JP2018153821A - Manufacturing method of laminated mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved manufacturing method of a laminated mold which makes a finally-obtained mold maintain high packing density, and exert excellent mold rigidity, and to provide the manufacturing method effective for the laminated mold which can improve the smoothness of a mold skin of a cast product.SOLUTION: A thin sand layer 20 is formed on a surface of a fire-resistance aggregate by using dry-coated sand which is obtained by forming a coating layer containing inorganic oxide particles having particle diameters smaller than that of the fire-resistance aggregate together with water glass as a binder, and after that, the sand layer 20 is heated after being sprayed with an aqueous medium. By repeating work for forming prescribed two-dimensional pattern mold layers 34, a purposed three-dimensional laminated mold is manufactured by laminating the mold layers 34.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for producing a laminated mold, and in particular, a thin sand layer is formed and repeatedly cured into a predetermined shape one by one, and the plurality of sand layers thus formed are laminated and integrated. Thus, the present invention relates to a method of manufacturing a target sand mold having a three-dimensional shape.

  In recent years, a lamination molding technique using a three-dimensional printing method has been actively studied and put into practical use. In addition, such lamination molding technology is applied to mold molding, and trial production of molds and production of molds for high-mix low-volume production are being studied all over the world. A mold forming method has been proposed. Among these laser systems and inkjet systems, the inkjet system manufacturing apparatus has the advantage that the apparatus is less expensive than the laser system.

  By the way, as a conventional method for layered modeling of a mold by a laser method, for example, a sand mold modeling method by a layering method as disclosed in Japanese Patent Laid-Open No. 9-168840 (Patent Document 1) has been proposed. ing. In the method, a resin layer-coated sand (resin coated sand) is sprayed to form a thin sand layer, and a predetermined step of the thinly layered sand layer is cured by laser irradiation. In this way, one layer of the sand mold is formed, and these steps are repeated in sequence, and a hardened sand layer corresponding to each cross-sectional shape of the target sand mold is sequentially laminated. A sand mold is shaped.

  However, in such a sand mold molding method using a laser laminating method, the resin-coated sand is heated and cured by heating by laser irradiation. In addition, the problem that organic odor is generated is inherent. Further, since a temperature difference is generated in the sand layer depending on the presence or absence of laser irradiation, internal stress is likely to occur, and there is a problem that warpage and distortion occur in the sand mold when stored for a long period of time. Furthermore, in order to heat and cure a predetermined part by laser irradiation, high output and precise control are required, and an expensive laser irradiation apparatus is required, and much energy is required for heating. The problem of becoming is also inherent.

  On the other hand, as a layered modeling method of a mold by an ink jet method, in Japanese Patent Application Laid-Open No. 2011-230421 (Patent Document 2), a layer forming step of forming a layer with a three-dimensional modeling powder containing a water-soluble polymer, and this layer formation A generation step of generating a layer having a product generated by dissolving the three-dimensional modeling powder in the modeling liquid by discharging a modeling liquid using water as a solvent from the inkjet head to the layer formed in the step. The manufacturing method of the three-dimensional molded object provided is clarified.

  Then, while suppressing evaporation of water, a thickening wetting agent that thickens the modeling liquid and a surfactant are contained in the used modeling liquid, and the pH is further adjusted to 7-9. It is said that the target three-dimensional model can be modeled according to the desired shape. However, when such a modeling liquid is discharged from the inkjet head to the three-dimensional model powder, manufacturing by additive manufacturing is performed. Compared to the case of molding with a mold, for example, the three-dimensional molded powder is not filled by pressurization etc., so the density of the mold is low, and the strength of the mold is also when molding with the mold There was a problem of getting worse. In addition, due to the properties of the layered modeling, there is a problem that steps and gaps between the layers are likely to occur on the surface of the mold, and the smoothness of the casting surface of the casting is deteriorated.

JP-A-9-168840 JP 2011-230421 A

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is that the mold finally obtained maintains a high packing density in the layered manufacturing. In addition, an object of the present invention is to provide an improved manufacturing method of a laminated mold capable of exhibiting excellent mold strength, and another object is to provide a laminate capable of improving the smoothness of a casting surface of a casting. The object is to provide an effective method for producing a mold.

  Under such circumstances, as a result of repeated studies by the present inventors on the additive manufacturing method, as a foundry sand, a fire-resistant aggregate is coated with a coating layer containing water glass and inorganic oxide particles having a predetermined particle diameter. In order to complete the present invention, it is found that the above-mentioned problems can be solved by using the coated sand formed and solidifying or curing the formed mold layer by spraying and heating an aqueous medium. It has come.

  And in order to solve the subject mentioned above, this invention can be implemented suitably in the various aspects as enumerated below. In addition, each aspect described below can be employed in any combination. Further, it is understood that the aspects and technical features of the present invention are not limited to those described below, and can be recognized based on the description of the entire specification and the inventive concept described in the drawings. Should be.

(1) After forming a thin sand layer using a coated sand formed by coating a fireproof aggregate with a binder, an aqueous medium is sprayed on the sand layer and heated to form a solidified layer having a predetermined two-dimensional pattern. When a solid mold or a hardened layer is laminated by repeating the operation of forming a hardened layer, the surface of the refractory aggregate is used as the coated sand. And a dry coated sand obtained by forming a coating layer containing inorganic oxide particles having a particle size smaller than that of the refractory aggregate together with water glass as a binder. A manufacturing method for laminated molds.
(2) With respect to the average particle diameter (d1) of the inorganic oxide particles, the average particle diameter (d2) of the refractory aggregate is represented by the following formula:
2 × d1 ≦ d2 ≦ 5000 × d1
The method for producing a laminated mold according to the aspect (1), wherein:
(3) The average particle diameter of the said inorganic oxide particle is 0.1-20 micrometers, The manufacturing method of the lamination | stacking mold as described in the said aspect (1) or the said aspect (2) characterized by the above-mentioned.
(4) The above aspect (1), wherein the inorganic oxide particles are spherical particles, and the aspect ratio defined by the ratio of the minor axis / major axis is 0.5 to 1.0. ) To the above aspect (
The manufacturing method of the lamination | stacking casting_mold | template as described in any one of 3).
(5) The aspect (1) to the aspect (1), wherein the inorganic oxide particles are a metal oxide selected from the group consisting of silicon dioxide, aluminum oxide, and titanium oxide.
4) The manufacturing method of the lamination | stacking mold as described in any one of 4).
(6) Content of the said inorganic oxide particle is a ratio of 0.1-500 mass parts with respect to 100 mass parts of solid content of the water glass in the said coated sand, The said aspect (1) characterized by the above-mentioned. The manufacturing method of the lamination | stacking mold as described in any one of the said aspect (5).
(7) The aspect (1) to the aspect (6), wherein the aqueous medium contains at least one of a curing accelerator, a surfactant, a humectant, a drying accelerator, and a preservative. ) A method for producing a laminated mold according to any one of the above.
(8) In any one of the above aspects (1) to (7), the aqueous medium has a viscosity of 0.1 to 50 cP and a surface tension of 15 to 50 mN / m. The manufacturing method of the laminated mold of description.
(9) The method for producing a laminated mold according to any one of the aspects (1) to (8), wherein the coated sand further contains a lubricant on the surface thereof.
(10) The above aspect, wherein the content of the lubricant is a ratio of 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand (
A method for producing a laminated mold according to 9).
(11) The laminated mold according to any one of the aspects (1) to (10), wherein the moisture content in the coated sand is 5 to 55 mass% of the solid content of water glass. Manufacturing method.
(12) The laminated mold according to any one of the aspects (1) to (11), wherein the dispersion of the aqueous medium on the sand layer is performed using an inkjet-type spraying device. Manufacturing method.

And according to the manufacturing method of the lamination mold | type according to such this invention, the various effects as enumerated below can be show | played.
(A) When the dry coated sand is wetted by moisture, inorganic oxide particles having a particle size smaller than that of the refractory aggregate, which is the main component of the coated sand, are concentrated in the gaps between such refractory aggregates. As a result, the filling property can be effectively improved.
(B) By forming a stone wall structure with inorganic oxide particles between the refractory aggregates of the coated sand that forms the sand layer, the number of contacts due to the binder that hardens or hardens increases. Therefore, it is possible to advantageously secure the strength that can withstand the high pressure at the time of casting the molten metal during casting.
(C) Since the coated sand (refractory aggregate) and the inorganic oxide particles form a stone wall structure, the gap between the coated sands can be effectively reduced. Insertion can be advantageously prevented, and the smoothness of the casting surface of the casting can be improved.
(D) When spherical particles are used as the inorganic oxide particles, the filling property can be further improved, the strength can be effectively increased, and the smoothness of the casting surface of the casting can be further improved. Come out.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows the 1st process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention, Comprising: (a) is the state which has spread | coated the coated sand, (b) is a plane of the coated coated sand. Each of the expanded states is shown. It is a schematic explanatory drawing which shows the 2nd process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention. It is a schematic explanatory drawing which shows the 3rd process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention. It is a schematic explanatory drawing which shows the form after the process of 1 turn of the manufacturing method of the lamination mold which consists of a process shown by FIGS. It is a schematic explanatory drawing which shows the state which repeated each process of the manufacturing method of the lamination mold | type according to this invention, and laminated | stacked and formed the multiple-layered mold layer. It is a schematic explanatory drawing which shows the lamination mold obtained in embodiment of the manufacturing method of the lamination mold according to this invention shown by FIGS.

  Hereinafter, in order to clarify the configuration of the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings.

  First, the coated sand (coated sand) used in the present invention is generally mixed with water glass in the state of an aqueous solution as a binder, and further mixed with inorganic oxide particles, to the refractory aggregate. And by evaporating moisture from the obtained mixture, in other words, by evaporating the moisture of the water glass in the state of an aqueous solution, the solid content of the water glass as a binder is produced. A dry coating layer containing inorganic oxide particles is formed on the surface of such a refractory aggregate at a predetermined thickness, and has a good room temperature fluidity It is.

  Here, the “dry coated sand having room temperature fluidity” in the present invention means a coated sand from which a measured value is obtained when the dynamic angle of repose is measured regardless of the moisture content. This dynamic angle of repose means that the coated sand to be measured is accommodated in a cylinder whose one end in the axial direction is closed with a transparent plate (for example, 7.2 cm in diameter × 10 cm in height). Put the coated sand into the container to half of its volume), hold the shaft center in the horizontal direction, and rotate around the horizontal shaft center at a constant speed (for example, 25 rpm) to flow in the cylinder The angle formed between the slope and the horizontal plane when the slope of the coated sand layer is flat. On the other hand, for example, when the coated sand is moist, the coated sand layer does not flow as a flat surface without flowing in the cylinder, and as a result, the dynamic angle of repose can be measured. What cannot be done is called wet coated sand.

  The dry coated sand having room temperature fluidity according to the present invention has a moisture content of 5 to 55 with respect to the solid content of water glass contained in the coating layer covering the surface of the refractory aggregate. The amount is preferably an amount corresponding to the proportion of mass%, more preferably 10 to 50 mass%, and most preferably 20 to 50 mass%. When the moisture content in the coated sand is less than the amount corresponding to 5% by mass with respect to the solid content of the water glass in the coating layer, the water glass is vitrified, and water is added again during mold forming. However, when the amount exceeds 55% by mass, the coated sand may not be in a dry state. In addition, it does not specifically limit as a measuring method of the moisture content in a coated sand, The method according to types, such as water glass, is employable suitably. Specifically, the measuring method described in the column of Examples described later can be exemplified. In addition, when an organic component containing moisture (for example, a surfactant or a humectant) is added as an additive to the coated layer of the coated sand, the moisture content is also taken into account with the moisture in the organic component. Must be measured (calculated).

  The refractory aggregate constituting the coated sand used in the present invention is a refractory substance that functions as a base material of a mold, and various refractory granules or powders conventionally used for molds. Any material can be used, specifically, silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag, Examples thereof include slag-based particles such as converter slag; artificial particles such as alumina-based particles and mullite-based particles, and regenerated particles thereof; alumina balls, magnesia clinker and the like. In addition, these fireproof aggregates may be fresh sand, or reclaimed sand or recovered sand that has been used once or more times as a molding sand for molding a mold. Even mixed sand made by adding fresh sand to the collected sand and mixing it can be anything. And such a refractory aggregate will generally be used as an AFS index with a particle size of about 40 to 200, preferably with a particle size of about 50 to 150.

  Moreover, in the coated sand used for this invention, what has water glass as a main component will be used as a binder which coat | covers the above refractory aggregates. Here, water glass is a water-soluble silicate compound. Examples of such a silicate compound include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and silicate. Although ammonium etc. can be mentioned, Among these, especially sodium silicate (sodium silicate) will be used advantageously in this invention. As a binder, as long as water glass is used as a main component, other known water-soluble binders such as thermosetting resins, saccharides, proteins, synthetic polymers, salts and inorganic polymers are used in combination. Is possible. When such other water-soluble binder is used in combination with water glass, the ratio of water glass in the whole binder is preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably. Is 90% or more.

Here, sodium silicate is usually classified into Nos. 1 to 5 according to the molar ratio of SiO ₂ / Na ₂ O and used. Specifically, sodium silicate No. 1 has a SiO ₂ / Na ₂ O molar ratio of 2.0 to 2.3, and sodium silicate No. 2 is SiO ₂ / Na ₂ O ₂ . The molar ratio is 2.4 to 2.6, and sodium silicate No. 3 has a SiO ₂ / Na ₂ O molar ratio of 2.8 to 3.3. In addition, sodium silicate No. 4 has a SiO ₂ / Na ₂ O molar ratio of 3.3 to 3.5, and sodium silicate No. 5 has a SiO ₂ / Na ₂ O molar ratio. Is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. In the present invention, these various sodium silicates may be used alone or in combination, and the molar ratio of SiO ₂ / Na ₂ O may be adjusted by mixing. Is possible.

In the present invention, in order to advantageously obtain a dry coated sand, the sodium silicate constituting the water glass used as a binder has a molar ratio of SiO ₂ / Na ₂ O of generally 1.9 or more, Preferably, it is 2.0 or more, more preferably 2.1 or more. In the above-mentioned classification of sodium silicate, sodium silicate corresponding to No. 1 and No. 2 is particularly advantageously used. Become. Such sodium silicates No. 1 and No. 2 provide dry coated sand having stable and good characteristics even when the sodium silicate concentration in the water glass is wide. Further, the upper limit of the molar ratio of SiO ₂ / Na ₂ O in such sodium silicate is appropriately selected according to the characteristics of the water glass in the form of an aqueous solution, but generally 3.5 or less. , Preferably 3.2 or less, more preferably 2.7 or less. Here, when the molar ratio of SiO ₂ / Na ₂ O is smaller than 1.9, the viscosity of the water glass is lowered, and it becomes difficult to make the coated sand dry unless the water content is considerably reduced. On the other hand, if it exceeds 3.5, the solubility in water decreases, the adhesion area cannot be gained, and the strength of the mold finally obtained may decrease.

  The water glass used in the present invention means a solution of a silicate compound in a state dissolved in water. In addition to being used in a stock solution as purchased in the market, water is added to such a stock solution. It is also possible to add and use in a diluted state. And, from such water glass, the non-volatile content (water glass component) excluding volatile substances such as water and solvent is called solid content, which corresponds to the above-described soluble silicate compound such as sodium silicate. To do. Moreover, the higher the proportion of such solid content (nonvolatile content), the higher the concentration of the silicate compound in the water glass. Therefore, the solid content of the water glass used in the present invention corresponds to the amount excluding the amount of water in the stock solution when it is composed only of the stock solution, while the stock solution is converted into water. When the diluted solution obtained by dilution is used, the amount excluding the amount of water in the stock solution and the amount of water used for dilution corresponds to the solid content of the water glass used. It becomes.

  Further, the solid content in the water glass is set to an appropriate ratio depending on the type of the water glass component (soluble silicate compound) and the like, but is preferably about 20 to 50% by mass. It is desirable that it is contained in a proportion. By making the water glass component corresponding to the solid content appropriately present in the aqueous solution, the water glass component can be uniformly and uniformly applied to the fire resistant aggregate during mixing (kneading) with the fire resistant aggregate. Thus, it becomes possible to advantageously shape the target mold. If the concentration of the water glass component in the water glass is too low and the total amount of solids is less than 20% by mass, the heating temperature is increased or the heating time is increased for drying the coated sand. For this reason, problems such as energy loss are caused. In addition, if the ratio of the solid content in the water glass becomes too high, it becomes difficult to uniformly coat the surface of the refractory aggregate with the water glass component, which causes a problem in improving the properties of the target mold. Therefore, it is desirable to adjust the water glass in the form of an aqueous solution so that the solid content is 50% by mass or less, and thus the water content is 50% by mass or more.

And it is desirable that such water glass is used in a proportion of 0.1 to 5.0 parts by mass in terms of solid content when considered as only non-volatile content with respect to 100 parts by mass of the refractory aggregate. A ratio of 0.3 to 4.0 parts by mass is particularly advantageously employed, and a predetermined coating layer is formed on the surface of the refractory aggregate. Here, the measurement of solid content is implemented as follows. That is, 10 g of a sample was weighed and contained in an aluminum foil dish (length: 90 mm, width: 90 mm, height: 15 mm), placed on a heating plate maintained at 180 ± 1 ° C., and left for 20 minutes. Invert the sample pan and leave it on the heating plate for another 20 minutes. Thereafter, the sample dish is taken out from the heating plate, allowed to cool in a desiccator, weighed, and the solid content (% by mass) is calculated by the following formula.
Solid content (mass%) = [mass after drying (g) / mass before drying (g)] × 100

  In the present invention, if the amount of water glass used is too small, it becomes difficult to form a coating layer on the surface of the refractory aggregate, and the solidification or hardening of the coated sand during molding is difficult to proceed sufficiently. There is a fear. In addition, even if the amount of water glass used is excessive, an excessive amount of water glass adheres to the surface of the refractory aggregate, making it difficult to form a uniform coating layer, and the coated sand adheres to each other. This may cause agglomeration (composite particles), which adversely affects the physical properties of the final mold and makes it difficult to remove the sand from the core after casting the molten metal. There is also a risk of triggering.

  By the way, in the coated sand used in the present invention, inorganic oxide particles having a particle diameter smaller than that of the refractory aggregate are further contained in the coating layer covering the surface of the refractory aggregate together with water glass. There is a big feature. When a sand layer is formed with the coated sand further containing inorganic oxide particles in the coating layer containing water glass, an aqueous medium is sprayed on the coated sand of the sand layer by inkjet or the like. The inorganic oxide particles in the layer, together with the water glass that has been made into a solution by the supplied water, effectively flow between the refractory aggregates and are concentrated in the gaps between the refractory aggregates. A structure is formed, and as a result, the filling property (density) between the coated sands forming the sand layer can be advantageously improved. In a mold obtained by solidifying or hardening the water glass with such improved filling properties, the inorganic oxide particles are effective in the gaps between adjacent refractory aggregates. Therefore, it exhibits excellent strength.

  That is, according to the present invention, in a mold obtained using dry coated sand having room temperature fluidity, it is similar to stone wall by refractory aggregate, inorganic oxide particles, and solidified or hardened water glass. Thus, the strength that can withstand the high pressure at the time of pouring the molten metal can be exhibited. Moreover, such a stone wall structure can effectively prevent the molten metal from being inserted when the molten metal is poured, and improve the smoothness of the casting surface of the casting. Furthermore, when high-temperature molten metal is injected into the mold, the water glass bonded between the refractory aggregates in the mold expands and becomes thin, but there are inorganic oxide particles between the refractory aggregates. Therefore, in the mold obtained in the present invention, the layer of water glass connecting the refractory aggregate is further thinned. Compared to the conventional laminated mold obtained by using coated sand with a coating layer of water glass only, it is easy to disintegrate early after the molten metal is poured, and the mold has excellent disintegration. It becomes.

  Here, in the dry coated sand having room temperature fluidity of the present invention, the inorganic oxide particles contained in the coating layer have a particle size smaller than that of the refractory aggregate, and the average particle size thereof is Preferably, 0.1 to 20 μm, more preferably 0.1 to 10 μm, and most preferably 0.5 to 5.0 μm are used. Moreover, in this invention, it is preferable that content of an inorganic oxide particle is a ratio of 0.1-500 mass parts with respect to 100 mass parts of solid content of the water glass in a coating layer, More preferably, it is 0. .3 to 300 parts by mass, more preferably 0.5 to 200 parts by mass, and most preferably 0.75 to 150 parts by mass. As described above, by incorporating inorganic oxide particles having a predetermined average particle diameter into the coating layer in a predetermined ratio, it is possible to enjoy the above-described effect more advantageously. The average particle size of the inorganic oxide particles can be obtained from the particle size distribution measured by a laser diffraction type particle size distribution measuring device or the like.

Further, in the present invention, when water is supplied to the sand layer of the coated sand in the mold forming process, in the gap between the adjacent refractory aggregates, together with the water glass in a solution state, inorganic oxidation is performed. The average particle size of the inorganic oxide particles: d1 and the average particle size of the refractory aggregate: d2 are as follows so that the product particles can effectively flow and intervene advantageously between the refractory aggregates. It is preferable to adjust so as to satisfy the formula (1), it is more preferable to satisfy the following formula (2), and it is most preferable to satisfy the following formula (3). The form of the refractory aggregate need not be spherical, and the average particle size can be determined from the particle size distribution measured by a laser diffraction type particle size distribution measuring device or the like.
4 × d1 ≦ d2 ≦ 5000 × d1 (1)
6 × d1 ≦ d2 ≦ 3000 × d1 (2)
7 × d1 ≦ d2 ≦ 2500 × d1 (3)

  The inorganic oxide particles used in the present invention may be either spherical particles or non-spherical particles. However, the spherical particles can better exhibit the characteristics of the present invention and obtain a particularly good casting surface. It can be said that it is preferable because it can be done. Such spherical particles only need to have a generally recognized spherical shape and are not necessarily required to have a true spherical shape, but usually have a sphericity of 0.5 or more. What is preferably 0.7 or more, more preferably 0.9 or more, is advantageously used. Here, the sphericity is an aspect ratio (ratio of minor axis / major axis) obtained from the projection shape of 10 single particles randomly selected in observation using a scanning electron microscope. Mean value. In addition, when inorganic oxide particles that are not spherical are used, the surface of the inorganic oxide particles has protrusions and depressions, so that the inorganic oxide particles are mixed with water glass that has become a solution by the supplied water. Even if it tries to flow between refractory aggregates, such protrusions will collide with refractory aggregates and other inorganic oxide particles at the time of flow, resulting in an anti-slip action, and between refractory aggregates. There is a risk that flow into the mold may be hindered, which may affect the filling properties and, consequently, the strength of the mold.

  The material constituting the inorganic oxide particles is not particularly limited as long as the particle diameter is smaller than that of the refractory aggregate, but is more preferably inorganic metal oxide particles. . As such inorganic metal oxide particles, particles of silicon dioxide, aluminum oxide, titanium oxide and the like are preferably used. You may use these individually or in mixture of 2 or more types. In the present invention, silicon dioxide is treated as an inorganic metal oxide.

  By the way, in the coated sand according to the present invention, in addition to the inorganic oxide particles described above, various known additives are appropriately contained or present in the coating layer or on the surface thereof, as necessary. I can do it.

  For example, as such an additive, there is a lubricant in particular, and it is preferably employed to contain (exist) such a lubricant on the surface of the coated sand. In particular, in the present invention, the addition of a lubricant is recommended in order to improve the fluidity of the coated sand since it is necessary to form a thin sand layer by thinly spreading the coated sand to a constant thickness. It is.

  Examples of the lubricant used in the present invention include waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; fatty acid amides such as stearic acid amide, oleic acid amide, and erucic acid amide; Alkylene fatty acid amides such as acid amide and ethylene bis-stearic acid amide; stearic acid, stearyl alcohol; stearic acid metal salts such as lead stearate, zinc stearate, calcium stearate, magnesium stearate; stearic acid monoglyceride, stearyl stearate; Hardened oil, graphite, molybdenum disulfide, talc, mica, etc. can be used. Among these, calcium stearate and the like are particularly preferably used.

  In addition, as a usage-amount of the lubricant used here, it is desirable that it is 0.1-10 mass parts with respect to 100 mass parts of solid content in the water glass in a coating layer, and 0.3-8 mass in particular among them. Part is preferable, and 0.5 to 5 parts by mass is particularly preferable. If the amount of the lubricant contained is too small, the above-mentioned effects may not be enjoyed advantageously, whereas if the amount of the lubricant is too large, the mold strength may decrease, Is not a good idea from a cost-effective perspective.

  Moreover, surfactant can be illustrated as another one of said additive. When this surfactant is included in the coating layer of the coated sand, the water permeability in the coated sand, in other words, the wettability of the coated sand to the water is effectively improved. Even when a small amount of moisture is supplied to the thin sand layer to be formed, the entire sand layer is advantageously moistened and can be made wet. In this way, the wettability of the coated sand is improved, and the amount of moisture added to the coated sand is suppressed to a small amount, so there is no variation in the curing of each layer in the laminate, and the layer can be stably laminated. At the same time, the obtained mold exhibits more excellent strength.

  In the present invention, various conventionally known surfactants such as cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, silicone surfactants, Any fluorosurfactant can be used as long as the object of the present invention is not impaired. Here, the silicone-based surfactant refers to a surfactant having a siloxane structure as a nonpolar site, and the fluorine-based surfactant refers to a surfactant having a perfluoroalkyl group. In addition, the content of the surfactant in the present invention is desirably a ratio of 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coating layer, and more preferably 0.5 to 0.5 parts by mass. To 15.0 parts by mass, particularly preferably 0.75 to 12.5 parts by mass. In addition, if the amount of the surfactant contained in the coating layer is too small, there is a possibility that the above-mentioned effects cannot be enjoyed advantageously. On the other hand, even if the amount of the surfactant is too large, the amount used is too large. Depending on the boiling point of the surfactant, there is a risk that when the water glass is dried, the surfactant does not solidify and the coated sand becomes wet. Moreover, it is not a good idea from the viewpoint of cost effectiveness.

  Further, the coating layer of the coated sand of the present invention may further contain a humectant. By further containing a moisturizing agent in the coating layer containing water glass, the wettability of the coated sand wetted with moisture during mold molding is stabilized until solidified or cured by heating. Can be maintained. In addition, as for content of the moisturizing agent in this invention, it is desirable that it is a ratio of 0.1-20.0 mass parts with respect to 100 mass parts of solid content of the water glass in a coating layer, Especially 0.5- 15.0 parts by mass is more desirable, and most desirably 0.75 to 12.5 parts by mass. Moreover, as such a humectant, polyhydric alcohol, water-soluble polymer, hydrocarbons, saccharides, protein, inorganic compounds, and the like can be used.

  Here, as the polyhydric alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, propylene glycol, butylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 2-ethyl-1,3-hexanediol, 1,6-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2, Examples include 6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane. The water-soluble polymer compound particularly refers to a compound having 5 to 25 alcoholic hydroxyl groups per 1000 molecular weight. Examples of such water-soluble polymer compounds include vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; celluloses such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose. Derivatives; starch derivatives such as alkyl starch, carboxymethyl starch and oxidized starch; and water-absorbing polymers such as sodium polyacrylate. Further, examples of the hydrocarbons include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum ether, petroleum benzyl, tetralin, decalin, tertiary amylbenzene, dimethylnaphthalene and the like. Furthermore, examples of the saccharide include monosaccharides, oligosaccharides, polysaccharides such as dextrin, and the like, among which saccharides are saccharides that cannot be decomposed into simpler saccharides by hydrolysis. , Preferably tricarbon sugar (monosaccharide having 3 carbon atoms) to decacarbon sugar (monosaccharide having 10 carbon atoms), more preferably hexose sugar (monosaccharide having 6 carbon atoms), Examples of proteins include gelatin. In addition, examples of inorganic compounds include sodium chloride, sodium sulfate, calcium chloride, magnesium chloride, and silicate. These various humectants can be used alone or in admixture of two or more.

  In addition, various conventionally known moisturizers include those that are water-soluble to those that are sparingly water-soluble. In the present invention, the viscosity increases when poured into water at room temperature (25 ° C.). A moisturizing agent with a low value will be used advantageously. Specifically, in the case of a water-soluble humectant, an amount of humectant corresponding to 20% of the mass of water is added to water at room temperature, and the mixture is stirred for 1 hour. Moisturizers with 8-10 cP, preferably 0.8-5 cP, are advantageously used. On the other hand, a poorly water-soluble humectant exhibits an effect as a humectant when dispersed in water. Even if it is a poorly water-soluble humectant, it is 20% of the mass of water in normal temperature water. It is preferable that a moisturizing agent in an amount corresponding to 1 is added, stirred for 1 hour, the solution after stirring (a mixture of water and moisturizing agent) is filtered, and the viscosity of the obtained filtrate is within the above range Used. From the above, the humectant advantageously used in the present invention includes cellulose derivatives such as glycerin and hydroxypropylmethylcellulose, water-absorbing polymers such as sodium polyacrylate, polysaccharides such as dextrin, and vinyl alcohols such as polyvinyl alcohol. And polyethylene glycol (polyethylene oxide) having a weight average molecular weight of 50,000 or more.

  Furthermore, as another additive for the coating layer, solid oxides and salts are also advantageously used. By containing these solid oxides and salts, the moisture resistance of the coated sand can be advantageously improved. Of these, as the solid oxide, it is effective to use oxides of silicon, zinc, magnesium, aluminum, calcium, lead, and boron, for example. In particular, among these, use of silicon dioxide, zinc oxide, aluminum oxide, and boron oxide is desirable. Of silicon dioxide, precipitated silicic acid and exothermic silicic acid are preferably used. On the other hand, as the salt, there are silicofluoride, silicate, phosphate, borate, tetraborate, carbonate, etc. Among them, zinc carbonate, basic zinc carbonate, potassium metaborate, tetraborate, etc. Use of sodium acid and potassium tetraborate is desirable. And these solid oxide and salt are generally used in the ratio of about 0.5-5 mass% with respect to the solid content in the water glass in the coating layer of a coated sand.

  In addition, as another additive, it is also effective to include a coupling agent that strengthens the bond between the refractory aggregate and water glass. For example, a silane coupling agent, a zircon coupling agent, a titanium coupling agent Etc. can be used. Furthermore, as release agents, paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, fine graphite particles, mica, meteorite, fluorine release agent, silicone release agent An agent or the like can also be used. Each of these other additives is generally 5% by mass or less, preferably 3% by mass or less with respect to the solid content of the water glass in the coated sand coating layer. It is contained in

By the way, when producing a dry coated sand having room temperature fluidity used in the present invention, generally, water glass as a binder is used for the refractory aggregate, inorganic oxide particles or necessary. It is kneaded or mixed with other additives that are used accordingly, and mixed uniformly to cover the surface of the refractory aggregate with water glass, and the coating layer is coated with inorganic oxide particles, etc. A method of forming a coating layer containing water glass, inorganic oxide particles and the like on the surface of the refractory aggregate by adding the above-mentioned additive and evaporating the water content of such water glass is employed. In such a technique, water vaporization of the coating layer needs to be performed quickly before the water glass solidifies or hardens, so that the water glass in the form of an aqueous solution is used against the refractory aggregate. In addition, it is desirable to remove the water content within 5 minutes, and more preferably within 3 minutes after the addition (mixing) of the predetermined additives, to obtain dry powder coated sand. If the transpiration time becomes longer, the mixing (kneading) cycle becomes longer, the productivity of the coated sand is lowered, and the time that the water glass is in contact with CO ₂ in the air becomes longer, resulting in inactivation. This is because there is a high risk of occurrence.

  Moreover, in the manufacturing process of the above-mentioned coated sand, as one of effective means for rapidly evaporating the water in the water glass, the refractory aggregate is preheated and water in the form of an aqueous solution is added. A method of kneading or mixing glass or a predetermined additive and mixing them is preferably employed. By mixing or mixing water glass and additives with this preheated refractory aggregate, the water in the water glass is very quickly heated by the heat of such refractory aggregate. Since the amount of water in the coated sand obtained can be effectively reduced, a dry powder having room temperature fluidity can be advantageously obtained. is there. In order to quickly evaporate moisture at this time, it is also effective to employ a method of blowing hot air into the kneading vessel, a method of heating the kneading vessel, and a method of reducing the pressure inside the kneading vessel. Here, the preheating temperature of the refractory aggregate is appropriately selected according to the water content of the water glass, the blending amount thereof, etc., but generally a temperature of about 100 to 200 ° C. is preferable. A temperature of about 120 to 180 ° C. is employed. If the preheating temperature is too low, it is not possible to effectively evaporate water, and it takes time to dry. Therefore, it is desirable to employ a temperature of 100 ° C. or higher. If the coating sand is too high, the water glass component is hardened when the resulting coated sand is cooled, and in addition, the formation of composite particles progresses, so the function as the coated sand, especially the strength of the final mold obtained. This causes problems in physical properties.

  In the coated sand used in the present invention, the inorganic oxide particles contained in the coating layer containing water glass and other additives used as necessary, such as a surfactant and a moisturizing agent, are preliminarily added. It may be added to the refractory aggregate in a mixed state with glass and kneaded.At the time of kneading, it may be added and kneaded separately from the water glass. A time difference between them may be added and kneaded. Therefore, the coating layer in the coated sand according to the present invention is, for example, in a state where the water glass and the inorganic oxide particles are integrally integrated, or outward from the surface of the refractory aggregate. While the concentration of the solid content (nonvolatile content) gradually decreases or increases, the concentration of the additive such as the inorganic oxide particles gradually increases or decreases.

(Layered modeling method)
By the way, the method for manufacturing a laminated mold according to the present invention is carried out using the coated sand obtained as described above, for example, as shown in FIGS. That is, first, as shown in FIG. 1, the mold forming apparatus used in the present invention has a rectangular table 12 that can be slid vertically in a vertical direction in a container-like frame 10 having a square planar shape. Is arranged. In addition, as shown in FIGS. 1 to 3, the modeling apparatus includes a storage tank 16 for supplying the coated sand 14 positioned above the frame 10, and a discharge tank provided at the lower portion of the storage tank 16. The coated sand 14 supplied from the outlet 18 to the upper surface of the table 12 is thinly spread on the surface to a predetermined thickness to form a thin sand layer 20 and a predetermined liquid on the sand layer 20 by the ink jet method. An ink jet spraying device 26 serving as a selective spraying means for spraying on a part and a heater 30 provided with a heating wire 32 as a heating element are provided, which are selectively used in accordance with each process of manufacturing the mold layer. It is switched and arranged.

  The ink jet spraying device 26 has a nozzle 28 that can move along the upper surface of the sand layer 20 as shown in FIG. 2 together with a storage device and a control device (not shown), and can spray the aqueous medium to be used. It has become. The storage device stores a predetermined two-dimensional pattern (planar shape) of a predetermined mold layer 34 (see FIG. 5) formed in each sand layer 20 as an image signal. While controlling the operation according to the image signal, a predetermined aqueous medium can be ejected (spread) in a predetermined plane shape (pattern) to each sand layer 20. Here, the switching of the equipment in each process is automatically performed, but of course, it is also possible to perform the switching by a manual or semi-automatic method.

  In addition, the heater 30 shown in FIG. 3 can be heated by using the heating wire 32 as a heating element. As the heating element for such a heating wire 32, various known types of heating elements can be used. Can be selected and used, for example, using metal heating elements (Nichrome wire, Kanthal wire, platinum wire, etc.), silicon carbide, molybdenum disilicide, lanthanum chromite, molybdenum, carbon, etc. It is also possible to heat. The heater 30 is not particularly limited as long as it can be heated, and an infrared generator, a microwave generator, or the like can also be used.

  In the above-described embodiment, the selective spraying means configured by the ink jet spraying device 26 is a device that can selectively spray a predetermined aqueous medium to a predetermined position on the sand layer 20. In addition, an ink jet type spraying apparatus as illustrated is advantageously used, but in addition, a mask in which a predetermined aqueous medium is sprayed only on a necessary portion of the sand layer 20 using a mask. A system-type spraying device or the like can also be employed as appropriate.

  Then, as one method for manufacturing the target laminated mold according to the present invention using the apparatus as described above, the following manufacturing procedure is adopted to manufacture the mold layer 34, and the mold layer is further manufactured. As a result of stacking and integrating 34, a three-dimensional stacked mold 36 (target mold) is formed.

<First step>
First, in the stage before manufacture, the upper surface of the frame 10 of the modeling apparatus and the upper surface of the table 12 are positioned on the same plane. Then, when the modeling process starts, the table 12 is slid downward by the height of the sand layer 20. Next, the coated sand 14 stored in the storage tank 16 is supplied so as to be evenly spread on the table 12 with a substantially uniform thickness while the supply amount from the discharge port 18 is controlled [FIG. ) State]. At this time, the height per one layer of the sand layer 20 is formed as a step corresponding to the distance that the table 12 slides downward, for example, a step of 0.3 mm. In addition, this level | step difference is formed so that it may become always uniform height for every layer laminated | stacked, and generally it is desirable to set it as a level | step difference of about 0.1 mm-3 mm.

  Then, when the supply of the coated sand 14 onto the table 12 is finished, the extending member 24 is moved in the horizontal direction along the upper surface of the frame 10, and the excess coated sand 14 is scraped off. Thereby, the sand layer 20 thinly developed on the table 12 is formed in a predetermined thickness [state of FIG. 1 (b)].

<Second step>
Next, as shown in FIG. 2, droplets, a liquid or mist-like aqueous medium 22 are sprayed from the nozzles 28 of the inkjet spraying device 26 toward the sand layer 20 for each minute region in a predetermined planar shape. Is done. Here, the determined planar shape is obtained by dividing the shape of the mold to be manufactured into a plurality of regions at equal intervals about the thickness of the sand layer, and depending on the mold to be manufactured. For each sand layer, the aqueous medium 22 is sprayed in order from the bottom based on the planar shape of each layer. For example, by obtaining sand mold shape data from CAD data of the product shape and using this as cross-sectional shape data for each thickness of the sand layer, a predetermined planar shape of each layer can be set. In this inkjet spraying device 26, the nozzle diameter of the nozzle 28 for ejecting the aqueous medium 22 is extremely small, for example, about 20 to 100 μm. However, since the liquid to be ejected is an aqueous medium, the nozzle There is no such problem as clogging.

  In this way, the coated sand 14 is moistened by the aqueous medium 22 sprayed onto the specific area of the sand layer 20, so that the water glass of the coating layer in the coated sand 14 is dissolved in the aqueous medium 22 in the fire resistance. Covering the aggregate, such water glass will aggregate between the sand grains. At this time, since the coated sand 14 contains water glass and inorganic oxide particles, when the coated sand 14 is wetted by moisture, the water glass is agglomerated between the sand grains, and thus, The oxide particles are concentrated in the space (gap) between the refractory aggregates, thereby improving the filling property of the mold to be layered. In addition, the aggregated sand grains and the inorganic oxide particles concentrate in the space between the refractory aggregates, so that the coated sand forms a stone wall structure with a thermosetting binder, thereby increasing the strength of the mold. You can get it.

  Here, as a spraying method of the aqueous medium 22, the method is particularly limited as long as an appropriate amount of the aqueous medium 22 can be sprayed on the sand layer 20 so as to wet the coated sand 14 so as not to increase too much. For example, in addition to the method of spraying the aqueous medium, a method of dropping the aqueous medium or spraying the aqueous medium in a mist form using a sprayer or the like is appropriately employed.

  Further, since it is necessary to dry the coated sand 14 after the coated sand 14 is moistened with the aqueous medium 22, it is desirable that the aqueous medium 22 to be sprayed is at a room temperature or a temperature higher than the room temperature. For this reason, it is desirable that the temperature of the aqueous medium is generally in the temperature range of about 20 ° C to 100 ° C, more preferably about 30 ° C to 95 ° C. In addition, when using the vapor | steam of an aqueous medium, it is preferable that it is 80 to 100 degreeC vapor | steam.

  In the present invention, water is typically used as the aqueous medium 22, and such water must be mixed with dust, dust, etc., such as pure water, tap water, distilled water, industrial water, and the like. For example, although not particularly limited, pure water or distilled water is preferable from the viewpoint of preventing clogging of the nozzle. Such water may contain an acid or an ester as a curing agent or a curing accelerator. Among them, sulfuric acid, hydrochloric acid, carbonic acid, and sulfonic acids are preferable as the acid, and γ-butyrolactone is preferable as the ester. Lactones such as ε-caprolactone, and esters derived from an alcohol having 1 to 10 carbon atoms and a carboxylic acid having 1 to 10 carbon atoms such as ethylene glycol diacetate, triacetin, diethylene glycol diacetate, and triethylene glycol diacetate. preferable. The alcohol having 1 to 10 carbon atoms may be monovalent or polyvalent. Further, drying accelerators for the above surfactants and moisturizers, and organic solvents such as alcohols such as methanol and ketones such as acetone and diacetone alcohol, PROXEL GXL [1, 2- A small amount of an antiseptic such as benzoisothiazol-3 (2H) -one] or PROXEL IB (polyhexamethylene biguanidine) can be added. In this case, the viscosity of the aqueous medium is generally 0.1 to 50 cP, and more preferably 0.3 to 40 cP, since problems such as clogging from the nozzle occur when the viscosity increases. Furthermore, in order to make the aqueous medium 22 easily adapted to the sand layer 20, the surface tension may be 15 to 50 mN / m, and more preferably 20 to 40 mN / m.

<Third step>
For the sand layer 20 after the aqueous medium 22 is sprayed, a heater 30 provided with a heating wire 32 is disposed above the sand layer 20 at a predetermined interval, and the sand layer 20 is heated by the heat of the heater 30. Thus, the wet coated sand 14 is dried (the state shown in FIG. 3). Thereby, the coated sand 14 is moistened with the aqueous medium 22 in the second step, the water glass of the coating layer is melted, and the moisture of the coated sand 14 moistened in the third step is evaporated from the adhered state. Thus, the refractory aggregate to which the water glass is applied is solidified or hardened in a state of being bonded to each other, whereby one mold layer 34 is formed. Further, since the portion wetted with the aqueous medium 22 has better heat conductivity than the portion not wetted, only the portion wetted with the aqueous medium 22 of the coated sand 14 is efficiently solidified or cured by heating. Will be able to. At this time, the heating by the heater 30 dries the coated sand 14 and solidifies or hardens it, so that the sand layer 20 is about 30 to 180 ° C, preferably 60 to 150 ° C, more preferably 80 to 140 ° C. It is only necessary to be able to heat to about 100 ° C., more preferably about 100 to 120 ° C., and since this does not cause much temperature difference in the sand layer 20, warping of the hardened sand layer (20) can be effectively suppressed. . Moreover, since the heating temperature at this time can be solidified or cured at a low temperature of about 100 ° C., the odor generated by heating the conventional coated sand to a high temperature (about 200 ° C. to 300 ° C.) is also effective. It can be suppressed. For this reason, the heater 30 does not need to have a high output, and exhibits features such as less energy consumption for heating.

  Here, when the sand layer 20 is heated and dried, the drying can be promoted by performing it in an atmosphere of heated air. As another method, curing can be promoted by heating and drying in an atmosphere containing carbon dioxide or gasified ester or in an atmosphere of an inert gas such as nitrogen. The method for implementing the above-described promotion means is not particularly limited as long as heating and drying can be performed in a predetermined gas atmosphere. For example, the inside of the apparatus is sealed and the internal atmosphere is changed. There are techniques such as replacing with heated air, carbon dioxide, gasified ester, or inert gas, and performing modeling in the substituted atmosphere. It is also possible to adjust the heating temperature inside the apparatus.

  In addition, before or after the heating, a gas such as air, heated air, superheated steam, carbon dioxide gas, gasified ester, or inert gas may be blown or ventilated. Furthermore, drying of the coated sand 14 can be promoted by flowing the gas. The method for spraying or venting gas is not particularly limited as long as the coated sand 14 can be carried out without being blown away by the gas to be sprayed or by ventilation. There is a method of ventilating by blowing a gas from a jet outlet installed on the top of the apparatus or circulating the atmosphere inside the apparatus.

  Furthermore, in order to prevent water vapor | steam remaining in an apparatus, the process of attracting | sucking the gas in an apparatus and exhausting it out of the system may be included. The gas suction is preferably performed after the sand layer is heated and dried in the third step. However, as long as each step is not adversely affected, it may be performed during the third step or during all the steps. Good.

<Repetition process>
Then, the series of mold layer 34 forming steps including the first step, the second step, and the third step described above are set as one turn (cycle), and the table 12 is further slid downward by the height of one sand layer. 4 (state of FIG. 4), by repeating the turn of the forming process of the template layer 34, a new template layer 34 is integrally formed on the already formed template layer 34. Thus, a laminated structure is realized. Further, by repeating the formation of the template layer 34 several times, the template layer 34 is sequentially laminated and integrated (the state shown in FIG. 5), and thus is constituted by an appropriate number of template layers 34. A desired three-dimensional shaped object 36 is manufactured. Then, the target mold | type (36) will be taken out by removing the sand which has not been hardened or hardened from the modeling apparatus (frame 10) (state of FIG. 6). At this time, the coated sand is bonded with a hardened or hardened binder to form a stone wall structure, so that it is possible to ensure the strength of the mold that can withstand the high pressure during molten metal injection. Furthermore, the feature which can suppress the insertion of a molten metal and can improve the smoothness of the casting surface of a casting will also be exhibited. Further, the obtained mold (36) may be further subjected to secondary firing in order to suppress variation in strength. As conditions for this secondary firing, it is performed for 5 minutes to 2 hours, preferably 10 minutes to 1 hour in a thermostat heated to about 100 to 200 ° C, preferably 120 to 180 ° C.

  In the mold layer forming process including the first process, the second process, and the third process described above, the switching of the equipment in each process is automatically performed, but of course, manually or semi-automatically. Even if the switching is performed, there is no problem.

  Hereinafter, the present invention will be more specifically clarified by using some examples, but the present invention is not construed as being limited in any way by the description of such examples. Should be understood. In the following examples and comparative examples, “%” and “parts” are shown on a mass basis unless otherwise specified. Moreover, the water content, average particle diameter, bulk specific gravity, bending strength, filling rate, and casting surface of the coated sand (CS) obtained in Examples and Comparative Examples were evaluated as follows.

-Measurement of water content with respect to solid content of water glass-
Each CS is weighed and accommodated in a crucible that has been baked and weighed, and the amount of moisture (W1) in the CS is calculated using the mass loss (%) after heating at 900 ° C. for 1 hour. It calculates from the following formula (4). The weighing is measured to the fourth decimal place. Next, the solid content (B1) of the water glass with respect to CS is calculated using the following formula (5), and then the water content (W1) in CS and the solid content (B1) of the water glass with respect to CS, The water content relative to the solid content of water glass (CS water content relative to the solid content of water glass in the coating layer: W2) is calculated using the following equation (6). W2 calculated as described above is shown as “moisture content” in Tables 1 to 3 below.
W1 = [(M1-M2) / M3] × 100 (4)
[W1: Moisture content (%) in CS, M1: Total mass (g) of crucible and CS before firing, M2: Total mass (g) of crucible and CS after firing, M3: Mass of CS before firing (G)]
B1 = [B2 / (100 + B2 + I × B2 / 100)] × (100−W1) (5)
[B1: solid content (%) of water glass relative to CS, B2: solid content (part) of water glass added to 100 parts of sand, I: added to 100 parts of water glass solid content Inorganic oxide particle amount (parts), W1: moisture content in CS (%)]
W2 = (W1 / B1) × 100 (6)
[W2: Moisture content (%) of CS with respect to solid content of water glass in coating layer, W1: Moisture content (%) in CS, B1: Solid content (%) of water glass with respect to CS]

-Average particle size-
Using a Microtrac particle size distribution measuring device (product name: MT3200II) manufactured by Nikkiso Co., Ltd., the particle size at an integrated value of 50% was measured as an average particle size (D50) from the particle size distribution. In addition, for the spherical particles and non-spherical particles used in the examples and comparative examples, the average particle diameter was measured using the above measuring apparatus, and the error between the published values of each manufacturer was within 10%. In the following, the average particle diameters of the spherical particles and the non-spherical particles indicate the published values of the manufacturer.

-Measurement of bulk specific gravity of CS-
It carried out based on JIS K6721-1995. The measurement of n = 3 was performed and the average value was calculated | required. Specifically, using a scale capable of weighing to the second decimal place, accurately weigh 50.0 g of the sample, put it in a funnel with a shutter, open the shutter, and gently flow into the graduated cylinder. Read the scale of the graduated cylinder and measure the volume of the coated sand. The bulk specific gravity of the coated sand is obtained from the following equation (7).
CS bulk density (g / cm ³ ) = 50.0 (g) / volume of coated sand (cm ³ ) (7)

−Measurement of bending strength−
About a test piece having a size of width: 1.0 cm × height: 1.0 cm × length: 6.0 cm obtained by layered modeling using each CS, a load was applied perpendicularly to the stacking direction, The breaking load is measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd .: Digital foundry sand strength tester). And the bending strength is calculated by the following formula (8) using the measured breaking load.
Folding strength (N / cm ² ) = 1.5 × LW / ab ² (8)
[L: distance between fulcrums (cm), W: breaking load (N), a: width of test piece (cm), b: thickness of test piece (cm)]

-Measurement of filling rate (%)-
Using each CS as a test piece, a mold having a size of width: 1.0 cm × height: 1.0 cm × length: 6.0 cm obtained by layered modeling is used as an aggregate. The ratio of the specific gravity of each test piece (calculated by dividing the mass by the volume of the test piece) with respect to the true specific gravity is calculated as a percentage by the following equation (9).
Filling rate (%) = {[mass (g) / volume (cm ³ ) of each test piece]
/ True specific gravity of aggregate (g / cm ³ )} × 100 (9)

-Casting surface judgment-
First, a hollow main mold for casting surface evaluation test (cavity: 60 mm × 60 mm × 60 mm) having a molten metal inlet on the upper part is produced by additive manufacturing using each CS. Next, molten aluminum alloy (temperature: 710 ± 5 ° C.) is poured from the melt inlet of the hollow main mold for cast surface evaluation test and solidified, then the main mold is broken and the casting is taken out. Then, when the room temperature is reached, the cast skin is evaluated based on the following criteria for the presence or absence of seizure of sand on the casting surface. When the sand does not adhere to the surface due to seizure, the smoothness of the casting surface of the casting is good. In addition, the visual evaluation about an external appearance WHEREIN: Ten panelists evaluate the external appearance of the shape | molded casting by the following references | standards, respectively, and evaluate by the average level. Moreover, in this invention, more than (triangle | delta) is made into the range which can be utilized as a casting, and x is set as rejection.
A: Sand hardly adheres to the casting surface.
○: Sand is slightly adhered to the casting surface, but it can be used without any problem as long as it can be removed by rubbing by hand.
Δ: A lot of sand adheres to the casting surface, but it can be used if the casting surface is modified by post-processing.
X: A lot of sand adheres to the casting surface, and even if the casting is post-processed, it cannot be used.

-Production Example 1 of Dry CS-
As refractory aggregate, Lunamos # 110 (trade name, manufactured by Kao Quaker Co., Ltd., average particle size: 126.5 μm), which is a commercially available artificial sand for casting, is prepared, and a commercially available product as water glass as a binder. No. 2 sodium silicate (trade name, manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.5, solid component: 41.3%) was prepared. And after heating said lunamos # 110 to the temperature of about 180 degreeC, it throws into a whirl mixer (product made from Enshu Iron Works Co., Ltd.), Furthermore, the said water glass is made into 7 parts with respect to 100 parts of lunamos # 110. It was added at a ratio of 26 parts (solid component: 3.0 parts), and silica powder PL (trade name, Maruto Co., Ltd., average particle diameter: 1.5 μm) as non-spherical silicon dioxide particles as inorganic oxide particles. ) At a ratio of 0.3 parts (10 parts with respect to 100 parts of the solid content of water glass) and kneading for 3 minutes to evaporate the water, while stirring and mixing until the sand granule collapses Further, 0.03 part of calcium stearate (1 part with respect to 100 parts of water glass solid content) was added, stirred and mixed, and then taken out to obtain dry coated sand having room temperature fluidity: CS It was obtained. When the moisture content of CS1 after such kneading was measured, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production Example 2- of Dry CS
Except that the inorganic oxide particles to be added were silica powder T-3 (trade name, Maruto Co., Ltd., average particle size: 7.9 μm), which is non-spherical silicon dioxide particles, the same as in Production Example 1 above. According to the procedure, dry coated sand: CS2 having room temperature fluidity was obtained. And when the moisture content of obtained CS2 was computed, it was the quantity equivalent to 29 mass% of solid content of the water glass in a coating layer.

-Production example of dry CS 3-
Except that the inorganic oxide particles to be added were silica powder T-1 (trade name, Maruto Co., Ltd., average particle size: 17.8 μm) which is non-spherical silicon dioxide particles, the same as in Production Example 1 above. According to the procedure, dry coated sand: CS3 having room temperature fluidity was obtained. And when the moisture content of obtained CS3 was computed, it was the quantity equivalent to 28 mass% of solid content of the water glass in a coating layer.

-Production Example 4- of Dry CS
The same procedure as in Production Example 1 except that the inorganic oxide particles to be added were KA-10 (trade name, manufactured by Titanium Industry Co., Ltd., average particle size: 0.4 μm) which is non-spherical titanium oxide particles. Thus, dry coated sand CS4 having room temperature fluidity was obtained. When the moisture content of the obtained CS4 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example of dry CS-
As water glass as a binder, commercially available No. 1 sodium silicate (trade name, manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 2.1, solid component: 48.5%) was used. The addition amount was 6.19 parts (solid component: 3.0 parts) with respect to 100 parts of the refractory aggregate (Lunamos # 110) according to the same procedure as in Production Example 2 above. A dry coated sand having fluidity: CS5 was obtained. When the moisture content of the obtained CS5 was calculated, it was an amount corresponding to 30% by mass of the solid content of water glass in the coating layer.

-Production example 6 of dry CS-
As water glass as a binder, commercially available No. 3 sodium silicate (trade name, manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 3.2, solid component: 38%) was used. According to the same procedure as in Production Example 2, except that the addition amount was 7.89 parts (solid component: 3.0 parts) with respect to 100 parts of the refractory aggregate (Lunamos # 110). Dry coated sand having CS: CS6 was obtained. When the moisture content of the obtained CS6 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production Example 7 of Dry CS-
Except that the inorganic oxide particles to be added were Elchem microsilica (trade name, manufactured by Elchem Japan Co., Ltd., average particle diameter: 0.15 μm, sphericity: 0.96), which are spherical silicon dioxide particles, According to the same procedure as in Production Example 1, dry coated sand CS7 having room temperature fluidity was obtained. When the moisture content of the obtained CS7 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production Example 8 of Dry CS-
Except that the inorganic oxide particles to be added are spherical silicon dioxide particles HS311 (trade name, manufactured by Nippon Steel & Sumikin Materials Co., Ltd., average particle size: 2.2 μm, sphericity: 0.98) According to the same procedure as in Production Example 1, dry coated sand: CS8 having room temperature fluidity was obtained. When the moisture content of the obtained CS8 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 9 of dry CS-
Except that the inorganic oxide particles to be added are HS312 (trade name, manufactured by Nippon Steel & Sumikin Materials Co., Ltd., average particle size: 9.5 μm, sphericity: 0.96) which are spherical silicon dioxide particles. According to the same procedure as in Production Example 1, dry coated sand: CS9 having room temperature fluidity was obtained. When the moisture content of the obtained CS9 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 10 of dry CS-
Except that the inorganic oxide particles to be added are spherical silicon dioxide particles HS206 (trade name, manufactured by Nippon Steel & Sumikin Materials Co., Ltd., average particle size: 12.0 μm, sphericity: 0.97). According to the same procedure as in Production Example 1, dry coated sand: CS10 having room temperature fluidity was obtained. When the moisture content of the obtained CS10 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production Example 11 of Dry CS-
Other than adding the inorganic oxide particles to be added to Sunsphere NP-200 (trade name, manufactured by AGC S-Tech Co., Ltd., average particle size: 18.2 μm, sphericity: 0.97), which are spherical silicon dioxide particles. Followed the same procedure as in Production Example 1 to obtain dry coated sand CS11 having room temperature fluidity. When the moisture content of the obtained CS11 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example 12 of dry CS-
Except that the inorganic oxide particles to be added were AZ2-75 (trade name, manufactured by Nippon Steel & Sumikin Materials Co., Ltd., average particle size: 2.5 μm, sphericity: 0.95) which are spherical aluminum oxide particles. According to the same procedure as in Production Example 1, dry coated sand CS12 having room temperature fluidity was obtained. When the moisture content of the obtained CS12 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 13 of dry CS-
The inorganic oxide particles to be added are SG-TO200 (trade name, manufactured by Sukgyung AT Co., Ltd., average particle size: 0.2 μm, sphericity: 0.93), which is spherical titanium oxide particles. Followed the same procedure as in Production Example 1 to obtain dry coated sand CS13 having room temperature fluidity. When the moisture content of the obtained CS13 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 14 of dry CS-
As water glass as a binder, commercially available No. 1 sodium silicate (trade name, manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 2.1, solid component: 48.5%) was used. The addition amount was set to 6.19 parts (solid component: 3.0 parts) with respect to 100 parts of the refractory aggregate (Lunamos # 110) according to the same procedure as in Production Example 10 above. A dry coated sand having fluidity: CS14 was obtained. When the moisture content of the obtained CS14 was calculated, it was an amount corresponding to 30% by mass of the solid content of water glass in the coating layer.

-Production example 15 of dry CS-
As water glass as a binder, commercially available No. 3 sodium silicate (trade name, manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 3.2, solid component: 38%) was used. According to the same procedure as in Production Example 10, except that the addition amount was 7.89 parts (solid component: 3.0 parts) with respect to 100 parts of the refractory aggregate (Lunamos # 110), room temperature fluidity Dry coated sand having CS: CS15 was obtained. When the moisture content of the obtained CS15 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 16 of dry CS-
Except that the added amount of the inorganic oxide particles to be added was 1.5 parts (50 parts with respect to 100 parts of the solid content of water glass), a dry solution having room temperature fluidity was prepared according to the same procedure as in Production Example 10 above. Coated sand: CS16 was obtained. When the moisture content of the obtained CS16 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 17 of dry CS-
Except that the added amount of the inorganic oxide particles to be added was 3.0 parts (100 parts with respect to 100 parts of the solid content of water glass), a dry solution having room temperature fluidity was prepared according to the same procedure as in Production Example 10 above. Coated sand of state: CS17 was obtained. When the moisture content of the obtained CS17 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production example 18 of dry CS-
Except that the inorganic oxide particles were not added, dry coated sand: CS18 having room temperature fluidity was obtained according to the same procedure as in Production Example 1 above. When the moisture content of the obtained CS18 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example 19 of dry CS-
Except that the inorganic oxide particles were not added, dry coated sand: CS19 having room temperature fluidity was obtained according to the same procedure as in Production Example 5 above. When the moisture content of the obtained CS19 was calculated, it was an amount corresponding to 30% by mass of the solid content of water glass in the coating layer.

-Production example 20 of dry CS-
Except that the inorganic oxide particles were not added, dry coated sand: CS20 having room temperature fluidity was obtained according to the same procedure as in Production Example 6 above. When the moisture content of the obtained CS20 was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

  Next, for the dry CS1-20 obtained above, according to the method for evaluating the bulk specific gravity of the coated sand described above, the bulk specific gravity was measured, and the results thereof were used in Examples and Comparative Examples in which the CS was used. As one of the evaluations, Tables 1 to 3 also show.

Example 1
A predetermined laminated mold (36) was modeled according to the embodiment shown in FIGS. 1 to 5 using a predetermined laminated mold modeling apparatus using CS1 prepared in advance. That is, first, in the first step, the table (12) is slid downward by 0.3 mm, and then a CS1 (14) is formed on the table (12) to form a thin sand layer (20), and then In the second step, such an aqueous medium is obtained by spraying a mist-like aqueous medium (22) by an ink jet method for each minute region so as to give a predetermined planar shape of 203 mm × 254 mm. The sand layer (20) part of the sprayed area of (22) was moistened. Thereafter, using a halogen lamp as a heater (30), a predetermined planar shape portion was heated and cured or solidified to obtain a mold layer (34) having a shape corresponding to the portion. The aqueous medium (22) used there had a composition of 93% by weight of water, 6% by weight of a humectant and 1% by weight of a surfactant (viscosity 1.1 mPa · s / 25 ° C., surface tension 31.5 mN). / M) and was used at a temperature of 25 ° C.

  Then, using the series of steps including the first step and the second step as one turn, until the thickness (height) of the laminated mold (modeled object 36) reaches a predetermined height, the mold layer The layered manufacturing operation (34) was repeated. Then, CS1 which is not solidified or hardened is removed from the laminated mold shaping apparatus, and the shaped article (36) is taken out and baked at a temperature of 150 ° C. for 10 minutes, whereby the target laminated mold (36) is obtained. Manufactured. And the bending strength measurement of this obtained lamination mold, the filling rate measurement, and the casting skin determination were performed, and those results were shown in following Table 1.

-Examples 2 to 17 and Comparative Examples 1 to 3
CS1 is replaced with CS2-20, respectively, and the layered modeling of the mold is performed in the same manner as in Example 1, and the resulting layered molded product is fired at a temperature of 150 ° C. for 10 minutes for the purpose. A laminated mold (36) was produced. In addition, as for CS18-20 used in Comparative Examples 1-3, as for all, inorganic oxide particle is not added. And the bending strength measurement of the obtained lamination mold, filling rate measurement, and cast skin judgment were performed, and those results were shown in the following Table 1-Table 3.

  As is clear from the comparison of the results in Tables 1 to 3, according to the present invention, using the coated sand: CS1 to CS17 having a coating layer containing predetermined inorganic oxide particles together with water glass, additive manufacturing is performed. By doing so, it is recognized that it is possible to obtain a laminated mold giving a good casting surface with a high bending strength and a high filling rate. In addition, it has also been clarified that by using spherical particles as the inorganic oxide particles, their characteristics can be further improved.

DESCRIPTION OF SYMBOLS 10 Frame 12 Table 14 Coated sand 16 Storage tank 18 Discharge port 20 Sand layer 22 Aqueous medium 24 Extension member 26 Inkjet spraying device 28 Nozzle 30 Heater 32 Heating wire 34 Mold layer 36 Molded article (lamination mold)

Claims (12)

A thin sand layer is formed using a coated sand formed by coating a fireproof aggregate with a binder, and then an aqueous medium is sprayed on the sand layer and heated to form a solidified layer or a hardened layer having a predetermined two-dimensional pattern. By repeating the operation of forming a layer and then laminating the solidified layer or the hardened layer, when producing a desired three-dimensional laminated mold,
As the coated sand, it is obtained by forming a coating layer containing inorganic oxide particles having a particle diameter smaller than that of the refractory aggregate, together with water glass as a binder, on the surface of the refractory aggregate. A method for producing a laminated mold characterized by using dry coated sand. The average particle diameter (d2) of the refractory aggregate with respect to the average particle diameter (d1) of the inorganic oxide particles is expressed by the following formula:
2 × d1 ≦ d2 ≦ 5000 × d1
The method for producing a laminated mold according to claim 1, wherein:   The average particle diameter of the said inorganic oxide particle is 0.1-20 micrometers, The manufacturing method of the lamination mold of Claim 1 or Claim 2 characterized by the above-mentioned.   The inorganic oxide particles are spherical particles, and the aspect ratio defined by the ratio of the minor axis / major axis is 0.5 to 1.0. The manufacturing method of the lamination mold of any one.   5. The laminated mold according to claim 1, wherein the inorganic oxide particles are a metal oxide selected from the group consisting of silicon dioxide, aluminum oxide, and titanium oxide. Manufacturing method.   The content of the inorganic oxide particles is a ratio of 0.1 to 500 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand. A method for producing a laminated mold according to any one of the above.   The said aqueous medium contains at least any one of a hardening accelerator, surfactant, a moisturizer, a drying accelerator, and an antiseptic | preservative, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. The manufacturing method of the laminated mold of description.   The method for producing a laminated mold according to any one of claims 1 to 7, wherein the aqueous medium has a viscosity of 0.1 to 50 cP and a surface tension of 15 to 50 mN / m. .   The method for producing a laminated mold according to any one of claims 1 to 8, wherein the coated sand further contains a lubricant on a surface thereof.   The laminated mold according to claim 9, wherein the content of the lubricant is 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand. Manufacturing method.   The method for producing a laminated mold according to any one of claims 1 to 10, wherein the moisture content in the coated sand is 5 to 55 mass% of the solid content of water glass. The method for producing a laminated mold according to any one of claims 1 to 11, wherein the dispersion of the aqueous medium on the sand layer is performed using an ink jet type spraying device.

Images