JP7537964B2 - Mold-making composition - Google Patents

Description

The present invention relates to a composition for casting.

In order to reduce gas defects and odors in castings that are caused by the pyrolysis gas of organic binders that is generated during casting, water glass, an inorganic binder, is sometimes used. A known method for hardening the water glass is a mold-making method that uses organic esters and carbon dioxide gas (Non-Patent Document 1).

However, molds using inorganic binders generally have the problem of low strength.
In response to the problem of reduced mold strength when inorganic binders are used, a composition for mold making has been proposed that contains a mixture of refractory particles, water glass, and amorphous silicon dioxide (amorphous silica) (Patent Document 1).
Furthermore, for the purpose of increasing the fluidity and thereby increasing the strength of the mold, inorganic coated sand having room temperature fluidity in which refractory particles are coated with an inorganic binder has been proposed (Patent Document 2).

: Edited by the Japan Foundry Association, Casting Handbook, Revised 4th Edition, Maruzen Co., Ltd., published on January 20, 1986, pp. 146-147

Special Publication No. 2008-511447 International Publication No. 2014/098129

Through the investigations of the present inventors, it has been newly discovered that conventional casting compositions using inorganic binders have the problem of low mold strength, and that when a casting mold having a complex, thin-walled shape is produced, the casting mold is exposed to high-temperature molten metal during casting and deforms, leaving room for improvement in terms of the dimensional accuracy of the casting.
Furthermore, it has been found that this problem also occurs when amorphous silica, which improves mold strength, is contained in a mold-making composition that contains an inorganic binder.

The present invention provides a composition for casting that improves mold strength and suppresses mold deformation that occurs during casting.

According to the present invention,
A foundry mold-making composition is provided that contains a refractory aggregate (component A), an inorganic binder (component B) and fly ash (component C).

The present invention provides a composition for mold making that can improve mold strength and suppress deformation of the mold that occurs during casting.

FIG. 2 is a cross-sectional view for explaining a method for measuring the deformation of a mold in the examples.

The following describes the embodiments of the present invention. In this specification, unless otherwise specified, "A-B" indicating a numerical range represents a range from A to B, and includes both ends of the range. In addition, the configurations and elements described in each embodiment can be appropriately combined as long as the effect of the invention is not impaired.

<Mold making composition>
In this embodiment, the composition for molding a foundry mold contains a refractory aggregate (component A), an inorganic binder (component B), and fly ash (component C). Specific examples of such a composition for molding a foundry mold include: The following aspects 1 and 2 can be mentioned.

(Aspect 1)
In this embodiment, a mold-making composition is obtained by mixing a refractory aggregate, an aqueous solution of an inorganic binder, and fly ash, and a mold is made by filling the mold-making composition into a heated molding die and heating and hardening it.
Specifically, in this embodiment, the aqueous inorganic binder solution is used by kneading it with the refractory aggregate in a wet state, and the aqueous inorganic binder solution is attached to the refractory aggregate as a liquid.

(Aspect 2)
The present embodiment relates to inorganic coated sand, more specifically, inorganic coated sand having a refractory aggregate and an inorganic binder layer formed on the surface of the refractory aggregate. In the present embodiment, the inorganic binder layer contains an inorganic binder and fly ash.
From the viewpoints of improving mold strength and excellent productivity, the inorganic coated sand of embodiment 2 is preferred.

Next, the components contained in the composition for molding a mold will be described in more detail. The following configurations can be applied to both the above-mentioned embodiment 1 and embodiment 2.
(Fire-resistant aggregate: component A)
The material of the refractory aggregate may be one or more selected from the group consisting of natural sand and artificial sand.

Examples of natural sand include one or more types selected from the group consisting of silica sand, which is mainly composed of quartz, chromite sand, zircon sand, olivine sand, and alumina sand.

Examples of the artificial sand include one or more types selected from the _group consisting of synthetic mullite sand, _SiO2 -based foundry sand mainly composed of _SiO2 , _{Al2O3 -} based foundry sand mainly composed of _Al2O3 , _SiO2 / _{Al2O3 -} based foundry sand, _SiO2 /MgO-based foundry sand, _SiO2 / _Al2O3 / _{ZrO2 -} based foundry sand, _SiO2 / _Al2O3 / _{Fe2O3 -} based foundry sand, and _slag -derived foundry sand. Here, the term "main component" refers to the component that is present in the greatest amount among the components contained in the sand.
Artificial sand is not found in nature, but is found in sand that has been artificially prepared from metal oxide components and melted or sintered. In addition, recycled sand made from recycled refractory aggregate and recycled sand that has been regenerated can also be used.

The refractory aggregate is preferably in a particulate form from the viewpoint of improving the flowability of the refractory aggregate and further improving the fillability into a molding die.
The average particle size of the refractory aggregate is preferably 0.05 mm or more, more preferably 0.1 mm or more, from the viewpoints of improving mold quality and mold strength, and of ease of mold making. When the average particle size of the refractory aggregate is equal to or more than the above lower limit, the amount of inorganic binder layer used during mold production can be reduced, which is also preferable in that it makes it easier to regenerate the inorganic coated sand.
The average particle size of the refractory aggregate is preferably 2 mm or less, more preferably 1 mm or less, and even more preferably 0.5 mm or less, from the viewpoints of improving the mold quality and strength, and of ease of mold making. In addition, when the average particle size of the refractory aggregate is equal to or less than the above upper limit, it is also preferable in that the porosity is reduced during mold production, and the mold strength can be increased.

(Method of measuring average particle size)
When the sphericity of the particle from the projected cross section is 1, the diameter (mm) is measured, whereas when the sphericity is <1, the major axis diameter (mm) and minor axis diameter (mm) of the randomly oriented particles are measured to determine (major axis diameter + minor axis diameter)/2, and the average value obtained for 100 random particles is used as the average particle diameter (mm). The major axis diameter and minor axis diameter are defined as follows. When a particle is stabilized on a flat surface and the projection image of the particle on the flat surface is sandwiched between two parallel lines, the width of the particle at which the distance between the parallel lines is the smallest is called the minor axis diameter, whereas the distance when the particle is sandwiched between two parallel lines perpendicular to the parallel lines is called the major axis diameter.
The major axis diameter and minor axis diameter of a particle can be determined by taking an image (photograph) of the particle using an optical microscope or a digital scope (for example, VH-8000 model, manufactured by Keyence Corporation) and subjecting the obtained image to image analysis.

(Inorganic binder: component B)
In the present embodiment, the inorganic binder is preferably a water-soluble silicate, such as sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, ammonium silicate, etc.
In the present embodiment, from the viewpoints of excellent productivity and easy availability, the inorganic binder is preferably at least one selected from sodium silicate and sodium metasilicate.
In the case of inorganic coated sand, from the viewpoint of improving the productivity of the inorganic coated sand and the productivity of the mold, the inorganic binder is more preferably sodium metasilicate or a hydrate thereof, and even more preferably sodium metasilicate hydrate.

Specific examples of sodium silicate include one or more types selected from the group consisting of sodium silicate No. 1 to No. 5. Sodium silicate is classified into No. 1 to No. 5 based on the molar ratio of SiO ₂ /Na ₂ O, and sodium silicate No. 1 to No. 3 are specified in JIS-K-1408. The molar ratio of SiO ₂ /Na ₂ O for each type is specifically as follows:
Sodium silicate No. 1: SiO ₂ /Na ₂ O molar ratio=2.0-2.3
Sodium silicate No. 2: SiO ₂ /Na ₂ O molar ratio=2.4-2.6
Sodium silicate No. 3: SiO ₂ /Na ₂ O molar ratio=2.8 to 3.3
Sodium silicate No. 4: SiO ₂ /Na ₂ O molar ratio=3.3-3.5
Sodium silicate No. 5: SiO ₂ /Na ₂ O molar ratio=3.6-3.8
Moreover, two or more kinds of sodium silicates may be mixed to adjust the SiO ₂ /Na ₂ O molar ratio to a desired level.

As the sodium metasilicate hydrate, from the viewpoints of excellent productivity and easy availability, at least one selected from sodium metasilicate pentahydrate and sodium metasilicate nonahydrate is preferred.

The content of sodium silicate and sodium metasilicate in the inorganic binder is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 98% by mass or more, and even more preferably substantially 100% by mass, from the viewpoints of improving mold strength, excellent productivity, and ease of availability. Here, "substantially" means including components that are unintentionally contained, for example, components other than sodium silicate and sodium metasilicate contained in the sodium silicate and sodium metasilicate that are raw materials.
The contents of sodium silicate and sodium metasilicate in the inorganic binder refer to the contents of sodium silicate and sodium metasilicate relative to the total components other than water in the inorganic binder.

In the embodiment 1, the inorganic binder is preferably used in the form of an aqueous solution from the viewpoint of improving the handling property. In particular, when the inorganic binder contains a silicate, it is more preferable to use the silicate in the form of an aqueous solution.
The concentration of the aqueous inorganic binder solution is preferably 20% by mass or more from the viewpoint of improving the strength of the mold.
From the viewpoint of improving the handleability of the aqueous inorganic binder solution and improving the strength of the mold, the concentration of the aqueous inorganic binder solution is preferably 60% by mass or less.
Here, the concentration of the aqueous inorganic binder solution is specifically the concentration of the non-volatile matter contained in the aqueous inorganic binder solution.

From the viewpoint of improving mold strength, the content of the inorganic binder (non-volatile content) in the foundry molding composition is preferably 0.1 parts by mass or more per 100 parts by mass of the refractory aggregate, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more.
In addition, from the viewpoint of improving the filling property of the mold, the content of the inorganic binder (non-volatile matter) in the mold making composition is preferably 5 parts by mass or less per 100 parts by mass of the refractory aggregate, more preferably 4 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

(Fly ash: component C)
The fly ash is fly ash type I or type II as specified in JIS A 6201, and its chemical composition falls within the composition range of the table “(1) Total of domestic and overseas chemical composition statistics of coal ash” on page IV-7 of the Coal Ash Handbook, 5th Edition (edited and published by the Japan Fly Ash Association, published in October 2010).
From the viewpoint of increasing mold strength, the fly ash preferably contains type I fly ash having a fine particle size as defined in JIS A 6201, and more preferably is type I fly ash as defined in JIS A 6201.

From the viewpoint of increasing mold strength, the average particle size d ₅₀ of the fly ash is preferably 0.5 μm or more, more preferably 1 μm or more, and is preferably 20 μm or less, more preferably 10 μm or less.
The average particle size d ₅₀ of the fly ash can be measured by a laser diffraction method using a laser diffraction scattering type particle size distribution measuring device.

The mass ratio of the fly ash content to the inorganic binder content (non-volatile content) in the foundry molding composition (component C/component B) is, from the viewpoint of suppressing deformation of the mold and improving the mold strength, preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, even more preferably 0.4 or more, even more preferably 0.6 or more, still more preferably 1.1 or more, and especially preferably 1.5 or more.
Furthermore, from the viewpoint of improving the surface condition of the mold, the above mass ratio (component C/component B) is preferably 3.5 or less, more preferably 3 or less, even more preferably 2.8 or less, and even more preferably 2.5 or less.

In the composition for mold making, the content of fly ash per 100 parts by mass of the refractory aggregate is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.4 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoints of suppressing deformation of the mold, improving the mold strength, and improving the filling ability of the mold.
In addition, from the viewpoint of improving the surface condition of the mold, the content of fly ash per 100 parts by mass of refractory aggregate in the mold making composition is preferably 9 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less.

(Other additives)
In addition to the above-mentioned components, the foundry molding composition may contain various additives as necessary, such as a humectant, a moisture resistance improver, a coupling agent for strengthening the bond between the refractory aggregate and the inorganic binder, a lubricant, a surfactant, etc.

(Inorganic coated sand)
The inorganic coated sand of embodiment 2 will be described below.
From the viewpoint of obtaining a high-strength mold, the moisture content in the inorganic coated sand is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the inorganic binder.
From the viewpoint of filling the molding die and obtaining a high-strength mold, the moisture content in the inorganic coated sand is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, even more preferably 150 parts by mass or less, and still more preferably 140 parts by mass or less, relative to 100 parts by mass of the inorganic binder.

The water content in the inorganic binder layer contained in the inorganic coated sand can be adjusted, for example, depending on the type of inorganic binder.

When the inorganic binder is sodium silicate, the water content in the inorganic binder layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of sodium silicate, from the viewpoint of obtaining a high-strength mold.
From the viewpoint of filling the molding die and obtaining a high-strength mold, the water content in the inorganic binder layer contained in the inorganic coated sand is preferably 55 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of sodium silicate.

When the inorganic binder is sodium metasilicate, from the viewpoint of obtaining a high-strength mold and from the viewpoint of easily producing the mold, the content of water in the inorganic binder layer is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, even more preferably 90 parts by mass or more, and still more preferably 110 parts by mass or more, relative to 100 parts by mass of sodium metasilicate; and from the viewpoint of improving the fluidity and further improving the fillability into the molding die, the content of water is preferably 180 parts by mass or less, more preferably 160 parts by mass or less, even more preferably 150 parts by mass or less, and still more preferably 140 parts by mass or less.
For example, when the inorganic binder constituting the inorganic binder layer is composed only of sodium metasilicate pentahydrate, the water content is 74 parts by mass, and when the inorganic binder is composed only of sodium metasilicate nonahydrate, the water content is 133 parts by mass.

The inorganic coated sand is specifically composed of a group of inorganic coated sand particles, and the fire-resistant aggregate is specifically composed of a group of fire-resistant aggregate particles.

From the viewpoint of improving the flowability and further improving the filling property into the molding die, the inorganic coated sand is preferably spherical. Here, spherical inorganic coated sand means a round shape like a ball.
More specifically, from the viewpoints of improving fluidity, mold quality, and mold strength, and of ease of mold making, the sphericity of the inorganic coated sand is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, still more preferably 0.95 or more, and especially preferably 0.97 or more. The upper limit of the sphericity is specifically 1 or less.

Here, the sphericity of the inorganic coated sand can be determined by analyzing an image (photograph) of the particle obtained with an optical microscope or a digital scope (for example, Keyence VH-8000 model) to determine the area of the projected cross section of the particle and the perimeter of the cross section, and then calculating [circumference (mm) of a true circle having the same area as the area of the projected cross section of the particle ( ^mm2 )] / [perimeter (mm) of the projected cross section of the particle], and averaging the values obtained for any 50 particles.

The average particle size of the inorganic coated sand is preferably 0.05 mm or more, more preferably 0.1 mm or more, from the viewpoints of improving mold quality and mold strength, and of ease of mold making. In addition, when the average particle size of the inorganic coated sand is equal to or more than the above lower limit, the amount of inorganic binder layer used during mold production can be reduced, which is also preferable in that the inorganic coated sand can be easily regenerated.
From the viewpoints of improving mold quality and strength, and of ease of mold making, the average particle size of the inorganic coated sand is preferably 2 mm or less, more preferably 1 mm or less, and even more preferably 0.5 mm or less. In addition, when the average particle size of the inorganic coated sand is equal to or less than the above upper limit, it is also preferable in that the porosity is reduced during mold production, and the mold strength can be increased.
The average particle size of the inorganic coated sand can be measured by the same method as that for the average particle size of the refractory aggregate.

<Method of manufacturing the foundry molding composition>
In this embodiment, the foundry mold composition is produced, for example, by a method in which an inorganic binder aqueous solution and fly ash are added simultaneously or sequentially to a refractory aggregate while stirring. From the viewpoint of uniformly mixing the raw material components, the inorganic binder aqueous solution is preferably added to the refractory aggregate before the fly ash.
The second embodiment of the composition for molding a foundry mold, that is, the method for producing the inorganic coated sand, will be described in more detail below.

(Method of manufacturing inorganic coated sand)
The method for producing the inorganic coated sand can be selected depending on, for example, the type of inorganic binder.

When the inorganic binder contains sodium metasilicate hydrate, for example, a dry inorganic coated sand can be obtained by a production method including a step of mixing refractory aggregate and sodium metasilicate hydrate at a temperature equal to or higher than the melting point of sodium metasilicate hydrate to obtain a mixture; and a step of cooling the mixture to a temperature lower than the melting point of sodium metasilicate hydrate.
According to this manufacturing method, since the inorganic binder layer can be crystallized, it is possible to obtain inorganic coated sand having superior fluidity compared to conventional manufacturing methods. In addition, since it is not necessary to use an aqueous solution of sodium metasilicate hydrate, a dehydration step is not necessary, and the manufacturing method of inorganic coated sand can be simplified.

Specifically, in the step of obtaining the mixture, the surface of the refractory aggregate is coated with fluidized sodium metasilicate hydrate at a temperature equal to or higher than the melting point of sodium metasilicate hydrate.
Examples of a method for mixing refractory aggregate and sodium metasilicate hydrate at a temperature equal to or higher than the melting point of sodium metasilicate hydrate include a method in which sodium metasilicate hydrate is added to refractory aggregate heated to a temperature equal to or higher than the melting point of sodium metasilicate hydrate, and the refractory aggregate and sodium metasilicate hydrate are mixed while melting the sodium metasilicate hydrate; and a method in which sodium metasilicate hydrate that has been heated and melted is added to the refractory aggregate and mixed.
Among these, the method of adding heated and melted sodium metasilicate hydrate to the refractory aggregate and mixing them is preferred from the viewpoint of shortening the coating time.
From the same viewpoint, it is preferable that in the step of obtaining a mixture, sodium metasilicate hydrate is mixed without being converted into an aqueous solution in advance, and it is also preferable that the step of obtaining a mixture does not include a step of intentionally adding water.
The mixing conditions such as the stirring speed and processing time when mixing the refractory aggregate and the sodium metasilicate hydrate can be appropriately determined depending on the processing amount of the mixture.

In the step of cooling the mixture, the mixture obtained in the step of obtaining the mixture is cooled to a temperature below the melting point of sodium metasilicate hydrate, thereby reducing the fluidity of sodium metasilicate hydrate and fixing the sodium metasilicate hydrate to the surface of the refractory aggregate, thereby forming a sodium metasilicate hydrate layer, i.e., an inorganic binder layer.

Next, when the inorganic binder contains sodium silicate, for example, an aqueous solution of water glass as an inorganic binder is kneaded or mixed uniformly with heated refractory aggregate, together with additives as necessary, to coat the surface of the refractory aggregate with the aqueous solution of water glass, and the water in the aqueous solution of water glass is evaporated, thereby obtaining dry inorganic coated sand that has fluidity at room temperature.

In addition, in the production of inorganic coated sand, there is no limitation on the method of adding fly ash. For example, refractory particles may be coated with an inorganic binder, and then coated with fly ash and, if necessary, other compounds.
Alternatively, the inorganic binder and the fly ash, and optionally other compounds, may be coated on the refractory particles together.
Alternatively, the inorganic binder and fly ash, and if necessary other compounds, may be coated on the refractory particles, and then the fly ash may be further coated on the refractory particles.
The fly ash may be added all at once or in several portions.

By the above method, inorganic coated sand can be obtained.
The resulting inorganic coated sand can then be molded into a desired shape, either alone or in combination with other known refractory aggregates and other additives.

<Mold>
In this embodiment, the mold is produced using the mold-making composition of this embodiment described above.
The method for producing the mold is selected, for example, depending on the embodiment of the composition for molding a mold.

When using the casting composition of embodiment 1, the casting method can be, for example, a method of filling a heated mold with the casting composition and heat-curing it, a method of making a self-hardening casting mold by mixing the casting composition with an organic ester and curing the mold, or a method of passing carbon dioxide gas through the casting composition to harden the mold.

When the inorganic coated sand of embodiment 2 is used, examples of the method for producing a mold include a molding method using a heated molding die, and a molding method in which water vapor is passed through a heated molding die and then hot air is passed through the die.
When the inorganic binder layer contains sodium metasilicate hydrate, a method of filling the inorganic coated sand into a heated mold for molding is preferred. When the inorganic binder layer contains sodium silicate, a method of adding water to the inorganic coated sand, kneading the mixture, and then filling the mixture into a heated mold for molding is preferred, or a method of filling the inorganic coated sand into a heated mold, ventilating the mixture with water vapor, and then ventilating the mixture with hot air is preferred.

When the inorganic binder layer contains sodium metasilicate hydrate, in a molding method using a heated mold, for example, first, inorganic coated sand is filled into a mold that provides the desired casting shape.
Here, from the viewpoint of improving mold productivity, the molding die is preferably preheated to keep it warm before filling with the inorganic coated sand. The heating temperature at this time is preferably 100° C. or higher, more preferably 150° C. or higher, and is preferably 300° C. or lower, more preferably 250° C. or lower, from the viewpoint of improving mold productivity and mold strength.

After filling the inorganic coated sand, the inorganic coated sand is hardened in a heated molding die without passing water vapor. When the inorganic binder layer contains sodium metasilicate hydrate, the inorganic coated sand can be hardened without a step of adding water to the inorganic coated sand and kneading it, or a step of passing water vapor through it, so that equipment for passing water vapor through is not required.
From the viewpoint of improving mold productivity and mold strength, the heating temperature is preferably 100° C. or higher, more preferably 150° C. or higher, and also preferably 300° C. or lower, more preferably 250° C. or lower. From the viewpoint of obtaining stable mold strength, the heating time is preferably 30 seconds or higher, more preferably 60 seconds or higher, and also preferably 600 seconds or lower.

When the inorganic binder layer contains sodium silicate, water is added to the inorganic coated sand, which is then kneaded and filled into a heated mold. In a molding method that uses steam, for example, the inorganic coated sand is filled into a mold that will produce the desired casting mold, and then steam is blown in. The filling phase of the inorganic coated sand is moistened by the steam passage, and becomes wet. Hot air is then passed through the mold, which has been heated to 90-200°C, to dry and harden the inorganic coated sand.

The inorganic coated sand in this embodiment can also be used in additive manufacturing.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.
<1> A composition for molding a foundry mold, comprising a refractory aggregate (component A), an inorganic binder (component B), and fly ash (component C).
<2> The composition for mold making according to <1>, which contains a refractory aggregate (component A), an inorganic binder (component B) and fly ash (component C), in which the mass ratio of the content of the fly ash to the content of the inorganic binder (component C/component B) is 0.1 or more and 3.5 or less, and the content of the inorganic binder (non-volatile content) per 100 parts by mass of the refractory aggregate is 0.1 part by mass or more and 5 parts by mass or less.
<3> The composition for mold making according to <1> or <2>, which contains a refractory aggregate (component A), an inorganic binder (component B), and fly ash (component C), in which the mass ratio of the content of the fly ash to the content of the inorganic binder (component C/component B) is 0.4 or more and 3 or less, and the content of the inorganic binder (non-volatile content) per 100 parts by mass of the refractory aggregate is 0.5 parts by mass or more and 3 parts by mass or less.

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.
First, the following examples show the materials used in the preparation of the foundry molding compositions.

(material)
・Fire-resistant aggregate Espearl #60L (manufactured by Yamakawa Sangyo Co., Ltd., artificial alumina sand, average particle size: 241 μm)
Inorganic binder: sodium _{metasilicate nonahydrate} ( _Na2SiO3.9H2O ) (manufactured by Nippon Chemical Industry Co., Ltd.)
No. 1 50 Water glass ( _SiO2 / _Na2O =2.1) (manufactured by Fuji Chemical Industry Co., Ltd.)

Fly ash: Fly ash JIS Class I equivalent Product name: "Finash" (manufactured by Shikoku Electric Power Co., Inc.)
Average particle size _d50 (laser particle size diffraction): 4.4 μm
Composition (X-ray fluorescence analysis): as follows
Ingredients %
_SiO2 57.7
_{Al2O3 26.2
Fe2O3 4.88}
MgO 1.2
CaO 3.11

Amorphous silica fine particles Denka fused silica SFP-20M (average particle size d ₅₀ : 0.4 μm) (manufactured by Denka Co., Ltd.)

Here, the average particle size of the fly ash and Denka fused silica and the composition analysis of the fly ash were performed using the following methods.

<Measurement of average particle diameter _d50 >
The particle size distribution of the inorganic fine particles was measured by a laser diffraction method using a laser diffraction scattering type particle size distribution measuring device LA-960V2 (manufactured by Horiba, Ltd.) From the measurement results, the particle size ( _d50 , average particle size) at 50% accumulation in the cumulative distribution based on weight of the inorganic fine particles was obtained.

<X-ray fluorescence analysis method>
The fly ash was adjusted to 0.1 μm or less using a vibration mill and heated at 1050° C. for 1 hour. Then, 5 g of lithium tetraborate and 0.5 g of fly ash were mixed and heated at 1200° C. for 10 minutes to melt, and then cooled to prepare a glassy sample. The sample was subjected to X-ray fluorescence analysis using the Fundamental Parameter (FP) method using a fluorescent X-ray analyzer ZSX Primus II (manufactured by Rigaku Corporation) to perform composition analysis.

<Examples 1 to 8 and Comparative Examples 1 to 5>
Espearl #60L (100 parts by mass) was charged into the mixer as a refractory aggregate. Then, sodium metasilicate nonahydrate (amount shown in Table 1) that had been heated to 80°C and melted was charged into the mixer and kneaded for 4 minutes. Furthermore, for Examples 1 to 8, fly ash was charged in the amount shown in Table 1, and for Comparative Examples 4 and 5, amorphous silica was charged in the amount shown in Table 1 and kneaded for 2 minutes to obtain inorganic coated sand for each example. Table 1 shows the blending composition of the inorganic coated sand.

<Examples 9 and 10, Comparative Examples 6 and 7>
Espearl #60L (100 parts by mass) was charged into the mixer as a refractory aggregate. Next, No. 1 50 water glass (amount shown in Table 2) was charged into the mixer and kneaded for 2 minutes. Furthermore, for Examples 9 and 10, fly ash was charged in the amount shown in Table 2, and for Comparative Example 7, amorphous silica was charged in the amount shown in Table 2 and kneaded for 2 minutes to obtain a mold-making composition for each example. Table 2 shows the blending compositions of the mold-making compositions.

(Evaluation Method)
Using the inorganic coated sand or the composition for molding a foundry mold obtained in each example, a mold was produced by the following method, and the deformation of the mold was evaluated. The evaluation results are shown in each table.

(Mold Creation)
A mold for 22.3 x 22.3 x 180 mm test pieces (5 pieces) was heated to 200°C. The inorganic coated sand of Examples 1 to 8 and Comparative Examples 1 to 5 and the foundry molding compositions of Examples 9 to 10 and Comparative Examples 6 to 7 were filled at a blow pressure of 0.45 MPa using a CSR-43 blow molding machine. The inorganic coated sand and the foundry molding composition were then left to stand for 2 minutes in this molding mold to harden, and a mold test piece for each example was obtained.

(Bending strength of mold)
The bending strength of the mold test pieces was measured at 25° C. using a universal strength testing machine PFG type (manufactured by George Fischer) equipped with a PBV bending attachment in advance. The mold test pieces were used immediately after removal from the metal mold and after being left in a thermostatic chamber at 25° C./55% RH for 1.0 hour (Hr).

(Mold Deformation)
1(a) and 1(b) are cross-sectional views for explaining a method for measuring the deformation of a mold. The mold test pieces of each example obtained by the above-mentioned method were left for 1 hour in a constant temperature room at 25°C/55%RH, and then cut into plate-shaped test pieces 10 of 5 x 22.3 x 90 mm. Metallic pedestals 11a and 11b (13 mm x 13 mm, height 13 mm) were arranged on an iron plate of an appropriate size so that the center-to-center distance was 90 mm, and the plate-shaped test piece 10 was placed on the pedestals so that both ends were located at the center of each pedestal (FIG. 1(a)). Furthermore, a weight 13 (4.7 g) was placed on the center of the plate-shaped test piece 10. Then, the iron plate on which the plate-shaped test piece 10 was placed was heated for 5 minutes in a muffle furnace heated at 700°C. After 5 minutes, the plate-shaped test piece 10 was removed from the muffle furnace and left for 1 hour to cool. Then, the deformation amount of the plate-shaped test piece 10 was measured. The maximum perpendicular distance from a straight line connecting both ends of the plate-shaped test piece 10 to the curved portion was defined as the deformation amount (FIG. 1(b)).

(Mold filling ability)
The weight (g) of the mold test piece obtained in the preparation of the mold was measured, and the weight was divided by the volume (89.5 cm ³ ) of the test piece to obtain the filling property (density) of the mold.

From Tables 1 and 2, between the examples in which the type of inorganic binder and the amount of inorganic binder added to the refractory aggregate are the same, that is, between Examples 1 and 2, and Comparative Examples 1 and 4;
Between Examples 3 to 5 and Comparative Example 2;
When comparing Examples 6 to 8, Comparative Examples 3 and 5, and Examples 9, 10, and Comparative Examples 6 and 7, each Example had an excellent balance of the effects of mold strength, suppression of deformation of the test piece, and mold filling properties.

10 Plate-shaped test pieces 11a, 11b Base 13 Weight

Claims (5)

Contains refractory aggregate (component A), inorganic binder (component B) and fly ash (component C),
The composition for mold making, wherein the inorganic binder comprises at least one selected from the group consisting of sodium metasilicate and potassium metasilicate . The mold-molding composition according to claim 1, wherein the mass ratio (component C/component B) of the fly ash content to the inorganic binder content in the mold-molding composition is 0.1 or more and 3.5 or less. The foundry molding composition according to claim 1 or 2, wherein the content of the inorganic binder (non-volatile content) per 100 parts by mass of the refractory aggregate in the foundry molding composition is 0.1 parts by mass or more and 5 parts by mass or less. The mold-making composition according to claim 1 , wherein the inorganic binder contains sodium metasilicate hydrate . The mold-molding composition according to any one of claims 1 to 4, wherein the mold-molding composition is inorganic coated sand.

Images