mm / s, more preferably 1 mm / s to 15 mm / s, and even more preferably 3 mm / s to 10 mm / s. By setting the moving speed of the inkjet head 26 within the above range, the ejection position accuracy of the droplets of the aqueous binder solution 4 can be improved. This can improve the shape accuracy of the binder layer 41, and the shape accuracy of the finally obtained layered object 6 can be improved.

[0047] If the moving speed of the inkjet head 26 is lower than the lower limit, the manufacturing efficiency of the layered object 6 may decrease. On the other hand, if the moving speed of the inkjet head 26 is higher than the upper limit, the accuracy of the droplet ejection position decreases, and the shape accuracy of the binder layer 41 may decrease.

[0048] The moving speed of the inkjet head 26 is the average speed of the inkjet head 26 measured at the timing of ejecting droplets of the aqueous binder solution 4 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 of ejecting droplets, and averaging the measured values.

[0049] The interval between droplets of the aqueous binder solution 4 is not particularly limited, but is preferably 1 μm to 90 μm, more preferably 5 μm to 80 μm, even more preferably 10 μm to 70 μm, and particularly preferably 20 μm to 60 μm. By setting the interval between droplets of the aqueous binder solution 4 within the above range, the aqueous binder solution 4 can be supplied uniformly and in a sufficient amount.

[0050] The interval between droplets of the aqueous binder solution 4 may be less than the lower limit, but in that case, the improvement in the shape precision of the layered object 6 cannot be expected to be significant, and it becomes difficult to increase the moving speed of the inkjet head 26, which may reduce the production efficiency of the layered object 6. On the other hand, if the interval between droplets of the aqueous binder solution 4 exceeds the upper limit, the droplets of the aqueous binder solution 4 that land on the powder layer 31 are too far apart, and a continuous coating film is not formed. As a result, there is a high probability that particles that cannot be bound will be generated, and the shape precision of the layered object 6 will decrease.

[0051] The interval between droplets of the aqueous binder solution 4 is determined by measuring the distance between droplets within a 5 mm x 5 mm area after discharging the aqueous binder solution 4 onto a smooth surface that does not absorb the aqueous binder solution 4 under the same conditions as when the aqueous binder solution 4 is discharged onto the formation region 60, and averaging the measured values. 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.

[0052] Furthermore, the volume of the droplets of the aqueous binder solution 4 discharged from the inkjet head 26 is not particularly limited, but is preferably 1 pL to 10 pL, more preferably 1 pL to 8 pL, and even more preferably 2 pL to 6 pL. By setting the volume of the droplets of the aqueous binder solution 4 within the above range, it is possible to improve the accuracy of the droplet discharge position, particularly at the outer edge of the binder layer 41. This makes it possible to improve the shape accuracy of the portion of the layered product 6 that corresponds to the outer edge of the binder layer 41.

[0053] If the volume of the droplets of the aqueous binder solution 4 falls below the lower limit, it becomes difficult to increase the moving speed of the inkjet head 26, and the production efficiency of the layered object 6 decreases. On the other hand, if the volume of the droplets of the aqueous binder solution 4 exceeds the upper limit, the mass of the droplets increases. This increases the impact when the droplets land on the powder layer 31, and the shape accuracy of the binder layer 41 decreases, leading to a decrease in the shape accuracy of the layered object 6.

[0054] The volume of the droplets of the aqueous 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 aqueous binder solution 4 onto a smooth surface that does not absorb the aqueous binder solution 4 under the same conditions as those for discharging the aqueous binder solution 4 onto the formation region 60. The average value is the average value of the volumes determined from 10 or more droplets randomly selected.

[0055] Simultaneously with or after the supply of the aqueous binder solution 4, a drying process may be performed on the powder layer 31 to which the aqueous binder solution 4 has been supplied. Examples of the drying process include a heating process and a gas blowing process. The drying process can promote the drying of the powder layer 31 to which the aqueous binder solution 4 has been supplied. This allows the penetration range of the aqueous binder solution 4 to be controlled as desired, and the shape precision of the layered object 6 finally obtained can be further improved.

[0056] The heating temperature when heating is not particularly limited, but is preferably from 50°C to 250°C, and more preferably from 70°C to 200°C.

[0057] Furthermore, in the case where the binder has photocuring properties or UV curing properties, the heat treatment may be a light irradiation treatment or a UV irradiation treatment, which allows the binder to be solidified or hardened in a shorter time.

[0058] 1.5.Repetitive process In the repeating step S108, the powder layer forming step S102, the filling degree adjusting step S104, and the binder solution supplying step S106 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 layered object 6 having a desired three-dimensional shape as shown in FIG. 10 is obtained.

[0059] Specifically, first, a new powder layer 31 shown in Fig. 7 is formed on a binder layer 41 shown in Fig. 6. Next, as shown in Fig. 8, an aqueous 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.

[0060] 1.6.Removal process In the removal step S110, the binder layer 41 is removed from the powder layer 31. In this way, the layered object 6 is obtained.

[0061] In addition, the molding powder 1 that does not form the binder layer 41 in the powder layer 31 is collected and reused as necessary, that is, it is provided again for manufacturing the layered object 6.

[0062] 2. Metal powder Next, the metal powder will be described.

[0063] 2.1.Constituent Materials The metal material contained in the metal powder is not particularly limited, but when a metal sintered body is produced from the additive manufacturing 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, Fe-based metal materials are preferably used as the metal material. Fe-based metal materials refer to metal materials in which the content of Fe exceeds 50% in terms of atomic ratio. Fe-based metal materials are easy to obtain and can be used to produce metal sintered bodies with excellent mechanical properties.

[0064] 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.

[0065] 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 a metal powder composed 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.

[0066] 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.

[0067] Examples of ferritic stainless steels include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.

[0068] Examples of martensitic stainless steel include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.

[0069] Examples of precipitation hardening stainless steel include SUS630 and SUS631.

[0070] Examples of austenitic-ferritic (duplex) stainless steels include SUS329J1, SUS329J3L, and SUS329J4L.

[0071] 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.

[0072] The layered object 6 may be manufactured using the powder for molding 1 containing different types of metal materials. For example, when the layered object 6 is composed of two or more binder layers 41, one binder layer 41 may be manufactured using the powder for molding 1 containing a first metal material, and another binder layer 41 may be manufactured using the powder for molding 1 containing a second metal material.

[0073] The powder for molding 1 has a coating that covers the surface of the core particle (metal particle) made of the above-mentioned metal material. This coating contains a compound derived from a coupling agent having a hydrophobic functional group. By providing such a coating, the powder for molding 1 can be obtained that maintains high fluidity and high packing ability when forming the powder layer 31 even when placed in a high-temperature and high-humidity environment. Also, by providing the coating, the affinity between the powder for molding 1 and the binder can be increased.

[0074] The coupling agent may be a compound having a hydrophobic functional group and a hydrolyzable group, and specific examples thereof include a silane coupling agent, a titanium coupling agent, and a zirconium coupling agent. The following chemical formula is an example of the molecular structure of a silane coupling agent.

[0075] [ka]

[0076] In the above formula, X is a functional group, Y is a spacer, and OR is a hydrolyzable group, and R is, for example, a methyl group or an ethyl group.

[0077] The hydrolyzable group is, for example, an alkoxy group, a halogen group, etc., and among these, in the case of an alkoxy group, a silanol is generated by hydrolysis. This silanol reacts with the hydroxyl group generated on the surface of the metal particle, and the coupling agent adheres to the surface of the metal particle.

[0078] The coupling agent may contain at least one such alkoxy group, but preferably contains two or more, and more preferably contains three alkoxy groups as shown in the above formula. In other words, the coupling agent preferably contains a dialkoxy group, and more preferably contains a trialkoxy group. A coupling agent containing a trialkoxy group reacts with three hydroxyl groups generated on the surface of the metal particles. For this reason, the coating derived from the coupling agent has good adhesion to the metal particles. In addition, a coupling agent containing a trialkoxy group has excellent film-forming properties, so a coating with excellent continuity can be obtained. Such a coating contributes to further increasing the fluidity of the powder for molding 1.

[0079] Examples of hydrophobic functional groups that the coupling agent has include alkyl groups, vinyl groups, cyclic structure-containing groups, fluoroalkyl groups, and fluoroaryl groups, and in particular, cyclic structure-containing groups, fluoroalkyl groups, and fluoroaryl groups are preferably used. These hydrophobic functional groups are not easily denatured even in high temperature and high humidity environments. Therefore, by using these hydrophobic functional groups, it is possible to obtain a molding powder 1 that has good fluidity and filling properties even when stored in a high temperature and high humidity environment.

[0080] Among these, examples of coupling agents having a cyclic structure-containing group include coupling agents having an aryl group and coupling agents having a cyclic ether group. The cyclic structure-containing group is preferably an aryl group, and more preferably a phenyl group. These have excellent heat resistance, and therefore contribute to the realization of a molding powder 1 that is less likely to lose fluidity or filling properties even when exposed to a high-temperature environment.

[0081] Examples of coupling agents having an aryl group include Phenyltrimethoxysilane represented by the following formula (A-1):

[0082] [ka]

[0083] Phenyltriethoxysilane represented by the following formula (A-2):

[0084] [ka]

[0085] Dimethoxydiphenylsilane represented by the following formula (A-3):

[0086] [ka]

[0087] 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane represented by the following formula (A-4):

[0088] [ka] etc.

[0089] Examples of coupling agents having a cyclic ether group include 3-glycidoxypropylmethyldimethoxysilane represented by the following formula (A-5):

[0090] [ka]

[0091] 3-glycidoxypropyltrimethoxysilane represented by the following formula (A-6):

[0092] [ka]

[0093] 3-glycidoxypropylmethyldiethoxysilane represented by the following formula (A-7):

[0094] [ka]

[0095] 3-glycidoxypropyltriethoxysilane represented by the following formula (A-8):

[0096] [ka] etc.

[0097] Examples of coupling agents having a fluoroalkyl group include: Trimethoxy(3,3,3-trifluoropropyl)silane represented by the following formula (B-1):

[0098] [ka]

[0099] Trimethoxy(1H,1H,2H,2H-tridecafluoro-n-octyl)silane represented by the following formula (B-2):

[0100] [ka]

[0101] Trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane represented by the following formula (B-3):

[0102] [ka] etc.

[0103] Examples of coupling agents having a fluoroaryl group include: Trimethoxy(11-pentafluorophenoxyundecyl)silane represented by the following formula (C-1):

[0104] [ka]

[0105] Pentafluorophenyldimethylchlorosilane represented by the following formula (C-2):

[0106] [ka] etc.

[0107] The amount of the coupling agent added is not particularly limited, but is preferably from 0.01% to 1.00% by mass, and more preferably from 0.05% to 0.50% by mass, based on the metal particles.

[0108] The coupling agent is supplied by placing it in a chamber containing metal particles, or by spraying it into the chamber. This causes the metal particles to react with the coupling agent. After that, by heating as necessary, a coating is formed on the surfaces of the metal particles.

[0109] 2.2.Various characteristics of metal powders Next, various characteristics of the metal powder will be described.

[0110] 2.2.1.Particle size distribution When the particle size distribution of a metal powder is obtained on a volume basis using a laser diffraction particle size distribution measuring device, the particle size at which the cumulative frequency is 10% from the small diameter side is defined as D10. Similarly, the particle sizes at which the cumulative frequency is 50% and 90% from the small diameter side are defined as D50 and D90. Examples of particle size distribution measuring devices include Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0111] The particle size D50 (average particle size D50) of the metal powder 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 filling property and flowability of the molding powder 1 to be compatible. As a result, a dense layered molded body 6 with high shape accuracy can be obtained, and by using this, a metal sintered body with high density and high shape accuracy can be finally manufactured.

[0112] If the particle size D50 is below the lower limit, the particles of the powder 1 for molding tend to aggregate. This reduces the fluidity of the powder 1 for molding, and reduces the filling ability and shape accuracy of the layered object 6. On the other hand, if the particle size D50 is above the upper limit, the particles of the powder 1 for molding tend to become large. This makes it easier for the particle shape to be reflected on the surface of the layered object 6, and reduces the shape accuracy.

[0113] 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 powder 1 for molding relatively uniform, making it easier to increase the fluidity and ensuring 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.

[0114] 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 powder 1 for molding 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 the sinterability may decrease. On the other hand, if the ratio D90 / D50 exceeds the upper limit, the particle size distribution widens and the fluidity may decrease.

[0115] 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 powder for molding 1, and provides high fluidity. As a result, the filling property of the powder for molding 1 is improved, and a dense layered molded body 6 with high shape accuracy can be obtained.

[0116] If the particle size difference D90-D10 is below the lower limit, the particle size distribution of the powder 1 for shaping becomes too narrow, making it difficult to increase the filling rate and possibly reducing the shape accuracy of the layered object 6. On the other hand, if the particle size difference D90-D10 exceeds the upper limit, the particle size distribution of the powder 1 for shaping becomes broader and the flowability decreases. As a result, the shape accuracy of the layered object 6 to be manufactured may decrease.

[0117] 2.2.2.Average circularity The average circularity of the metal powder is 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 to roll easily even if the particle size of the powder for molding 1 is small, and the packed state can be made close to the closest packing. As a result, it is possible to achieve both the packing property and the fluidity of the powder for molding 1. This makes it possible to obtain a dense layered molded body 6 with high shape accuracy, and by using this, it is possible to finally manufacture a metal sintered body with high density and high shape accuracy.

[0118] If the average circularity is below the lower limit, the fluidity of the powder for molding 1 decreases and the filling rate decreases. On the other hand, if the average circularity is above the upper limit, the manufacturing difficulty increases and the manufacturing efficiency of the powder for molding 1 decreases.

[0119] The average circularity of the metal powder is measured as follows. First, an image (secondary electron image) of the metal powder is taken with a scanning electron microscope (SEM). Next, the obtained image is loaded into image processing software. For example, the image processing software used is "Mac-View", an image analysis type particle size distribution measurement software made by Mountec Co., Ltd. The imaging magnification is adjusted so that 50 to 100 particles are captured in one image. Then, multiple images are taken so that a total of 300 or more particle images are obtained.

[0120] 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 the metal powder. Note that when the circularity is e, the area of ​​the particle image is S, and the perimeter of the particle image is L, the circularity e can be calculated using the following formula. e=4πS / L 2

[0121] 2.2.3.Oxygen content The oxygen content of the metal powder is preferably 1000 ppm to 4000 ppm by mass, more preferably 1500 ppm to 3500 ppm by mass, and even more preferably 2000 ppm to 3000 ppm by mass. If the oxygen content of the metal powder is within the above range, it is possible to suppress the adsorption of moisture and the change in characteristics over time. In other words, a molding powder 1 with high storage stability can be obtained.

[0122] If the oxygen content is below the lower limit, the oxide film on the surface of the metal powder particles may become thin and may be easily deteriorated over time. On the other hand, if the oxygen content is above the upper limit, the metal powder may easily adsorb moisture, and the moisture content of the metal powder may increase, which may reduce the flowability of the powder for molding 1.

[0123] The oxygen content of the metal powder is measured, for example, in accordance with the general rules for determining oxygen content in metallic materials as specified in JIS Z 2613: 2006. Specifically, the oxygen content can be measured using a LECO oxygen / nitrogen analyzer, TC-300 / EF-300, a LECO oxygen / nitrogen / hydrogen analyzer, ONH836, or the like.

[0124] 3.Metal powder manufacturing method Next, an example of a method for producing metal powder will be described.

[0125] The metal powder may be produced by any method, for example, by the atomization method. In the atomization method, molten metal is allowed to flow down from a crucible and collide with a fluid such as a liquid or gas sprayed at high speed. The molten metal that collided with the fluid falls by inertia, and the droplets are made spherical at that time. As a result, it is possible to produce a metal powder that has a relatively small diameter but a high average circularity and a relatively small specific surface area.

[0126] The produced metal powder may be classified as necessary by a method such as dry classification, such as sieving classification, inertial classification, or centrifugal classification, or wet classification, such as sedimentation classification.

[0127] 4. Manufacturing method of metal sintered body A metal sintered body is obtained by subjecting the layered molded body 6 to a sintering treatment. In the sintering treatment, the layered molded body 6 is heated to cause a sintering reaction.

[0128] FIG. 11 is a process diagram for explaining the method for producing a metal sintered body. The manufacturing method for a metal sintered body shown in Figure 11 includes a manufacturing process S202 for obtaining an additive manufacturing body 6 by the manufacturing method for an additive manufacturing body described above, and a sintering process S204 for sintering the additive manufacturing body 6 to obtain a metal sintered body.

[0129] 4.1. Molding process In the modeling step S202, the layered object 6 is obtained by the above-mentioned method for manufacturing the layered object.

[0130] 4.2.Sintering process In the sintering step S204, the layered molded body 6 is sintered to obtain a metal sintered body.

[0131] The sintering temperature varies depending on the constituent material and particle size of the 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.

[0132] 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.

[0133] When the sintering process performed under the above conditions is referred to as "main sintering", at least one of "pre-sintering" and "degreasing" corresponding to pre-treatment for the main sintering may be performed on the layered product 6 as necessary. This makes it possible to remove at least a part of the binder contained in the layered product 6 and sinter a part of the layered product 6. This makes it possible to suppress unintended deformation during the main sintering.

[0134] 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 powder for molding 1, but is preferably 100° C. or more and 500° C. or less, and more preferably 150° C. or more and 300° C. or less. The time for the preliminary sintering and degreasing is preferably 5 minutes or more, more preferably 10 minutes or more and 120 minutes or less, and even more preferably 20 minutes or more and 60 minutes or less, within the above temperature range. The atmosphere for the preliminary sintering and degreasing can be, for example, an air atmosphere, an inert atmosphere such as nitrogen or argon, or a reduced pressure atmosphere obtained by reducing the pressure of these atmospheres.

[0135] 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.

[0136] 5. Advantages of the above embodiment As described above, the method for manufacturing a layered object according to the embodiment includes a powder layer forming step S102, a packing degree adjusting step S104, and a binder solution supplying step S106. In the powder layer forming step S102, particles for shaping (powder for shaping 1) having metal particles and a coating film provided on the surface of the metal particles and containing a compound derived from a coupling agent having a hydrophobic functional group are laid in a layer to form a powder layer 31. In the packing degree adjusting step S104, the powder layer 31 is compressed so that the relative density is 40% or more. In the binder solution supplying step S106, an aqueous binder solution 4 having a surface tension of 20 mN / m or more and 40 mN / m or less is supplied to the powder layer 31 that has been subjected to the packing degree adjusting step S104.

[0137] According to this configuration, the aqueous binder solution 4 is supplied to the powder layer 31 in which the distance between the particles for shaping is sufficiently small, so that the aqueous binder solution 4 can easily penetrate even if the surfaces of the particles for shaping are made hydrophobic. Therefore, the penetration range of the aqueous binder solution 4 can be controlled as desired, and a uniform binding layer 41 can be formed. As a result, the layered object 6 with high shape accuracy can be manufactured.

[0138] In addition, since the surfaces of the shaping particles are given hydrophobicity, the particles can maintain high fluidity and packing properties even when placed in a high-temperature and high-humidity environment. Therefore, the powder layer 31 has excellent packing properties for the shaping particles, and from this viewpoint, the shape precision of the layered object 6 can be improved.

[0139] Furthermore, in the method for manufacturing a layered object according to the embodiment, the binder solution supplying step S106 may include a drying process for drying the powder layer 31 to which the aqueous binder solution 4 has been supplied.

[0140] This configuration can promote drying of the powder layer 31 to which the aqueous binder solution 4 has been supplied. This allows the penetration range of the aqueous binder solution 4 to be controlled as desired, and the shape precision of the final layered object 6 can be further improved.

[0141] Moreover, in the method for manufacturing an additive manufacturing object according to the embodiment, the powder layer forming step S102, the filling degree adjusting step S104, and the binder solution supplying step S106 are repeated multiple times. According to this configuration, a layered object 6 having a desired three-dimensional shape can be obtained.

[0142] In the method for producing an additive manufacturing object according to the embodiment, the hydrophobic functional group is a fluoroalkyl group, a fluoroaryl group, or a group containing a ring structure.

[0143] According to this configuration, a powder for modeling 1 is obtained that exhibits good fluidity and filling properties even when stored in a high-temperature and high-humidity environment, so that a layered model 6 with high shape accuracy can be ultimately manufactured.

[0144] In the method for producing an additive manufacturing object according to the embodiment, the hydrophobic functional group is a phenyl group.

[0145] The phenyl group has excellent heat resistance, and therefore contributes to realizing a molding powder 1 that is resistant to deterioration in fluidity and filling properties, even when exposed to a high-temperature environment.

[0146] In the method for manufacturing an additive manufacturing object according to the embodiment, the powder layer forming step S102 and the filling degree adjusting step S104 may be performed simultaneously. According to such a configuration, the efficiency of manufacturing the layered object 6 can be improved.

[0147] The above describes the method for manufacturing an additive manufacturing object of the present invention based on the illustrated embodiment. However, the present invention is not limited to this embodiment. For example, any purposed process may be added to the embodiment. EXAMPLES

[0148] Next, specific examples of the present invention will be described. 6. Manufacturing of powder for modeling First, metal powders with different particle sizes were produced by water atomization while changing the manufacturing conditions. The material of the metal powder was precipitation hardening stainless steel SUS630 (17-4PH).

[0149] 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.

[0150] Next, a coating was formed on the particle surface of the metal powder using a coupling agent shown in Table 1. In this way, the molding powder of each sample No. was obtained.

[0151] In Table 1, layered objects manufactured using a manufacturing method corresponding to the present invention are referred to as "Examples", and layered objects manufactured using a manufacturing method not corresponding to the present invention are referred to as "Comparative Examples".

[0152] Moreover, compound D-1 shown in Table 1 is propyltrimethoxysilane, and compound D-2 is vinyltrimethoxysilane.

[0153] 7. Evaluation of Powders for Molding 7.1. Filling properties of powder for molding 50g of each sample No. of the molding powder was subjected to a heat treatment at 200°C for 24 hours in an air atmosphere. The heat-treated molding powder was then placed in a 50mL screw cap bottle. The screw cap bottle was then held upright and the height from the bottom to the top of the powder was measured. The measured height was then compared to the following evaluation criteria to evaluate the filling property of the molding powder. The evaluation results are shown in Table 1.

[0154] A: Height is 25mm or less (especially high filling ability) B: Height is greater than 25 mm and less than 30 mm (slightly high filling ability) C: Height is over 30 mm (poor filling ability)

[0155] 7.2. Penetration time of aqueous binder solution into powder layer The molding powder of each sample number was placed in a transparent container and compressed to the relative density shown in Table 1 to obtain a molding powder packing that imitated a powder layer. The container used was a rectangular prism-shaped container made of fluororesin, measuring 6.0 mm wide, 6.3 mm long, and 35.0 mm high.

[0156] Next, the container containing the filler was set in a contact angle meter. Then, 25 μL of the aqueous binder solution shown in Table 1 was dropped onto the filler, and the contact angle meter was used to measure the time it took for the aqueous binder solution to penetrate (penetration time). The measured penetration time was then evaluated against the following evaluation criteria to evaluate the penetration time of the aqueous binder solution into the powder layer. The evaluation results are shown in Table 1.

[0157] A: The penetration time is 10 seconds or less (the penetration speed is particularly fast). B: The penetration time is more than 10 seconds and less than 30 seconds (the penetration speed is somewhat fast). C: Penetration time is more than 30 seconds (slow penetration rate)

[0158] 8. Evaluation of the additive manufacturing product 8.1. Density of the additively manufactured object In 7.2, the aqueous binder solution was allowed to penetrate into the powder for modeling, and then the aqueous binder solution was dried and solidified to obtain a modeled body in which the particles of the powder for modeling were bound together by the binder.

[0159] The mass and volume of the obtained molded object were measured, and the density of the molded object was calculated from the measurement results. The density of the layered molded object was evaluated by comparing the calculation results with the following evaluation criteria. The evaluation results are shown in Table 1.

[0160] A: The density of the additive manufacturing body is particularly high. B: The density of the additive manufacturing body is somewhat high. C: The density of the additive manufacturing object is low

[0161] 8.2. Shape Accuracy of Layered Objects First, a rectangular parallelepiped layered object was fabricated by the binder jet method using the modeling powder of each sample number. The size of the layered object fabricated was 40 mm in length, 20 mm in width, and 5 mm in thickness. For the aqueous binder solution, a PVP aqueous solution containing PVP at a concentration of 10% by mass and a humectant at a concentration of 12% by mass was used. In addition, the volume of the droplets of the aqueous binder solution, the moving speed of the inkjet head, and the ejection interval of the droplets of the aqueous binder solution in the binder jet method were set to the values ​​shown in Table 1.

[0162] Next, the obtained layered object was observed with a digital microscope that functions as a non-contact surface roughness measuring device. Next, the arithmetic mean roughness Ra of the surface of the layered object was measured based on the observation results. The shape accuracy of the layered object was evaluated based on the measurement results against the following evaluation criteria. The evaluation results are shown in Table 1.

[0163] A: The arithmetic mean roughness Ra is 4.0 μm or less (particularly high shape precision) B: The arithmetic mean roughness Ra is greater than 4.0 μm and less than 7.0 μm (shape precision is somewhat high) C: The arithmetic mean roughness Ra is more than 7.0 μm (low shape accuracy)

[0164] [Table 1]

[0165] As shown in Table 1, in each example, the filling property of the powder for modeling was sufficiently high, and the powder layer formed using the powder for modeling had good permeability of the aqueous binder solution. It was also found that the layered objects obtained in each example had high density and high shape accuracy. [Explanation of symbols]

[0166] 1...Powder for modeling, 2...Layered modeling device, 4...Aqueous binder solution, 6...Layered model, 21...Device body, 22...Powder supply elevator, 23...Modeling stage, 24...Coater, 25...Roller, 26...Inkjet head, 31...Powder layer, 41...Binder layer, 60...Formation area, 211...Powder storage section, 212...Modeling section, S102...Powder layer formation process, S104...Filling degree adjustment process, S106...Binder solution supply process, S108...Repeat process, S110...Removal process, S202...Modeling process, S204...Sintering process

Claims

1. a powder layer forming step of laying a layer of shaping particles having metal particles and a coating film formed on the surface of the metal particles and containing a compound derived from a coupling agent having a hydrophobic functional group; a packing density adjusting step of compressing the powder layer so that the relative density is 40% or more; a binder solution supplying step of supplying an aqueous binder solution having a surface tension of 20 mN / m or more and 40 mN / m or less to the powder layer that has been subjected to the filling degree adjusting step; A method for producing a layered object, comprising:

2. The method for manufacturing an layered object according to claim 1 , wherein the binder solution supplying step includes a drying process for drying the powder layer to which the aqueous binder solution has been supplied.

3. The method for producing an layered object according to claim 1 or 2, wherein the powder layer forming step, the filling degree adjusting step, and the binder solution supplying step are repeated a plurality of times.

4. The method for producing an layered object according to claim 1 or 2, wherein the hydrophobic functional group is a fluoroalkyl group, a fluoroaryl group, or a group containing a ring structure.

5. The method for producing an additive manufacturing object according to claim 1 or 2, wherein the hydrophobic functional group is a phenyl group.

6. The method for producing an additive manufacturing object according to claim 1 or 2, wherein the powder layer forming step and the packing degree adjusting step are carried out simultaneously.

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