JP2020093298A - Casting mold production method and die for molding casting mold - Google Patents

Abstract

To provide a production method of a casting mold and a die for molding a casting mold having high intensity and capable of easily producing even a complicated shaped casting mold.SOLUTION: A production method of a casting mold comprises: a step (I) for filling a dry fireproof granular material in a die 10 for molding a casting mold; a step (II) for immersing the die 10 for molding a casting mold in which the fireproof granular material is filled in water for acquiring a molded article; a step (III) for drying the acquired molded article while being filled in the die 10 for molding a casting mold. The die 10 for molding a casting mold comprises a plurality of holes 14 which do not interfere permeation of water into inside, and inhibit outflow of the fireproof granular material from inside. At least one of the fireproof granular material used in the step (I) and water used in the step (II) includes a water soluble inorganic binder mixed thereto, and the water soluble inorganic binder is one or more kinds selected from a group formed of a sulfuric acid compound, a phosphate compound, chloride and a carbonate compound.SELECTED DRAWING: Figure 1

Description

The present invention relates to a mold manufacturing method and a mold for molding.

Conventionally, casting molds (hereinafter, also simply referred to as “molds”) include ordinary molds and special molds, and ordinary molds include a raw mold and a dry mold. On the other hand, special molds include thermosetting molds, self-hardening molds, and gas curing molds.
A refractory granular material such as silica sand is used as the material for the mold, but a refractory granular material alone tends to collapse when dried, so a binder is added to prevent it from collapsing.
Usually, clay such as bentonite is used as a binder in the mold. On the other hand, an organic binder such as phenol resin, furan resin, urethane resin or an inorganic binder such as water glass is used for the special mold.

A liquid produced by melting a metal such as iron, copper, or aluminum at a high temperature is poured into a mold manufactured by various methods to obtain a casting. The casting is taken out by disassembling the mold. Further, it is general that the refractory granular material is regenerated from the disassembled mold and reused in the manufacture of the mold.
The mold using the organic binder is excellent in disintegration upon dismantling. However, when the molten metal is poured, the organic binder is easily decomposed by heat to generate a gas (pyrolysis gas), which easily causes defects in the casting and deteriorates the working environment.
On the other hand, in the mold using the inorganic binder, the inorganic binder is less likely to be thermally decomposed, and thus the thermally decomposed gas of the binder is less likely to be generated during pouring. However, the mold using water glass as the inorganic binder is less likely to deteriorate in strength after pouring and is less likely to disintegrate (inferior in disintegrating property), and thus is more difficult to disassemble than the mold using the organic binder. ..

As a method for producing a mold using an inorganic binder instead of water glass, for example, in Patent Document 1, a water-soluble binder containing a sulfuric acid compound such as magnesium sulfate and water are added to a refractory granular material. The first step of obtaining the kneading sand (casting sand), the second step of molding the kneading sand, and the drying of the kneading sand while maintaining the state that the sulfuric acid compound in the kneading sand contains at least a part of crystal water. And a third step of obtaining a mold is disclosed.

Japanese Patent No. 4223830

To mold the kneading sand, it is common to fill the kneading sand into a wood mold, a resin mold, a metal mold, etc. (hereinafter collectively referred to as “mold molding mold”) to mold the kneading sand. ..
However, in the method described in Patent Document 1, the kneading sand in a wet state is filled in the mold for molding. The wet kneaded sand has low fluidity. Therefore, as the shape of the mold for molding becomes more complicated, it becomes more difficult to fill the kneading sand with each other, resulting in poor filling and lowering of mold strength.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mold manufacturing method and a mold for molding, which have high strength and can easily manufacture even a mold having a complicated shape.

The present invention has the following aspects.
[1] a step (I) of filling the inside of a mold for molding with a dry refractory granular material,
A step (II) of obtaining a molded article by immersing the mold for molding in which the refractory granular material is filled in water,
A step (III) of drying the obtained molded article while being filled in a mold for molding.
Including,
The mold for molding has a plurality of holes that do not prevent water from penetrating into the inside and that prevent the refractory granular material from flowing out from the inside.
At least one of the refractory granular material used in the step (I) and the water used in the step (II) is mixed with a water-soluble inorganic binder,
The method for producing a mold, wherein the water-soluble inorganic binder is at least one selected from the group consisting of a sulfuric acid compound, a phosphoric acid compound, a chloride and a carbonic acid compound.
[2] The method for producing a mold according to [1], wherein the water-soluble inorganic binder is mixed with at least water used in the step (II).
[3] The method for producing a mold according to [1] or [2], wherein the refractory granular material is coated with silicate.
[4] The mold for molding is made of a material that transmits microwaves,
In the step (III), the method for producing a mold according to any one of [1] to [3], wherein the molded product is irradiated with microwaves and dried.
[5] The method for producing a mold according to any one of [1] to [4], wherein the step (III) is performed under reduced pressure.
[6] A mold for molding for molding a mold using a refractory granular material in a dry state,
When the refractory granular material is filled inside and immersed in water, a plurality of holes are formed which do not prevent water from penetrating into the interior and inhibit the refractory granular material from flowing out from the inside. Has been used for mold making.

According to the present invention, it is possible to provide a mold manufacturing method and a mold for molding that have high strength and can easily manufacture a mold having a complicated shape.

It is a perspective view showing one embodiment of the mold for mold making of the present invention. It is a figure which shows the casting mold for making the test piece used in the Example and the comparative example, (a) is a perspective view, (b) is a top view. It is a photograph which shows the result of the slump test in the evaluation of fluidity, (a) is Example 1 and (b) is Comparative Example 1. It is a graph which shows the result of Examples 2-8. It is a graph which shows the result of Examples 9-12. It is a graph which shows the result of Examples 13-20.

[Mold for mold making]
The mold for molding according to the present invention is a mold for molding a mold by using a dry refractory granular material.
The refractory granular material will be described later.

FIG. 1 shows a mold for molding a core for molding a core according to an embodiment of the present invention. The core is a mold that is fitted into a mold that serves as a main mold as a part corresponding to the hollow part when manufacturing a casting having a hollow part.
The casting mold 10 shown in FIG. 1 includes an upper die 11 and a lower die 12.
The upper mold 11 and the lower mold 12 have a recess 13 corresponding to the shape of the mold. Among the depressions 13, 13a is a depression in a portion corresponding to the core body, and 13b is a depression in a portion corresponding to a skirting board. The upper mold 11 and the lower mold 12 are overlapped so that these recesses 13 are on the inside, and specifically, the first convex portion 15a and the first concave portion 16a, the second convex portion 15b and the second concave portion 16b, The refractory granular material is filled in the space inside the mold 10 for molding, which is formed by superposing the third convex portion 15c and the third concave portion 16c, and the fourth convex portion 15d and the fourth concave portion 16d, respectively.

A plurality of holes 14 are formed in the mold 10 for mold making. The holes 14 do not prevent water from penetrating into the inside of the mold 10 for molding the refractory granular material when immersed in water, and the refractory granular material flows out from the inside. Is formed so as to inhibit the.
Examples of the shape of the hole 14 include, but are not limited to, a circle, an ellipse, a polygon (for example, a triangle, a quadrangle, a pentagon, a hexagon, a rhombus, a trapezoid, etc.) and a slit shape.
Although water easily penetrates into the slit-shaped holes, there is a tendency that linear protrusions along the slit-shaped holes are formed in the mold. A convex portion tends to be formed in the mold corresponding to the circular, elliptical, or polygonal hole, but is less noticeable than the linear convex portion along the slit-shaped hole. Therefore, for example, as shown in FIG. 1, it is preferable that a circular hole 14a in which a pattern is less noticeable when transferred to the mold is formed in the recess 13a in the portion corresponding to the core body. Instead of the circular hole 14a, an oval or polygonal hole may be formed in the recess 13a in the portion corresponding to the core body. On the other hand, it is preferable that a slit-like hole 14b is formed in the recess 13b in the portion corresponding to the skirting board so that water easily permeates.

The size of the holes 14 is preferably equal to or smaller than the particle diameter of the refractory granular material filled in the mold 10 for molding. However, if the so-called stone wall effect is obtained, in which a refractory granular material with a small particle size is filled into the gap between the refractory granular materials with a large particle size, and a dense packing state is obtained, the outflow of the refractory granular material is The size of the holes 14 may be larger than the particle size of the refractory granular material, as it can inhibit.
Specifically, the size of the hole 14 is preferably 0.05 to 1 mm, more preferably 0.1 to 1 mm. When the size of the hole 14 is equal to or larger than the above lower limit value, the hole 14 can be easily formed and water can easily permeate. If the size of the holes 14 is equal to or smaller than the above upper limit value, the outflow of the refractory granular material is likely to be hindered.
In the present specification, the size of the hole 14 means the diameter of a circle when the shape is circular, the minor diameter of the ellipse when the shape is elliptical, and the diameter of the inscribed circle when the shape is polygonal, and the slit. In case of the shape, it is the slit width.

0.1-10% is preferable and, as for the opening rate of the mold 10 for mold making, 1-5% is more preferable. If the opening ratio is equal to or more than the above lower limit value, water easily penetrates. If the opening ratio is not more than the above upper limit, the surface of the mold will be smooth.
In the present specification, the opening ratio refers to the area ratio of the holes 14 on the surface of the recess 13 portion of the mold 10 for molding.

The material of the mold 10 for molding a mold is not particularly limited as long as it can form the holes 14, and resin, metal, wood and the like can be mentioned.
As will be described later in detail, when a refractory granular material is filled and immersed in water, the obtained molded product is irradiated with microwaves while being filled in the mold 10 for molding to dry the mold. Is preferably made of a material that transmits microwaves.
The transmission of microwaves means that at least a part of the microwaves passes through the mold 10 for molding a mold to an extent that the heat required to dry the molded product is generated. It means that the ratio (ε _r ) is 7 or less. The relative permittivity is preferably 6 or less, more preferably 5 or less. The lower limit of the relative dielectric constant is not particularly limited.
The relative permittivity is obtained by the cavity resonance perturbation method. Specifically, for example, at room temperature, a material is molded into a size of width 50.0 mm×length 50.0 mm×thickness 1.5 mm, and the obtained molded product is subjected to a cavity resonance perturbation method to obtain a relative dielectric constant (ε _r ) is measured.

Examples of materials that transmit microwaves include glass, preferably soda-lime glass (ε _r =6.0 to 8.0), polyamide (ε _r =3.5 to 5.0), epoxy resin (ε _r =). 2.5-6.0), polystyrene (ε _r =2.4-2.6), silicone resin (ε _r =3.5-5.0), polyurethane (ε _r =5.0-5.3). ), polylactic acid (ε _r =about 3), polyphenylene sulfide (ε _r =3 to 4) and the like. These materials may be used alone or in combination of two or more.

The manufacturing method of the mold 10 for molding a mold is not particularly limited, but it has a high degree of freedom in shape, can easily manufacture even a complicated shape, and easily forms the hole 14 of a desired size at a desired position. From the viewpoint that it is possible, it is preferable to manufacture the mold 10 for mold making by an additive manufacturing method such as three-dimensional additive manufacturing. Among the three-dimensional additive manufacturing, the selective laser sintering method (SLS method: Selective Laser Sintering method) is preferable.
Hereinafter, an example of a method for manufacturing a mold for molding by the selective laser sintering method will be described.

First, three-dimensional data of the cross-sectional shape of the target mold making die 10 at regular intervals is created in advance, and based on this three-dimensional data, a thin layer of powdered material is laminated on the workbench. Examples of powdery materials that can be used include glass, polyamide, polyphenylene sulfide, polystyrene, polypropylene, polybutylene terephthalate, polyether ether ketone, polyallyl ether ketone, and fluororesin. Among these, a mixture of glass (preferably soda-lime glass) and polyamide is preferable because it can transmit microwaves.
Next, the powdery material is sintered by scanning and irradiating the obtained thin layer with laser. Then, another thin layer made of the powdery material is laminated on the sintered thin layer, and the operation of scanning and irradiating with a laser is repeated to form a mold made of the powdery material melt-bonded. A molding die 10 is obtained.

The mold 10 may be manufactured by a method other than the additive manufacturing method. For example, a molded product having a desired shape may be manufactured by injection molding or cutting, and a hole having a desired size may be formed at a desired position of the resulting molded product to manufacture the mold 10 for molding.

[Mold manufacturing method]
<First aspect>
The method for producing a mold according to the first aspect of the present invention includes the following step (I-1), step (II-1) and step (III-1). The mold manufacturing method of the first aspect may additionally include the following step (IV-1).
Step (I-1): Step of filling dry refractory granular material into the inside of mold for molding Step (II-1): A mold for molding filled with refractory granular material is treated with a water-soluble inorganic adhesive. Step of dipping in a water mixed with a binder to obtain a molded article Step (III-1): Step of drying the obtained molded article while being filled in a mold for molding Step (IV-1): Molded article Further heating process

(Process (I-1))
The step (I-1) is a step of filling the refractory granular material in a dry state into the mold for molding.
The mold for molding used in the step (I-1) is provided with a plurality of holes that do not prevent water from penetrating into the inside and prevent the refractory granular material from flowing out from the inside. As such a mold for molding, the above-described mold for molding of the present invention may be used.

The refractory granular material in the dry state has better flowability than the refractory granular material in the wet state. Therefore, by using the refractory granular material in a dry state, even if the shape of the mold for molding is complicated, it is possible to uniformly and quickly fill, and it is possible to suppress defective filling and decrease in mold strength. In addition, the refractory granular material in a dry state is likely to cause a capillary phenomenon, so that water easily penetrates in the step (II-1).
In the present invention, the dry state means a state in which it is not aggregated when visually observed. The state of objective aggregation can be confirmed by a slump test. In the present invention, a slump cone having an upper bottom diameter of 70 mm, a lower bottom diameter of 60 mm, and a height of 80 mm is filled with a refractory granular material, and then the slump cone is gently pulled up vertically. The material spread (slump flow) is preferably 150 mm or more.

As the refractory granular material, natural sand such as silica sand, chromite sand, zircon sand, olivine sand, amorphous silica, alumina sand and mullite sand; conventionally known materials such as artificial sand can be used. Further, it is also possible to use a product obtained by collecting used refractory granular material (recovered sand) or a product subjected to a recycling treatment (reclaimed sand). These refractory granular materials may be used alone or in combination of two or more.
From the viewpoint of production cost, natural sand is preferable, and silica sand is more preferable. Artificial sand is preferable from the viewpoint of being less likely to expand due to heat. Natural sand and artificial sand may be mixed and used in consideration of the balance between production cost and heat resistance.

The particle size of the refractory granular material is preferably 50 to 600 μm, more preferably 60 to 500 μm, further preferably 70 to 300 μm, and particularly preferably 75 to 150 μm. When the particle diameter of the refractory granular material is not less than the above lower limit value, handling is excellent and workability can be favorably maintained. When the particle size of the refractory granular material is not more than the above upper limit value, a mold having high strength can be obtained. In addition, the surface properties of a casting that is cast using the mold are also excellent.
The particle diameter of the refractory granular material is the median diameter of the cumulative volume of 50% of the refractory granular material measured by the dynamic light scattering method.

The refractory particulate material is preferably coated with silicate. Higher strength molds are obtained with silicate coated refractory particulate materials. Moreover, since the strength of the mold is increased, the amount of the water-soluble inorganic binder described below can be reduced. The water-soluble inorganic binder may contain crystal water, but when the amount of the water-soluble inorganic binder used increases, the amount of crystal water contained in the obtained template also increases. The mold is exposed to high temperature during pouring, but at this time, the water-soluble inorganic binder itself is less likely to be thermally decomposed, but crystal water evaporates to generate gas, which may cause gas defects. If the use amount of the water-soluble inorganic binder can be reduced, the gas generation amount at the time of pouring can also be reduced, so that gas defects can be suppressed.
Examples of the silicate include sodium silicate and potassium silicate.
If a refractory granular material that is not coated with silicate is used, a mold having a better disintegration property can be obtained. In addition, the refractory granular material is regenerated from the dismantled mold, and it is also excellent in the recycling rate when reused in the manufacture of the mold.

In order to coat the refractory granular material with silicate, it is preferable to coat the refractory granular material with water glass. For example, by adding water glass to a refractory granular material heated to 100 to 120° C. and mixing, a refractory granular material coated with silicate can be obtained. By adding water glass to the heated refractory particulate material, the water evaporates and the silicate remains on the refractory granular material, coating the surface of the refractory granular material.

The water glass is not particularly limited, and conventionally known glass can be used. For example, sodium silicate (specifically, No. 1, No. 2, No. 3 and sodium metasilicate (1 type, 2 types) described in JIS K 1408: 1966), potassium silicate, or a mixture thereof may be used. it can.
As the water glass, it is preferable to use water glass having a molar ratio (SiO ₂ /M) of SiO ₂ and M (M=K ₂ O or Na ₂ O) of 1.6 to 4.0. It is more preferable to use water glass having a ratio of 2.15 to 2.5. When the molar ratio is small, the curing speed tends to be slow and the adhesive strength tends to be high. On the contrary, when the molar ratio is large, the curing speed is high and the adhesive strength tends to be low.

The Baume degree at 25° C. of water glass is preferably 36 to 50. When the Baume degree of water glass becomes smaller, more water evaporates when coating the refractory granular material with water glass, so the heating temperature of the refractory granular material required for coating is set higher and the mixing time is longer. I need to do it. On the contrary, when the Baume degree of the water glass is increased, the viscosity of the water glass is increased and it becomes difficult to uniformly coat the refractory granular material.

The ratio of the silicate, that is, the coating amount is preferably 0.1 to 5.0 parts by mass, and more preferably 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the uncoated refractory granular material. When the ratio of silicate is not less than the above lower limit, the strength of the mold is further increased. When the proportion of silicate is equal to or lower than the above upper limit, the disintegration property of the mold after casting can be favorably maintained, and the regeneration rate of the refractory granular material tends to increase.

(Process (II-1))
In the step (II-1), the mold for molding the refractory granular material is filled with water, in which a water-soluble inorganic binder is mixed, that is, water containing a dissolved water-soluble inorganic binder (hereinafter, " This is also a step of immersing in a binder aqueous solution) to obtain a molded article.
The term “water-soluble” as used in the present invention means that the solubility in water at 20° C. is 2 g/100 mL or more.

The mold for molding has a plurality of holes which do not prevent water from penetrating into the mold and prevent the refractory granular material from flowing out from the inside. Therefore, by immersing the casting mold in the binder aqueous solution, the binder aqueous solution penetrates through the holes formed in the casting mold, and the entire refractory granular material filled in the casting mold is filled. Impregnated with the dissolved water-soluble inorganic binder. Moreover, since the refractory granular material filled in the mold for molding is in a dry state, it is easy to uniformly impregnate the binder aqueous solution.

The water-soluble inorganic binder is at least one selected from the group consisting of sulfuric acid compounds, phosphoric acid compounds, chlorides and carbonic acid compounds.
Examples of the sulfuric acid compound include magnesium sulfate, aluminum sulfate, zinc sulfate, copper sulfate, sodium sulfate, nickel sulfate, manganese sulfate, iron sulfate and the like. These sulfuric acid compounds may be used alone or in combination of two or more.
Examples of the phosphoric acid compound include trisodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, tripotassium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium monohydrogen phosphate, magnesium phosphate. And so on. These phosphoric acid compounds may be used alone or in combination of two or more.
Examples of the chloride include sodium chloride, potassium chloride, calcium chloride, magnesium chloride and the like. These chlorides may be used alone or in combination of two or more.
Examples of the carbonic acid compound include sodium carbonate and potassium carbonate. These carbonate compounds may be used alone or in combination of two or more.

These sulfuric acid compounds, phosphoric acid compounds, chlorides and carbonic acid compounds may be anhydrides or hydrates.

The ratio of the water-soluble inorganic binder to 100 parts by mass of the refractory granular material filled in the mold for molding is preferably 0.5 to 15 parts by mass, more preferably 1 to 13 parts by mass, and 2 to 12 parts by mass. Parts are more preferred. When the proportion of the water-soluble inorganic binder is within the above range, the strength of the mold is further increased.
When the refractory granular material is coated with silicate, the mass of the silicate is included in the mass of the refractory granular material.

When the refractory granular material is coated with a silicate, for example, if the refractory granular material is coated with water glass having a Baume degree in the above range, the mass ratio of the silicate and the water-soluble inorganic binder is The (silicate: water-soluble inorganic binder) is preferably 1:0.5 to 1:12, more preferably 1:2 to 1:6. As the proportion of silicate increases, the strength of the mold tends to increase, and as the proportion of water-soluble inorganic binder increases, the disintegration property of the mold increases and the regeneration rate of the refractory granular material also tends to increase.

To keep the ratio of the water-soluble inorganic binder to 100 parts by mass of the refractory granular material and the mass ratio of the silicate and the water-soluble inorganic binder within the above ranges, the concentration of the binder aqueous solution and the mold for molding The permeation amount of the aqueous binder solution may be adjusted.
The concentration of the binder aqueous solution, that is, the content of the water-soluble inorganic binder with respect to the total weight of the binder aqueous solution is preferably 5 to 35% by mass, and more preferably 10 to 25% by mass.
The permeation amount of the binder aqueous solution into the mold for molding is preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass, relative to 100 parts by mass of the refractory granular material filled in the mold for molding. ..
The permeation amount of the binder aqueous solution into the mold for molding can be adjusted by the immersion time and the opening ratio of the mold for molding.

The time for immersing the mold for molding in the binder aqueous solution is not particularly limited, and may be adjusted depending on the size of the mold for molding. The longer the immersion time is, the more the dissolved water-soluble inorganic binder is impregnated into the refractory granular material, but the effect reaches the ceiling when the immersion time is too long.

(Process (III-1))
Step (III-1) is a step of drying the molded article obtained in step (II-1) while being filled in the mold for molding.
When the water-soluble inorganic binder contains water of crystallization, in step (III-1), the solvent of the aqueous binder solution contained in the molded product is removed so that the water of crystallization of the water-soluble inorganic binder remains. Dry the model. If the water of crystallization remains, the strength of the mold increases.

As a method of drying the molded product while it is filled in the mold for molding, a method of irradiating the mold for molding filled with the molded product with microwaves to dry it, a method of performing drying under reduced pressure, and filling of the molded product Examples of the method include a method of placing the formed mold for molding in a dryer or an electric furnace for drying, a method of applying hot air to the mold for molding in which the molded product is filled, and drying. Among these, from the viewpoint that the solvent of the binder aqueous solution can be easily removed, and the molded product can be dried so as to leave the water of crystallization of the water-soluble inorganic binder, the mold filled with the molded product is a micro mold. A method of irradiating a wave to dry and a method of drying under reduced pressure are preferable. Further, by using these methods together, the drying time can be shortened.
When the mold for molding filled with the molded product is irradiated with microwaves to be dried, a mold made of a material that transmits microwaves is used as the mold for molding.

As the microwave irradiation conditions, the output and the irradiation time may be controlled according to the size of the obtained template, the type of the water-soluble inorganic binder and the usage amount (permeation amount).
If the output is too high, the mold for molding may melt. Therefore, the output is preferably 1000 W or less, more preferably 900 W or less. Further, from the viewpoint of being able to shorten the irradiation time, it is preferably 200 W or higher, more preferably 300 W or higher.
If the irradiation time is too long, the mold for molding may melt. Therefore, it is preferable to set the irradiation time according to the output.
Further, at least one of the output and the irradiation time may be changed and the microwave may be irradiated in plural times.

The pressure (vacuum degree) for drying under reduced pressure is preferably 50 kPa or less, and more preferably 20 kPa or less, from the viewpoint of shortening the drying time. The lower limit of the degree of vacuum is not particularly limited, but is usually 5 kPa or more.

As described above, the refractory granular material after the step (II-1) is impregnated with the binder aqueous solution. By drying the molded product while it is filled in the mold for molding, the water that is the solvent of the binder aqueous solution impregnated in the refractory granular material evaporates, and the dissolved water-soluble inorganic binder solidifies. By doing so, the refractory granular material is solidified in the shape of the mold for mold making, and by removing the mold, a mold having a desired shape can be obtained.
When the water-soluble inorganic binder contained in the binder aqueous solution contains a phosphoric acid compound, the following step (IV-1) may be carried out.

(Process (IV-1))
Step (IV-1) is a step of further heating the molded article.
When the water-soluble inorganic binder contains water of crystallization, in step (IV-1), the molded article is further heated so as to remove at least a part of the water of crystallization of the water-soluble inorganic binder.
By removing at least a part of the water of crystallization of the water-soluble inorganic binder, the amount of gas generated during pouring can be reduced, so that gas defects can be suppressed.

Examples of the method of heating the molded article include a method of heating the molded article in a dryer or an electric furnace, a method of directly applying hot air to the molded article, and a method of directly applying a burner to the molded article. These methods may be carried out under normal pressure or under reduced pressure. Among these, from the viewpoint of easily removing at least a part of the water of crystallization of the water-soluble inorganic binder, the method of heating the molded article in an electric furnace is preferable.

The heating temperature for heating the molded article is preferably 100 to 700° C. and more preferably 250 to 700° C. under normal pressure. The heating time at this time is not particularly limited as long as at least a part of the water of crystallization of the water-soluble inorganic binder is removed, and may be adjusted according to the size of the mold for molding.

In the step (IV-1), if the mold for molding has heat resistance, the molded product may be heated while being filled in the mold for molding. When the heat-resistant temperature of the mold for molding is low, the mold may be removed from the mold and only the molded product may be heated.

When the loss on heating (α) of the thus obtained mold is 1.0% or less, it can be judged that at least a part of the water of crystallization of the water-soluble inorganic binder has been removed. That is, it means that the manufacturing process has advanced to step (IV-1). The heating loss (α) is obtained as follows.
The mold is weighed and heated in an electric furnace previously held at 300° C. for 2 hours, then allowed to cool to 25° C., the mass of the mold after cooling is measured, and the heating loss is calculated from the following formula (1).
Heating loss (α)={(mass of mold before heating-mass of mold after cooling)/mass of mold before heating}×100 (1)

(Effect)
According to the method for producing a mold of the first aspect of the present invention described above, since the refractory granular material in a dry state is filled inside the mold for molding, even if the shape of the mold for molding is complicated. It is possible to uniformly and quickly fill the refractory granular material, and prevent defective filling and deterioration of mold strength. Moreover, since the mold for forming the mold of the present invention has specific holes formed therein, the binder aqueous solution permeates the entire refractory granular material filled in the mold for forming the mold, and the dissolved water-soluble inorganic material. The binder is impregnated. Therefore, a mold having a desired shape can be obtained by drying the molded product while it is filled in the mold for molding. In particular, in the method for producing the mold of the first aspect, the water-soluble inorganic binder dissolved in water is immersed in the mold for molding the refractory granular material, so that the dissolved water-soluble inorganic binder is Easy to spread evenly throughout the refractory granular material.
As described above, according to the mold manufacturing method of the first aspect of the present invention, a mold having high strength and a complicated shape can be easily manufactured.

In the mold manufacturing method of the first aspect, a water-soluble inorganic binder may be mixed with the refractory granular material used in step (I-1).

<Second mode>
The method for producing a mold according to the second aspect of the present invention includes the following step (I-2), step (II-2) and step (III-2). The method for producing a mold of the second aspect may additionally include the following step (IV-2).
Step (I-2): Filling a dry refractory granular material mixed with a water-soluble inorganic binder into the mold for molding Step (II-2): Filling the refractory granular material The step of immersing the obtained mold for molding in water to obtain a molded article Step (III-2): The step of drying the obtained molded article while being filled in the mold for molding Step (IV-2): The molded article Further heating process

(Process (I-2))
Step (I-2) is the same as step (I-1) of the first aspect, except that the water-soluble inorganic binder is mixed with the refractory granular material before filling.
Examples of the fire-resistant granular material and the water-soluble inorganic binder in the dry state include the fire-resistant granular material and the water-soluble inorganic binder described above in the description of the first embodiment.

The proportion of the water-soluble inorganic binder is preferably 0.5 to 15 parts by mass, more preferably 1 to 13 parts by mass, and even more preferably 2 to 12 parts by mass with respect to 100 parts by mass of the refractory granular material. When the ratio of the water-soluble inorganic binder is at least the above lower limit value, the strength of the mold will be further increased.
When the refractory granular material is coated with silicate, the mass of the silicate is included in the mass of the refractory granular material.

When the refractory granular material is coated with silicate, the mass ratio of silicate and water-soluble inorganic binder (silicate: water-soluble inorganic binder) is preferably 1:0.5 to 1:12. , 1:2 to 1:6 are more preferable. As the proportion of silicate increases, the strength of the mold tends to increase, and as the proportion of water-soluble inorganic binder increases, the disintegration property of the mold increases and the regeneration rate of the refractory granular material also tends to increase.

(Process (II-2))
Step (II-2) is a step of immersing a mold for molding, which is mixed with a water-soluble inorganic binder and is filled with the dry refractory granular material, in water to obtain a molded product.
The mold for molding has a plurality of holes which do not prevent water from penetrating into the mold and prevent the refractory granular material from flowing out from the inside. Therefore, by immersing the mold for molding in water, water permeates through the holes formed in the mold for molding, and the water-soluble inorganic binder mixed in the refractory granular material dissolves and becomes fire resistant. Impregnate the entire granular material. Moreover, since the refractory granular material filled in the mold for molding is in a dry state, it is easily impregnated with water uniformly.

The amount of water permeated into the mold for molding is preferably 5 to 35 parts by mass, and more preferably 10 to 25 parts by mass, relative to 100 parts by mass of the refractory granular material filled in the mold for molding.
The amount of water permeating into the mold for molding can be adjusted by the immersion time and the opening ratio of the mold for molding.
The immersion time of the mold for molding is not particularly limited, and the immersion time may be adjusted depending on the size of the mold for molding. The longer the immersion time is, the more the water penetrates, but if the immersion time is too long, the effect reaches the ceiling. If the immersion time is too long, the water-soluble inorganic binder may flow out of the mold for molding.

(Process (III-2))
The step (III-2) is a step of drying the molded article obtained in the step (II-2) while being filled in the mold for molding.
When the water-soluble inorganic binder contains water of crystallization, in step (III-2), the solvent of the aqueous solution of the binder contained in the molded product is removed so that the water of crystallization of the water-soluble inorganic binder remains. Dry the model. If the water of crystallization remains, the strength of the mold increases.
The specific drying method is the same as the step (III-1) of the first aspect.

By drying the molded product while it is filled in the mold for molding, the water impregnated in the refractory granular material evaporates and the dissolved water-soluble inorganic binder solidifies, so that the refractory granular material Is solidified in the shape of the mold for molding, and by removing the mold, a mold having a desired shape can be obtained.
When the water-soluble inorganic binder contained in the binder aqueous solution contains a phosphoric acid compound, the following step (IV-2) may be performed.

(Process (IV-2))
Step (IV-2) is a step of further heating the molded article.
When the water-soluble inorganic binder contains water of crystallization, in step (IV-2), the molded article is further heated so as to remove at least a part of the water of crystallization of the water-soluble inorganic binder. By removing at least a part of the crystal water, the amount of gas generated during pouring can be reduced, so that gas defects can be suppressed.
The specific heating method is the same as the step (IV-1) of the first aspect.

When the loss on heating (α) of the thus obtained mold is 1.0% or less, it can be judged that at least a part of the water of crystallization of the water-soluble inorganic binder has been removed. That is, it means that the manufacturing process has advanced to the process (IV-2).
The method for measuring the heating loss (α) is the same as the method for measuring the heating loss (α) in the first embodiment.

(Effect)
According to the method for producing a mold of the second aspect of the present invention described above, since the water-soluble inorganic binder is mixed, the dry refractory granular material is filled in the mold for molding, therefore, for molding Even if the shape of the mold is complicated, it is possible to uniformly and quickly fill the refractory granular material, and it is possible to suppress the filling failure and the decrease of the mold strength. Moreover, since the mold for forming a mold of the present invention has specific holes formed therein, water permeates, and the water-soluble inorganic binder filled in the mold for forming a mold dissolves to the entire refractory granular material. Impregnate. Therefore, a mold having a desired shape can be obtained by drying the molded product while it is filled in the mold for molding.
Thus, according to the mold manufacturing method of the second aspect of the present invention, a mold having high strength and a complicated shape can be easily manufactured.

[template]
Since the mold obtained according to the present invention contains a water-soluble inorganic binder as a binder, the thermal decomposition gas of the water-soluble inorganic binder is unlikely to be generated during pouring. In addition, the mold maintains its shape and its strength is maintained by the water-soluble inorganic binder, but since the water-soluble inorganic binder easily dissolves in water, it is easy to apply water to the mold after casting. The mold collapses. Further, since the water-soluble inorganic binder is dissolved in water, the refractory granular material can be easily regenerated from the disassembled mold by solid-liquid separation. Further, if water is removed from the liquid obtained by solid-liquid separation, the water-soluble inorganic binder can be reused.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. The refractory granular material, water-soluble inorganic binder and water glass used in each example are shown below. Further, various measuring methods and evaluation methods, and a method for manufacturing a mold for molding are as follows.

<Fireproof granular material>
The following were used as the refractory granular material. In addition, all of the refractory granular materials (i) to (v) shown below are in a dry state.
· Refractory particulate material (i): one containing 95 wt% of artificial sand _{(Al 2} O 3 -SiO ₂ obtained by the sintering method, Itochu Ceratec K.K. "CB-X # 1450", particles Diameter 53-150 μm).
· Refractory particulate material (ii): one containing 95 wt% of artificial sand _{(Al 2} O 3 -SiO ₂ obtained by the sintering method, Itochu Ceratec K.K. "CB-X # 650", particles Diameter 106-212 μm).
· Refractory particulate material (iii): Natural silica sand (silica sand containing SiO ₂ 98 wt%, Mitsubishi Building Materials K.K. "Hula tally sand", particle diameter 106~212μm).
-Refractory granular material (iv): artificial sand obtained by a melting method (containing 75% by mass of Al ₂ O ₃ and 25% by mass of SiO ₂ , trade name "Alsand #650" manufactured by Ito Kiko Co., Ltd., Particle size 106-212 μm).
· Refractory particulate material (v): those artificial sand (SiO ₂ obtained by the flame fusion method comprising 98 wt%, CHINA MINERAL PROCESSING LIMITED Co., Ltd. under the trade name "SPHERESAND SL SLH # 65", the particle size 106~212μm ).

<Water-soluble inorganic binder>
Anhydrous magnesium sulfate was used as the water-soluble inorganic binder.

<Water glass>
As the water glass, “sodium silicate” manufactured by Fuji Chemical Co., Ltd. (molar ratio (SiO ₂ /Na ₂ O): 2.5, Baume degree: 48 (25° C.), water content: 50% by mass) was used.

<Measurement and evaluation>
(Evaluation of liquidity)
The fluidity of the samples (refractory granular material and kneaded sand) was evaluated based on a slump test.
In the slump test, a slump cone having an upper bottom diameter of 70 mm, a lower bottom diameter of 60 mm and a height of 80 mm was used.
After the sample was packed in the slump cone, the spread of the sample (slump flow) when the slump cone was gently pulled up vertically was measured.

(Measurement of bending strength)
The bending strength of the test pieces obtained in each of the examples and comparative examples was measured using the measuring method described in JACT test method SM-1.

<Manufacture of mold for mold making (1)>
Soda lime glass (product name "Glass beads" manufactured by Potters Ballotini Co., Ltd., average particle size 50 μm, ε _r =6.0) 7.5 kg, and polyamide 11 (product name "RILSAN INVENT NATURAL manufactured by Arkema Co., Ltd." , Average particle diameter 50 μm, and ε _r =4.3) 7.5 kg were mixed for 5 minutes with a screw type mixer to obtain a material for an additional production method.
Based on the SLS method, the additive manufacturing material was selectively laser-sintered with a laser sintering machine ("EOSINT P380" manufactured by EOS Co., Ltd.) to fabricate a mold 10 for molding as shown in FIG. A circular hole 14a having a diameter of 0.8 mm is formed in the recess 13a in the portion corresponding to the core body, and a slit-like hole 14b having a length of 75 to 81 mm is formed in the recess 13b in the portion corresponding to the skirting board. It is formed and the aperture ratio is 3.1%.

<Manufacture of mold for mold making (2)>
A material for an additional production method was obtained in the same manner as in the production (1) of the mold for molding.
Based on the SLS method, a plurality of parts were manufactured by selectively laser-sintering the additive manufacturing material with a laser sintering machine ("EOSINT P380" manufactured by EOS Co., Ltd.). As shown in FIG. 2, a plurality of parts thus obtained are combined to form a mold 20 for forming a test piece, in which five parallelepiped-shaped depressions 13 each having a length of 60 mm, a width of 10 mm, and a depth of 10 mm are formed. did. A slit-shaped hole 14b having a width of 0.3 mm and a length of 8 to 30 mm is formed on the side surface and the bottom surface of the depression 13, and the aperture ratio is 7.9%.

[Example 1]
A slump test was performed on the refractory granular material (i) to evaluate the fluidity of the refractory granular material (i). The results are shown in Fig. 3(a).

Separately, a water-soluble inorganic binder was dissolved in water so as to have a concentration of 25% by mass to prepare an aqueous binder solution.
The refractory granular material (i) was filled in the recess 13 of the mold 10 for molding shown in FIG. 1 (step (I-1)). Then, the mold 10 for molding a mold filled with the refractory granular material (i) was immersed in a binder aqueous solution for 30 seconds (step (II-1)). Then, the casting mold 10 is pulled up from the aqueous binder solution, placed in a microwave vacuum dryer (manufactured by Saikou Engineering Co., Ltd.), and dried for 5 minutes under conditions of a microwave output of 1000 W and a vacuum degree of 10 kPa (step). (III-1)), a mold weighing 250 g was taken out from the mold 10 for molding.

[Comparative Example 1]
3 parts by weight of a water-soluble inorganic binder and 2.4 parts by weight of water were added to 100 parts by weight of the refractory granular material (iii), and the mixture was kneaded for 1 minute to obtain kneaded sand.
The kneaded sand thus obtained was subjected to a slump test to evaluate the fluidity of the kneaded sand. The results are shown in Fig. 3(b).

From the results of FIG. 3, the refractory granular material (i) had a slump flow of 210 mm and was excellent in fluidity. Further, when the refractory granular material (i) was filled in the mold 10 for molding a mold shown in FIG. 1, it was possible to sufficiently fill it. Furthermore, a mold could be produced by allowing the binder aqueous solution to permeate and then drying.
On the other hand, since the kneading sand was wet, the slump flow was 70 mm and the flowability was poor.
Therefore, it was shown that by using the dry refractory granular material, even if the shape of the mold for molding is complicated, it is possible to uniformly and quickly fill, and it is possible to suppress filling failure and decrease in mold strength.

[Example 2]
100 parts by mass of the refractory granular material (i) and 2 parts by mass of the water-soluble inorganic binder were mixed, and the obtained mixture was filled in the recess 13 of the mold 20 for molding shown in FIG. 2 (step (I- 2)). Then, the mold 20 for molding a mold filled with the refractory granular material (i) and the water-soluble inorganic binder was immersed in water for 30 seconds (step (II-2)). Then, the mold 20 for mold making is lifted from water, put in a microwave vacuum dryer (manufactured by Saikou Engineering Co., Ltd.), and dried for 1.5 minutes under the conditions of a microwave output of 800 W and a vacuum degree of 10 kPa (step ( III-2)), 5 test pieces (molds) were taken out from the mold 20 for molding.
The bending strength was measured for the five test pieces taken out, and the average value was obtained. The results are shown in Table 1 and FIG.
The amount of water permeated into the mold for molding 20 was 20 parts by mass with respect to 100 parts by mass of the refractory granular material (i) filled in the mold for molding 20.
Further, the loss on heating (α) of the test piece was measured by the above-mentioned measuring method and was found to be 1.4%, which confirmed that the water of crystallization of the water-soluble inorganic binder in the test piece remained. It was

[Examples 3 to 8]
A test piece was produced in the same manner as in Example 2 except that the addition amount of the water-soluble inorganic binder was changed to the value shown in Table 1, and the bending strength was measured. The results are shown in Table 1 and FIG.

From the results shown in Table 1 and FIG. 4, a test piece having high strength was obtained from each example.

[Example 9]
The water-soluble inorganic binder was dissolved in water to prepare a binder aqueous solution so that the concentration was 25% by mass.
The refractory granular material (iii) was filled in the depression 13 of the mold 20 for molding shown in FIG. 2 (step (I-1)). Next, the mold 20 for molding a mold filled with the refractory granular material (iii) was immersed in the binder aqueous solution for 30 seconds (step (II-1)). Next, after pulling up the mold 20 for casting a mold from the aqueous binder solution, putting it in a microwave vacuum dryer (manufactured by Saikou Engineering Co., Ltd.) and drying for 1.5 minutes under the conditions of a microwave output of 800 W and a vacuum degree of 10 kPa. (Step (III-1)), 5 test pieces (molds) were taken out from the mold 20 for molding.
The bending strength was measured for the five test pieces taken out, and the average value was obtained. The results are shown in Table 2 and FIG.
The penetration amount of the binder aqueous solution into the casting mold 20 is 6 when the amount of the water-soluble inorganic binder impregnated in 100 parts by mass of the refractory granular material filled in the casting mold 20 is 6. The amount was part by mass.

[Examples 10 to 12]
A test piece was manufactured in the same manner as in Example 9 except that the type of refractory granular material shown in Table 2 was used, and the bending strength was measured. The results are shown in Table 2 and FIG.

The “concentration of the binder aqueous solution” in Table 2 and the following Table 3 is the content (mass %) of the water-soluble inorganic binder with respect to the total mass of the binder aqueous solution.
In Table 2 and the following Table 3 and "Proportion of water-soluble inorganic binder" in Fig. 6, the water-soluble inorganic material impregnated into 100 parts by mass of the refractory granular material filled in the mold 20 for molding a mold is shown. It is the amount (parts by mass) of the binder.

From the results of Table 2 and FIG. 5, a test piece having high strength was obtained from each example.

[Examples 13 to 16]
The binder aqueous solution was prepared so that the concentration of the water-soluble inorganic binder with respect to the total mass of the binder aqueous solution was the value shown in Table 3.
A test piece was produced in the same manner as in Example 9 except that the obtained binder aqueous solution and the refractory granular material (i) were used, and the bending strength was measured. The results are shown in Table 3 and FIG. Table 3 shows the amount of the water-soluble inorganic binder impregnated in 100 parts by mass of the refractory granular material (i) filled in the mold 20 for molding.

[Examples 17 to 20]
100 parts by weight of the refractory granular material (i) was heated to 110°C. Next, 1 part by mass of water glass was added to the heated refractory granular material (i), and the mixture was stirred for 5 minutes with a mixer to obtain a silicate-coated refractory granular material (i). The ratio of the silicate, that is, the coating amount is 0.5 parts by mass with respect to 100 parts by mass of the uncoated refractory granular material (i).
Separately, a binder aqueous solution was prepared so that the concentration of the water-soluble inorganic binder with respect to the total mass of the binder aqueous solution was the value shown in Table 3.
A test piece was produced in the same manner as in Example 9 except that the obtained binder aqueous solution and the refractory granular material (i) coated with silicate were used, and the bending strength was measured. The results are shown in Table 3 and FIG. Table 3 shows the amount of the water-soluble inorganic binder impregnated in 100 parts by mass of the refractory granular material (i) (however, including the mass of silicate) filled in the mold 20 for molding. ..

From the results of Table 3 and FIG. 6, a test piece having higher strength was obtained by using the refractory granular material coated with silicate.

10 Mold for mold making 11 Upper mold 12 Lower mold 13 Cavity 13a Cavity in the part corresponding to the core body 13b Cavity in the part corresponding to a skirting board 14 Hole 14a Circular hole 14b Slit-like hole 15a First convex part 15b No. Two convex portions 15c Third convex portion 15d Fourth convex portion 16a First concave portion 16b Second concave portion 16c Third concave portion 16d Fourth concave portion 20 Mold for molding

Claims (6)

Filling the interior of the mold for molding with a dry refractory granular material (I),
A step (II) of obtaining a molded article by immersing the mold for molding in which the refractory granular material is filled in water,
A step (III) of drying the obtained molded article while being filled in a mold for molding.
Including,
The mold for molding has a plurality of holes that do not prevent water from penetrating into the inside and that prevent the refractory granular material from flowing out from the inside.
At least one of the refractory granular material used in the step (I) and the water used in the step (II) is mixed with a water-soluble inorganic binder,
The method for producing a mold, wherein the water-soluble inorganic binder is at least one selected from the group consisting of a sulfuric acid compound, a phosphoric acid compound, a chloride and a carbonic acid compound. The method for producing a mold according to claim 1, wherein at least the water used in the step (II) is mixed with the water-soluble inorganic binder. The method for producing a mold according to claim 1 or 2, wherein the refractory granular material is coated with a silicate. The mold for molding is made of a material that transmits microwaves,
The method for producing a mold according to claim 1, wherein in the step (III), the molded article is irradiated with microwaves and dried. The method for producing a mold according to claim 1, wherein the step (III) is performed under reduced pressure. A mold for molding a mold using a refractory granular material in a dry state,
When the refractory granular material is filled inside and immersed in water, a plurality of holes are formed which do not prevent water from penetrating into the interior and inhibit the refractory granular material from flowing out from the inside. Has been used for mold making.