WO2023120316A1 - グラファイトの造形方法、および、グラファイト造形物 - Google Patents

グラファイトの造形方法、および、グラファイト造形物 Download PDF

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Publication number
WO2023120316A1
WO2023120316A1 PCT/JP2022/046019 JP2022046019W WO2023120316A1 WO 2023120316 A1 WO2023120316 A1 WO 2023120316A1 JP 2022046019 W JP2022046019 W JP 2022046019W WO 2023120316 A1 WO2023120316 A1 WO 2023120316A1
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Prior art keywords
powder
graphite
silicon carbide
laser beam
mol
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PCT/JP2022/046019
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English (en)
French (fr)
Japanese (ja)
Inventor
元毅 沖仲
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Canon Inc
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Canon Inc
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Priority to CN202280084929.XA priority Critical patent/CN118510722A/zh
Publication of WO2023120316A1 publication Critical patent/WO2023120316A1/ja
Priority to US18/750,045 priority patent/US20240336487A1/en
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/30—Producing shaped prefabricated articles from the material by applying the material on to a core or other moulding surface to form a layer thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
    • C04B35/565—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present invention relates to a technology for manufacturing an article containing graphite as a main component using a raw material powder containing graphite, using a powder bed fusion bonding method.
  • Graphite has excellent properties such as heat resistance, heat dissipation, electrical conductivity, and chemical resistance, so structures containing graphite are used in various fields.
  • Patent Document 1 discloses a method for obtaining a compact by compression molding a graphite mixture containing rhombohedral graphite and optionally additives and/or binders, followed by heat treatment in the absence of oxygen. It is
  • Patent Document 2 a graphite molded body is produced by combining a step of removing the solvent from a graphene oxide molded product obtained by molding a graphene oxide solvent dispersion, and reducing the product by electric heating and a step of applying pressure. has been proposed.
  • the powder bed fusion method which is one of the additive manufacturing technologies (so-called 3D printing), is being used for the manufacture of articles.
  • the powder bed fusion method is a method of shaping an article to be manufactured by irradiating a raw material powder such as a metal or resin with a laser to melt the article according to the shape data of the article to be manufactured.
  • the use of the powder bed fusion method provides a high degree of freedom in shaping and allows a shaped article to be obtained in a relatively short period of time.
  • graphite has a very high melting point of 3,700 to 4,000°C, making it difficult to shape graphite powder by irradiating it with a laser to melt it.
  • the present invention is a method for manufacturing an article containing graphite, comprising the steps of laying powder and irradiating the powder with laser light to solidify the powder, wherein the powder is carbonized with graphite powder
  • the silicon powder is included, and in the step of solidifying the powder, the laser is irradiated under the condition that the silicon carbide powder is decomposed into carbon and silicon.
  • FIG. 1 is a schematic diagram of an apparatus according to the invention
  • FIG. It is the schematic which shows the order of laser irradiation in this invention. It is a schematic diagram showing the order of laser irradiation in the prior art. It is a figure which shows the focus position of a laser beam.
  • FIG. 4 is a diagram showing light intensity distributions at a focus position and a defocus position of laser light; It is a figure showing a mode that the laser beam is irradiated in the defocused state, and modeling is carried out.
  • the raw material powder is spread evenly to a predetermined thickness, and the laser beam is scanned according to the slice data generated from the shape data of the modeling model to melt the powder in milliseconds and then solidify it. It is a method of repeating the process.
  • Graphite has a very high melting point of 3700-4000°C, so it is difficult to mold while scanning the laser beam and melting the graphite powder in milliseconds.
  • resin is mixed with graphite powder and melted by laser light to form a binder, organic substances must be removed (degreasing) at the end, and the formed object shrinks due to the degreasing.
  • a high level of proficiency is required of the operator.
  • silicon carbide has a higher resistivity than graphite, it is equivalent to graphite in heat resistance, thermal conductivity, linear expansion coefficient, etc., and is a material superior in mechanical strength to graphite.
  • the physical properties of the article obtained by the present invention deviate from the physical properties of graphite alone depending on the mixing ratio of graphite powder and silicon carbide powder. It is possible.
  • Silicon carbide is a sublimation substance that vaporizes at 3500° C., but decomposes into carbon and silicon in a temperature range of 2800° C. or more and less than 3500° C., and at least part of the thermally decomposed silicon exists in the state of melt. . Therefore, when a mixed powder of graphite powder and silicon carbide powder is irradiated with a laser at a temperature at which silicon carbide decomposes into carbon and silicon, that is, at a temperature of 2800° C. or more and less than 3500° C., the silicon melt is used as a binder. Graphite powder can be solidified. If the temperature is less than 2800° C., silicon carbide does not thermally decompose, so that no silicon melt is generated.
  • silicon carbide can be decomposed. It can be pyrolyzed to form a silicon melt. The silicon melt soaks into the graphite powder and solidifies after the laser beam passes through. As a result, the graphite powder is solidified and modeling becomes possible.
  • the binder is silicon, unlike organic binders, there is no need to degrease afterward, and it is possible to maintain the accuracy during modeling.
  • the temperature of silicon carbide is raised to a temperature range of 2800° C. or higher and lower than 3500° C., the silicon carbide can be decomposed and a silicon melt can be generated. preferable. Within this temperature range, it is possible to stably generate a silicon melt.
  • the raw material powder used in the present invention is a mixed powder of graphite powder and silicon carbide powder.
  • the total amount of graphite powder and silicon carbide powder should be 90% mol % or more of the entire powder, preferably 95 mol% or more. Preferably, it is 98 mol % or more.
  • the raw material powder must contain 20 mol % or more of silicon carbide powder.
  • the silicon carbide powder contained in the raw material powder is preferably 50 mol % or less. Therefore, the silicon carbide powder contained in the powder is preferably 20 mol % or more and 50 mol % or less, more preferably 25 mol % or more and 40 mol % or less.
  • the amount of resin contained in the powder is preferably less than 0.2 mol %, preferably 0.1 mol % or less, and more preferably 0.05 mol % or less.
  • the particle diameter of the particles contained in the raw material powder is preferably 0.5 ⁇ m or more and 200 ⁇ m or less, more preferably 1 ⁇ m or more and 70 ⁇ m or less. If the particles contained in the raw material powder fall within this range, particle fluidity suitable for laying the powder during molding can be obtained, and molding of fine shapes becomes possible.
  • the temperature of the laser beam irradiation part is generally adjusted by the irradiation intensity of the laser beam (laser power), the scanning speed of the laser beam, the scanning interval of the laser beam, and the thickness of the powder. be.
  • the silicon carbide of the laser beam irradiation part can be kept in a more appropriate temperature range. It becomes possible to raise the temperature to As a result, it is possible to stably thermally decompose silicon carbide to generate a silicon melt.
  • FIG. 1 shows an outline of the configuration of a modeling apparatus 100 used in the powder bed fusion method.
  • the modeling apparatus 100 includes a chamber 101 provided with a gas introduction port 113 and an exhaust port 114. By introducing gas through the gas introduction port 113 and exhausting it through the exhaust port 114, the internal atmosphere can be controlled. can.
  • a pressure adjusting mechanism such as a butterfly valve may be connected to the exhaust port 114 in order to adjust the pressure. (referred to as blow replacement) may be connected.
  • FIG. 1 is an example of a modeling apparatus, and the present invention is not limited to this, and can be modified as appropriate.
  • the modeling container 120 for modeling a three-dimensional object, and a powder container 122 containing raw material powder (hereinafter sometimes simply referred to as powder) 106.
  • the modeling container 120 has a heating function, and can heat the powder and the modeled object in the container.
  • the bottoms of the modeling container 120 and the powder container 122 can be changed in vertical position by the lifting mechanism 109, respectively.
  • the bottom of the modeling container 120 also functions as a modeling stage 108 on which a base plate 121 can be installed.
  • the raw material powder contained in the powder container 122 is conveyed to the modeling container 120 by the powder spreading mechanism 107 and laid on the base plate 121 installed on the modeling stage 108 with a predetermined thickness.
  • the moving direction and moving amount of the lifting mechanism 109 are controlled by the control unit 115 according to the thickness of the raw material powder laid on the base plate 121 . Since the raw material powder is generally laid on the base plate 121 with a thickness of 10 ⁇ m or more and 50 ⁇ m or less, the height resolution of the lifting mechanism 109 is preferably 1 ⁇ m or less.
  • the powder spreading mechanism 107 has at least one of a squeegee and a roller to convey the raw material powder 106 from the powder container 122 to the modeling container 120 and evenly spread the raw material powder 106 to a set thickness.
  • a squeegee and a roller In order to increase the density of the modeled object, it is preferable to have both a squeegee and a roller, and after adjusting the thickness of the powder with the squeegee, pressurize the powder with the roller to increase the density of the powder.
  • the modeling apparatus 100 further includes a laser light source 102 for melting the laid raw material powder, scanning mirrors 103A and 103B for biaxially scanning the laser light 112, and condensing the laser light 112 on the irradiation section.
  • An optical system 104 is provided for. Since the laser beam 112 is irradiated from the outside of the chamber 101, the chamber 101 is provided with an introduction window 105 for introducing the laser beam 112 inside. Various parameters related to the laser beam 112 are controlled by the controller 115 .
  • the positions of the modeling container 120 and the optical system 104 are preferably adjusted in advance so that the beam diameter of the laser beam has a desired value on the surface of the laid raw material powder 106 . Since the beam diameter on the surface of the laid raw material powder 106 affects the molding accuracy, it is preferably 30 ⁇ m or more and 100 ⁇ m or less, more preferably 30 ⁇ m or more and 50 ⁇ m or less.
  • a galvanomirror can be preferably used as the scanning mirrors 103A and 103B. Since the galvanomirror operates at high speed while reflecting laser light, it is desirable that it be made of a material that is lightweight and has a low coefficient of linear expansion.
  • a YAG laser which is highly versatile, is often used as the laser light source 102, but a CO 2 laser, a semiconductor laser, or the like may also be used.
  • the drive system may be a pulse system or a continuous irradiation system.
  • As the laser beam 112 light having a wavelength corresponding to the absorption wavelength of the raw material powder 106 may be selected. It is preferable to use light with a wavelength at which the raw material powder 106 has an absorptivity of 50% or more, and more preferably light with a wavelength at which the absorptance is 80% or more.
  • the base plate 121 is placed on the modeling stage 108, and the interior of the chamber 101 is replaced with an inert gas such as nitrogen or argon.
  • an inert gas such as nitrogen or argon.
  • the raw material powder 106 is laid on the modeling surface of the base plate 121 by the powder spreading mechanism 107 .
  • the thickness of the raw material powder 106 to be laid is determined based on the slice pitch of slice data generated from the shape data of the three-dimensional model to be manufactured, that is, the lamination pitch.
  • the raw material powder 106 is scanned with the laser beam 112 according to the slice data, and the raw material powder in a predetermined area is irradiated with the laser beam.
  • the raw material powder 106 is solidified in the region irradiated with the laser beam 112 to become a solidified portion 110, and the region not irradiated with the laser beam 112 becomes the unsolidified portion 111 where the powder remains.
  • the elevation mechanism 109 lowers the modeling stage 108 and raises the bottom of the powder container 122 according to the layer pitch. Then, the raw material powder 106 in the powder container 122 is conveyed to the molding container 120 by the powder spreading mechanism 107, and the raw material powder is newly laid on the molding surface composed of the solidified portion (modeled object) 110 and the unsolidified portion 111. , the laser beam 112 is irradiated while scanning.
  • the solidified portion 110 corresponding to one layer of slice data will be referred to as a solidified layer, and the layered and integrated solidified layers will be referred to as a solidified portion 110 .
  • the base plate 121 is made of a fusible material such as stainless steel.
  • a fusible material such as stainless steel.
  • silicon carbide is a sublimation substance, if there is a portion heated to 3500° C. or higher in the region irradiated with the laser beam, it will rapidly vaporize and scatter the surrounding powder. This makes it difficult to form. Therefore, in the present invention, as described above, in addition to the laser power, the scanning speed of the laser beam, the scanning interval of the laser beam, and the thickness of the powder, dispersed irradiation of the laser beam, reduction of the temperature gradient in the irradiation spot, auxiliary heating By controlling the temperature, more stable modeling is possible.
  • Methods of controlling laser power include a method of controlling in-plane power density and a method of controlling spatial power density.
  • the in-plane power density is the irradiation intensity of the laser light per unit area, and the unit is J/mm 2 .
  • Spatial power density is the irradiation intensity of laser light per unit volume and is expressed as J/mm 3 .
  • JV W/(PxVxD)
  • W is the laser power
  • P is the irradiation pitch (scanning interval) of the laser light
  • V is the scanning speed of the laser light
  • D is the thickness of the raw material powder.
  • the laser power W is 10 W or more and 1000 W or less
  • the laser beam irradiation pitch P is 5 ⁇ m or more and 500 ⁇ m or less
  • the laser beam scanning speed is 10 mm/sec or more and 10000 mm/sec or less
  • the raw material powder thickness D is 5 ⁇ m. It is more than 500 micrometers or less.
  • the parameters of W, P, V, and D may be controlled using the above range as a guide so that JV is 10 J/mm 3 or more and 100 J/mm 3 or less.
  • the lower limit of 10 J/mm 3 is the energy required to melt the powder to the extent that the silicon carbide powder can be solidified
  • the upper limit of 100 J/mm 3 is the energy required to vaporize the silicon carbide to form a model. This is an area where it becomes impossible.
  • the irradiation region into a plurality of regions and perform discrete irradiation.
  • An example of irradiation order is described in each region.
  • the size of the irradiation area is preferably a rectangle with a side of 1 mm or more and 5 mm or less and an area of 1 mm 2 or more and 25 mm 2 or less.
  • the shape of the irradiation area does not necessarily have to be rectangular, and may be polygonal, circular, or a combination thereof as long as the area is 1 mm 2 or more and 25 mm 2 or less. It is preferable to be able to fill the plane with combinations.
  • the size of one area divided into rectangles is preferably 5 mm ⁇ 5 mm or less, more preferably 2 mm ⁇ 2 mm or less.
  • a focus state and a defocus state will be described with reference to conceptual diagrams in FIGS. 3A and 3B.
  • a focused state refers to a state in which the laser beam is focused on the surface of the laid powder
  • a defocused state refers to a state in which the laser beam is not focused on the surface of the laid powder.
  • the defocus state refers to a state in which the focal position specified by the condensing optical system of the device being used is deviated from the surface of the laid powder.
  • the light intensity distribution at the focus position of the laser beam 112 (cross section A-A' in FIG. 3A) is a steep Gaussian distribution as shown in the upper diagram of FIG. 3B.
  • the intensity distribution of the laser beam 112 at the defocus position is gentler than that at the focus position, as shown in the lower diagram of FIG. 3B.
  • the difference in light intensity between the central part and the peripheral part of the irradiation spot becomes large. There is a risk that heating exceeding 3500 ° C.
  • a method of defocusing has been described as a method of reducing the temperature gradient within the irradiation spot of the laser beam, but it is not limited to this method.
  • a method of irradiating the modeling powder with a top-hat distribution of light intensity using a beam shaping element is also preferable.
  • FIG. 4 shows how raw material powder 117 laid on modeling surface 116 is irradiated with laser light 112 in a defocused state for modeling.
  • the raw material powder 117 indicates powder that is laid to form one solidified layer.
  • the focus position F is shifted upward (in the direction away from the base plate 121) from the surface of the raw material powder 117 laid on the modeling surface 116.
  • FIG. 4 shows how raw material powder 117 laid on modeling surface 116 is irradiated with laser light 112 in a defocused state for modeling.
  • the raw material powder 117 indicates powder that is laid to form one solidified layer.
  • the focus position F is shifted upward (in the direction away from the base plate 121) from the surface of the raw material powder 117 laid on the modeling surface 116.
  • the defocus amount S is preferably greater than 0 mm and 15 mm or less, more preferably 5 mm or more and 10 mm or less, although it depends on the optical system of the modeling apparatus used.
  • the thickness of the raw material powder to be laid per time is preferably 5 ⁇ m or more and 200 ⁇ m or less so that molding can be performed while sufficiently maintaining the adhesion between the solidified layers. Considering the time required for modeling and the modeling accuracy, the thickness is more preferably 10 ⁇ m or more and 100 ⁇ m or less.
  • a metal material with a relatively low melting point such as aluminum or stainless steel, is often used for the base plate 121 . This is because, when forming the first solidified layer, a part of the base plate 121 is melted to integrate the solidified layer and the base plate 121, thereby fixing the solidified portion 110 to the base plate 121. Since these metal materials have high thermal conductivity, when the temperature is raised by the irradiation of the laser beam, the heat is likely to diffuse to the surroundings. can be difficult to secure to As the molding progresses and the solidified portion 110 rises, the diffusion of heat to the base plate decreases. , there is a tendency that the powder cannot be heated sufficiently by the irradiation of the laser beam.
  • a heating mechanism in the modeling container 120 and preheat the powder of the base plate 121 , the solidified portion (modeled object) 110 and the unsolidified portion 111 .
  • the heating mechanism is preferably capable of heating the powder of the solidified portion (modeled object) 110 and the unsolidified portion 111 to 30°C or higher and 100°C or lower.
  • a heater may be installed around the modeling container 120, or a laser for preheating may be provided in addition to the laser for melting the powder.
  • the preheating temperature is less than 30° C., the raw material powder cannot be sufficiently melted due to heat diffusion during laser light irradiation, and the solidified layer between the base plate 121 and the solidified section 110 or laminated with the solidified section 110 is formed. A space may be generated between and peeling may occur. If the preheating temperature exceeds 100°C, the raw material powder tends to agglomerate.
  • the resulting shaped article contains silicon and carbon generated by thermal decomposition in addition to graphite as it is, but when the shaped article is subjected to a heat treatment, the carbon and silicon contained in the shaped article react and are carbonized. It becomes silicon, and it is possible to improve the physical properties of the modeled object.
  • the melting point of silicon is 1414° C.
  • silicon carbide is thermally decomposed at 2800° C. or higher
  • the heat treatment temperature after molding is preferably 1300° C. or higher and 2800° C. or lower, more preferably 1500° C. or higher and 2500° C. or lower.
  • a characteristic structure can be seen in the modeled object produced by the above method.
  • a modeled object that has undergone heat treatment after modeling or after modeling is evaluated by Raman spectroscopy in the depth direction from the surface of the last modeled side
  • the closer to the base plate 121 the closer to the base plate 121 the area with the thickness corresponding to one solidified layer A large amount of silicon carbide is detected.
  • a structure in which regions where the ratio of silicon carbide and graphite changes in one direction appears periodically according to the thickness of the powder to be laid (thickness of the solidified layer) and the number of layers is observed.
  • the silicon carbide on the surface layer side is thermally decomposed into silicon and carbon, and the molten silicon penetrates into the laid powder by gravity and reacts with graphite. It is presumed that the silicon carbide changes to silicon carbide and solidifies to bind the surrounding powder.
  • the modeled object manufactured by the above procedure contains voids inside according to the packing density of the laid powder. Even if the powder is densely packed, only a filling rate of about 70% can be obtained, and scattering of the powder during molding cannot be eliminated. Therefore, it is also preferable to impregnate the shaped article to improve the density, that is, the mechanical strength. By performing pitch impregnation, the voids can be converted to graphite, so that the properties of the finally obtained article can be brought closer to those of graphite.
  • the modeled object is first immersed in pitch, and pressure is applied to impregnate the pitch inside the modeled object.
  • the pitch can be more easily impregnated by defoaming the shaped article in a vacuum or by heating to a temperature equal to or higher than the softening point of the pitch.
  • the pitch-impregnated shaped article is sintered at 700° C. to 1000° C. to carbonize the pitch, the pitch impregnation and sintering are repeated multiple times as necessary.
  • the article is heated at 2700 to 3000° C. to convert the carbonaceous matter into graphite, depending on the properties required for the article.
  • the crystal structure develops and physical property values peculiar to graphite can be obtained.
  • the resulting article has a higher proportion of graphite and exhibits physical properties closer to those of graphite.
  • Example 1 As raw material powders, graphite powder with an average particle size of 30 ⁇ m (manufactured by Ito Graphite Industry Co., Ltd., product name SG-BL30, graphite 99.0 at %) and silicon carbide powder with an average particle size of 14.7 ⁇ m (produced by Taiheiyo Rundum Co., Ltd. , product name NC#800, silicon carbide 98.7 at %) was used. A base plate 121 made of stainless steel was installed on the stage 108 .
  • Graphite powder:silicon carbide powder 50 mol %:50 mol %
  • the N2 gas may be argon gas.
  • the heater of the modeling container 120 was set to 40° C. to preheat the mixed powder and the base plate 121 .
  • the height of the stage 108 was adjusted, and the mixed powder in the powder container 122 was supplied onto the stage 108 by the powder spreading mechanism 107 and laid on the base plate 121 to a thickness of 50 ⁇ m.
  • the powder was irradiated with a laser beam for modeling.
  • the defocus amount S of the laser beam 112 was adjusted to 7 mm by moving the stage up and down.
  • a Nd:YAG laser with a wavelength of 1060 nm was used as a laser light source.
  • a laser power of 100 W, a pitch of 40 ⁇ m, and a scanning speed of 2000 mm/sec were set.
  • the spatial laser power density at this time is calculated as 25 J/mm 3 .
  • the stainless steel used for the base plate 121 has a relatively high thermal conductivity, the irradiation heat of the input laser light may dissipate, and the adhesion between the modeled object and the base plate may become low. In such a case, in addition to preheating, it is advisable to increase the spatial laser power density to 50 J/mm 3 when forming the first 1 to 3 layers.
  • Dispersed irradiation was performed with the laser light. Specifically, the irradiation area was a square with a side of 1 mm, the distance between the centers of adjacent squares was 0.8 mm, and the adjacent irradiation areas were overlapped by 0.1 mm.
  • the subsequently formed solidified layer is formed by moving the irradiated area parallel to the first formed solidified layer by 0.25 mm in a fixed direction within the modeling plane. The angle in the plane was rotated by 18°. With these measures, it was possible to ensure temperature uniformity within the molding surface, and to obtain a relatively high-strength molded object.
  • the modeled object When the irradiation area is not translated and rotated within the modeling surface, the modeled object is formed by stacking square solidified layers with a side of 1 mm, and the square prisms are aligned and closely attached. In such a modeled article, the joining force between the quadrangular prisms was weak, and the modeled article tended to be easily damaged.
  • the modeled object When the modeling by laser irradiation is completed, the modeled object is immersed in the pitch, pressure is applied, and then the pitch-impregnated modeled object is baked at 1000°C, and the process is repeated 2-3 times to reduce the porosity. let me Subsequently, the shaped article was electrically heated to raise the temperature to 3000° C., and the carbonaceous matter of the impregnated pitch was changed to graphite.
  • the porosity of the obtained shaped article before pitch impregnation was about 50%, but the pitch impregnation filled the voids with graphite, and the final composition was approximately 75 mol % graphite and 25 mol % silicon carbide.
  • Bending strength was evaluated by a three-point bending test. Five test pieces were prepared by the above method, and for each of them, the maximum load when broken was P [N], the distance between the external fulcrums was L [mm], the width of the test piece was w [mm], and the test piece When the thickness of is t [mm], 3 ⁇ P ⁇ L/(2 ⁇ w ⁇ t) (Formula 1) was calculated using, and the average value thereof was taken as the bending strength.
  • the resulting product had a bending strength of 54.3 MPa and an electrical resistivity of 13.3 ⁇ m, which are similar to conventional graphite.
  • Example 2 a modeled object was produced in the same manner as in Example 1, except that the composition of the silicon carbide powder used as a binder was changed in graphite modeling.
  • graphite powder with an average particle size of 30.0 ⁇ m manufactured by Ito Graphite Industry Co., Ltd., trade name: SG-BL30, graphite 99.0 at %) and SiC powder with an average particle size of 14.7 ⁇ m (Taiheiyo Random Co., Ltd. (trade name: NC#800) was used.
  • the raw material powder contains 20 mol % or more of silicon carbide that functions as a binder.
  • the composition after pitch impregnation was 90 mol % graphite and 10 mol % silicon carbide.
  • the flexural strength and electrical resistivity were evaluated in the same manner as in Example 1, the flexural strength was 45.1 MPa and the electrical resistivity was 11.9 ⁇ m. was taken.
  • Graphite powder with an average particle size of 30.0 ⁇ m (manufactured by Ito Graphite Industry Co., Ltd., trade name SG-BL30, graphite 99.0 at %) was used as the raw material powder.
  • Modeling Apparatus 102 Energy Beam Source 106 Raw Material Powder 107 Powder Spreading Mechanism 108 Stage 110 Modeled Object 111 Powder Layer 112 Energy Beam

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