JP2019115932A - Hydraulic composition for addition manufacturing apparatus and manufacturing method of mold - Google Patents

Abstract

To provide a hydraulic composition for an addition manufacturing apparatus being excellent in strength development property, in particular early strength development property, and hardly generating defects due to a bad gas and bad graphite spheroidization in the manufacture of a mold.SOLUTION: A hydraulic composition for an addition manufacturing apparatus contains 28-60 pts.mass of water and sand to total 100 pts.mass of a composite binder containing 1-12 pts.mass of polyvinyl alcohol to total 100 pts.mass of an inorganic binder. A manufacturing method of a mold molding the mold by using the addition manufacturing apparatus and the hydraulic composition for the addition manufacturing apparatus is provided.SELECTED DRAWING: None

Description

  The present invention relates to a hydraulic composition for an additive manufacturing apparatus (3D printer) having high early strength development and less generation of gas (volatile component), and a method of manufacturing a mold using the composition.

Casting is a traditional metalworking method in which molten metal is poured into a mold to produce a casting. The self-hardening molds used for this casting are organic and inorganic, depending on the caking agent (binder) to be used. Among these, inorganics are mainly water glass and cement. However, in the cement-based self-hardening mold, depending on the casting temperature, the contained gypsum is thermally decomposed to generate a gas, causing a defect in the casting, and the appearance and the function are impaired. In addition, although the production of the mold requires the production of a model or a wood mold as a pre-process, this pre-process takes time and cost.
Then, the aesthetics etc. of a casting are not impaired but the manufacturing method of the casting_mold | template which does not need this front-end process is desired.

By the way, recently, the additive manufacturing apparatus has attracted attention as a rapid and precise forming means. Among the additional manufacturing apparatuses, for example, a powder lamination molding apparatus is an apparatus that forms a solidified product, which is obtained by laying a powder on a flat surface and then injecting an aqueous binder onto the powder to solidify, sequentially laminating in the vertical direction It is. The feature of this device is that the data of three-dimensional molding created by three-dimensional CAD or the like is divided into a large number of horizontal surfaces, and the shapes of these horizontal surfaces are sequentially laminated to produce a molded body.
Therefore, if the mold can be manufactured using the above-mentioned apparatus, it is expected that the above-mentioned pre-process becomes unnecessary and the working time and cost can be reduced.

For example, in Patent Document 1, 15 to 50% of quick-hardening cement is blended with fireproof sand such as silica sand, olivine sand, and artificial sand as a hydraulic composition for an additive manufacturing apparatus suitable for a powder lamination molding method and kneaded. There is disclosed a technology for obtaining a molded body by adding an aqueous binder to the (mixed) material, solidifying and laminating. Here, the powder lamination molding method is a layer in which a molding liquid is dropped or sprayed through a nozzle such as an ink jet to solidify in a predetermined range of powder material placed on a loading table (base), and successively solidified Are laminated to form a desired shape.
In order to prevent breakage during transportation immediately after production and to ensure production quantity and non-defective products, molded articles produced using this bonding material injection method have high early strength development, and at the time of production of castings. Also high strength is required.
Further, the molding material described in Patent Document 2 is a molding material for a powder adhering and laminating method in which an aggregate and a powdery precursor which is a binder for binding the aggregate are mixed, and the bone The content of the material is 70% by weight or more, and the powdery precursor is cement or the like.

However, when the molding material containing a relatively large amount of gypsum is used as a mold, a gas such as sulfur oxide is generated at a high temperature to easily cause defects such as blow holes, and defects due to inhibition of spheroidization of graphite occur. There is a case. On the other hand, in cement which does not contain much gypsum, it is difficult to obtain sufficient early strength development.
As described above, when cement-based material is used as a mold production material for an additional production apparatus, it is possible to simultaneously prevent the occurrence of casting defects due to a gas such as sulfur oxide or graphite spheroidization failure and early strength development. It was difficult.

JP, 2011-51010, A JP, 2010-110802, A

  Therefore, the object of the present invention is to provide a hydraulic composition and the like for an additional manufacturing apparatus, which exhibits high strength development, particularly high early strength development, and less defects due to gas or graphite spheroidization defects in casting manufacture. Do.

As a result of intensive studies to solve the above problems, the inventor of the present invention achieves the above object by a hydraulic composition for an additive manufacturing device containing an inorganic binder such as calcium aluminate, polyvinyl alcohol, and water in a specific ratio. We have found what we can do to complete the present invention.
That is, the present invention is a hydraulic composition etc. for an additional manufacturing apparatus having the following constitution.

[1] An additive manufacturing apparatus further comprising 28 to 60 parts by mass of water and sand with respect to a total of 100 parts by mass of the composite binder containing 1 to 12 parts by mass of polyvinyl alcohol per 100 parts by mass of the inorganic binder Hydraulic composition.
[2] The hydraulic composition for addition production devices according to the above [1], wherein the inorganic binder contains 50 to 100 mass% of calcium aluminates, based on 100 mass% of the entire inorganic binder.
[3] The hydraulic composition for an additive manufacturing device according to the above [1] or [2], wherein the inorganic binder contains 0.5% to 5.0% by mass of gypsum based on 100% by mass of the entire inorganic binder. .
[4] The hydraulic composition for an additive manufacturing device according to any one of the above [1] to [3], wherein the inorganic binder further contains a quick-hardening cement.
[5] The hydraulic composition for an additive manufacturing device according to any one of the above [1] to [4], wherein the volatile content at a material age of 3 days is 5.5% by mass or less.
[6] The hydraulic composition for an addition manufacturing device according to any one of the above [1] to [5], wherein the degree of saponification of the polyvinyl alcohol is 80 to 90 mol%.
[7] The hydraulic composition for an addition manufacturing device according to any one of the above [1] to [6], wherein the average particle diameter of the polyvinyl alcohol is 150 μm or less.
[8] A method for producing a mold, which molds a mold using the additive production apparatus and the hydraulic composition for additive production apparatus according to any one of the above [1] to [7].
[9] The method for producing a mold according to the above [8], wherein the curing temperature of the mold is 10 to 80 ° C.

  The hydraulic composition for an additive manufacturing device according to the present invention has high strength development, particularly high early strength development, and less generation of gas (volatile component) and defects due to defects of graphite spheroidization in the production of castings.

  As described above, the present invention further contains 28 to 60 parts by mass of water and sand, based on 100 parts by mass of the inorganic binder per 100 parts by mass of the composite binder containing 1 to 12 parts by mass of polyvinyl alcohol. And a hydraulic composition for an additive manufacturing apparatus (hereinafter sometimes abbreviated as "hydraulic composition") and the like. Hereinafter, the present invention will be described separately for the inorganic binder, the composite binder, the hydraulic composition, and the method for producing a mold.

1. Inorganic Binder The inorganic binder is a binder which contains at least one selected from the following calcium aluminates as an essential component, and further contains gypsum, quick-hardening cement, etc. as an optional component.
Next, calcium aluminates, gypsum, quick-hardening cement and the like will be separately described in detail.

(1) Calcium aluminates wherein the calcium aluminates _{may, 3CaO · Al 2 O 3,} 2CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 5CaO · 3Al 2 O 3, CaO · Al 2 O 3, 3CaO · _5Al 2 _{O 3,} or calcium aluminate such as _{CaO · 2Al 2 O 3,;} 2CaO · Al 2 O 3 · Fe 2 O 3 , or calcium alumino ferrite etc. _{4CaO · Al 2 O 3 · Fe} 2 O 3,; calcium calcium halophosphate aluminate containing calcium fluoroalkyl aluminate such as _{3CaO · 3Al 2 O 3 · CaF} 2, and _{11CaO · 7Al 2 O 3 · CaF} 2 halogen is dissolved or substituted aluminate; 8CaO _· Na 2 O _· 3Al ₂ O _3, and _{3CaO · 2Na 2 O · 5Al 2} O 3 Calcium sodium aluminate; calcium lithium aluminate; alumina cement; and additionally, trace elements (including oxides, etc.) such as Na, K, Li, Ti, Fe, Mg, Cr, P, F, S etc. Or more selected from mineral minerals.
Among these inorganic binders, calcium aluminate is preferable, and amorphous calcium aluminate is particularly preferable, because it has high strength development and little gas generation when used as a template. Since amorphous calcium aluminate is produced by melting and quenching the raw material, it has substantially no crystal structure, and the vitrification rate is usually 80% or more, and the higher the vitrification rate Since the early strength development is high, the vitrification rate is preferably 90% or more.

The molar ratio of calcium aluminates to CaO / Al ₂ O ₃ is preferably 1.5 to 3.0, more preferably 1.7 to 2.4. When the molar ratio is 1.5 or more, the early development of the strength of the hydraulic composition is high, and when it is 3.0 or less, the heat resistance of the hydraulic composition is high.
Also, in order to obtain sufficient early strength development and to suppress the generation of dust, the brane specific surface area (powder degree specified in JIS R 5201) of calcium aluminates is preferably 1000 to 6000 cm ² / g, more preferably Preferably it is 1500-5000 cm < ² > / g. The brane specific surface area of the calcium aluminates is more preferably 1500 to 4000 cm ² / g, particularly preferably 2000, in order to ensure uniform spreading in the addition production apparatus and not to decrease the strength of the mold. It is ~ 3000 cm ² / g.
The content of calcium aluminates in the inorganic binder is preferably 50 to 100% by mass. . When the value is 50% by mass or more, the early development of strength and heat resistance of the hydraulic composition are high. The value is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 95% by mass. Among calcium aluminates, amorphous calcium aluminate is preferred as described above.

(2) Gypsum The inorganic binder may further contain gypsum as an optional component in order to further improve early strength development. Examples of the gypsum include one or more selected from anhydrite, hemihydrate gypsum, and dihydrate gypsum. Among these, hemihydrate gypsum is preferable because it has higher early strength development. The content of gypsum in the inorganic binder improves the early development of strength and prevents the generation of gas and defects in the spheroidization of graphite at the time of production of castings. Preferably it is 0.5-5.0 mass%, More preferably, it is 0.8-3.0 mass% or less, More preferably, it is 1.0-2.0 mass% or less.
The gypsum may be gypsum contained in cement. Gypsum in cement is generally present in the form of a mixture of gypsum dihydrate and gypsum hemihydrate (mixed gypsum). Since the hemihydrate gypsum is generated by dewatering from dihydrate gypsum by the heat generated by the grinding of cement, the content ratio of hemihydrate gypsum and dihydrate gypsum fluctuates under the influence of the milling conditions.

(3) Rapid Hardening Cement The inorganic binder can contain rapid curing cement (super rapid curing cement) as an optional component for further improvement of early strength development, and is preferably measured according to JIS R 5210. It is quick-hardening cement (super rapid-hardening cement) or water-stopping cement whose set (initial development) is within 30 minutes. In addition, commercial products such as quick-hardening cement are Super Jet Cement (manufactured by Pacific Cement Co., Ltd.), Jet Cement (manufactured by Sumitomo Osaka Cement Co., Ltd.), Lion Shisui (registered trademark, manufactured by Sumitomo Osaka Cement Co., Ltd.), or Denka Super Cement (Denka Super Cement). Company company). Fast-hardening cement containing gypsum is preferable because it exhibits high early strength development and facilitates addition of a small amount of gypsum.
The content of quick-hardening cement in the inorganic binder improves early development of strength and reduces the amount of gas generation when used as a mold, so the entire inorganic binder is preferably 100% by mass, preferably 0. It is 50 mass%, More preferably, it is 0-30 mass%, More preferably, it is 5-20 mass%.

(4) Other components in inorganic binder The inorganic binder may contain cement as another component (optional component).
The cement is preferable if the setting (starting) measured according to JIS R 5210 is within 3 hours and 30 minutes, because the early strength development after 3 hours from molding is high, and more preferably within 1 hour .
The cement may be one or more selected from ordinary Portland cement, early-strength Portland cement, moderate-heat Portland cement, low-thermal Portland cement, white Portland cement, eco cement, blast furnace cement, fly ash cement, and cement clinker powder. In the present invention, cement clinker powder is also included in cement.
Moreover, the content rate of the calcium silicate in cement makes the whole cement 100 mass%, Preferably it is 25 mass% or more. If the content is 25% by mass or more, strength development after 1 day of material age is high, and if long-term strength development is required, the content is preferably 45% by mass or more.
The content of cement in the inorganic binder is preferably 0 to 50 mass%, more preferably 0 to 30 mass%, and still more preferably 100 mass% of the entire inorganic binder for the improvement of early strength development. It is 0-20 mass%.

2. Composite binder The composite binder is a binder containing 1 to 12 parts by mass of polyvinyl alcohol with respect to 100 parts by mass of the inorganic binder. If the blending ratio of polyvinyl alcohol is less than 1 part by mass, the strength improvement effect is low, and if it exceeds 12 parts by mass, depending on the shape, the shrinkage of the molded product may cause deformation or cracking, and a mold having a complicated shape can not be manufactured. In addition, there are cases where gas is generated when manufacturing a casting to cause defects such as blow holes in the casting or an offensive odor at the manufacturing site. The blending ratio of polyvinyl alcohol is more preferably 2 to 10 parts by mass, and still more preferably 3 to 9 parts by mass with respect to 100 parts by mass of the inorganic binder.
The degree of saponification of the polyvinyl alcohol is preferably 80 to 90 mol% because it has high solubility and high strength.
The average particle diameter (median diameter, D50) of polyvinyl alcohol is preferably 150 μm or less, more preferably 90 μm or less, and still more preferably 10 to 75 μm because high strength can be obtained. In addition, the content of particles of polyvinyl alcohol larger than 94 μm is preferably 90% by mass or less, more preferably 45% by mass or less, and still more preferably 30% by mass or less. The content of particles of polyvinyl alcohol larger than 77 μm is preferably 90% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less.

3. Hydraulic composition The hydraulic composition is a composition comprising 28 to 60 parts by mass of water and sand with respect to a total of 100 parts by mass of the composite binder. If the mixing ratio of water is in the above range, strength development can be ensured. In addition, the compounding ratio of water is preferably 30 to 55 parts by mass, more preferably 32 to 46 parts by mass from the viewpoint of further enhancing the strength and dimensional accuracy of the mold.
In addition, the blending ratio of sand is preferably 100 to 600 parts by mass, more preferably 150 to 500 parts by mass, and still more preferably 200 to 400 parts by mass with respect to 100 parts by mass of the composite binder. If the blending ratio of sand is within the above range, similarly, strength development can be secured.
The sand is not particularly limited as long as it is refractory sand, and one or more types selected from silica sand, olivine sand, zircon sand, chromite sand, alumina sand, artificial sand and the like can be mentioned. As the water, normal tap water, well water and the like can be used. In addition, even if water is used in combination with one or more selected from thickeners, lubricants, fluidizers, surfactants, and surface tension reducing agents in order to impart various functions required. Good.
The volatile content of molded articles of 3 days old using the hydraulic composition is preferably 5.5% by mass or less, more preferably 5.0% by mass or less, still more preferably 4.5% by mass or less It is. If the ignition loss is 5.5% by mass or less, defects such as blow holes do not occur in the casting. Here, the volatile matter is an index of the amount of gas generated when used as a mold, and includes moisture, sulfur and the like. Volatile matter may be measured when used as a mold, but it is preferably measured after curing for 3 days, more preferably after 3 hours for curing, when it is managed more strictly, or when it is more strictly managed.

4. Other Components in Hydraulic Composition In order to facilitate the operation (depowdering) of removing the uncured powder of the hydraulic composition remaining after molding from the molded body, the hydraulic composition of the present invention further comprises The hydrophobic fumed silica may be contained as an optional component in an amount of 0.1 to 2.0 parts by mass, more preferably 0.5 to 1.5 parts by mass, based on 100 parts by mass of the composite binder. Here, the hydrophobic fumed silica is a silica powder in which the surface of fumed silica is treated with silane or siloxane to make the surface hydrophobic.
Moreover, in order to raise the removal efficiency of the powder of a hydraulic composition more, BET specific surface area of hydrophobic fumed silica becomes like this. Preferably it is 30-300 m < ² > / g. If the BET specific surface area of the hydrophobic fumed silica is within the above range, the flowability of the powder is improved, the surface spread by the additive manufacturing apparatus is flat, and the weight of the mold can be reduced without lowering the strength. . In addition, hydrophobic fumed silica is effective in preventing caking of powder and improving mixing properties.

  The hydraulic composition of the present invention may further contain optional components such as blast furnace slag, fly ash, silica fume, fine silica stone powder, and limestone powder as a strength-increasing adjusting material and the like.

5. Method for Producing a Mold The production method is a method for producing a mold using an additive production apparatus and the hydraulic composition of the present invention. The additive manufacturing apparatus is not particularly limited, and commercially available products such as a powder laminate type additive manufacturing apparatus can be used. Also, the hydraulic composition prior to containing water is prepared by mixing the above-mentioned components with a commercially available mixer or manually. When a plurality of materials are used as the binder, the binder may be previously mixed by a commercially available mixer or by hand, or may be mixed and pulverized by a grinder.
As a method of curing the mold, there is a method of air curing alone, a method of air curing followed by water curing, or surface impregnation agent curing. Among these, from the viewpoint of early strength development and suppression of water vapor generated at the time of production of castings, air curing alone is preferred. Further, from the viewpoint of strength enhancement by calcium aluminate, quick-hardening cement, polyvinyl alcohol and the like, the temperature of atmospheric curing is preferably 10 to 100 ° C., more preferably 30 to 80 ° C. Further, the relative humidity of atmospheric curing is preferably 10 to 90%, more preferably 15 to 80%, and still more preferably 20 to 60%, in view of sufficient strength expression and production efficiency. Furthermore, the atmospheric curing time is preferably 1 hour to 1 week, more preferably 2 hours to 5 days, and still more preferably 3 hours to 4 days, in view of sufficient strength expression and production efficiency.

  The hydraulic composition may be heated to reduce the amount of gas evolved when used as a mold after curing. In order to remove moisture, heating is preferably performed at 100 ° C. or more, more preferably 200 ° C. or more. Moreover, when also removing polyvinyl alcohol, Preferably it heats at 400 degreeC or more, More preferably, it is 600 degreeC or more. Furthermore, when it is desired to prevent the generation of gas due to sulfur oxides in cement, it is preferable to heat at 1250 ° C. or higher.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.
1. Materials used (1) Calcium aluminates
(i) Amorphous calcium aluminate (abbreviation: CA)
The molar ratio of CaO / Al ₂ O ₃ is 2.2, the vitrification ratio is 95% or more, and the Blaine specific surface area is 2040 cm ² / g.
(ii) Alumina cement (abbreviation: AC)
Denka Alumina Cement No. 1 (trade name), with a specific surface area of 4570 cm ² / g, manufactured by Denka Co., Ltd.
(2) Quick-hardening cement
(i) Super jet cement (trade name), the content of calcium silicate is 47% by mass, setting (initial) is 30 minutes, and the specific surface area of blaine is 4700 cm ² / g. However, 14% by mass of anhydrous gypsum is included. Made by Pacific Cement Co., Ltd.
(ii) Water-stopping cement Lion Shisui 105 (trade name) manufactured by Sumitomo Osaka Cement Co., Ltd.
(3) Early-Strength Portland Cement The calcium silicate content is 75% by mass, the setting (initial) is 30 minutes, and the brane specific surface area is 4000 cm ² / g, manufactured by Pacific Cement Co., Ltd.
(4) Plaster Natural anhydrite, brane specific surface area is 7200 cm ² / g and is from Thailand.
(5) Sand The following two types of artificial casting sand were used in equal amounts by mixing.
Espar # 180 L (trade name), alumina-based, manufactured by Yamakawa Sangyo Co., Ltd.
NAIGAI THERABEADS # 1450 (registered trademark), Alumina-based, Itochu Celatech Co., Ltd.
(6) Polyvinyl alcohol
(i) Polyvinyl alcohol a
The product number is 22-88S1 (PVA 217 SS), manufactured by Kuraray.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 60 μm, the content of particles larger than 94 μm is 29% by mass, and the content of particles larger than 77 μm is 47% by mass, 10% The diameter (D10) is 25 μm, and the 90% diameter (D90) is 121 μm.
(Ii) polyvinyl alcohol b
The product number is KP18-88S1, manufactured by Kuraray.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 57 μm, the content of particles larger than 94 μm is 30% by mass, and the content of particles larger than 77 μm is 44% by mass, 10% The diameter (D10) is 23 μm, and the 90% diameter (D90) is 123 μm.
(Iii) polyvinyl alcohol c
The product number is 22-88 S1 (PVA 217 S), manufactured by Kuraray.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) 113 μm, the content of particles larger than 94 μm is 81% by mass, and the content of particles larger than 77 μm is 87% by mass, 10% diameter (D10) is 57 μm, and the 90% diameter (D90) is 162 μm.
The particle diameter of the polyvinyl alcohol was measured by SALD-2000J manufactured by Shimadzu Corporation using silicone oil as a medium.
(7) Water A 3% by mass aqueous solution of glycerol (a binder solution for ProJet 660 Pro), manufactured by Sliedy System.

2. Preparation of hydraulic composition and specimen 90 parts by mass of the amorphous calcium aluminate (CA), 10 parts by mass of super jet cement, an amount of polyvinyl alcohol shown in Table 1, and 200 parts by mass of sand, A powder mixture (water-free hydraulic composition) was prepared.
Next, using the powder mixture and a binder jet powder lamination molding apparatus (trade name: ProJet 660Pro, manufactured by 3D System Co., Ltd.) as an additional manufacturing apparatus, under the conditions of room temperature (20 ° C.) and relative humidity 60%. After producing a compact having a cross-sectional dimension of 10 mm in length, 16 mm in width and 80 mm in length by the binder injection method, the compact is subjected to conditions of 20 ° C., 40 ° C., and 60 ° C. and 30% relative humidity. The specimens were manufactured by air curing for 3 to 72 hours.
In the manufacture of a molded body by the above apparatus, a predetermined position of the powder mixture is selected, the water amount setting value of the apparatus is adjusted from the nozzle, and water is jetted to the outside and the inside of the powder mixture. The mixture solidified.
The volatile content of the specimen was determined by heating the specimen as it is at 1400 ° C. for 12 hours without drying or crushing the specimen after the aging time of 72 hours and measuring the mass of the specimen before and after heating.

3. Measurement of Bending Strength, etc. of the Specimen Next, using the above-mentioned specimen, a three-point bending test is performed by a bending strength tester (model number: MODEL-2257, manufactured by EIKO ENGINEERING CO., LTD.) To measure the bending strength of the specimen. did. The results are shown in Table 1. From the viewpoint of practicality, the target value for bending strength was 1.0N / mm ² or more at 3 hours of material age and 1.8N / mm ² or more at 3 days of material age was accepted (practical) .
As shown in Table 1, the bending strength of the example satisfies the reference value, but the bending strength of the comparative example does not satisfy the reference value.

4. Preparation of hydraulic composition and test body According to the composition of Table 2, calcium aluminates, cement, gypsum, polyvinyl alcohol a, and sand are mixed to obtain a powder mixture (water-free hydraulic composition) Made.
Next, using the powder mixture and a binder injection type powder layer forming apparatus (trade name: ProJet 660Pro, manufactured by 3D System Co., Ltd.) as an additive manufacturing apparatus, the cross section size is 10 mm long and 16 mm wide by a binder injection method. After preparing a molded body of 80 mm in length and 80 mm in length, the molded body was air-cured for 3 to 72 hours under the conditions of 40 ° C. and relative humidity 30% to manufacture a test body.
In the manufacture of a molded body by the above apparatus, a predetermined position of the powder mixture is selected, and water is injected from the nozzle to the outside and the inside of the sample according to the water amount setting value of the apparatus shown in Table 2 The mixture solidified.

5. Measurement of Bending Strength, etc. of Specimen Next, a three-point bending test is performed using the above-mentioned specimen and a bending strength tester (model number: MODEL-2257, manufactured by AICO ENGINEERING CO., LTD.) To measure the bending strength of the specimen. did. In addition, volatile matter from the specimen at 3 days of material age was measured. The results are shown in Table 2. From the viewpoint of practicality, flexural strength as a target value the age of 3 hours at 1.0 N / mm ² or more were deemed passing 1.8 N / mm ² or more within three days an age (practical).
As shown in Table 2, the bending strengths of the examples satisfied the reference value, and all volatile components from the specimen at the material age of 3 days of the examples were all as low as 5.0 mass% or less.

6. Further, a mold and a core for producing a water bottle having a size of about 10 cm were produced under the same composition and production conditions as the production of the test body of Example 7 above, and molten cast iron (pouring temperature is about Pour in 1450 ° C). As a result, no gas was generated during casting, and a casting having a smooth surface was produced.

Claims (9)

  A hydraulic composition for an additive manufacturing device, further comprising 28 to 60 parts by mass of water and sand relative to a total of 100 parts by mass of the composite binder containing 1 to 12 parts by mass of polyvinyl alcohol based on 100 parts by mass of the inorganic binder object.   The hydraulic composition for addition manufacturing devices according to claim 1, wherein the inorganic binder contains 50 to 100 mass% of calcium aluminates, based on 100 mass% of the entire inorganic binder.   The hydraulic composition for addition manufacturing devices according to claim 1 or 2, wherein the inorganic binder contains 0.5 to 5.0% by mass of gypsum based on 100% by mass of the entire inorganic binder.   The hydraulic composition for an additive manufacturing device according to any one of claims 1 to 3, wherein the inorganic binder further contains a quick-hardening cement.   The hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-4 whose volatile matter in material age 3 is 5.5 mass% or less.   The hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-5 whose saponification degree of the said polyvinyl alcohol is 80-90 mol%.   The hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-6 whose average particle diameter of the said polyvinyl alcohol is 150 micrometers or less.   The manufacturing method of a casting_mold | template which shape | molds a mold using an addition manufacturing apparatus and the hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-7. The method for producing a mold according to claim 8, wherein a curing temperature of the mold is 10 to 80 ° C.