Thixotropic molding material, method for producing thixotropic molding material, and thixotropic molded body

Abstract

To provide a thixomolded body with high mechanical strength and high rigidity, and to provide a material for thixomolding capable of manufacturing such a thixomolded body, and a manufacturing method thereof.SOLUTION: A material for thixomolding includes: a metal body mainly composed of Mg; and a coating part comprising SiO2 particles adhering on the surface of the metal body via a binder, and mainly composed of SiO2. An average particle diameter of the SiO2 particles is less than 20.0 μm, and a mass fraction of the SiO2 particles with respect to the total mass of the metal body and the SiO2 particles is 1.0 mass% or more and 40.0 mass% or less. Further, the binder preferably contains waxes. Furthermore, the content of the binder is preferably 0.001 mass% or more and 0.200 mass% or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a material for thixotropic molding, a method for producing a material for thixotropic molding, and a thixotropic molded article. [Background technology]

[0002] Magnesium has a low specific gravity and is excellent in electromagnetic shielding, vibration damping, machinability, and biological safety. For these reasons, magnesium alloy parts are beginning to be used in products such as automobiles, aircraft, mobile phones, and laptops.

[0003] For example, Patent Document 1 discloses a method for manufacturing a semiconductor device using a first material having magnesium and a second material having SiO 2 A step of mixing the magnesium alloy with a second material containing the component to obtain a mixture, a step of filling the mixture into a die to obtain a powder compact, and a step of heating the powder compact to obtain a mixture of magnesium and SiO. 2 and reacting a magnesium-based composite material with

[0004] Furthermore, Patent Document 2 discloses a method for producing a magnesium-based composite material, which includes the steps of compacting magnesium composite powder in which silica powder is attached to the surfaces of magnesium alloy coarse particles, heating the resulting solidified body to generate compound particles in the solidified body by solid-phase reaction synthesis, and densifying the solidified body in which the compound particles are generated.

[0005] In the magnesium-based composite material produced in this way, SiO 2 By adding (silica), it is possible to improve the strength, wear resistance, etc. of the magnesium alloy. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO 03 / 069001

Patent Document 2

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The manufacturing methods described in Patent Documents 1 and 2 as such go through a process of compressing and molding a mixture or magnesium composite powder. For this reason, there is a problem that the shape of the molded body to be manufactured is restricted and the degree of freedom of the shape is low. Further, in these methods, since the interface between magnesium and SiO 2 is an interface between solids, the contact property between the interfaces is poor. For this reason, in these methods, the reactivity between magnesium and SiO 2 is low, and the magnesium alloy cannot be sufficiently improved, so that there is a problem that the mechanical strength and rigidity of the molded body to be manufactured are insufficient.

MEANS FOR SOLVING THE PROBLEMS

[0008] The thixoforming material according to an application example of the present invention is a metal body mainly composed of Mg, SiO2 particles mainly composed of SiO2 that adhere to the surface of the metal body via a binder and a coating portion including the SiO2 particles, having an average particle diameter of the SiO2 particles of less than 20.0 μm, a mass fraction of the SiO2 particles in the total mass of the metal body and the SiO2 particles of 1 .0 mass% or more and 40.0 mass% or less , The content rate of the binder in the thixotropic molding material obtained after degreasing is 0.00 1 mass% or more and 0.200 mass% or less. characterized by that.

[0009] The manufacturing method of the thixoforming material according to an application example of the present invention is a metal body mainly composed of Mg, SiO2 particles mainly composed of SiO2, and a binder , a preparation step of preparing a mixture containing a solvent and, a stirring step of stirring the mixture, heating the stirred mixture to remove at least one part of the binder contained in the mixture to obtain a thixotropic molding material, a degreasing step, having, the mass fraction of the SiO2 particles in the total mass of the metal body and the SiO2 particles is 1 .0 mass% or more and 40.0 mass% or less, After the degreasing process, the content of the binder in the thixotropic molding material is 0 .001 mass% or more and 0.200 mass% or less.

[0010] The thixotropic molded body according to the application example of the present invention, a matrix part mainly composed of Mg, a first particle part dispersed in the matrix part and mainly composed of Mg2Si, dispersed in the matrix part and existing independently of the first particle part, with MgO as the main component, a second particle part, having, observing the cross-section, in the range of 500 μm square centered at a point 1 mm deep from the surface the total area fraction of the first particle part and the second particle part is 1.0% or more and 55.0% or less and , Let the average particle diameter of the first particle part be D(Mg2Si), and the average particle diameter of the second particle part be D( MgO). When the ratio of the average particle diameters D(Mg2Si) / D(MgO) is 0.4 or more and 2. 0 or less. characterized by this.

Brief Description of the Drawings

[0011] [Fig. 1] It is a cross-sectional view showing an example of an injection molding machine used in the thixotropic molding method. [Fig. 2] It is a cross-sectional view schematically showing a thixotropic molding material according to an embodiment. [Fig. 3] It is a process diagram for explaining a method for manufacturing a thixoforming material according to an embodiment. [Fig. 4] It is a partial cross-sectional view schematically showing a thixoformed body according to an embodiment. [Fig. 5] It is an example of an X-ray diffraction pattern obtained for a thixoformed body according to an embodiment. [Fig. 6] It is an observation image (secondary electron image) when the cut surface of a thixoformed body corresponding to an example is observed with a scanning electron microscope.

Mode for Carrying Out the Invention

[0012] Hereinafter, the thixoforming material, the method for manufacturing the thixoforming material, and the thixoformed body of the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0013] 1. Thixoforming method First, the thixoforming method in which the thixoforming material according to the embodiment is used will be described.

[0014] The thixoforming method is a molding method in which a pellet-shaped or chip-shaped material is heated in a cylinder to a solid-liquid coexisting state in which a liquid phase and a solid phase coexist, and then thixotropy is expressed by the rotation of a screw, and the obtained semi-solidified material is injected into a mold. According to such a thixoforming method, since the fluidity of the semi-solidified material is enhanced by heating and shearing, for example, compared with the die-casting method, thin-walled parts and parts with complex shapes can be molded. FIG. 1 is a cross-sectional view showing an example of an injection molding machine used in the thixoforming method.

[0015] As shown in FIG. 1, the injection molding machine 1 includes a mold 2, a hopper 5, a heating cylinder 7, a screw 8, and a nozzle 9. The mold 2 forms a cavity Cv. When the thixotropic molding material 10 is put into the hopper 5, the thixotropic molding material 10 is supplied to the heating cylinder 7. The thixotropic molding material 10 supplied to the heating cylinder 7 is transferred while being sheared by the screw 8 while being heated by the heater 6. As a result, the thixotropic molding material 10 is semi-melted and slurried. The obtained slurry is injected into the cavity Cv in the mold 2 through the nozzle 9 without being exposed to the atmosphere. Then, by cooling the slurry injected into the cavity Cv, a thixotropic molded body is obtained.

[0016] In addition, other materials may be put into the hopper 5 together with the thixotropic molding material 10.

[0017] 2. Thixotropic Molding Material Next, the thixotropic molding material according to the embodiment will be described. FIG. 2 is a cross-sectional view schematically showing the thixotropic molding material according to the embodiment.

[0018] The thixotropic molding material 10 shown in FIG. 2 is a raw material used in the thixotropic molding method, and includes a chip-shaped metal body 11, a coating portion 12 attached to the surface of the metal body 11, and an adhesive portion 13 including a binder that bonds the metal body 11 and the coating portion 12.

[0019] 2.1. Metal Body The metal body 11 is, for example, a slice obtained by cutting or severing an Mg-based alloy cast in a mold or the like. Note that the manufacturing method of the metal body 11 is not limited to this.

[0020] The metal body 11 has Mg as the main component and contains various additive components. Examples of the additive components include lithium, beryllium, calcium, aluminum, silicon, manganese, iron, nickel, copper, zinc, strontium, yttrium, zirconium, silver, tin, gold, rare earth elements, etc. A mixture of one or more of these is used. Examples of the rare earth element include cerium.

[0021] The main component refers to the element with the highest content rate in the metal body 11. The content rate of the main component is preferably more than 50% by mass, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0022] The additive components preferably include aluminum and zinc. Thereby, the melting point of the metal body 11 is lowered and the fluidity of the slurry is improved. As a result, the moldability of the thixoforming material 10 can be enhanced.

[0023] In addition, the additive components preferably include at least one selected from the group consisting of manganese, yttrium, strontium, and rare earth elements in addition to aluminum and zinc. Thereby, the mechanical properties, corrosion resistance, wear resistance, and thermal conductivity of the thixoformed body can be enhanced.

[0024] The additive components can exist in the metal body 11 in the form of a single substance, alloy, oxide, intermetallic compound, etc. Also, the additive components may be segregated at the grain boundaries of the metal structure such as Mg or Mg alloy in the metal body 11, or may be uniformly dispersed.

[0025] The average particle size of the thixoforming material 10 is not particularly limited, but is preferably 0.5 mm or more, and more preferably 1.5 mm or more and 10.0 mm or less. By setting the average particle size within the above range, the occurrence of bridges and the like in the heating cylinder 7 of the injection molding machine 1 can be suppressed.

[0026] The average particle diameter of the thixotropic molding material 10 is the average value of the diameters of circles having the same area as the projected area of the thixotropic molding material 10. The average value is calculated from 100 or more thixotropic molding materials 10 randomly selected.

[0027] The average aspect ratio of the thixotropic molding material 10 is preferably 5.0 or less, more preferably 4.0 or less. The thixotropic molding material 10 having such an average aspect ratio enhances the filling property in the heating cylinder 7 and improves the temperature uniformity during heating. As a result, a thixotropic molded body having high mechanical properties and high dimensional accuracy can be obtained.

[0028] The average aspect ratio of the thixotropic molding material 10 is the average value of the aspect ratios calculated by the major axis / minor axis in the projected image of the thixotropic molding material 10. The average value is calculated from 100 or more thixotropic molding materials 10 randomly selected. Also, the major axis is the maximum length that can be taken in the projected image, and the minor axis is the maximum length in the direction perpendicular to the major axis.

[0029] 2.2. Coating portion The coating portion 12 contains SiO 2 particles 14 having SiO 2 as the main component. Specifically, for example, the coating portion 12 is formed by a plurality of SiO 2 particles 14 adhering to the surface of the metal body 11.

[0030] The coating portion 12 preferably covers the entire surface of the metal body 11, but may cover a part of the surface.

[0031] SiO 2 The particles 14 are not particularly limited as long as they are particles having silicon oxide as the main component, and may be particles having amorphous SiO 2 (silica glass) as the main component, or particles having SiO 2 crystals (such as quartz) as the main component.

[0032] SiO 2The average particle size of the particles 14 is less than 20.0 μm, preferably 0.5 μm or more and 10.0 μm or less, and more preferably 1.0 μm or more and 8.0 μm or less. SiO 2 By setting the average particle size of the particles 14 within the above range, the balance between the coating rate of the coating portion 12 and the SiO content in the thixotropic molding material 10 can be optimized. Also, when the SiO 2 particles 14 are adhered to the surface of the metal body 11, the SiO 2 particles can be uniformly distributed, and the SiO 2 particles 14 are less likely to fall off. 2 If the average particle size of the particles 14 is less than the lower limit value, the particles 14 are difficult to disperse, so the above-mentioned balance may deteriorate. On the other hand, if the average particle size of the particles 14 exceeds the upper limit value, the particles 14 may be likely to fall off.

[0033] In addition, SiO 2 Regarding the mass fraction of the particles 14 in the total mass of the metal body 11 and the SiO 2 particles 14 in the thixotropic molding material 10, it is 1.0 mass% or more and 40.0 mass% or less, preferably 1.5 mass% or more and 30.0 mass% or less, and more preferably 5.0 mass% or more and 20.0 mass% or less. By setting the mass fraction of the SiO 2 particles 14 within the above range, it is possible to suppress a significant decrease in the mechanical strength of the produced thixotropic molded body while suppressing a decrease in the moldability of the thixotropic molding material 10. 2 If the mass fraction of the particles 14 is less than the lower limit value, there is a possibility that the mechanical strength of the thixotropic molded body cannot be sufficiently increased. On the other hand, if the mass fraction of the particles 14 exceeds the upper limit value, the moldability of the thixotropic molding material 10 may decrease.

[0034] Among the thixotropic molding material 10, the mass fraction of the SiO 2 particles 14 in the total mass of the metal body 11 and the SiO 2 particles 14 is 1.0 mass% or more and 40.0 mass% or less, preferably 1.5 mass% or more and 30.0 mass% or less, and more preferably 5.0 mass% or more and 20.0 mass% or less. By setting the mass fraction of the SiO 2 particles 14 within the above range, it is possible to suppress a significant decrease in the mechanical strength of the produced thixotropic molded body while suppressing a decrease in the moldability of the thixotropic molding material 10.

[0035] In addition, SiO 2 If the mass fraction of the particles 14 is less than the lower limit value, there is a possibility that the mechanical strength of the thixotropic molded body cannot be sufficiently increased. On the other hand, if the mass fraction of the particles 14 exceeds the upper limit value, the moldability of the thixotropic molding material 10 may decrease. 2 If the mass fraction of the particles 14 exceeds the upper limit value, the moldability of the thixotropic molding material 10 may decrease.

[0036] The coating portion 12 may contain substances other than the SiO 2 particles 14. In that case, the content of the substances other than the SiO 2 particles 14 may be less than the content of the SiO 2 particles 14 in terms of mass ratio.

[0037] Also, the SiO 2 particles 14 may contain elements other than Si and O. In that case, the content of the elements other than Si and O may be less than the content of Si and less than the content of O in terms of mass ratio.

[0038] 2.3. Adhesive portion The adhesive portion 13 is interposed between the metal body 11 and the SiO 2 particles 14 or between the SiO 2 particles 14.

[0039] The adhesive portion 13 contains a binder. As the binder, an organic material that binds the metal body 11 and the coating portion 12 is used. For example, polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate, polyethers, polyvinyl alcohol, polyvinyl pyrrolidone, or copolymers thereof, various resins, waxes, alcohols, higher fatty acids, fatty acid metals, higher fatty acid esters, higher fatty acid amides, nonionic surfactants, silicone-based lubricants, etc. are used. Also, the binder may be a mixture containing at least one of these components and other components, or a mixture containing two or more of these components.

[0040] Among these, the binder preferably contains waxes, and more preferably contains paraffin wax or its derivatives. Waxes have good binding properties and are between the metal body 11 and the SiO 2 particles 14 or between the SiO 2Particles 14 can be strongly bonded to each other, and by combining with degreasing conditions, a thixotropic molding material capable of suppressing the generation of gas during molding can be realized.

[0041] Examples of waxes include natural waxes such as candelilla wax, carnauba wax, rice wax, wood wax, plant-based waxes such as jojoba oil, beeswax, lanolin, animal-based waxes such as whale wax, montan wax, ozokerite, mineral-based waxes such as ceresin, paraffin wax, microcrystalline wax, petroleum-based waxes such as petrolatum, synthetic hydrocarbons such as polyethylene wax, modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, hydrogenated waxes such as hydrogenated castor oil, hydrogenated castor oil derivatives, fatty acids such as 12-hydroxy stearic acid, acid amides such as stearic acid amide, and synthetic waxes such as imide phthalate anhydride.

[0042] As described above, the thixotropic molding material 10 according to the embodiment includes a metal body 11 and a coating portion 12. The metal body 11 has Mg as a main component. The coating portion 12 adheres to the surface of the metal body 11 via a binder and contains SiO 2 particles 14 having SiO 2 as a main component. The average particle size of the SiO 2 particles 14 is less than 20.0 μm. Further, the mass fraction of the SiO 2 particles in the total mass of the metal body 11 and the SiO 2 particles 14 is 1.0 mass% or more and 40.0 mass% or less.

[0043] When thixotropic molding is performed using such a thixotropic molding material 10, SiO 2 can be uniformly dispersed when it is in a semi-molten state. As a result, in thixotropic molding, Mg 2 Si and MgO are precipitated while being uniformly dispersed. As a result, a thixotropic molded body having high mechanical strength and high rigidity can be obtained.

[0044] Further, the thixotropic molding material 10 may contain additives other than the above-described metal body 11, coating portion 12, and adhesive portion 13. Examples of the additives include coupling agents, surfactants, dispersants, lubricants, antioxidants, ultraviolet absorbers, thickeners, rust preventives, antiseptics, fungicides, and the like.

[0045] 3. Manufacturing Method of Thixotropic Molding Material Next, a method for manufacturing the above-described thixotropic molding material 10 will be described. FIG. 3 is a process diagram for explaining the manufacturing method of the thixotropic molding material according to the embodiment.

[0046] The manufacturing method of the thixotropic molding material 10 shown in FIG. 3 includes a preparation step S102, a drying step S104, a stirring step S106, and a degreasing step S108.

[0047] 3.1. Preparation Step In the preparation step S102, a mixture containing the metal body 11, SiO 2 particles 14, a binder, and a solvent is prepared. The metal body 11 is the same as the above-described metal body 11. Also, SiO 2 particles 14 are the same as the above-described SiO 2 particles 14.

[0048] The solvent is not particularly limited as long as it is a liquid that disperses the binder. Examples of the solvent include water, isopropanol, acetone, and the like. For mixing, a mixer, a kneader, or the like is used. Note that this step may be a step of preparing a previously prepared mixture.

[0049] The content of the binder in the mixture is not particularly limited, but is preferably 1.0% by mass or more and 30.0% by mass or less, more preferably 2.0% by mass or more and 15.0% by mass or less, and even more preferably 3.0% by mass or more and 10.0% by mass or less. By setting the content of the binder within the above range, the SiO 2 particles 14 can be uniformly dispersed based on the dispersing action of the binder.

[0050] In addition, when the content of the binder is less than the lower limit value, the amount of the binder is insufficient, and it becomes difficult to uniformly adhere the SiO 2 particles 14 to the metal body 11, and there is a possibility that it becomes difficult to uniformly disperse the SiO 2 particles 14. On the other hand, when the content of the binder exceeds the upper limit value, the amount of the binder becomes excessive, and the SiO 2 particles 14 that are not adhered to the metal body 11 are likely to aggregate, and in the debinding step S108 described later, the amount of binder residue increases, and internal defects are likely to occur in the thixoformed body.

[0051] The temperature of the solvent is preferably set to be equal to or higher than the melting point of the binder as necessary. Thereby, the binder is likely to dissolve in the solvent. As a result, the binder can be dispersed more uniformly. The temperature of the solvent is preferably set 10°C or more higher than the melting point of the binder, and more preferably set 20°C or more and 50°C or less higher.

[0052] In this case, the above-described mixture may be put into a container and the whole container may be heated from the outside using a hot bath or the like.

[0053] The melting point of the binder to be used is not particularly limited, but is preferably 40°C or more and 80°C or less, more preferably 43°C or more and 65°C or less, and even more preferably 45°C or more and 60°C or less. If the melting point of the binder is within the above range, the binder can be efficiently melted in a short time. Further, if the melting point of the binder is within the above range, the thixoforming material 10 to be produced has good lubricity in thixoforming and can enhance the flowability of the slurry.

[0054] 3.2. Drying step In the drying step S104, the mixture is dried. Thereby, the SiO 2 particles 14 are adhered to the surface of the metal body 11 via the binder, and the solvent is volatilized to obtain a dried body. Further, in the present embodiment, the SiO 2Since the particles 14 are dispersed, SiO particles 14 can be adhered to the surface of the metal body 11 with a uniform thickness. 2

[0055] For drying, methods such as heating the mixture or exposing the mixture to gas are used. Among these, when heating the mixture, for example, the entire container containing the mixture may be heated using a hot bath or the like. Note that in the drying step S104, all the solvents in the mixture may be removed, or some solvents may remain without being removed.

[0056] The temperature when heating the mixture may be equal to or higher than the temperature at which the solvent volatilizes and the binder softens. Specifically, it is set according to the composition of the solvent, preferably 40°C or higher and 120°C or lower, and more preferably 50°C or higher and 80°C or lower. Thereby, while suppressing the SiO particles 14 adhered to the surface of the metal body 11 from falling off, the solvent can be volatilized and removed. 2

[0057] Also, the heating time of the mixture is appropriately set according to the heating temperature. As an example, it is preferably 10 minutes or more and 300 minutes or less, and more preferably 20 minutes or more and 200 minutes or less.

[0058] Note that the drying step S104 may be performed as necessary, may be omitted, or the drying step S104 and the stirring step S106 may be performed simultaneously.

[0059] 3.3. Stirring Step In the stirring step S106, the mixture is stirred. When the drying step is performed, the dried mixture is stirred. For stirring, methods such as using a stirring rod or a stir bar, or shaking the container containing the mixture with a lid are used. By such stirring, SiO particles 14 can be adhered to the surface of the metal body 11 via the binder. Note that 2 2 ​​​A part of the particles 14 may adhere directly to the surface of the metal body 11 without passing through a binder. Also, aggregation of the metal bodies 11 into lumps can be suppressed by stirring.

[0060] Note that after the stirring step S106, the drying step S104 and the stirring step S106 may be repeated as necessary. Thereby, since the adhesion of the SiO 2 particles 14 is repeated, the SiO 2 particles 14 can be adhered to the surface of the metal body 11 in multiple layers. As a result, more SiO 2 particles 14 can be adhered to the surface of the metal body 11. The number of repetitions is not particularly limited, but is, for example, 2 or more and 10 or less. Also in this case, the drying step S104 and the stirring step S106 may be performed simultaneously.

[0061] 3.4. Degreasing Step In the degreasing step S108, the stirred mixture is subjected to a degreasing treatment. Thereby, the thixotropic molding material 10 is obtained. Examples of the degreasing treatment include a method of heating the mixture and a method of exposing the mixture to a gas that decomposes the binder. Thereby, at least a part of the binder contained in the mixture can be removed. As a result, it is possible to prevent a large amount of the binder from being transferred into the heating cylinder 7 and suppress the generation of a large amount of gas in the heating cylinder 7.

[0062] The heating temperature of the mixture in the degreasing treatment is not particularly limited as long as it is a temperature at which the binder is thermally decomposed, but is preferably 200°C or higher and 500°C or lower, and more preferably 250°C or higher and 450°C or lower. By setting the heating temperature within the above range, the binder can be appropriately removed while suppressing the adverse effect on the metal body 11 due to the degreasing treatment.

[0063] Note that if the heating temperature is lower than the lower limit value, a large amount of binder that cannot be removed remains, and there is a risk of generating a large amount of gas in the heating cylinder 7. On the other hand, if the heating temperature exceeds the upper limit value, there may be an adverse effect on the metal body 11 due to heat, or all the binder may be removed, and SiO 2 particles 14 may fall off from the metal body 11.

[0064] The heating time of the mixture in the degreasing process is not particularly limited, and for example, it may be 5 minutes or more, but preferably 1 hour or more and 100 hours or less, and more preferably 10 hours or more and 50 hours or less. Thereby, while suppressing the adverse effect on the metal body 11 accompanying the degreasing process, the binder can be appropriately removed.

[0065] The amount of the binder after degreasing, that is, the content of the binder in the thixoforming material 10 is not particularly limited, but is preferably 0.001% by mass or more and 0.200% by mass or less, more preferably 0.010% by mass or more and 0.100% by mass or less, and even more preferably 0.015% by mass or more and 0.040% by mass or less. By setting the content of the binder in the thixoforming material 10 within the above range, while ensuring the adhesiveness of the coating portion 12 by the adhesive portion 13, it is possible to prevent the amount of the binder that thermally decomposes in the heating cylinder 7 from becoming more than necessary.

[0066] Note that if the content of the binder is lower than the lower limit value, the amount of the binder is insufficient, and the coating portion 12 may easily fall off. On the other hand, if the content of the binder exceeds the upper limit value, the amount of the binder becomes excessive, a large amount of gas is generated in the heating cylinder 7, and voids are likely to occur in the thixoformed body.

[0067] As described above, the method for manufacturing the thixoforming material 10 according to the present embodiment includes a preparation step S102, a stirring step S106, and a degreasing step S108. In the preparation step S102, a metal body 11 mainly composed of Mg and SiO 2 mainly composed of SiO 2Prepare a mixture containing particles 14, a binder, and a solvent. In the stirring step S106, stir the mixture. In the degreasing step S108, heat the stirred mixture to remove at least a part of the binder contained in the mixture, thereby obtaining the thixotropic molding material 10. Then, the total mass of the metal body 11 and SiO 2 In the mass of the particles 14, the mass fraction of the SiO 2 particles 14 is 1.0% by mass or more and 40.0% by mass or less. Also, the content rate of the binder in the thixotropic molding material 10 is 0.001% by mass or more and 0.200% by mass or less.

[0068] According to such a configuration, even if the amount of the SiO 2 particles 14 is large, the SiO 2 particles 14 can be attached to the surface of the metal body 11 via the binder. Therefore, the SiO 2 particles 14 can be uniformly dispersed in the heating cylinder 7. As a result, the reaction opportunities between Mg and SiO 2 are ensured equally, and a thixotropic molded body in which Mg 2 Si and MgO are precipitated while being uniformly dispersed can be manufactured. And Mg 2 Si and MgO can function as fillers and can refine the Mg crystals precipitated during the solidification process. As a result, a thixotropic molded body having high mechanical strength and high rigidity can be obtained.

[0069] Note that the thixotropic molding material 10 does not necessarily have to be manufactured by this manufacturing method. That is, the thixotropic molding material 10 may be manufactured, for example, without going through the degreasing step S108.

[0070] 4. Thixotropic Molded Body Next, the thixotropic molded body according to the embodiment will be described. FIG. 4 is a partial cross-sectional view schematically showing the thixotropic molded body according to the embodiment.

[0071] The thixoformed body 100 shown in Fig. 4 is a formed body obtained by the thixoforming method, and has a matrix part 200, a first particle part 300, and a second particle part 400. The matrix part 200 is a part mainly derived from the metal body 11 of the thixoforming material 10, and has Mg as a main component. The first particle part 300 is a part mainly derived from the reaction product of the coating part 12 of the thixoforming material 10 and Mg, and has Mg 2 Si as a main component. The second particle part 400 is a part mainly derived from the reaction product of the coating part 12 of the thixoforming material 10 and Mg, and has MgO as a main component. Then, when observing the cross section of the thixoformed body 100, the total area fraction Ac of the first particle part 300 and the second particle part 400 in the range of 500 μm square centered at the point where the depth from the surface is 1 mm is 1.0% or more and 55.0% or less.

[0072] As shown in Fig. 4, when looking at the cross section of the thixoformed body 100, the area occupied by the matrix part 200 is larger than the area occupied by the first particle part 300 and the area occupied by the second particle part 400. Therefore, the first particle part 300 and the second particle part 400 are in a state of being dispersed in the matrix part 200, respectively. Also, the second particle part 400 exists independently of the first particle part 300.

[0073] Mg 2 Si simple substance and MgO simple substance each have a higher Young's modulus than Mg simple substance. For this reason, the first particle part 300 and the second particle part 400 function as fillers for increasing rigidity. Therefore, the thixoformed body 100 having the first particle part 300 and the second particle part 400 has high rigidity.

[0074] Also, the first particle part 300 and the second particle part 400 suppress the coarsening of Mg crystals contained in the matrix part 200. For this reason, in the matrix part 200, the refinement of Mg crystals is achieved. Thereby, the thixoformed body 100 has high mechanical strength.

[0075] Furthermore, the second particle part 400 having MgO as a main component is Mg 2It also has a function of inhibiting the abnormal growth of the first particle portion 300 mainly composed of Si into dendritic or acicular shapes. Due to this function, the first particle portion 300 has an isotropic shape, making it difficult to become a starting point for cracks and the like. Therefore, in the thixoformed body 100 having both the first particle portion 300 and the second particle portion 400, the mechanical strength is further enhanced.

[0076] Elemental analysis is used to identify the matrix portion 200, the first particle portion 300, and the second particle portion 400.

[0077] Examples of elemental analysis methods include atomic absorption spectrometry for iron and steel specified in JIS G 1257:2000, ICP emission spectrometry for iron and steel specified in JIS G 1258:2007, spark discharge emission spectrometry for iron and steel specified in JIS G 1253:2002, fluorescent X-ray analysis for iron and steel specified in JIS G 1256:1997, and gravimetric, titrimetric, and absorptiometric methods specified in JIS G 1211~G 1237.

[0078] In FIG. 4, a range A1 of 500 μm square starting from the surface 101 of the thixoformed body 100 and a range A2 of 500 μm square centered on a point 1 mm deep from the surface 101 are illustrated. When the total area fraction of the first particle portion 300 and the second particle portion 400 in the range A1 is As [%] and the total area fraction of the first particle portion 300 and the second particle portion 400 in the range A2 is Ac [%], in the thixoformed body 100, |As - Ac| / Ac is preferably 50.0% or less, more preferably 40.0% or less, and even more preferably 20.0% or less.

[0079] In such a thixoformed body 100, the difference in the occupied area of the first particle portion 300 and the second particle portion 400 is suppressed to be small between the range A1 located near the surface 101 and the range A2 located deeper than that. That is, in such a thixoformed body 100, the uneven distribution of the first particle portion 300 and the second particle portion 400 is suppressed. Thereby, the rigidity of the thixoformed body 100 can be particularly enhanced.

[0080] The total area fraction As of the first particle portion 300 and the second particle portion 400 in the range A1 is calculated as follows. First, in the observation image of the range A1, the total area of the first particle portion 300 and the second particle portion 400 is calculated by image processing. For the image processing, for example, image analysis software such as OLYMPUS Stream can be used. Also, the magnification of the observation image is preferably 300 times or more. Next, the ratio of the total area of the first particle portion 300 and the second particle portion 400 to the total area of the range A1 is calculated. This ratio becomes the area fraction As. Note that the range A1 is a range forming a square with a side length of 500 μm, and at least a part thereof may be in contact with the surface 101.

[0081] The total area fraction Ac of the first particle portion 300 and the second particle portion 400 in the range A2 is also calculated in the same manner as the area fraction As.

[0082] Note that the range A2 is a range forming a square with a side length of 500 μm, and its center point O is a point at a depth of 1 mm from the surface 101. Also, in the cross section of the thixotropic molded body 100, when the length in the depth direction is less than 2 mm, the midpoint of the length in the depth direction can be regarded as the center point O.

[0083] The area fraction As and the area fraction Ac are each determined by the content of SiO in the thixotropic molded body 100, but are preferably 1.0% or more and 55.0% or less, more preferably 2.0% or more and 50.0% or less, and even more preferably 3.0% or more and 45.0% or less. When the area fraction As and the area fraction Ac are within the above ranges, the effect that the rigidity and mechanical strength of the thixotropic molded body 100 are increased becomes more remarkable. 2 The area fraction As and the area fraction Ac are each determined by the content of SiO in the thixotropic molded body 100, but are preferably 1.0% or more and 55.0% or less, more preferably 2.0% or more and 50.0% or less, and even more preferably 3.0% or more and 45.0% or less. When the area fraction As and the area fraction Ac are within the above ranges, the effect that the rigidity and mechanical strength of the thixotropic molded body 100 are increased becomes more remarkable.

[0084] Also, let the area fraction of the first particle portion 300 in the ranges A1 and A2 be A(Mg 2 Si), and let the area fraction of the second particle portion 400 be A(MgO).

[0085] At this time, the ratio of the area fractions A(Mg 2Si) / A(MgO) is preferably 0.5 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and even more preferably 1.1 or more and 2.0 or less. If the ratio of the area fraction is within the above range, the balance between the first particle portion 300 and the second particle portion 400 becomes good. Therefore, while ensuring the function of improving the mechanical strength and rigidity by both the first particle portion 300 and the second particle portion 400, the function of inhibiting the abnormal growth of the first particle portion 300 by the second particle portion 400 can be obtained.

[0086] Let the average particle diameter of the first particle portion 300 be D(Mg 2 Si), and let the average particle diameter of the second particle portion 400 be D(MgO). The average particle diameters D(Mg 2 Si), D(MgO) are each preferably 0.5 μm or more and 10.0 μm or less, and more preferably 1.0 μm or more and 5.0 μm or less. If the average particle diameters D(Mg 2 Si), D(MgO) are within the above range, the first particle portion 300 and the second particle portion 400 are less likely to become the starting points of cracks and the like. Thereby, the mechanical strength such as the bending strength and tensile strength of the thixotropic molded body 100 can be increased.

[0087] The average particle diameters D(Mg 2 Si), D(MgO) are calculated as follows. First, in the range A1 and the range A2, all the particle diameters of the included first particle portion 300 and the second particle portion 400 are measured. The particle diameter of the first particle portion 300 is the intermediate value between the length of the major axis and the length of the minor axis in the observation image of the first particle portion 300. The average value of the particle diameters calculated in this way is the average particle diameter of the first particle portion 300. The particle diameter of the second particle portion 400 is the intermediate value between the length of the major axis and the length of the minor axis in the observation image of the second particle portion 400. The average value of the particle diameters calculated in this way is the average particle diameter of the second particle portion 400.

[0088] Also, the ratio of the average particle diameters D(Mg 2 Si) / D(MgO) is preferably 0.4 or more and 2.0 or less, more preferably 0.5 or more and 1.4 or less, and even more preferably 0.6 or more and 1.1 or less. The ratio of the average particle diameters D(Mg2 If Si) / D(MgO) is within the above range, the functions of improving the mechanical strength and rigidity by both the first particle portion 300 and the second particle portion 400 and the function of inhibiting the abnormal growth of the first particle portion 300 by the second particle portion 400 can be better balanced.

[0089] Note that although not shown in the figure, the thixoformed body 100 may have a third particle portion mainly composed of SiO 2 SiO also has a Young's modulus higher than that of magnesium. Therefore, by having the third particle portion, the rigidity of the thixoformed body 100 can be increased. 2

[0090] Also, the tensile strength of the thixoformed body 100 is preferably 180 MPa or more and 300 MPa or less, and more preferably 190 MPa or more and 250 MPa or less. Further, the Young's modulus of the thixoformed body 100 is preferably 43 GPa or more and 80 GPa or less, and more preferably 48 GPa or more and 70 GPa or less.

[0091] The thixoformed body 100 with the tensile strength and Young's modulus within the above range will have particularly high specific strength and specific rigidity. Such a thixoformed body 100 is lightweight and has high strength, so it is suitable for, for example, parts used in transportation equipment such as automobiles and aircraft, and parts used in mobile devices such as mobile phones and notebook computers.

[0092] Furthermore, the 0.2% proof stress of the thixoformed body 100 is preferably 155 MPa or more and 300 MPa or less, and more preferably 165 MPa or more and 240 MPa or less.

[0093] The tensile strength of the thixoformed body 100 is measured as follows. First, a test piece is cut out from the thixoformed body 100. Examples of the test piece include No. 13 test pieces specified in JIS. Next, the test piece is attached to a tensile testing machine, and the stress corresponding to the maximum force applied to the test piece at 25°C is calculated. The obtained stress is taken as the tensile strength of the thixoformed body 100.

[0094] Also, the Young's modulus of the thixoformed body 100 is measured as follows. First, a test piece is cut out from the thixoformed body 100. Next, the test piece is attached to a tensile testing machine, and a tensile load is applied to the test piece at 25°C. Next, the amount of change in tensile strain when the tensile load is varied and the amount of change in tensile stress when the tensile load is varied are calculated respectively. Then, the ratio of the latter change amount to the former change amount is calculated, and this is taken as the Young's modulus of the thixoformed body 100. Incidentally, the Young's modulus of the thixoformed body 100 may be a value measured by a method other than the above measurement method, for example, the resonance method or the ultrasonic pulse method.

[0095] Also, the Vickers hardness of the surface 101 of the thixoformed body 100 is preferably 75 or more and 200 or less, more preferably 80 or more and 120 or less, and even more preferably 85 or more and 100 or less.

[0096] If the Vickers hardness is within the above range, it is possible to realize a thixoformed body 100 with high surface hardness and difficult to be scratched.

[0097] The Vickers hardness of the surface 101 of the thixoformed body 100 is measured in accordance with the method of the Vickers hardness test specified in JIS Z 2244:2009. Incidentally, the measurement load is 5 kgf.

[0098] FIG. 5 is an example of an X-ray diffraction pattern obtained for the thixoformed body according to the embodiment.

[0099] As shown in FIG. 5, when the crystal structure analysis of the thixoformed body 100 is performed by the X-ray diffraction method, a peak derived from α-Mg, a peak derived from β-Mg 17 Al 12 a peak derived from Mg 2 Si, and a peak derived from MgO are included in the obtained X-ray diffraction pattern. α-Mg is the matrix phase of the matrix part 200 and is a solid solution mainly containing Mg.

[0100] When using CuKα rays as X-rays, the main peak derived from α-Mg is observed at 2θ = 36.5 to 37.5°. The main peak derived from α-Mg refers to the peak with the maximum peak intensity among the peaks derived from α-Mg. β-Mg 17 Al 12 The main peak derived from it is observed at 2θ = 35.5 to 36.5°. β-Mg 17 Al 12 The main peak derived from it refers to β-Mg 17 Al 12 Among the peaks derived from it, it refers to the one with the maximum peak intensity. Mg 2 The main peak derived from MgSi is observed at 2θ = 39.5 to 40.5°. Mg 2 The main peak derived from MgSi refers to Mg 2 Among the peaks derived from MgSi, it refers to the one with the maximum peak intensity. The main peak derived from MgO is observed at 2θ = 42.5 to 43.5°. The main peak derived from MgO refers to the peak with the maximum peak intensity among the peaks derived from MgO.

[0101] Mg 2 When the peak intensity of the main peak derived from MgSi is set to 100 with respect to the peak intensity of the main peak derived from α-Mg, it is preferably 5 or more and 100 or less, and more preferably 10 or more and 50 or less. In the thixoformed body 100 having such a peak intensity ratio, α-Mg and Mg 2 Si are present in a well-balanced manner, so high rigidity and high strength are compatible.

[0102] When the peak intensity of the main peak derived from MgO is set to 100 with respect to the peak intensity of the main peak derived from α-Mg, Mg 2 It is preferably smaller than the peak intensity of the main peak derived from Si, and more preferably 10% or more and 50% or less of the peak intensity of the main peak derived from Si. In the thixoformed body 100 having such a peak intensity ratio, α-Mg and Mg 2 Si and MgO are present in a well-balanced manner, so high rigidity and high strength are compatible. 2 Si and MgO are present in a well-balanced manner, so high rigidity and high strength are compatible.

[0103] The above-described thixotropic molding material, method for producing a thixotropic molding material, and thixotropic molded body of the present invention have been described based on the illustrated embodiments. However, the thixotropic molding material and thixotropic molded body of the present invention are not limited to the above-described embodiments, and for example, arbitrary components may be added to the above-described embodiments. Further, the method for producing a thixotropic molding material of the present invention may be one in which a process for an arbitrary purpose is added to the above-described embodiment.

Example

[0104] Next, specific examples of the present invention will be described. 5. Production of Thixotropic Molding Material

[0105] 5.1. Sample No. 1 First, a magnesium alloy chip, which is a metal body, SiO 2 particles, a binder, and a solvent were mixed to obtain a mixture. For the magnesium alloy chip, a 4 mm × 2 mm × 1 mm chip made of AZ91D alloy manufactured by STU Co., Ltd. was used. The AZ91D alloy is a Mg-based alloy containing 9% by mass of Al and 1% by mass of Zn. Also, as the binder, "Paraffin Wax 115" manufactured by Nippon Seiko Co., Ltd. was used. The melting point of Paraffin Wax 115 was 48°C. Further, 35 mL of isopropanol was used per 4.5 g of the binder as the solvent.

[0106] Next, the obtained mixture was heated to obtain a dried body. Subsequently, the obtained dried body was stirred. Thereafter, the operation of heating and then stirring the stirred dried body was repeated three times. For stirring, a method of shaking the container containing the dried body was used.

[0107] Next, the stirred dried body was subjected to a degreasing treatment. As a result, at least a part of the binder was removed to obtain a thixotropic molding material. In the obtained thixotropic molding material, almost the entire surface of the magnesium alloy chip was covered with SiO 2 particles. The manufacturing conditions in the above manufacturing method are shown in Table 1. In Table 1, SiO 2The input amount of the particles is the ratio of the mass of the input SiO 2 particles to the total mass of the magnesium alloy chips and the SiO 2 particles. Also, the input amount of the binder is the ratio of the mass of the input binder to the total mass of the thixoforming material.

[0108] 5.2. Sample Nos. 2 to 5 A thixoforming material was obtained in the same manner as in Sample No. 1, except that the manufacturing conditions were changed as shown in Table 1.

[0109] 5.3. Sample No. 6 A thixoforming material was obtained in the same manner as in Sample No. 1, except that no SiO 2 particles and binder were used.

[0110] 5.4. Sample Nos. 7 to 15 A thixoforming material was obtained in the same manner as in Sample No. 1, except that the manufacturing conditions were changed as shown in Table 1. When manufacturing the thixoforming material of Sample No. 14, the degreasing treatment was omitted.

[0111] 5.5. Sample No. 16 A thixoforming material was obtained in the same manner as in Sample No. 1, except that SiO 2 particles were used while no binder was used.

[0112] In Table 1, for the thixoforming materials of each sample No., those corresponding to the present invention were designated as "Examples", and those not corresponding to the present invention were designated as "Comparative Examples".

[0113] 6. Evaluation of the thixoforming material 6.1. Amount of SiO 2 particles after degreasing For the thixoforming materials of each sample No., the amount of SiO 2 particles after degreasing was calculated by the following method.

[0114] First, the mass M1 of the thixoforming material was measured. Since the thixoforming material has undergone degreasing treatment, the remaining binder is considered to be almost zero and is not taken into account in the calculation. Next, the thixoforming material was immersed in acetone and washed with an ultrasonic cleaner for 10 minutes. As a result, the attached SiO 2 particles can be removed, and only the magnesium alloy chips can be taken out. Next, the washed magnesium alloy chips were taken out of the acetone, dried, and then the mass M2 was measured.

[0115] Then, the mass fraction of SiO 2 particles with respect to the magnesium alloy chips, calculated by (M1 - M2) / M1 × 100, was taken as the amount [%] of SiO 2 particles after degreasing. The calculation results are shown in Table 1.

[0116] 6.2. Adhesion rate of SiO 2 particles The amount of SiO 2 particles after degreasing was divided by the input amount of SiO 2 particles to calculate the adhesion rate of SiO 2 particles. The calculation results are shown in Table 1.

[0117] 6.3. Amount of binder after degreasing For the thixoforming materials of each sample No., the amount of binder after degreasing was calculated by the following method.

[0118] First, for one thixoforming material, the thermogravimetric change in the temperature range of 50 to 450°C was measured using a differential thermal thermogravimetric simultaneous measurement device (TGA / DSC 1LF) manufactured by Mettler Toledo. The temperature increase was carried out in the atmosphere while flowing air at a flow rate of 30 mL / min and at a temperature increase rate of 10°C / min. Then, to eliminate the influence of the solvent, based on 200°C, the weight change at 450°C was calculated as the amount of binder after degreasing. The calculation results are shown in Table 1.

[0119]

Table 1

[0120] As shown in Table 1, in the thixoforming material corresponding to the example, although the amount of the binder is minimized by degreasing, SiO particles were observed to adhere with a sufficient adhesion rate. 2

[0121] 7. Manufacture of Thixoformed Body 7.1. Sample No. 17 The thixoforming material of Sample No. 1 was put into an injection molding machine to obtain a thixoformed body of Sample No. 17. As the injection molding machine, a magnesium injection molding machine JLM75MG manufactured by Japan Steel Works, Ltd. was used.

[0122] 7.2. Samples No. 18 to 29 Thixoformed bodies were obtained in the same manner as Sample No. 17, except that the manufacturing conditions were changed as shown in Table 2.

[0123] 8. Analysis of Thixoformed Body The thixoformed bodies of each sample number were cut, and the cut surfaces were observed with a scanning electron microscope. Fig. 6 is an observation image (secondary electron image) when the cut surface of the thixoformed body corresponding to the example was observed with a scanning electron microscope. In Fig. 6, a first particle portion, a second particle portion, and a matrix portion are recognized.

[0124] Also, ranges A1 and A2 were specified, and the ratio of area fractions A(MgSi) / A(MgO), the ratio of average particle diameters D(MgSi) / D(MgO), the area fraction Ac, and |As - Ac| / Ac were calculated. The calculation results are shown in Table 2. 2 2

[0125] 9. Evaluation of Thixoformed Body 9.1. Formability The thixoformed bodies of each sample number were observed, and the molding state of the thixoformed bodies was evaluated based on the flowability of the molten metal, and the presence or absence of internal defects such as casting cavities and entrained air. Specifically, those with poor flowability of the molten metal and many internal defects were rated as "NG", and those with relatively few such defects were rated as "OK". The evaluation results are shown in Table 2.​​​

[0126] 9.2. Tensile Strength For each thixomolded body of each sample No., the tensile strength was measured. Specifically, test pieces conforming to JIS standards were formed from the thixomolded body, and the tensile strength was measured using a tensile testing machine. The measurement results are shown in Table 2.

[0127] 9.3. Young's Modulus For each thixomolded body of each sample No., the Young's modulus was measured. The measurement results are shown in Table 2.

[0128] 9.4. Vickers Hardness For each thixomolded body of each sample No., the Vickers hardness of the surface was measured. The measurement results are shown in Table 2.

[0129]

Table 2

[0130] As is clear from Table 2, it was confirmed that the thixomolded bodies corresponding to the examples had higher mechanical strength and higher rigidity than the thixomolded bodies corresponding to the comparative examples. Also, when the content of SiO 2 was too low, the mechanical strength and rigidity could not be sufficiently increased. On the other hand, when the content of SiO 2 was too high, it was recognized that the moldability deteriorated.

[0131] Furthermore, in the comparative example where no binder was added in the production of the thixomolding material, the mechanical strength and rigidity of the thixomolded body could not be increased. The reason for this is that SiO 2 particles fell off from the magnesium alloy chips, and SiO 2 particles could not be sufficiently dispersed.

Explanation of Symbols

[0132] 1... Injection molding machine, 2... Mold, 5... Hopper, 6... Heater, 7... Heating cylinder, 8... Screw, 9... Nozzle, 10... Thixoforming material, 11... Metal body, 12... Coating part, 13... Adhesive part, 14... SiO 2 Particles, 100... Thixoformed body, 101... Surface, 200... Matrix part, 300... First particle part, 400... Second particle part, A1... Range, A2... Range, Cv... Cavity, O... Center point, S102... Preparation process, S104... Drying process, S106... Stirring process, S108... Debinding process

Claims

1. A metal body mainly composed of Mg, SiO2 particles mainly composed of SiO2 adhered to the surface of the metal body via a binder and a coating portion comprising the same, which has the average particle size of the SiO2 particles is less than 20.0 μm, the mass fraction of the SiO2 particles in the total mass of the metal body and the SiO2 particles is 1 .0 mass% or more and 40.0 mass% or less, the content of the binder in the thixotropic molding material obtained after degreasing is 0.00 1 mass% or more and 0.200 mass% or less, a thixotropic molding material characterized by this.

2. The thixotropic molding material according to claim 1, wherein the binder contains waxes.

3. A preparation step of preparing a mixture containing a metal body mainly composed of Mg, SiO2 particles mainly composed of SiO2, a binder, and a solvent; a stirring step of stirring the mixture; a degreasing step of heating the stirred mixture to remove at least a part of the binder contained in the mixture to obtain a thixotropic molding material, which has the mass fraction of the SiO2 particles in the total mass of the metal body and the SiO2 particles is 1 .0 mass% or more and 40.0 mass% or less, the content of the binder in the thixotropic molding material obtained after the degreasing step is 0 .001 mass% or more and 0.200 mass% or less, a method for producing a thixotropic molding material characterized by this.

4. A matrix part mainly composed of Mg, a first particle part dispersed in the matrix part and mainly composed of Mg2Si, a second particle part dispersed in the matrix part and existing independently of the first particle part and mainly composed of MgO, which has observing a cross section, the total area fraction of the first particle part and the second particle part in a range of 500 μm square centered at a point with a depth of 1 mm from the surface is 1.0% or more and 55.0% or less, when the average particle size of the first particle part is D(Mg2Si) and the average particle size of the second particle part is D( MgO), the ratio of the average particle sizes D(Mg2Si) / D(MgO) is 0.4 or more and 2. .0 or less, a thixotropic molded body characterized by this.

5. Observing a cross section, the total area fraction of the first particle part and the above-mentioned second particle part in a range of 500 μm square starting from the surface is defined as As [%], and the total area of the first particle part and the second particle part in a range of 500 μm square centered at a point with a depth of 1 mm from the surface of the above-mentioned second particle part of the above-mentioned second particle part of the above-mentioned second particle part of the above-mentioned second particle part of the above-mentioned second particle part of the above-mentioned second particle part of the above-mentioned second particle part When the fraction is Ac [%], the thixotropic molded body according to claim 4, wherein |As - Ac| / Ac is 50.0% or less. The thixotropic molded body according to claim 1. **Claim 6** The thixotropic molded body according to claim 4 or 5, wherein the tensile strength is 180 MPa or more and 300 MPa or less, and the Young's modulus is 43 GPa or more and 80 GPa or less. 。

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