Laminated molded object and laminated molding method

Abstract

To provide a laminate in which a plurality of iron-based bodies and a plurality of oxide bodies are overlapped alternately by laminated molding.SOLUTION: A laminated molded object comprises a laminate in which a plurality of iron-based bodies and a plurality of oxide bodies are arranged while being overlapped alternately. For example, the iron-based body contains Si and / or Al, and the oxide body contains one or more of Fe, Si, Cr, Al, Mn, Mg, Ca, or Ti. As an example, the iron-based body is a soft magnetic material, and the oxide body is an insulator. Such a laminate is obtained, for example, when a molten pool formed by melting a raw material powder by irradiation with a high energy beam is separated into an iron-based liquid phase and an oxide liquid phase, the iron-based liquid phase solidifies to form the iron-based body, and the oxide liquid phase solidifies while surrounding the iron-based body to form the oxide body.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to a layered object having a polymer of an iron substrate and an oxide body. [Background technology]

[0002] Unlike conventional subtractive processes (cutting, grinding, cutting, etc.) and molding processes (casting, forging, pressing, etc.), additive manufacturing (AM) is attracting attention as it allows desired objects to be produced without the need for dedicated molds or large machine tools. Additive manufacturing, which involves repeated layering, can produce objects (additively manufactured objects) that were difficult to produce using conventional manufacturing methods.

[0003] Additive processing is broadly classified into seven types (ASTM standard): directed energy deposition (DED), powder bed fusion (PBF), binder jetting, material jetting, material extrusion, vat photopolymerization, and sheet lamination.

[0004] Of these, DED and PBF can produce practical objects made of metal or ceramic. Both DED and PBF have in common the fact that they produce objects by melting and solidifying (bonding) raw material powders (including mixed powders) using a high-energy beam (heat source such as a laser or electron beam). DED aims to reduce the amount of raw material powder used and expand the degree of freedom in modeling. Many proposals have been made regarding this type of additive manufacturing, and for example, there are related descriptions in the following literature. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kanamaru et al., Proceedings of the 2021 Autumn Meeting of the Japan Society for Precision Engineering, (2021) p. 326. [Non-patent document 2] Hideaki Ikehata, et al., Grain refinement of Fe-Ti alloys fabricated by laser powder bed fusion, Materials &Design, 204(2021), 109665 Summary of the Invention [Problem to be solved by the invention]

[0006] Non-Patent Document 1 describes FeSi and FeCoV shaped objects produced by DED, but does not disclose their specific alloy compositions, structures, etc.

[0007] Non-Patent Document 2 reports that in order to improve the mechanical properties of additively manufactured products made of iron-based alloys, the crystal grains generated by PBF (L-PBF) or DED (L-DED) using a laser as a heat source are changed from columnar to fine isotropic crystals.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a new layered object or the like having a polymer of an iron substrate and an oxide body. [Means for solving the problem]

[0009] As a result of extensive research, the inventors have succeeded in producing a polymer in which multiple iron substrates and oxide bodies are alternately layered by additive manufacturing. By expanding on this result, the present invention, which will be described below, has been completed.

[0010] "Layered objects" (1) The present invention is an additive manufacturing object having a polymer in which iron substrates and oxide bodies are alternately stacked and arranged in multiple layers.

[0011] (2) The layered product of the present invention (also referred to simply as the "product" or "polymer") exhibits additive or synergistic properties, functions, or performance of the alternatingly arranged iron substrate and oxide body, and can exhibit excellent effects as a whole product (polymer).

[0012] For example, a polymer composed of an iron substrate with excellent magnetic and mechanical properties and an oxide with excellent insulating and corrosion resistance can stably and efficiently exhibit high performance as an entire molded object. Furthermore, polymers obtained by additive manufacturing not only have a high degree of freedom in shape, but also allow for control of structure and organization. Therefore, the molded object of the present invention is expected to achieve high functionality and high performance that cannot be achieved with conventional products, such as those made by laminating oxide-coated steel plates.

[0013] Additive manufacturing method / manufacturing method (1) The present invention can also be understood as a manufacturing method (additive manufacturing method) for obtaining a polymer or a shaped object. For example, the present invention may be an additive manufacturing method (manufacturing method) for obtaining a polymer in which a molten pool formed by melting raw material powder with irradiation of a high-energy beam is solidified to obtain a polymer in which iron substrates and oxide bodies are alternately stacked and arranged in multiple layers. In this case, for example, the molten pool contains a separated iron-based liquid phase and an oxide liquid phase, and the iron substrate is formed by solidifying the iron-based liquid phase, and the oxide body is formed by solidifying the oxide liquid phase so as to surround the iron substrate.

[0014] The polymer may be the entire object or a part of the object. The object may be a standalone object, or may be formed on the surface of a substrate or the like and integrated with another component (an object produced separately from the object).

[0015] (2) The reason why the shaped object of the present invention can be obtained is thought to be as follows: The molten pool formed by melting the raw material powder can separate into two liquid phases: an iron-based liquid phase and an oxide liquid phase. At this time, the oxide liquid phase usually moves (floats) above the iron-based liquid phase due to the difference in specific gravity (density).

[0016] The separated liquid phases usually have different liquidus and solidus temperatures and do not solidify simultaneously. Therefore, as the temperature of the molten pool decreases, the low-density oxide liquid phase solidifies while remaining in a state where it migrates above the high-density iron-based liquid phase. In this way, a shaped object is obtained in which a low-density oxide body is formed on a high-density iron substrate. By repeating this type of additive manufacturing, oxide bodies are interposed between the iron substrates and the outer surface of the iron substrate is surrounded by oxide bodies. In this way, it is possible to obtain a polymer in which multiple iron substrates and oxide bodies are alternately and closely adjacent to each other through additive manufacturing.

[0017] (3) Additive manufacturing is performed by, for example, directed energy deposition (DED) or powder bed fusion (PBF). DED, in particular, can efficiently fabricate polymers made of iron or oxide substrates in the desired shape at the desired location.

[0018] The heat source (high-energy beam) that melts the powder is a laser beam, an electron beam, a plasma arc, etc. For convenience, this specification will mainly focus on L-DED (LMD) that uses a laser beam, which is a typical heat source.

[0019] Powder for additive manufacturing The present invention can also be understood as a raw material powder (powder for additive manufacturing) to be used in an additive manufacturing method. The powder for additive manufacturing may be a single type of alloy powder or a mixed powder consisting of multiple types of powder. The component composition (blended composition) of the raw material powder and the overall composition of the molded object (total composition of the iron substrate and oxide body) do not necessarily have to be the same. The component composition may be affected by factors such as melting into the substrate that forms the molded object. The powder composition may be adjusted taking this into consideration.

[0020] "others" (1) The iron substrate and the oxide body may be laminated, for example, in 3 or more layers, 5 or more layers, or even 10 or more layers. The polymer may be formed from the iron substrate and the oxide body without changing the raw material powder.

[0021] (2) The term "iron-based" as used herein may refer to pure iron or an iron alloy. It may also refer to a composite material that uses either of these as a matrix. The iron substrate and the iron-based liquid phase do not need to have the same composition.

[0022] (3) Unless otherwise specified, "x to y" in this specification includes a lower limit value x and an upper limit value y. Any numerical value included in the various numerical values ​​or numerical ranges described in this specification may be used as a new lower limit or upper limit value to create a new range such as "a to b." In this specification, "x to y μm" means x μm to y μm. The same applies to other unit systems. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram illustrating additive manufacturing by LMD. [Figure 2A] FIG. 10 is a schematic diagram showing the process of forming a single piece. [Figure 2B] The photographs show the appearance of the prototype (actual product) and a microscopic image of the cross section (including a magnified image). [Figure 3A] 1 is a schematic diagram illustrating a polymer shaping process. FIG. [Figure 3B] This is a photograph showing the exterior of the prototype (actual product). [Figure 4A] 1 shows microscopic images of cross sections of polymers with different line spacings. [Figure 4B] 1 shows microscopic images of cross sections of polymers having different blend compositions of raw material powders. [Figure 5A] FIG. 1 is a schematic diagram showing a state in which an iron substrate and an oxide body are layer-by-layer manufactured using different raw material powders. [Figure 5B] FIG. 1 is a schematic diagram showing an iron alloy body and an oxide body shaped in the direction of polymerization using different raw material powders. DETAILED DESCRIPTION OF THE INVENTION

[0024] The components of the present invention may be supplemented with one or more components arbitrarily selected from the present specification. The contents described in this specification apply not only to "products" (e.g., shaped objects, powders) but also to "methods" (e.g., shaping methods, manufacturing methods), as appropriate.

[0025] Polymer / Sculpture (1) A polymer is composed of multiple iron substrates (iron alloy substrates) and oxide substrates arranged alternately and closely. As long as there are two or more iron substrates, the specific number of iron substrates and oxide substrates arranged is not important. In a polymer immediately after additive manufacturing, the iron substrate is usually covered with oxide substrates. Therefore, when viewed in the direction in which the iron substrates are arranged in order (polymerization direction), if there are multiple iron substrates, there will also be multiple oxide substrates (number of iron substrates + 1). Of course, if all or part of the oxide substrates on the outer surface of the polymer are removed, the number of oxide substrates viewed in the polymerization direction may be the same as the number of iron substrates, or may be less than the number of iron substrates (for example, number of iron substrates - 1).

[0026] The spacing or thickness of the iron substrates or oxide bodies as viewed in the direction of stacking can be adjusted by the trajectory of the high-energy beam (the number and spacing of its scanning lines) and the component composition of the raw material powder. For example, increasing the line spacing or increasing the oxide or oxygen content in the raw material powder increases the spacing of the iron substrates or the thickness of the oxide bodies. Conversely, decreasing the line spacing or decreasing the oxide or oxygen content in the raw material powder decreases the spacing of the iron substrates or the thickness of the oxide bodies.

[0027] The line spacing and the distribution of the number of lines may be constant, may vary periodically, or may differ for each desired location. In addition, a single line of an object may correspond to one (scanning) line, or a single line of an object may be formed corresponding to multiple lines.

[0028] The number of overlaps (the number of iron substrates or oxide bodies arranged in the overlapping direction) is adjusted by the number of lines or the number of line groups (bundles). The length of the iron substrate and oxide body is adjusted by the distance in the scanning direction. The height of the iron substrate and oxide body is adjusted by the number of layers. The length and height may be constant or may vary depending on the location or region.

[0029] (2) The form and use of the iron substrate and oxide body are not important. For example, the substrate may be wall-shaped, plate-shaped (including thin plate-shaped), or foil-shaped. The oxide body may be layered or film-shaped. The iron substrate may have a controlled metal structure as well as a controlled appearance (shape). For example, an iron substrate having a metal structure with grain growth along the easy axis of magnetization can exhibit excellent magnetic properties in a desired direction. Conversely, an iron substrate having an isotropic metal structure can exhibit non-directional magnetic properties. Therefore, for example, the iron substrate may be a soft magnetic material and the oxide body may be an insulator. Such a polymer can be a substitute for, for example, a laminate of insulating-coated electrical steel sheets.

[0030] The oxide body may be a single structure entirely made of oxide (metal oxide), or a composite structure with particles dispersed in a matrix. At least one of the matrix and the dispersed particles (at least one type) may be an oxide. For example, one of the matrix and the dispersed particles may be an oxide, and the other may be a metal or other compound (including an intermetallic compound). The oxide body may contain pores or voids inside. The shaped object (polymer) may be any of a raw material, intermediate material, final product, etc.

[0031] (3) The iron substrate (or iron-based liquid phase) may be pure iron or an iron alloy containing Si, Ni, Mo, Mn, Cr, Al, Mg, Ti, Zr, C, or the like. For example, the Si content is 0.5 to 14% or 1 to 6.5%, the Cr content is 0.1 to 5% or 1 to 3%, the Al content is 0.02 to 4% or 0.2 to 2%, the Ni content is 1 to 40% or 5 to 20%, and the Mo content is 1 to 20% or 2 to 8% based on the total iron substrate. Furthermore, the Mn, Mg, Ti, Zr, and the like content is less than 3%, 2% or less, or 1% or less. The C content is 0.8% or less or 0.4% or less. The iron substrate may also contain O. Unless otherwise specified, the component composition (concentration) referred to in this specification is the atomic ratio (atomic %) relative to the total target, and is appropriately indicated by "%" or only a numerical value.

[0032] The oxide body (or oxide liquid phase) may contain, for example, one or more of Fe, Si, Cr, Al, Mn, Mg, Ca, Ti, etc., along with O. Oxides that can form the oxide body include FeO, Fe2O3, Fe3O4, Cr2O3, Al2O3, Fe2SiO4, Cr2FeO4, TiO2, Ti2O3, etc.

[0033] For example, Fe is contained in an amount of 15 to 35% or 20 to 30%, Si in an amount of 5 to 20% or 8 to 15%, and Cr in an amount of 1 to 15% or 3 to 10% relative to the entire oxide body. Note that Ni, Mo, etc. are hardly contained in the oxide body (oxide liquid phase).

[0034] 《Raw material powder》 The raw material powder used in additive manufacturing should have a component composition that allows a molten pool (liquid phase) to form when irradiated with a high-energy beam and separate into an iron-based liquid phase and an oxide liquid phase. The raw material powder can be prepared by any method, form (shape, size), or manufacturing process. For example, the raw material powder may be a single alloy powder, a mixed powder made up of multiple types of powders, or a granulated powder. The raw material powder may be an atomized powder or a pulverized powder. The particle size of the raw material powder is, for example, 5 to 150 μm or 20 to 105 μm. The particle size referred to in this specification is determined, for example, by sieving (classification).

[0035] The raw material powders may be adjusted in composition so that an iron-based liquid phase and an oxide liquid phase are present in the molten pool. For example, the iron-based powder and oxide powder may be blended in a mass ratio of 70:30 to 97:3 or 75:25 to 96:4 relative to the total mass.

[0036] The overall composition of the raw material powder may be, for example, 25-45% or 30-40% of the total of one or more of Fe, Cr, Al, Mn, Mg, Ca, and Ti, 3-20% or 5-10% of Si, and the balance: O and (unavoidable) impurities. In particular, the raw material powder preferably contains 20-45% or 25-35% of Fe and / or 0-25% or 3-15% of Cr.

[0037] 《Application》 The polymer (shaped object) can be used, for example, as a soft magnetic member (yoke, core, etc.) to be used in an alternating magnetic field. Specifically, it can be used as all or part of a rotor or stator of an electric motor (including a generator), an iron core for a transformer, etc. The thickness of such an iron substrate in the direction of polymerization is, for example, 0.3 to 3 mm or 0.5 to 1.5 mm. The thickness of the oxide body is, for example, 0.01 to 1.5 mm or 0.1 to 0.7 mm. The electrical resistivity of the oxide body can be, for example, 1 to 10 7 Ωcm or 10 1 ~10 6 Oxides with high electrical resistivity usually have excellent corrosion resistance and contribute to the corrosion prevention of iron substrates. [Example]

[0038] A sample was fabricated by additive manufacturing using LMD (L-DED) of an iron substrate and a polymer of an oxide body, and its appearance and structure (cross section) were evaluated. The present invention will be described in more detail based on this specific example.

[0039] <<Sample Preparation>> (1) Raw material powder Pure Fe powder (particle size <106 μm) was prepared as the iron-based powder, and O-30.0Fe-8.5Si-15Cr powder (%) was prepared as the oxide powder. In this example, atomized powder (single type) of molten metal prepared to the desired composition was used, but a mixed powder in which multiple types of elemental powders were weighed and blended may also be used.

[0040] The oxide powder used was a mixed powder of SiO2 powder (D50: 100 μm), FeO powder (D50: 30 μm), and pure Cr powder (<63 μm) blended in the above composition. Each powder was used after removing powder with a particle size of less than 45 μm. The particle size of the powder was indicated by classification using a sieve (mesh) or by the median diameter (D50).

[0041] (2) Additive Manufacturing Additive manufacturing was performed on a substrate (steel plate / SS400) using L-DED (LMD), as shown in Figure 1. The direction in which the processing head (laser) moves linearly is called the scanning direction (Y direction), the direction in which linear objects (called "lines") are arranged adjacent to each other in sequence is called the stacking direction (X direction), and the direction in which the lines are stacked is called the stacking direction (Z direction).

[0042] The details of the molding conditions are as follows: The raw material powder placed in the powder feeder (powder box) of the LMD device (laser processing test machine manufactured by Enshu Co., Ltd.) was supplied to the powder nozzle using carrier gas (Ar).

[0043] The raw material powder was prepared by mixing the iron-based powder and oxide powder described above. In this example, unless otherwise specified, a mixed powder was used in which the iron-based powder and oxide powder were weighed and mixed in a mass ratio of 80:20. The composition of the mixed powder as a whole was Fe-2.5Si-13.5O-4.4Cr (%).

[0044] The irradiation conditions for the fiber laser (YLS-4000 manufactured by IPG Corporation / laser wavelength: 1070 nm) were: output: 800 W, beam diameter (focus diameter): 2.5 mm, scanning speed: 800-1600 mm / min. Powder supply rate: 0.06 g / s, Ar flow rate: 10 L / min. All molding was performed in air at room temperature. One line formed by one pass along the scanning direction was approximately 1.5-2 mm wide x 11-15 mm long x 0.1-0.3 mm high. Unless otherwise specified, the number of layers was 20.

[0045] (3) Non-consolidated First, as shown in Figure 2A, a wall-shaped (rod-shaped, plate-shaped) unit (basic shape) was formed by repeatedly stacking layers on one line. Figure 2B shows a photograph of the appearance of the resulting actual product (approximately 2 mm wide x 15 mm long x 3 mm high), as well as a microscopic image of its longitudinal cross section (XZ cross section) observed with a digital microscope (Keyence Corporation) and a magnified image.

[0046] As can be seen from FIG. 2B, a shaped article was obtained in which the entire outer peripheral surface of the wall-shaped iron alloy body (iron substrate) was surrounded (coated) with an oxide layer (oxide body).

[0047] Thus, even when the structures were stacked in the stacking direction, the iron alloy layer and the oxide layer did not alternate in the stacking direction. Moreover, the oxide layer (thickness: approximately 200 to 250 μm) was in close contact with the iron alloy body (thickness: approximately 1.5 mm) and surrounded the iron alloy body.

[0048] The reason why such a shaped object (single object) was obtained is thought to be that each time the laser was irradiated, a separation into two liquid phases occurred: an iron alloy liquid phase (iron-based liquid phase) and an oxide liquid phase, and the oxide liquid phase, which has a lower specific gravity, moved above the iron alloy liquid phase and solidified on the sides and top of the iron alloy body.

[0049] Furthermore, when the cross section of the single piece was analyzed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM), it was found that the composition of the iron alloy body was almost entirely Fe (Fe≧97%), and the oxide layer was mainly composed of oxides containing Fe, Si, and Cr (FeO, Fe2SiO4, Cr2FeO4, etc.). Furthermore, the white particles scattered throughout the oxide layer were iron-based particles (Fe≧97%).

[0050] (4) Polymer Next, as shown in Figure 3A, we repeated the process of forming one layer at a time in the stacking direction on each of the three lines arranged in the direction of stacking. The line spacing (distance between center lines) was 2 mm (equidistant). A photograph of the appearance of the resulting actual product (approximately 6 mm wide x 11 mm long x 4.5 mm high) is shown in Figure 3B.

[0051] Microscope images (including enlarged images) of the longitudinal cross sections (XZ cross sections) are shown in Figures 4A and 4B. Figure 4A also shows cross sections of polymers with line spacings of 2.25 mm and 2.5 mm. In both cases, the blending ratio (mass ratio) of iron-based powder to oxide powder was 80:20. In both cross-sectional images, the width (in the direction of polymerization) of the iron alloy body was approximately 1.5 mm, and as the line spacing was increased, the width (thickness) of the oxide layer expanded in the following order: approximately 500 μm, approximately 700 μm, and approximately 1000 μm.

[0052] Furthermore, Figure 4B also shows cross sections of polymers with iron-based powder and oxide powder blending ratios of 90:10 and 95:5. The line spacing was fixed at 2 mm. In this case, the width of the iron alloy body (in the direction of polymerization) was approximately 1.5 mm, and the width (thickness) of the oxide layer expanded with the increase in oxide powder.

[0053] In this way, a polymer was obtained with an oxide layer interposed between the wall-shaped iron alloy bodies formed in the polymerization direction. The outer surface of the iron alloy body was also covered with an oxide layer. Furthermore, it was found that the thickness of the oxide layer formed between the iron alloy bodies could be adjusted by varying the line spacing and the blending of raw material powders. It was also found that excessive line spacing or excessive oxide powder resulted in the formation of iron-based particles and voids in the oxide layer. Incidentally, the width (thickness) of the iron alloy body can be adjusted, for example, by changing the focused diameter of the laser or the component composition of the raw material powder, or by increasing or decreasing the number of lines per iron alloy body.

[0054] "supplement" (1) As shown in Figure 5A, even if the raw material powder is changed for each layer and the process of forming an oxide layer on an iron alloy layer is repeated, a polymer in which the iron alloy body and the oxide body are arranged alternately in the stacking direction cannot be obtained. This is because the oxide layer resolidifies and moves upward each time an iron alloy layer is formed. Therefore, it is difficult to obtain a polymer in which the polymerization direction is the stacking direction using an additive manufacturing method.

[0055] (2) As shown in Figure 5B, by repeatedly changing the raw powder for each adjacent line and molding it, it appears at first glance that a polymer in which iron alloy bodies and oxide bodies are arranged alternately can be obtained. However, it is practically difficult to mold only oxide bodies in the stacking direction. Oxides are brittle ceramics, and the large heat input received with each stack causes distortion to accumulate, resulting in large cracks inside the oxide or peeling at the interface with the adjacent iron alloy.

[0056] From the above, it was confirmed that the present invention can provide a polymer in which iron substrates and oxide bodies are alternately stacked in a direction different from the stacking direction.

Claims

1. An additive manufacturing object having a polymer in which iron substrates and oxide bodies are alternately stacked and arranged in multiple layers.

2. The layered object according to claim 1 , wherein the iron substrate and the oxide body are formed into at least three layers.

3. The iron substrate is in the form of a plate or foil, The additive manufacturing method according to claim 1 , wherein the oxide body is in the form of a layer or a film.

4. the iron substrate is a soft magnetic material, The layered object according to any one of claims 1 to 3, wherein the oxide body is an insulator.

5. This is an additive manufacturing method in which a raw material powder is melted by irradiating it with a high-energy beam, and the resulting molten pool is solidified to obtain a polymer in which iron substrates and oxide bodies are alternately stacked and arranged in multiple layers, the molten pool comprises a separated iron-based liquid phase and an oxide liquid phase; The iron substrate is formed by solidifying the iron-based liquid phase, The oxide body is formed by solidifying the oxide liquid phase while surrounding the iron substrate.

6. The layered manufacturing method according to claim 1 , wherein the iron substrate and the oxide body are manufactured without changing the raw material powder.

7. The additive manufacturing method according to claim 5, which is carried out by directed energy deposition or powder bed fusion.

8. The layered manufacturing method according to any one of claims 5 to 7, wherein the thickness of the oxide body is adjusted by the line spacing for scanning the high-energy beam and / or the component composition of the raw material powder.

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