JP7109444B2 - Mold material and method for manufacturing same, method for manufacturing mold, and method for recycling recovered refractory aggregate - Google Patents

Description

The present invention relates to a mold material and its manufacturing method, a mold manufacturing method, and a recycling method of recovered refractory aggregate. The present invention relates to a mold material that inhibits adhesion and exhibits excellent mold strength and mold filling properties.

Conventionally, as one of the molds used for casting molten metal, coated sand, which is obtained by coating mold sand made of refractory aggregate with a predetermined binder, is used as a mold material to obtain a desired shape. Those obtained by molding are used. Specifically, in "Casting Engineering Handbook" edited by the Japan Foundry Engineering Society, pp. 78-90, as a binder for such coated sand, inorganic binders such as water glass, phenol resins, Organic binders using resins such as furan resin and urethane resin have been clarified, and techniques for forming self-hardening molds using these binders have also been clarified.

For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-76115), the surface of a refractory aggregate is coated with a solid coating layer containing a water-soluble inorganic compound such as water glass as a binder. A binder-coated refractory (coated sand) with good properties has been demonstrated. There, such a binder-coated refractory (coated sand) with good fluidity is filled into the molding cavity of a mold for mold making, and then is allowed to pass through the water vapor. A method of solidifying a binder-coated refractory (coated sand) and obtaining a desired mold has been clarified.

However, in the conventional coated sand made by using an inorganic binder such as water glass as disclosed in Patent Document 1, since it contains only a small amount of organic matter, heating accompanying injection of molten metal The amount of gas generated by the process is small, so there is no appropriate gap between the casting (cast product) and the mold during casting, and the coated sand (and/or its solidified product) adheres to the casting product. Problems can occur. Organic binders generally lose their adhesiveness when heated, but inorganic binders do not lose their adhesiveness only by heating. substance) often remains on the surface of the cast product even after heating in the casting process and the subsequent heat treatment process. For this reason, after these processing steps, a step of removing the coated sand (and/or its solidified substance) adhering to the surface of the casting product is required, which is a problem of great labor. In addition, conventional coated sands using inorganic binders such as water glass are still insufficient in collapsibility of molds obtained by using them, and in this respect, there is still room for improvement. It is done.

JP 2012-76115 A

"Casting Engineering Handbook" pp.78-90

Here, the present invention has been made against the background of such circumstances, and the problem to be solved is that in the finally obtained mold, the mold material for the casting product and / or its solidified product To provide a mold material which suppresses adhesion and exhibits excellent mold strength and mold filling properties. In addition, the present invention provides a method for advantageously producing such excellent mold materials, a method for producing molds using such excellent mold materials, and furthermore, recycling of recovered refractory aggregates. Providing a method is also a problem to be solved.

In order to solve the above-described problems, the present invention can be suitably implemented in various aspects as listed below, and each aspect described below can be employed in any combination. It is possible. It should be noted that the aspects and technical features of the present invention are not limited to those described below, and can be recognized based on the inventive idea that can be grasped from the description of the entire specification. should be understood.

(1) A powdery product of (a) a refractory aggregate, (b) a water-soluble inorganic binder, and (c) an iron-containing compound, having an average particle size of 0.01 μm or more and less than 50 μm A coating layer containing the water-soluble inorganic binder and the powder of the iron- containing compound is formed on the surface of the refractory aggregate. A casting mold material consisting of fluid coated sand in a dry state.
(2) The mold material according to aspect (1), wherein the iron-containing compound is iron oxide.
(3) The mold material according to aspect (2), wherein the iron oxide is selected from the group consisting of magnetite, maghemite, ferrite, and mixtures of two or more thereof.
(4) The above aspects (1) to 500 parts by mass of the iron-containing compound powder are contained in a proportion of 1 to 500 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder. The mold material according to any one of the aspects (3).
(5) When an aqueous solution containing 30% by mass of the solid content of the water-soluble inorganic binder is used as a blank solution, and the transmittance of light at a wavelength of 660 nm of the blank solution is assumed to be 100%, the blank solution's 100 The average value of the light transmittance at a wavelength of 660 nm of the dispersion obtained by mixing 5 parts by mass of the powder of the iron-containing compound with respect to the parts by mass is 20% or less. A mold material according to any one of aspects (4).
(6) The mold material according to any one of the aspects (1) to (5), wherein the iron-containing compound powder is spherical.
(7) The mold material according to any one of the aspects (1) to (6), further comprising a surfactant.
(8) The mold material according to any one of the aspects (1) to (7), wherein the water-soluble inorganic binder is water glass.
(9) A water-soluble inorganic binder and a powdered iron-containing compound having an average particle size of 0.01 μm or more and less than 50 μm are added to the heated refractory aggregate, and kneaded or mixed. and evaporating water in the mixture to form a coating layer containing the water-soluble inorganic binder and the iron-containing compound powder on the surface of the refractory aggregate. A method for producing a mold material, characterized by producing a dry coated sand having fluidity at normal temperature.
(10) The method for producing a mold material according to the aspect (9) , wherein water is further added to prepare the mixture.
(11) After filling the mold material according to any one of the above aspects (1) to (8) into a heated mold, steam is passed through and held in the mold. and solidifying or hardening to obtain a desired mold.
(12) The mold manufacturing method according to the aspect (11) , wherein the mold is heated to a temperature of 80°C to 200°C.
(13) Water is added to the mold material according to any one of the above aspects (1) to (8) to make it wet, and the wet mold material is placed in a heated mold. A mold manufacturing method characterized by obtaining a desired mold by holding it in the mold after filling and solidifying or hardening it.
(14) The mold manufacturing method according to the aspect (13) , wherein the mold is heated to a temperature of 80°C to 300°C.
(15) The mold manufacturing method according to any one of the aspects (11) to (14) , wherein hot air or superheated steam is passed through the mold while the mold is being held.
(16) The aqueous solution containing the powder of the iron-containing compound obtained after casting using a mold made of the mold material according to any one of the aspects (1) to (8) . A method for regenerating recovered refractory aggregates containing refractory aggregates to which organic inorganic binders are adhered,
After the refractory aggregate is recovered, the recovered refractory aggregate is polished to scrape off the water-soluble inorganic binder adhering to the surface thereof, and then the refractory aggregate is The solid matter of the water-soluble inorganic binder scraped from the wood is attracted to the refractory bone by utilizing the action of attracting the powdery matter of the iron-containing compound contained in the solid matter to the magnet. A method for regenerating recovered refractory aggregate, characterized by performing a magnetic separation treatment for separating from the aggregate.
(17) The method for regenerating recovered refractory aggregate according to the aspect (16) , wherein the magnetic separation treatment is performed by a magnetic separator having a magnetic flux density within the range of 500 to 10000 gauss.
(18) The firing treatment of the refractory aggregate is performed prior to the polishing treatment, between the polishing treatment and the magnetic separation treatment, and/or after the magnetic separation treatment. The method for recycling recovered refractory aggregate according to the aspect (16) or the aspect (17) .

According to the mold material, the manufacturing method thereof, and the mold manufacturing method according to the present invention, various effects as listed below can be achieved.
(A) In a mold made of the mold material according to the present invention (hereinafter simply referred to as mold in this paragraph), the adhesion of the mold material and/or solidified products thereof to the casting product manufactured using the mold is effectively suppressed. be done. That is, the powdery iron-containing compound having an average particle size within a predetermined range exhibits excellent dispersibility in the water-soluble inorganic binder (and the mixture with water), and therefore the present invention. It exists in a well-dispersed state even in a mold made of the mold material, so that the adhesion of the mold material and/or its solidified product to the casting product is evenly suppressed on the outer surface of the casting product. becomes.
(B) The surface roughness of the cast product manufactured using the mold is improved.
(C) The mold exhibits excellent strength.
(D) Excellent fillability in the mold.

Further, according to the method for recycling recovered refractory aggregate according to the present invention, various effects described below can be achieved.
(E) The solid matter of the water-soluble inorganic binder scraped off by the grinding process can be easily separated from the refractory aggregate using magnetic force.
(F) It is possible to easily separate scraped water-soluble inorganic binder solids adhering to the surface due to the action of static electricity, etc., which cannot be completely removed by ordinary dust collection operations.
(G) In the solid matter of the water-soluble inorganic binder scraped off by polishing,
The iron-containing compound powder is advantageously present, and the subsequent magnetic separation treatment can efficiently remove even fine solids. When molded, it is possible to advantageously suppress the decrease in strength.

FIG. 2 is an explanatory longitudinal cross-sectional view of a casting test sand mold used to evaluate the state of adhesion of coated sand to castings in Examples. FIG. 2 is a vertical cross-sectional explanatory view of an aluminum alloy casting containing a waste core in an example.

By the way, the mold material containing the refractory aggregate and the water-soluble inorganic binder is classified into a dry mold material and a wet mold material depending on the state after preparation. First, the dry mold material has a form in which a coating layer made of a water-soluble inorganic binder is formed on the surface of a refractory aggregate, and does not have adhesiveness in a dry state ( Although it does not exhibit adhesiveness), when moisture is supplied by ventilation of water vapor, etc., the coating layer (water-soluble inorganic binder) covering the surface of the refractory aggregate dissolves and exhibits adhesiveness. It is. Such a dry mold material is, for example, filled in a mold in a state in which moisture is added to exhibit adhesive strength, and heated and dried, or molded in a dry state. After being filled in the mold and supplied with moisture by, for example, passing water vapor into the mold, it is heated and dried to proceed with the solidification or curing reaction, thereby forming the desired mold. It is to be done. On the other hand, the wet mold material exhibits a wet state (appearance) as a whole, in which the water-soluble inorganic binder exhibits stickiness. Such a wet mold material is, for example, filled in a mold and heated and dried in the mold to proceed with a solidification or hardening reaction, thereby forming the desired mold. It is to be done. Whether the mold material exhibits a dry state or a wet state is determined by the water content relative to the solid content of the water-soluble inorganic binder in the mold material. The water content at which the mold material assumes a dry or wet state is different. For example, when the water-soluble inorganic binder is water glass, a mold material containing water in an amount corresponding to 5 to 55% by mass of the solid content exhibits a dry state, while 55% by mass of the solid content of water glass is present in a dry state. A mold material containing a water content corresponding to an amount greater than % by weight exhibits a wet state.

The dry mold material (coated sand) having normal temperature fluidity in the present invention means a mold material ( coated sand). Here, the dynamic angle of repose is defined as the mold material (coated sand) placed in a cylinder with one transparent flat surface (for example, a container with a diameter of 7.2 cm and a height of 10 cm, filled with a half volume of the mold). material), rotate at a constant speed (e.g., 25 rpm), the slope of the layer of the mold material flowing in the cylinder becomes flat, and the angle formed between the slope and the horizontal surface is measured. be. The dynamic angle of repose is preferably 80° or less, more preferably 45° or less, and even more preferably 30° or less. Especially when the refractory aggregate is spherical, a dynamic angle of repose of 45° or less can be easily achieved. On the other hand, the mold material (coated sand) does not flow in the cylinder in a wet state, the slope of the mold material (coated sand) layer is not formed as a plane, and therefore the dynamic repose angle cannot be measured. is the wet mold material (coated sand).

As the refractory aggregate constituting the mold material according to the present invention, various refractory granular or powdery materials that are refractory substances that function as the base material of the mold and have been conventionally used for molds are used. Any of them can be used, and specifically, silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag, converter slag, etc. slag-based particles, artificial particles such as alumina-based particles and mullite-based particles, regenerated particles thereof, alumina balls, magnesia clinker, and the like. It should be noted that these refractory aggregates may be new sand, or recycled or recovered sand that has been used as foundry sand once or several times for molding molds, and furthermore, such recycled sand may be used. Mixed sand obtained by adding new sand to sand or recovered sand and mixing them may be used without any problem. Such refractory aggregates are generally used with a particle size of about 40 to 130, preferably about 60 to 110 in terms of AFS index. In addition, the refractory aggregate used in the present invention is preferably spherical, and specifically has a particle shape coefficient of 1.2 or less, more preferably 1.0 to 1.1. . By using a refractory aggregate with a grain shape factor of 1.2 or less, the flowability and filling properties during mold production are improved, and the number of contact points between refractory aggregates increases, so the same strength can be obtained. It is possible to reduce the amount of water-soluble inorganic binders and additives required to express. The particle shape index of the refractory aggregate used here is generally adopted as a scale indicating the outer shape of the particles, and is also called the particle shape index. , which means to approach a sphere (perfect sphere). Such a particle shape factor is represented by a value calculated using the surface area (sand surface area) of the refractory aggregate measured by various known methods. It means the value obtained by measuring the surface area of actual refractory aggregate particles (sand grains) per gram using a device (manufactured by George Fisher) and dividing it by the theoretical surface area. The theoretical surface area is the surface area when all the refractory aggregate particles (sand grains) are assumed to be spherical.

As the water-soluble inorganic binder in the mold material according to the present invention, one or more selected from water glass, sodium chloride, sodium phosphate, sodium vanadate, sodium aluminum oxide, potassium chloride, potassium carbonate, etc. is used advantageously. Among these, water glass and those containing water glass as a main component are particularly preferable from the viewpoint of ease of handling, moisture resistance, and strength of the finally obtained mold. Here, water glass is an aqueous solution of a soluble silicate compound, and examples of such silicate compounds include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, Ammonium silicate and the like can be mentioned, but sodium silicate (sodium silicate) is particularly advantageously used in the present invention. In the present invention, as long as water glass is used as the main component, it is also possible to use other water-soluble binders such as thermosetting resins, sugars, proteins, synthetic polymers, salts and inorganic polymers. be. When water glass is used in combination with another water-soluble binder, the ratio of water glass to the total amount of the binder is 60% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. be.

Here, sodium silicate is usually classified into types 1 to 5 according to the molar ratio of SiO ₂ /Na ₂ O and used. Specifically, sodium silicate No. 1 has a SiO ₂ /Na ₂ O molar ratio of 2.0 to 2.3, and sodium silicate No. 2 has a SiO ₂ /Na ₂ O molar ratio of 2.0 to 2.3. The molar ratio is 2.4 to 2.6, and sodium silicate No. 3 has a SiO ₂ /Na ₂ O molar ratio of 2.8 to 3.3. In addition, sodium silicate No. 4 has a SiO ₂ /Na ₂ O molar ratio of 3.3 to 3.5, and sodium silicate No. 5 has a SiO ₂ /Na ₂ O molar ratio of is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. These sodium silicates may be used singly or in combination, and two or more of them may be mixed to adjust the SiO ₂ /Na ₂ O molar ratio. is also possible.

In order to advantageously obtain the mold material according to the present invention, the sodium silicate constituting the water glass used as the binder should generally have a SiO ₂ /Na ₂ O molar ratio of 1.9 or more, preferably 2. .0 or more, more preferably 2.1 or more, and sodium silicates corresponding to Nos. 1 and 2 in the above classification of sodium silicates are particularly advantageously used. Such sodium silicate Nos. 1 and 2 provide mold materials that are stable and have good properties even over a wide range of sodium silicate concentrations in water glass. Also, the upper limit of the molar ratio of SiO ₂ /Na ₂ O in such sodium silicate is appropriately selected according to the properties of the water glass in the form of an aqueous solution, but is generally 3.5 or less, It is preferably 3.2 or less, more preferably 2.7 or less. Here, when the SiO ₂ /Na ₂ O molar ratio is less than 1.9, a large amount of alkali is present in the water glass, so the solubility of the water glass in water increases, and the mold material deteriorates due to moisture absorption. It may become easier. On the other hand, sodium silicate with a molar ratio of SiO ₂ /Na ₂ O greater than 3.5 has low solubility in water, so that the finally obtained mold cannot increase the bonding area between the refractory aggregates. , there is a risk of causing a problem that the mold strength is reduced.

Further, the water glass used in the present invention means a solution of a silicic acid compound dissolved in water. In addition to being used, water is added to such a stock solution to be used in a diluted state. The non-volatile content (water glass component) obtained by removing volatile substances such as water and solvents from such water glass is called solid content, which corresponds to the soluble silicate compound such as sodium silicate described above. It is. Also, the higher the proportion of such solids, the higher the silicic acid compound concentration in the water glass. Therefore, the solid content of the water glass used in the present invention, when it is composed only of the undiluted solution, corresponds to the ratio excluding the water content in the undiluted solution. When a diluted solution obtained by diluting with becomes.

The solid content in such water glass is set to an appropriate proportion depending on the type of the water glass component (soluble silicic acid compound), etc., and is preferably 20 to 50% by mass. It is desirable to contain in. Water glass in which a water glass component corresponding to the solid content is appropriately present in an aqueous solution is kneaded or mixed with a refractory aggregate, whereby the water glass component is added to the refractory aggregate. It is possible to prepare a mixture that is evenly and uniformly dispersed, thereby making it possible to advantageously mold the desired mold according to the present invention. If the concentration of the water glass component (soluble silicic acid compound) in the water glass becomes too low and the total amount of the water glass component (solid content) becomes less than 20% by mass, for example, a dry mold material is produced. In some cases, it is necessary to raise the heating temperature or lengthen the heating time for drying the refractory aggregate, powdered iron-containing compound and water glass mixture. As for the mold material, it becomes necessary to raise the heating temperature in the mold and lengthen the heating time, which causes problems such as energy loss. On the other hand, if the proportion of solids in the water glass becomes too high, it becomes difficult to prepare a mixture in which the water glass components are evenly and uniformly dispersed in the refractory aggregate. Since this may cause problems in the properties of the mold, it is advisable to prepare the water glass in the form of an aqueous solution such that the solids content is 50% by weight or less and therefore the water content is 50% by weight or more. desirable.

In the present invention, sodium chloride (NaCl), which can be used as a water-soluble inorganic binder, is edible, harmless to the human body, and inexpensive and easy to use. It is possible. Further, since it is easily dissolved in water, a mold material using sodium chloride as a binding agent can be used to manufacture molds that are easily disintegrated by water. In particular, the solubility of sodium chloride in water in the temperature range of 0 to 100° C. is 35.7 to 39.1 g per 100 g of water, and the change with water temperature is small, so workability is good. Furthermore, since the melting point of sodium chloride is 1413° C., which is relatively high, a mold with high heat resistance can be produced.

Examples of sodium phosphate include monosodium phosphate hydrate (NaH ₂ PO ₄ ·xH ₂ O; x is a known integer), disodium phosphate hydrate (Na ₂ HPO ₄ ·x'H ₂ O x' is a known integer), trisodium phosphate hydrate (Na ₃ PO ₄ ·x"H ₂ O; x" is a known integer). Then, sodium phosphate is soluble in water, as typified by the fact that the amount of trisodium phosphate hydrate dissolved in 100 g of water is 1.5 g (0 ° C.), and disodium phosphate water The melting point of sodium phosphate is relatively high, as typified by the melting point of 1340° C. of the hydrate. Therefore, a mold material using sodium phosphate as a water-soluble inorganic binder is easily disintegrated by water, and a mold with high heat resistance can be produced.

Furthermore, sodium vanadate (Na ₃ VO ₄ ) is soluble in water and has a relatively high melting point of 866°C. Therefore, a mold material using sodium vanadate as a water-soluble inorganic binder is easily disintegrated by water, and a mold with high heat resistance can be produced.

In addition, sodium aluminum oxide (NaAlO ₂ ) is soluble in water and has a high melting point of 1700° C. or higher. Therefore, a mold material using sodium aluminum oxide as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

Potassium chloride (KCl) dissolves easily in water, and is inexpensive, with a solubility of 28.1 g (0° C.) in 100 g of water. Also, the melting point is relatively high at 776°C. Therefore, a mold material using potassium chloride as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

Furthermore, potassium carbonate (K ₂ CO ₃ ) is easily dissolved in water, with a solubility of 129.4 g (0° C.) in 100 g of water, and has a relatively high melting point of 891° C. Therefore, a mold material using potassium carbonate as a water-soluble inorganic binder is easily disintegrated by water, and a mold having high heat resistance can be produced.

The above-described various water-soluble inorganic binders, in the casting mold material according to the present invention, have a mass in the case of a solid, and a solid content conversion when considering only the solid content in the case of a liquid, as a refractory aggregate. It is used in an amount of 0.1 to 5 parts by mass, preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of. Among them, an amount of 0.2 to 2.0 parts by mass is particularly advantageously employed. Here, the measurement of solid content is carried out as follows. That is, 10 g of the sample was placed in an aluminum foil sample dish (length: 9 cm, width: 9 cm, height: 1.5 cm), weighed, placed on a heating plate maintained at 180 ± 1 ° C. After standing for 20 minutes, the sample pan is inverted and left on the heating plate for an additional 20 minutes. Next, the sample dish is taken out from the heating plate, allowed to cool in a desiccator, weighed, and the solid content (% by mass) is calculated according to the following equation.
Solid content (% by mass)
= {[mass of sample dish after drying (g) - mass of sample dish (g)]
/ [mass of sample dish before drying (g) - mass of sample dish (g)]}
×100

In the present invention, if the amount of the water-soluble inorganic binder used is too small, it becomes difficult for the dry mold material to form a coating layer on the surface of the refractory aggregate, and the mold material solidifies or hardens. In addition, in the wet mold material, the water-soluble inorganic binder is uniformly dispersed in the refractory aggregate ( template material) can be difficult to prepare. On the other hand, even if the amount of the water-soluble inorganic binder used is too large, in the dry mold material, an excessive amount of the water-soluble inorganic binder adheres to the surface of the refractory aggregate, resulting in uniformity. In addition, in both the dry and wet mold materials, the mold materials may adhere to each other and form nodules (composite particles) before the mold is molded. Therefore, it adversely affects the physical properties of the finally obtained mold, and also causes problems such as difficulty in removing sand from the core after metal is cast (removal of solidified mold material). become.

In the mold material according to the present invention, together with the water-soluble inorganic binder such as water glass, the average particle size is 0.01 μm or more and less than 50 μm, preferably 0.05 μm or more and 25 μm or less, more preferably 0.1 μm. The iron-containing compound powder having a size of 10 μm or more, more preferably 0.2 μm or more and 3 μm or less is contained. As described above, the mold material of the present invention contains a powdery iron-containing compound having an average particle size within a predetermined range. , Between the casting product and the mold, more specifically between the casting product and the solidified (hardened) binder, a moderate gap is formed due to the powder of the iron-containing compound. As a result, adhesion of the mold material and/or its solidified product to the cast product is effectively prevented. Further, the powdery iron-containing compound having an average particle size within a predetermined range used in the present invention exhibits excellent dispersibility in a water-soluble inorganic binder (and a mixture with water). Since such powdery matter exists in a well-dispersed state even in a mold made of the mold material of the present invention, the adhesion of the mold material and/or its solidified product to the casting product is In this way, unevenness is suppressed without causing unevenness on the outer surface of the product. In addition, by containing such a powdery iron-containing compound, a mold made with the mold material of the present invention has a high thermal conductivity and exhibits excellent collapsibility during casting. In addition, iron-containing compounds are inexpensive compared to other metal-containing compounds, have a small impact on the manufacturing cost of mold materials, and have excellent thermal conductivity and high specific heat, so the final product The risk of adversely affecting the physical properties of the mold used is very small.

Here, the iron-containing compound used in the present invention means a compound having an iron atom, in other words, all compounds having Fe in the chemical formula. Specifically, iron, iron alloys, Examples include iron oxide, iron oxyhydroxide, iron hydroxide, mixed crystal ferrite in which a part of iron oxide is replaced with another metal, and the like. In addition, in the present invention, iron oxide is advantageously used in consideration of the risk of fire and explosion because the iron-containing compound powder is used. Examples of iron oxide include ferrous oxide, ferric oxide, triiron tetroxide (magnetite), iron oxyhydroxide, iron hydroxide, maghemite, and ferrite. Of these iron oxides, those having magnetism, specifically magnetite, maghemite, ferrite, and mixtures of two or more of these are particularly preferred. The magnetic iron oxide powder exhibits better dispersibility in water-soluble inorganic binders (and mixtures with water), so castings made with the final mold Product WHEREIN: It can suppress generation|occurrence|production of the surface roughness more effectively. It should be noted that having magnetism means having a magnetizing ability.

The mold material according to the invention also has the advantage that the regeneration of the refractory aggregate recovered after casting with molds made of such mold material can be advantageously carried out. That is, after casting using a mold made of the mold material of the present invention, after recovering the refractory aggregate to which the water-soluble inorganic binder containing the powder of the iron-containing compound adheres, the recovered refractory A polishing treatment is performed in which the aggregate is polished to scrape off the water-soluble inorganic binder adhering to its surface. The powdery iron-containing compound is dispersed in the solid matter of the water-soluble inorganic binder that has been scraped off. By carrying out the magnetic separation treatment to separate from the material, it becomes possible to separate the solid matter of the water-soluble inorganic binder scraped off by the polishing treatment from the refractory aggregate more easily using magnetic force. It is possible to more efficiently remove even fine particles of the solid matter of the inorganic binder. When regenerating the refractory aggregate according to such a regenerating method, magnetic materials such as magnetite, maghemite, ferrite, and mixtures of two or more of these are used as the iron-containing compound contained in the mold material. is more preferred.

In addition, the shape of the powder of the iron-containing compound is not particularly limited, and it is possible to use powder having a spherical shape, a polyhedral shape (hexahedron, octahedron, etc.), a needle shape, a columnar shape, or the like. However, spherical powder is preferably used. Among iron-containing compound powders having a spherical shape, those having an aspect ratio (minor axis/major axis) of 0.7 or more, preferably 0.8 or more, and more preferably sphericity. is 0.9 or more. Spherical powder is easy to loosen and hard to agglomerate, so it is easy to disperse in a water-soluble inorganic binder (and a mixture with water), and the fluidity of the mixture is improved when manufacturing (preparing) the mold material. become good. The sphericity of a powdery material exhibiting a spherical shape is defined by randomly selecting 10 single particles in observation with a scanning electron microscope and obtaining an aspect ratio (minor axis/major axis of ratio) means the average value.

Furthermore, the powdery iron-containing compound used in the present invention is mixed with the water-soluble inorganic binder that together constitutes the mold material. It is desirable to have the following properties between it and the agent. That is, when an aqueous solution containing 30% by mass of a water-soluble inorganic binder as a solid content is used as a blank solution, and the transmittance of light at a wavelength of 660 nm is 100%, the iron-containing compound is added to 100 parts by mass of the blank solution. It is desirable that the average transmittance of light at a wavelength of 660 nm of the dispersion obtained by mixing 5 parts by mass of the powdery material is 20% or less. More specifically, assuming that the transmittance of light with a wavelength of 660 nm in a blank liquid (an aqueous solution containing 30% by mass of a solid content of a water-soluble inorganic binder) is 100%, iron-containing per 100 parts by mass of the blank liquid Add 5 parts by mass of powder of the compound, mix and stir to prepare a dispersion, and use a spectrophotometer for the dispersion 15 minutes after the preparation (15 minutes after the end of mixing and stirring) and measure the transmittance of light with a wavelength of 660 nm three times. Then, the iron-containing compound powder having an average transmittance of 20% or less, preferably 10% or less in the dispersion for light having a wavelength of 660 nm, calculated from the three measurements, is used in the present invention. It is used to advantage. The fact that the average value of the transmittance of light with a wavelength of 660 nm in the dispersion is 20% or less means that the iron-containing compound powder contained in the dispersion exists in a good dispersed state in the dispersion. This means that the iron-containing compound powder exhibits high dispersibility even in a water-soluble inorganic binder (and/or its aqueous solution).

As a method for directly confirming the dispersed state of the iron-containing compound powder in the mold, a method of measuring the color difference: ΔE using a color difference meter can be exemplified. That is, when the powder of the iron-containing compound is poorly dispersed in the mold, the color difference between the mold and the mold that does not contain the powder of the iron-containing compound: the value of ΔE is low. Color difference: ΔE tends to be high when is good. Accordingly, when the color difference ΔE is 1.0 or more, preferably 2.0 or more, it can be determined that the iron-containing compound powder is well dispersed in the mold. In a mold in which the iron-containing compound powder is well dispersed, a more uniform gap is formed between the mold surface and the cast product, and the mold material and/or its solidified product adheres to the cast product. is more effectively suppressed, and the decrease in mold strength due to agglomeration of iron-containing compound powders is also advantageously suppressed.

The powdery iron-containing compound described in detail above should be added in an amount of 1 to 500 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder in order to advantageously enjoy the effects of its blending. It is contained in the mold material of the present invention in an amount that is preferably 10 to 300 parts by mass, more preferably 20 to 200 parts by mass.

Further, in the casting mold material according to the present invention, it is preferable that a surface active agent is further contained together with the above powdery iron-containing compound. By incorporating a surfactant, there is an advantage that the water permeability of the mold material of the present invention, in other words, the wettability with water is improved. More specifically, with respect to the dry mold material containing a surfactant according to the present invention, when water is supplied during mold molding, a surfactant is formed between the supplied water and the water-soluble inorganic binder. Through the mediation of the agent, even a small amount of moisture can effectively wet the entire mold material. In the case of supply, it is possible to minimize the time required for water vapor ventilation), and 2) As a result of suppressing the amount of water supplied to the mold (molding cavity) to a small amount, it is possible to mold In the casting mold, it is possible to advantageously enjoy effects such as exhibiting excellent strength in addition to being excellent in releasability from the mold. Furthermore, with respect to the surfactant-containing wet template material according to the present invention, 1) the presence of the surfactant minimizes the amount of water added during its preparation (manufacturing). 2) the surface tension of water is suppressed and the fluidity of the mold material is improved; and 3) the molded mold has excellent releasability from the mold. In addition to this, it is possible to advantageously enjoy effects such as exhibiting excellent strength.

Here, the amount of surfactant contained in the mold material of the present invention is desirably 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder. , Among them, 0.5 to 15.0 parts by mass is preferable, and 0.75 to 12.5 parts by mass is particularly preferable. If the amount of the surfactant contained is too small, the above-mentioned effects may not be advantageously obtained. No improvement is observed, and depending on the surfactant, the water-soluble inorganic binder may not solidify when dried, and even if an attempt is made to obtain a dry mold material, it may not be possible. , is not a good idea from a cost-effectiveness point of view. In the present invention, any of cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, silicone surfactants and fluorosurfactants can be used as surfactants. can also be used.

Specific examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, and imidazolinium salts. Examples of anionic surfactants include fatty acid soaps, N-acyl-N-methylglycine salts, N-acyl-N-methyl-β-alanine salts, N-acylglutamates, alkyl ether carboxylates, acyl peptide, alkylsulfonate, alkylbenzenesulfonate, alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkylsulfoacetate, α-olefinsulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol Sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglysulfate, fatty acid alkylolamide sulfate, alkyl ether phosphorus acid ester salts, alkyl phosphate salts, and the like. Furthermore, amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine, and the like. In addition, nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, polyoxyethylene alkylphenyl ethers (e.g., Emulgen 911), polyoxyethylene sterol ethers, polyoxyethylene lanolin derivatives. , polyoxyethylene polyoxypropylene alkyl ether (e.g. Newpol PE-62), polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, Polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetylene glycol, Acetylene alcohol etc. are mentioned.

Among various surfactants, those having a siloxane structure as a non-polar site are called silicone-based surfactants, and those having a perfluoroalkyl group are called fluorine-based surfactants. Examples of silicone surfactants include polyester-modified silicones, acrylic-terminated polyester-modified silicones, polyether-modified silicones, acrylic-terminated polyether-modified silicones, polyglycerin-modified silicones, aminopropyl-modified silicones, and the like. In addition, fluorine-based surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, perfluoroalkyltrimethylammonium salts, perfluoroalkylethylene oxide adducts, and perfluoroalkyl groups. containing oligomers, and the like.

In the present invention, various surfactants as described above can be used alone or in combination of two or more. However, some surfactants may react with the water-soluble inorganic binder and may lose or lose their surfactant ability over time. is used, anionic surfactants, nonionic surfactants and silicone surfactants that do not react with such water glass are advantageously used.

Furthermore, the casting mold material according to the present invention may contain various known additives, if necessary, in addition to the surfactants described above. When adding such additives to the mold material, a method of preliminarily blending a predetermined additive with a water-soluble inorganic binder and then kneading or mixing with a refractory aggregate, or a method of kneading or mixing with a water-soluble inorganic A method of adding a predetermined additive to the refractory aggregate separately from the caking agent and uniformly kneading or mixing the whole is adopted.

Moisture resistance improvers can be exemplified as additives that can be used in the present invention. In the present invention, any moisture resistance improver conventionally used in mold materials can be used as long as it does not impair the effects of the present invention. Specifically, carbonates such as zinc carbonate, basic zinc carbonate, iron carbonate, manganese carbonate, copper carbonate, aluminum carbonate, barium carbonate, magnesium carbonate, calcium carbonate, lithium carbonate, potassium carbonate, sodium carbonate, tetraborate Sodium, potassium tetraborate, lithium tetraborate, ammonium tetraborate, calcium tetraborate, strontium tetraborate, silver tetraborate, sodium metaborate, potassium metaborate, lithium metaborate, ammonium metaborate, metaboric acid Borates such as calcium, silver metaborate, copper metaborate, lead metaborate, magnesium metaborate, sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate, titanium sulfate, aluminum sulfate, Sulfates such as zinc sulfate and copper sulfate, sodium phosphate, sodium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, lithium phosphate, lithium hydrogen phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, aluminum phosphate , phosphates such as zinc phosphate, lithium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide, hydroxides such as zinc hydroxide, silicon, zinc, magnesium, aluminum , oxides of calcium, lithium, copper, iron, boron, zirconium, and the like. Among them, basic zinc carbonate, sodium tetraborate, potassium metaborate, lithium sulfate, and lithium hydroxide are particularly advantageous in improving moisture resistance when water glass is used as the water-soluble inorganic binder. It is possible. Moisture resistance improvers such as those mentioned above may be used alone, or may be used in combination of two or more. Some of the compounds listed above as moisture resistance improvers include compounds that can be used as water-soluble inorganic binders. When using the agent, it can act as a moisture resistance improver, and when water glass is used as the water-soluble inorganic binder, it acts more effectively as a moisture resistance improver.

The amount of such a moisture resistance improver used is generally 0.5 to 10% by mass, preferably 1 to 8% by mass, based on the solid content in the water-soluble inorganic binder. . In order to advantageously enjoy the effect of adding the moisture resistance improver, it is desirable that the amount used is 0.5% by mass or more. is desirably set to 10% by mass or less because there is a risk of causing problems such as a reduction in the strength of the mold finally obtained.

Nitrates such as alkali metal nitrates and alkaline earth metal nitrates may be added in order to improve the collapsibility of the template. It is also possible to add polyhydric alcohols, water-soluble polymer compounds, carbohydrates, sugars, proteins, inorganic compounds, etc. in order to increase the viscosity and improve mold releasability. The total amount of such additives used is generally about 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, based on 100 parts by mass of the solid content of the water glass. is more preferable, and 2 to 15 parts by mass is particularly preferable.

Furthermore, as other additives, it is also effective to contain a coupling agent that strengthens the bond between the refractory aggregate and the water-soluble inorganic binder. A coupling agent or the like can be used. It is also effective to contain a lubricant that contributes to the improvement of the fluidity of the mold material. For example, waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; Fatty acid amides; alkylene fatty acid amides such as methylenebisstearic acid amide and ethylenebisstearic acid amide; stearic acid, stearyl alcohol; stearic acid metal salts such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate; Acid monoglycerides, stearyl stearates, hydrogenated oils and the like can be used. Furthermore, release agents include paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, vermiculite, fluorine-based release agent, silicone-based release agent. Agents and the like can also be used. These other additives are generally contained in a proportion of 5% by mass or less, preferably 3% by mass or less, relative to the solid content in the water-soluble inorganic binder.

By the way, when producing a dry mold material having room temperature fluidity according to the present invention, generally, a water-soluble inorganic binder in the form of an aqueous solution is added as a binder to the refractory aggregate. The refractory aggregates are kneaded or mixed together with additives that are used accordingly to prepare a mixture in which the surface of the refractory aggregate is uniformly covered with the water-soluble inorganic binder, and then the mixture is prepared. By evaporating (evaporating) the moisture contained in the mixture, a method of obtaining the desired dry powdery molding material (dry coated sand) having normal temperature fluidity is adopted. In such a method, it is necessary that the moisture in the mixture evaporate rapidly before the solidification or hardening of the water-soluble inorganic binder proceeds. In contrast, after adding (mixing) the water-soluble inorganic binder in the form of an aqueous solution, within 5 minutes, more preferably within 3 minutes, the contained water is removed to form a dry coated sand. is desirable. If the transpiration time becomes longer, the kneading (mixing) cycle becomes longer, productivity decreases, and the water-soluble inorganic binder becomes inactive due to longer contact time with CO ₂ in the air. This is because the risk of causing When water glass is used as the water-soluble inorganic binder, the water content in the dry coated sand obtained in this manner is 5 to 55% by mass with respect to the solid content of the water glass. It is preferably adjusted to 10 to 50% by mass, more preferably 20 to 50% by mass.

In the manufacturing process of such a dry coated sand (mold material), as one of the effective means for rapidly evaporating the moisture in the mixture, the refractory aggregate is preheated. In addition, a technique of kneading or mixing a water-soluble inorganic binder in the form of an aqueous solution to prepare a mixture is adopted. By kneading or mixing the water-soluble inorganic binder in the form of an aqueous solution with the preheated refractory aggregate, the water derived from the water-soluble inorganic binder in the form of the aqueous solution is , the heat of such refractory aggregates can transpire very quickly, thereby effectively reducing the water content of the resulting mold material, resulting in a dry state with room-temperature fluidity. of coated sand is advantageously obtained. The preheating temperature of the refractory aggregate is appropriately selected according to the type and amount of the water-soluble inorganic binder used, and the amount of water in the aqueous solution of the water-soluble inorganic binder. In the case of water glass, for example, it is generally desirable to heat the refractory aggregate to a temperature of about 100 to 160°C, preferably about 100 to 140°C. If the preheating temperature is too low, the water cannot evaporate effectively and it takes a long time to dry the mixture. Also, if the preheating temperature is too high, solidification (hardening) of the water-soluble inorganic binder component proceeds during cooling of the resulting coated sand (mold material), and in addition, formation of composite particles also proceeds. Therefore, there is a possibility that problems will occur in the function as a mold material, particularly in physical properties such as strength.

On the other hand, when producing a wet mold material that does not have room temperature fluidity, it is generally necessary to add a water-soluble inorganic binder in the form of an aqueous solution to a refractory aggregate at room temperature. Room-temperature fluidity consisting of a mixture in which a refractory aggregate and an aqueous water-soluble inorganic binder (and additives) are uniformly mixed by kneading or mixing together with additives accordingly. A technique is employed to obtain a wet mold material (coated sand) that does not have any properties. The wet mold material (coated sand), which does not have room temperature fluidity, is adjusted to a wet state if necessary. is used, the water content of the mold material (coated sand) is more than 55% by weight, preferably 70 to 900% by weight, more preferably 95 to 500% by weight of the solid content of the water glass. % and manufactured. In the wet mold material (coated sand) with the water content adjusted in this way, it is dried by the blown air when filling the mold during mold making, and the filling into the mold is hindered. In addition to being able to effectively prevent this and keep the wet mold material (coated sand) moist, it is also excellent in molds made using such mold materials (coated sand). It is given a characteristic. In the present invention, a mold material in a wet state that does not have normal temperature fluidity refers to a mold material whose dynamic angle of repose cannot be measured regardless of the water content.

The mold material according to the present invention may be used in either a dry state or a wet state. It is more desirable to have a dry state with room temperature fluidity.

Further, in the dry or wet mold material manufacturing process, the iron-containing compound powder is pre-mixed with an aqueous water-soluble inorganic binder and added to the refractory aggregate, They may be kneaded or mixed, may be added separately during kneading and kneaded, or may be kneaded with a time lag during kneading. Therefore, in the case of the dry mold material according to the present invention, the coating layer covering the surface of the refractory aggregate is composed of a layer in which a water-soluble inorganic binder and an iron-containing compound powder are mixed. Alternatively, a layer containing a water-soluble inorganic binder and a powder of an iron-containing compound may be formed around the outer periphery of a layer made of a water-soluble inorganic binder. In order to enjoy the effect of (1) more advantageously, the coating layer covering the surface of the refractory aggregate is preferably a layer in which the water-soluble inorganic binder and the powdery iron-containing compound are mixed. In addition, without using a powder of an iron-containing compound, a dry state in which the surface of a refractory aggregate is covered with a coating layer made of a water-soluble inorganic binder is produced, In addition, water, a powder of an iron-containing compound, and, if necessary, other additives are added to such a dry state, and the mixture is kneaded and used as the mold material. In the production of the dry or wet mold material according to the present invention, the water-soluble inorganic binder used as the binder is solid. In some cases, it is used after being dissolved in water in advance. Even a liquid water-soluble inorganic binder can be diluted with water to adjust its viscosity. It is also possible to separately add a solid or liquid water-soluble inorganic binder and water to the refractory aggregate or the like during kneading or mixing with the refractory aggregate or the like.

Using the mold material (coated sand) thus obtained according to the present invention, the state of the mold material (coated sand) to be used, that is, the state of the mold material (coated sand) to be used, i. It is roughly classified as follows depending on whether it is in a dry state with fluidity at room temperature or in a dry state.

When a mold is molded using a wet mold material (coated sand) that does not have normal temperature fluidity, the mold material is filled into the mold cavity of the mold that provides the desired mold, while the mold is closed. It is heated to a temperature of 80-300° C., preferably 100-200° C. and held in the mold until the mold material filled therein is dry. The solidification or hardening of the filled mold material progresses by heating and holding in such a mold.

That is, by filling and holding a wet mold material (coated sand) that does not have normal temperature fluidity into the cavity of the heated mold, the mold material that constitutes the filling phase in the cavity is wet. As a result, the refractory aggregates are bonded to each other via the water-soluble inorganic binder to form an assembly (combination) of mold materials exhibiting an integral mold shape. The water-soluble inorganic binder usually solidifies by evaporation of water to dryness if no additives are added, and if an oxide or salt is added as a curing agent, It will harden. In the present invention, the assembly (bond) of the mold material includes both those that are simply solidified and those that are cured with a curing agent. In addition, it should be understood that the expression "solidified material" in this specification is used in the meaning including "cured material".

In addition, the wet mold material (coated sand) that does not have normal temperature fluidity is preheated to 80 to 300° C. and held for a certain period of time in the mold that is kept at that temperature. , and is dried by evaporation of water to solidify or harden. The heat retention temperature for this preheating is 80 to 300.degree. C., preferably 100 to 200.degree. C., more preferably 120 to 180.degree. From the viewpoint of accelerating drying and shortening molding time and improving moisture resistance strength by additives, the temperature is preferably 80 ° C. or higher, and moisture is absorbed before the bonds between the refractory aggregates are sufficiently formed. The temperature is preferably 300° C. or less from the viewpoint of preventing the occurrence of the problem that the mold strength does not develop due to evaporation. By heating the mold at a temperature within such a temperature range, the moisture resistance strength of the finally obtained mold can be improved and the drying of the mold material can be advantageously advanced. In addition, while the mold material is held in the mold, hot air or superheated steam may be blown into the mold in order to promote drying. In order to accelerate the curing, carbon dioxide (CO ₂ gas), an ester, or the like as a curing accelerator may be made gaseous or misted and passed through the mold.

On the other hand, when a mold is made using a dry mold material (coated sand) having room temperature fluidity, the first method is to wet the dry mold material by kneading it with water at the mold making site. The wet mold material is preheated to 80 to 300° C. and held at that temperature for a certain period of time in the molding cavity of the mold until the mold material is dried. . In the first method, a temperature of 80 to 300.degree. C., preferably 90 to 250.degree. C., more preferably 100 to 200.degree. As a second method, the molding cavity of a mold preheated to 80 to 200 ° C. and kept at that temperature is filled with a dry mold material, and then steam is blown into the molding cavity, It is intended to allow water vapor to pass through the filled phase of the mold material, and the water vapor is supplied to the mold material in a dry state to bring it into a wet state. It is held in the mold until dry. In the second method, the heat retention temperature of the mold by preheating is 80 to 200.degree. C., preferably 90 to 150.degree. C., more preferably 100 to 140.degree.

In the first method, when kneading (mixing) the dry mold material (coated sand) and water, the dry mold material is transported to the molding site where the mold is manufactured, and then to the molding site. Then, after adding water to make it wet, the resulting wet mold material is filled into a mold to mold the desired mold. In the step of adding water to the mold material to make it wet, it is sufficient to wet the mold material by simply putting the dry mold material and a predetermined amount of water into a suitable mixer and mixing them. Therefore, it can be carried out with extremely simple work, and can be carried out very simply and easily even at a molding site where the working environment is bad. When water is added, one or more substances selected from other additives, curing accelerators, and water-soluble inorganic binders for readjusting mold strength may be added together. Moreover, water may be used in which water is contained in a solution.

In the second method, when steam is blown into the mold material (filling phase) filled in the molding cavity, the temperature of the steam is generally about 80 to 150°C, more preferably about 95 to 120°C. It is said that If high-temperature steam is used, a large amount of energy is required for its production, so a steam temperature of around 100° C. is particularly advantageous. In addition, as the pressure of water vapor to be aerated according to the present invention, a gauge pressure of about 0.01 to 0.3 MPa, more preferably about 0.01 to 0.1 MPa is advantageously adopted. Furthermore, as the ventilation time, generally, a ventilation time of about 2 seconds to about 60 seconds is adopted. This is because if the aeration time of the water vapor becomes too short, it becomes difficult to sufficiently wet the surface of the dry mold material. This is because problems such as dissolution and outflow of the water-soluble inorganic binder constituting the layer may occur.

Here, in the above-described first and second methods, hot air or superheated steam is blown into the mold to actively dry the filled phase composed of the wet mold material, and the filled phase is ventilated. A method to make it so is preferably adopted. Such ventilation of hot air or superheated steam (hot air, etc.) quickly dries even the inside of the filled phase of the mold material, thereby promoting the solidification or curing of the filled phase more advantageously, thereby curing. In addition to advantageously increasing the speed, the properties of the resulting mold such as bending strength can be advantageously improved, and the molding time of the mold can be advantageously shortened. In the first method, the solidification or hardening of the filling phase is more advantageously performed, for example, before the aeration of hot air or the like, and in the second method, for example, between the aeration of water vapor and the aeration of hot air or the like. In order to accelerate the curing, carbon dioxide (CO ₂ gas), ester, etc. may be gaseous or misted as a curing accelerator, and the carbon dioxide, ester, etc. should be used to neutralize the water-soluble inorganic binder. It is possible to further promote the solidification or curing. It should be noted that the aeration of carbon dioxide, ester, etc. may be performed simultaneously with the aeration of hot air or the like in the first method, or with the aeration of water vapor or with the aeration of hot air or the like in the second method. No problem.

Examples of the curing accelerator include carbon dioxide (carbonated water), methyl formate, ethyl formate, propyl formate, γ-butyrolactone, γ-propionlactone, ethylene glycol diacetate, diethylene glycol diacetate, glycerin diacetate, triacetin, In addition to esters such as propylene carbonate, organic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, carboxylic acid, p-toluenesulfonic acid, and monohydric alcohols such as methanol, ethanol, butanol, hexanol, octanol, etc. , can be exemplified. These curing accelerators may be used alone or in combination of two or more. These curing accelerators should be gaseous or misted while the mold is held, and should be passed through the mold. A curing accelerator may be added to the mold material along with the water.

In addition to the methods described above, various known molding techniques can be appropriately adopted as the method for manufacturing a mold using the mold material according to the present invention. For example, layers of the mold material are sequentially laminated. It is also possible to adopt a layered manufacturing technique in which a three-dimensional mold is directly formed by hardening the portion corresponding to the desired mold while hardening.

Using molds manufactured according to various manufacturing methods as described above, predetermined molten metal is cast to manufacture the desired metal parts (cast products). , It is not particularly limited, and various known casting techniques can be employed.

Since the mold material according to the present invention contains a powder of an iron-containing compound, the refractory aggregate can be advantageously regenerated, for example, by following the regeneration method detailed below. When carrying out the recycling method described below, after casting using a mold made of the mold material of the present invention, the used mold is pulverized or cracked according to a known method using a pulverizer or the like. It is crushed and collected into small pieces, preferably particles having a size of several millimeters or less, and more preferably particles having a size close to each particle of the refractory aggregate.

The method for recycling recovered refractory aggregates described in detail below is mainly intended for refractory aggregates recovered from used molds after casting as described above. Refractory aggregate recovered in the form of mold material discharged in the molding process of All of these recovered refractory aggregates contain powdered iron-containing compounds in the water-soluble inorganic binder that adheres to them. The refractory aggregate containing the iron-containing compound powder in the water-soluble inorganic binder forms the whole recovered refractory aggregate to which the recycling method of the present invention is applied. Although it is generally a thing, there is no problem even if it constitutes a part of it. More preferably, it is present at a rate of 20% by mass or more. Needless to say, the higher the ratio of the refractory aggregate containing the iron-containing compound in the recovered refractory aggregate, the more advantageous the characteristics of the present invention can be exhibited. As other refractory aggregates used together with refractory aggregates containing such iron-containing compounds, regardless of the presence or absence of iron-containing compounds and regardless of the types of clay components, Any refractory aggregate recovered from the refractory or casting process is of interest.

In the method for regenerating recovered refractory aggregates according to the present invention, in order to regenerate the recovered refractory aggregates as described above, first, the A polishing treatment is performed to scrape off the solid matter of the water-soluble inorganic binder, and then the scraped off solid matter is attracted to the magnet by the magnetic force of the iron-containing compound powder contained in the solid matter. Magnetic separation treatment is carried out to separate from the refractory aggregate using force (action).

In the grinding process, the collected refractory aggregate is ground to scrape off the solid matter of the water-soluble inorganic binder, which is a solid substance remaining on the surface of the aggregate, and separate it from the aggregate. Specifically, the recovered refractory aggregate is put into a conventionally known polishing apparatus, and a water-soluble inorganic binder such as water glass that coats or adheres to the surface of the aggregate is used as the caking component. The solid binder is scraped off. At that time, if the refractory aggregate that is put in is in a nodular state, it is ground one by one by the rotating rotor of the polishing machine. After being pulverized into particles, the surface is further polished. The polishing method in this polishing process is not particularly limited, but for example, a polishing method using a rotary reclaimer, a sand fresher, a sand shiner, or the like is appropriately adopted. In addition, the polishing conditions such as the polishing time in the polishing process are appropriately selected according to the state of solid matter adhered to the surface of the recovered refractory aggregate.

In addition, the refractory aggregate taken out from the grinding treatment step contains a mixture of solid powder of the water-soluble inorganic binding agent scraped off by the grinding treatment, and such a binding agent The powder or dust thereof cannot be sufficiently or reliably removed by a dust collector or the like normally provided in the polishing apparatus, and is physically attached to the surface of the refractory aggregate. Therefore, in the present invention, the processed material taken out from such a polishing process is further subjected to a magnetic separation process using a suitable magnetic separator to obtain a solid water-soluble inorganic caking. By utilizing the action (force) that the iron-containing compound powder dispersed and contained in the binder powder is attracted to a magnet, such a binder powder or dust can be used as a refractory bone. It is separated from the material. That is, the magnetic separation treatment is applied to the ground material in which the refractory aggregate and the solid binder powder are mixed, and the refractory aggregate to which the binder is not adhered is separated from the magnetic separator. The solid binder powder containing iron-containing compounds is recovered in the iron-containing compound recovery section provided below the magnetic separator while the solid binder powder containing iron-containing compounds is recovered in the refractory aggregate recovery section provided below. -ing

As magnetic separators used in the magnetic separation process, various systems such as a semi-magnetic outer ring system, a suspension system, and a magnet pulley system are known. The structure and form are not particularly limited as long as the solid binder powder containing the iron-containing compound can be separated from the substance, and known ones can be appropriately adopted. Become. Also, the magnetic force in such a magnetic separator should have a magnetic flux density of 500-10000 gauss, preferably 1000-8000 gauss, for good separation of the refractory aggregate and the solid binder powder containing the iron-containing compound. Gauss, more preferably in the range of 1500-6000 Gauss. If the magnetic flux density is lower than 500 gauss, the binder powder cannot be advantageously separated by magnetic separation treatment. They are strongly attracted to the magnetic separator and become magnetically attached, causing problems such as difficulty in recovering them.

As described above, since the mold material according to the present invention contains a powdery substance of an iron-containing compound, it is inevitable that the solid matter of the water-soluble inorganic binder adhering to the recovered refractory aggregate contains iron. A solid water-soluble inorganic binder (powder) that is scraped off by grinding and magnetic separation of such recovered refractory aggregate, which contains a powdery compound. can be easily separated from the refractory aggregate using magnetic forces. Moreover, the scraped solid binder powder adhering to the surface of the refractory aggregate due to static electricity or the like, which cannot be completely removed by ordinary dust collection or the like, can be easily separated from the aggregate. As described above, according to the method for recycling recovered refractory aggregates according to the present invention, it is possible to advantageously provide recycled refractory aggregates of good quality. Furthermore, the refractory aggregate thus regenerated is obtained by removing the scraped solid water-soluble inorganic binder powder sufficiently and reliably, so that it can be used again for molding. When used, the reduction in strength of the obtained mold can be effectively suppressed, and a mold having excellent strength can be provided.

By the way, in the recycling method of the present invention, it is also possible to advantageously employ a calcining treatment for calcining the recovered refractory aggregate to be recycled. This firing treatment can be performed before the polishing treatment according to the present invention, and can also be performed between such polishing treatment and magnetic separation treatment, or after magnetic separation treatment. It is also possible to carry out two or more times before, during and after the polishing/magnetic separation treatment. In addition, for the firing treatment of such recovered refractory aggregates, for example, a roasting furnace such as a rotary kiln or a tunnel kiln is used, and the recovered refractory aggregates are charged into the roasting furnace at any time while firing. is adopted.

By carrying out such a calcination treatment prior to the polishing treatment or the magnetic separation treatment according to the present invention, it becomes possible to burn and remove deposits, dust, and impurities on the refractory aggregate. The firing temperature in the roasting furnace in such firing treatment is generally about 200 to 700°C, preferably about 300 to 700°C, more preferably about 350 to 650°C, and even more preferably about 400 to 600°C. It will be done. If the firing temperature is lower than 200°C, there is a risk that deposits, dust, and impurities on the refractory aggregate will not burn sufficiently. As the force attracted to the magnet decreases, the water-soluble inorganic binder is sintered, causing problems such as difficulty in peeling from the refractory aggregate.

Further, in the case where such firing treatment is carried out after the magnetic separation treatment according to the present invention, even if the binding agent adheres to the recovered refractory aggregate, the water-soluble inorganic It becomes possible to deactivate the caking agent. The firing temperature in the roasting furnace in such firing treatment is generally about 200 to 1000°C, preferably about 300 to 900°C, more preferably about 350 to 850°C, still more preferably about 400 to 800°C. It is desirable to have If the firing temperature is lower than 200°C, the water-soluble inorganic binder adhering to the refractory aggregate may not be sufficiently deactivated. On the other hand, if the baking temperature exceeds 1000° C., the roasting furnace may be overloaded and the heating cost may increase.

Furthermore, in the method for regenerating recovered refractory aggregate according to the present invention, it is also effective to classify the treated refractory aggregate taken out from the grinding treatment or magnetic separation treatment. be. If firing treatment is performed after polishing treatment or magnetic separation treatment according to the present invention, this classification treatment is performed after such firing treatment. In addition, such a classification process consists of a dust collection step in which the treated refractory aggregate is made to flow by an air flow, fine powder contained in the treated refractory aggregate is removed by a dust collector, and a sieve is used to remove the refractory aggregate. and a sieving step for removing foreign matter contained in the treated elastic aggregate. Specifically, in the dust collection process, the treated refractory aggregate is made to flow by an air flow, and the shavings, dust, and dust that could not be removed in the previous steps contained in the treated refractory aggregate are removed. Fine powder such as fine powder is removed by the dust collector in a driven state, whereby fine residues are effectively removed from the treated refractory aggregate after grinding or magnetic separation. In addition, in the sieving process, a sieve is used to classify the particle size of the treated refractory aggregate, thereby removing foreign matter contained in such treated refractory aggregate that could not be removed in the previous steps. is done. This removes large residues from the refractory aggregate after magnetic separation and selectively extracts aggregates of appropriate particle size.

The classification process employed here is not limited to the one having the dust collection process and the sieving process as described above. There is no problem at all, and there is no problem even if the dust collection process is executed after the sieving process is executed. Furthermore, the classification step can employ any other known technique as long as it is a technique capable of classifying the refractory aggregate into predetermined sizes.

Then, as described above, the refractory aggregate regenerated by the method for regenerating recovered refractory aggregate according to the present invention is again provided to the molding process of the mold, and aggregate (castings) capable of giving a mold with excellent characteristics It will be used advantageously as sand).

It should be noted that the above-described casting mold material and manufacturing method thereof, casting mold manufacturing method, and recovered refractory aggregate recycling method according to the present invention are interpreted in any limited way by the specific descriptions of the above-described exemplary embodiments. Based on the knowledge of those skilled in the art, the present invention can be implemented in embodiments with various changes, modifications, improvements, etc., and such embodiments are considered to be the present invention. It should be understood that any of them belong to the scope of the present invention as long as they do not deviate from the spirit of the present invention.

For example, in each step of the polishing treatment and the magnetic separation treatment in the above-described method for regenerating the recovered refractory aggregate, fine powder is scattered in the air during the treatment, so the dust collection step is Alternatively, the operation of vacuuming the atmosphere to remove fines during each step will be suitably employed.

Some examples of the present invention will be shown below to clarify the present invention more specifically, but the present invention is not subject to any restrictions by the description of such examples. needless to say. Note that "%" and "parts" shown in the following description are based on mass unless otherwise specified. Further, in the following examples and comparative examples, the average particle size of the powder, the light transmittance of the dispersion of the powder, the water content of the coated sand (CS) serving as the mold material, the magnetization rate of the CS, and each CS The adhesion of sand (adherence of CS) and the surface roughness of the casting surface were measured and evaluated as follows.

(1) Average particle size of the powdery material About the average particle size of the powdery material, using a Microtrac particle size distribution analyzer (product name: MT3200II) manufactured by Nikkiso Co., Ltd., particles with an integrated value of 50% from the particle size distribution The diameter is measured as mean particle size ( _D50 ). In addition, when the average particle size of the powdery substances used in Examples and Comparative Examples was measured using the above-mentioned measuring device, the error between the published value of each manufacturer was within 10%. The average particle size of the powdery material indicates the published value of the manufacturer.

(2) Light transmittance of dispersion liquid of powdery material The transmittance of light with a wavelength of 660 nm is measured using a U-2800 manufactured by Hitachi High-Tech Science Co., Ltd., and the transmittance is adjusted to 100%. Next, 5 parts by mass of the powdery material is added to 100 parts by mass of the blank liquid and stirred for 1 minute to prepare a dispersion liquid. After 15 minutes have passed since the dispersion liquid is placed in a measurement container and allowed to stand still, the transmittance of light having a wavelength of 660 nm is measured. This measurement was performed three times, and the average value of the light transmittance calculated from the three measurements is shown in Tables 1 to 6 below as "light transmittance of dispersion".

(3) Water content of CS When water glass is used as a water-soluble inorganic binder, the water content in CS (water content relative to the solid content of water glass contained in CS) is measured and calculated according to the following procedure. did. 10 g of each CS was weighed and placed in a crucible that had been air-fired and weighed, and the amount of water (W1) in the CS was calculated using the mass loss (%) after exposure to heat at 900°C for 1 hour. It is calculated from the following formula (1). In addition, the weighing amount is measured to the fourth decimal place. Next, the solid content (B1) of water glass relative to CS is calculated using the following formula (2), and then from the water content (W1) in CS and the solid content (B1) of water glass relative to CS, The water content relative to the solid content of water glass (the water content of CS relative to the solid content of water glass in the coating layer: W2) is calculated using the following formula (3). W2 calculated as described above is shown as "moisture content" in Tables 1 to 6 below.
W1=[(M1−M2)/M3]×100 (1)
[W1: Moisture content in CS (%), M1: Total mass of crucible and CS before firing (g), M2: Total mass of crucible and CS after firing (g), M3
: mass of CS before firing (g)]
B1=[B2/(100+B2)]×(100−W1) (2)
[B1: Solid content (%) of water glass with respect to CS, B2: 100 of sand
Solid content (parts) of water glass added to parts, W1: water content in CS (%)]
W2=(W1/B1)×100 (3)
[W2: the water content of CS with respect to the solid content of water glass in the coating layer (
%), W1: water content in CS (%), B1: solid content of water glass to CS (%)]

(4) Magnetization Percentage of CS As for the dry CS, 100 g was taken out from the dry CS and used as a sample. On the other hand, as for the wet CS, after holding the CS in a dryer at 110° C. for 30 minutes, the dried CS was thawed, and 100 g of the thawed CS was taken out and used as a sample. The removed sample was attached to a magnet of 5000 gauss, and the magnetic attachment rate of the sample (CS) was calculated from the amount of the sample attached to the magnet using the following formula.
Magnetic adhesion rate (%) = [attached mass (g)] / [sample amount (g)] × 100

(5) Evaluation of adhesion state of CS First, as shown in FIG. Inside a cracked hollow main mold 6 (cavity diameter: 6 cm, height: 6 cm), a circular airless element 10 (diameter: 5 cm, height: 5 cm) having a skirting part 8 made using each CS is placed. , and fixed by the baseboard fixing portion 4, and then the half-split hollow main mold 6 is further adhered and fixed to each other to prepare the sand mold 12 for casting test. Next, molten aluminum alloy (temperature: 710±5° C.) was poured from the pouring port 2 of the sand mold 12 for casting test and allowed to solidify. 16 is taken out, and when it reaches room temperature, the casting is cut in half together with the inner core using a lathe or the like. After that, the core part was removed, and the adhesion of core sand (CS) to the casting was visually confirmed. In addition, in the present invention, evaluations of Δ and ◯ are regarded as acceptable. The evaluation results for each CS are shown in Tables 1 to 4 as "state of sand adhesion after casting".
◯: Adhesion of sand was not observed at all.
Δ: Adhesion of sand was observed on part of the casting surface.
x: Adhesion of sand was observed over the entire casting surface.

(6) Evaluation of surface roughness of casting surface For castings for which the sand adhesion state has been confirmed according to the above "(5) Evaluation of CS adhesion state", the surface roughness of the casting was visually and felt when touched with a finger. , was evaluated according to the following criteria. When sand (CS) adhered to the surface of the casting, the surface of the casting was evaluated after removing the adhering sand (CS) with a brass brush or the like. In the present invention, evaluations of Δ and ◯ are regarded as acceptable.
◯: There is almost no unevenness that can be visually observed, and fingertips are not caught.
Δ: Some unevenness is visually observed, but fingertips are not caught.
x: Large unevenness is visually recognized and the fingertip is caught.

-Production example 1 of wet CS-
Lunamos #60 (trade name, manufactured by Kao-Quaker Co., Ltd.), which is commercially available artificial sand for casting, is used as the refractory aggregate, and commercial product No. 2 sodium silicate (product Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.5, solid content: 41.3%) and magnetite powder as an iron-containing compound (spherical, average particle size: 0.3%). 25 μm) was prepared. For water glass in an amount equivalent to 1.0 parts (solid content: 0.41 parts) per 100 parts of aggregate (Lunamos #60), per 100 parts of aggregate (Lunamos #60) An amount of magnetite powder equivalent to 0.125 parts was added and mixed to form a liquid mixture, and then 100 parts of the aggregate (Lunamos #60) was added to a Shinagawa universal stirrer (5DM) at room temperature. -r type, manufactured by Dalton Co., Ltd.), and then the previously prepared liquid mixture (water glass + magnetite powder) is put into the stirrer and kneaded for 3 minutes until uniform. Stir mixed. After that, the mixed material was taken out from the stirrer to obtain a wet mold material (coated sand): CS1 consisting of a mixed material of aggregate, water glass and magnetite powder. When the water content of CS1 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 2 of wet CS-
A wet mold material: CS2 was obtained in the same manner as in Production Example 1 above, except that the amount of magnetite powder added was 0.25 parts. When the water content of CS2 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 3 of wet CS-
A mold material in a wet state: CS3 was obtained in the same manner as in Production Example 1 above, except that the amount of magnetite powder added was 0.50 parts. When the water content of CS3 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 4 of wet CS-
A wet mold material: CS4 was obtained in the same manner as in Production Example 1 above, except that the amount of magnetite powder added was 1.00 parts. When the water content of the obtained CS4 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 5 of wet CS-
A wet mold material CS5 was obtained in the same manner as in Production Example 3, except that magnetite powder having a spherical shape and an average particle size of 0.10 μm was used. When the water content of CS5 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 6 of wet CS-
A wet mold material CS6 was obtained in the same manner as in Production Example 3, except that magnetite powder having a spherical shape and an average particle size of 3.0 μm was used. When the water content of the obtained CS6 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 7 of wet CS-
A wet mold material: CS7 was obtained in the same manner as in Production Example 3, except that magnetite powder having an octahedral shape and an average particle size of 0.30 μm was used. When the water content of the obtained CS7 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 8 of wet CS-
In place of the magnetite powder, ferrite powder (needle-shaped, average particle size: φ0.2 × 1.0 µm) was used. Template material: CS8 was obtained. When the water content of the obtained CS8 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 9 of wet CS-
The above production example except that instead of the magnetite powder, iron oxide powder (needle-shaped, average particle size: φ0.08 × 0.8 μm) that does not correspond to either magnetite or ferrite was used. Wet mold material: CS9 was obtained following the same procedure as in 3. When the water content of the obtained CS9 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 10 of wet CS-
In Production Example 3 above, except that a commercially available anionic surfactant (trade name: Olfin PD-301, manufactured by Nissin Chemical Industry Co., Ltd.) was added in the proportion shown in Table 2 below. Following the same procedure as in Production Example 3, a wet mold material: CS10 was obtained. When the water content of CS10 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 11 of wet CS-
In the above Production Example 3, except that a commercially available nonionic surfactant (trade name: Olfine E1004, manufactured by Nissin Chemical Industry Co., Ltd.) was added at the ratio shown in Table 2 below. Wet mold material: CS11 was obtained following the same procedure as in 3. When the water content of CS11 obtained was measured, it was found to be an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 12 of wet CS-
Lunamos #60 (trade name, manufactured by Kao-Quaker Co., Ltd.), which is a commercially available artificial sand for casting, as a refractory aggregate, magnetite powder (spherical, average particle size: 0.25 μm) as an iron-containing compound, Further, sodium chloride (Na chloride), which is a water-soluble inorganic binder, was dissolved in water to prepare an aqueous sodium chloride solution having a solid component (concentration) of 20% by mass. Then, the aggregate (Lunamos #60) at room temperature is put into a Shinagawa type universal stirrer (5DM-r type, manufactured by Dalton Co., Ltd.), and 100 parts of the aggregate (Lunamos #60) is added with an aqueous sodium chloride solution. At a rate of 3.0 parts (solid component: 0.6 parts), magnetite powder is added at a rate of 0.50 parts to 100 parts of the aggregate (Lunamos #60), Added in stirrer. Here, the magnetite powder was added in a state in which it was previously mixed with an aqueous sodium chloride solution. After this addition, kneading was performed for 3 minutes in a stirrer, and stirring and mixing were performed until uniform. After that, the mixed material was taken out from the stirrer to obtain a wet mold material: CS12 consisting of a mixed material of aggregate, sodium chloride and magnetite powder. When the water content of the obtained CS12 was calculated, it was an amount corresponding to 79% by mass of the solid content of the sodium chloride aqueous solution, in other words, 79% by mass of the sodium chloride (solid content) contained in CS.

-Production example 13 of wet CS-
A wet mold material: CS13 was obtained according to the same procedure as in Production Example 1 above, except that the powdered magnetite was not used in Production Example 1 above. When the water content of the obtained CS13 was calculated, it was an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 14 of wet CS-
A wet mold material: CS14 was obtained in the same manner as in Production Example 3, except that magnetite powder having a spherical shape and an average particle size of 160.2 μm was used. When the water content of CS14 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Production example 15 of wet CS-
A wet mold material CS15 was obtained in the same manner as in Production Example 3, except that magnetite powder having a spherical shape and an average particle size of 106.5 μm was used. The water content of the obtained CS15 was calculated and found to be an amount corresponding to 140% by mass of the solid content of the water glass.

-Production example 16 of wet CS-
A wet mold material was prepared in the same manner as in Production Example 3 above, except that copper oxide powder (amorphous, average particle size: 32.1 μm) was used instead of magnetite powder: CS16 was obtained. When the water content of CS16 obtained was calculated, it was an amount corresponding to 140% by mass of the solid content of water glass.

-Molding Example I (Examples 1 to 12, Comparative Examples 1 to 4)-
CS1 to 16 (temperature: 20 ° C.) produced according to the above procedures were filled in a mold heated to 150 ° C., held in the mold, and filled in the mold. By solidifying (hardening) each of the CSs, a mold used as a test piece (φ50×50 cm) of a circular no-aerial element was produced. Tables 1 and 2 below show the CS used in producing the molds (test specimens) for Examples 1 to 12 and Comparative Examples 1 to 4.

As is clear from the results in Tables 1 and 2, in the mold obtained using the wet mold material (CS: coated sand) according to the present invention, the casting (cast product) produced using it Adhesion of the mold material (CS: coated sand) to the surface is effectively inhibited.

Next, a dry coated sand (CS) according to the present invention was produced and tested in the same manner as the wet CS.

-Production Example 17 of Dry CS-
Lunamos #60 (trade name, manufactured by Kao-Quaker Co., Ltd.), which is commercially available artificial sand for casting, is used as the refractory aggregate, and commercial product No. 2 sodium silicate (product Fuji Chemical Co., Ltd., molar ratio of SiO ₂ /Na ₂ O: 2.5, solid content: 41.3%) and magnetite powder as an iron-containing compound (spherical, average particle size: 0.3%). 25 μm) was prepared. For water glass in an amount equivalent to 1.0 parts (solid content: 0.41 parts) per 100 parts of aggregate (Lunamos #60), per 100 parts of aggregate (Lunamos #60) After adding an amount of magnetite powder equivalent to 0.50 part and mixing to form a liquid mixture, 100 parts of aggregate (Lunamos #60) heated to about 130 ° C. was added to a whirl mixer (Enshu Iron Works). ), and the previously prepared liquid mixture (water glass + magnetite powder) is added to the mixer and kneaded for 3 minutes to evaporate the water contained in the water glass. Stir and mix until the sand grain clumps collapse. Thereafter, sand grains are taken out from the mixer to obtain a dry mold material (coated sand): CS17 in which a coating layer containing water glass and a powder of an iron-containing compound is formed on the surface of the aggregate. rice field. The water content of the obtained CS17 was calculated and found to be an amount corresponding to 32% by mass of the solid content of the water glass in the coating layer.

-Production Example 18 of Dry CS-
In the above Production Example 17, a commercially available anionic surfactant (trade name: Olfine PD-301, manufactured by Nissin Chemical Industry Co., Ltd.) was further added at the ratio shown in Table 3 below. , a dry mold material: CS18 was obtained according to the same procedure as in Production Example 17 above. The water content of the obtained CS18 was calculated and found to be an amount corresponding to 34% by mass of the solid content of the water glass in the coating layer.

-Production Example 19 of Dry CS-
A dry mold material: CS19 was obtained in the same manner as in Production Example 17, except that the powdered magnetite was not used. The water content of the obtained CS19 was calculated and found to be an amount corresponding to 32% by mass of the solid content of the water glass in the coating layer.

-Production example 20 of dry CS-
A dry mold material: CS20 was obtained in the same manner as in Production Example 17, except that magnetite powder having a spherical shape and an average particle size of 106.5 μm was used. The water content of the obtained CS20 was calculated and found to be an amount corresponding to 34% by mass of the solid content of the water glass in the coating layer.

-Molding Example II (Examples 13-14, Comparative Examples 5-6)-
CS17 to 20 (temperature: 20 ° C.) produced according to each procedure described above was blown into a mold heated to 110 ° C. at a gauge pressure of 0.3 MPa, and after filling, further 0 Under a gauge pressure of 0.05 MPa, water vapor at a temperature of 99° C. was blown for 4 seconds to aerate the coated sand (CS) phase filled in the mold. Next, after such ventilation of water vapor is completed, hot air at a temperature of 150°C is blown for 2 minutes under a gauge pressure of 0.03 MPa to solidify (harden) the CS filled in the mold. , a mold used as a test piece (φ50×50 cm) of a circular aneuron was produced. Table 3 below shows the CS used to prepare the molds (test specimens) for Examples 13 and 14 and Comparative Examples 5 and 6.

-Molding Example III (Examples 15-16, Comparative Examples 7-8)-
CS17 to 20 (temperature: 20 ° C.) produced according to the above procedures are charged into a Shinagawa universal stirrer (5DM-r type, manufactured by Dalton Co., Ltd.) at room temperature, and water is added to 100 of CS. A wet-state CS (template material) was prepared by adding 1.0 part to 1 part in a stirrer and stirring. The CS in a wet state taken out from the stirrer is filled into a molding die heated to 150° C. and held in the molding die, and the CS filled in the molding die is solidified (cured). ) to prepare a mold used as a test piece (φ50×50 cm) of a circular no-aerator. Table 4 below shows the CS used to prepare the molds (test specimens) of Examples 15-16 and Comparative Examples 7-8.

As is clear from the results in Tables 3 and 4 above, the dry mold material (CS: coated sand) according to the present invention also yielded a casting ( It can be seen that the adhesion of the mold material (CS) to the casting product) is effectively inhibited. In particular, the molds (specimen) according to Examples 13 and 14 were molded with a mold material (CS) that was moistened by aeration of water vapor, and the molds according to Examples 15 and 16 ( Test piece) was molded with a mold material that was made wet by the addition of water. It is recognized that even in the mold (specimen) obtained by the molding method, adhesion of the mold material (CS) to the casting (cast product) is effectively suppressed.

-Molding Example IV (Examples 17-18, Comparative Examples 9-10)-
Using each of CS3, CS7, CS10, CS11, CS13 and CS15, according to the procedure of "Molding example I" described above, a mold as a test body (width: 2.54 cm × height: 2.54 cm × length: 20 cm), and the resulting mold (test piece) was subjected to bending strength measurement and filling rate (%) measurement according to the methods described below. The measurement results are shown in Table 5 below.

(7) Bending strength The breaking load of the mold (test piece) obtained using each CS is measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd.; digital casting sand strength tester). Then, using this measured breaking load, the bending strength is calculated from the following formula.
Bending strength (N/cm ² )=1.5×(L×W)/(a×b ² )
[L: distance between fulcrums (cm), W: breaking load (N), a: width of specimen (
cm), b: thickness of specimen (cm)]

(8) Filling rate For molds (specimen) obtained using each CS, the ratio of the specific gravity of each mold (specimen) to the true specific gravity of the aggregate (calculated by dividing the mass by the volume of the specimen) is calculated as a percentage.
Filling rate (mass%)
= {[mass of specimen (g)/volume of specimen (cm ³ )]
/ true specific gravity of aggregate (g/cm ³ )}×100

As is clear from the results in Table 5, the mold obtained using the mold material according to the present invention exhibits excellent mold strength and is also excellent in fillability. It is possible.

-Production Example of Recycled CS and Mold Forming Example V (Examples 21 and 22, Comparative Example 11)-
A half-split hollow main mold 6 (cavity: diameter 6 cm x height) shown in FIG. 6 cm) with a circular airless element 10 (5 cm diameter x 5 cm high) having a baseboard 8 made using each of the three mold materials (CS3, CS10, CS13) described above. , and fixed by the baseboard fixing portion 4, and then the half-split hollow main mold 6 was further adhesively fixed to each other to prepare a sand mold 12 for casting test. In addition, in order to prevent molten metal from leaking during casting, the bonded main mold was firmly fixed by clamping it with a vise or the like, or by wrapping the circumference of the main mold with a wire. Molten aluminum alloy (temperature: 710±5° C.) was poured from the pouring port 2 of the casting test sand mold 12 and solidified. 16 was taken out, and when the temperature reached room temperature, the core was disassembled using an air hammer, and the mold piece of the core was recovered. Then, the collected mold pieces were pulverized until the size (maximum length) thereof became 3 mm or less.

500 parts of the crushed mold pieces (refractory aggregate to which water glass adheres) are placed in a ball mill as a grinder and subjected to grinding treatment for 30 minutes, and then magnetic separation treatment of 5000 gauss. A magnet was used to remove powders and particulates that were attracted to the magnet from the refractory aggregate after the grinding treatment. After that, as a dust collection step, a dust collector was provided above a 280-mesh sieve, and fine particles were removed by blowing air from below during sieving to obtain a regenerated refractory aggregate. Hereinafter, 1) the above-mentioned casting is performed using a core made of CS3, and then a recycled aggregate a is a refractory aggregate that is recycled from the mold pieces of the recovered core, and 2) a core made of CS10. After that, the refractory aggregate regenerated from the recovered core mold pieces is used as the recycled aggregate b, and 3) the above casting is performed using the core made of CS13. The refractory aggregate regenerated from the recovered core mold pieces is indicated as regenerated aggregate c. Then, 1) using the recycled aggregate a, a wet mold material: recycled CS3′ according to the same manufacturing method as CS3 described above, and 2) using the recycled aggregate b, the same manufacturing method as CS10 described above. Wet mold material: regenerated CS10' was obtained according to 3) Regenerated aggregate c, and wet mold material: regenerated CS13' was obtained according to the same production method as CS13 described above.

Using the obtained regenerated CS3′, regenerated CS10′ and regenerated CS13′, a mold as a specimen (width: 2.54 cm×height: 2.54 cm) was prepared according to the procedure of “Molding Example I” described above. x length: 20 cm), and the resulting mold (test specimen) was measured for bending strength according to the method shown in "(7) Measurement of bending strength" described above. Then, from 1) the bending strength of CS3 (the bending strength of Example 17) and the bending strength of the regenerated CS3′ obtained using the regenerated aggregate of CS3 (regenerated aggregate a), 2) CS10 From the bending strength (the bending strength of Example 19) and the bending strength of the recycled CS10′ obtained using the recycled aggregate of CS10 (the recycled aggregate b), 3) the bending strength of CS13 (comparative example 9) and the bending strength of the regenerated CS13′ obtained using the regenerated aggregate of CS13 (regenerated aggregate c), the strength expression rate (%) was calculated based on the following formula. The results are shown in Table 6 below.
Strength expression rate (%)
= [CS bending strength (N/cm ² )
/Bending strength of recycled CS (N/cm ² )]×100

As is clear from the results in Table 6, it was confirmed that the mold materials (recycled CS3', recycled CS10') using the refractory aggregate recycled from the mold material according to the present invention had a high strength development rate. (Examples 21-22). On the other hand, in the mold material (recycled CS13') using the refractory aggregate recycled from the mold material in which the iron-containing compound powder was not used, the strength development rate was low, and it was recovered. It was confirmed that it is difficult to regenerate refractory aggregate efficiently.

2 Molten metal injection port 4 Baseboard fixing part 6 Main mold 8 Baseboard part 10 Circular airless element 12 Casting test mold 14 Waste core discharge port 16 Casting

Claims (18)

(a) a refractory aggregate;
(b) a water-soluble inorganic binder;
(c) the water-soluble inorganic caking agent and the iron-containing compound, comprising at least a powdery iron-containing compound having an average particle size of 0.01 µm or more and less than 50 µm ; A mold material comprising dry coated sand having normal temperature fluidity, wherein a coating layer containing a compound powder is formed on the surface of the refractory aggregate . The mold material of claim 1, wherein said iron-containing compound is iron oxide. 3. The mold material of claim 2, wherein said iron oxide is selected from the group consisting of magnetite, maghemite, ferrite, and mixtures of two or more thereof. 4. Any one of claims 1 to 3, wherein the iron-containing compound powder is contained in a proportion of 1 to 500 parts by mass with respect to 100 parts by mass of the solid content of the water-soluble inorganic binder. 1. The mold material according to claim 1. An aqueous solution containing 30% by mass of the water-soluble inorganic binder as a solid content is used as a blank liquid, and when the light transmittance of the blank liquid at a wavelength of 660 nm is 100%, the above-mentioned 5. The dispersion according to any one of claims 1 to 4, wherein the average value of light transmittance at a wavelength of 660 nm of the dispersion obtained by mixing 5 parts by mass of the iron-containing compound powder is 20% or less. mold material. 6. The mold material according to any one of claims 1 to 5, wherein the iron-containing compound powder is spherical. 7. The mold material according to any one of claims 1 to 6, further comprising a surfactant. The mold material according to any one of claims 1 to 7, wherein the water-soluble inorganic binder is water glass. A water-soluble inorganic binder and a powder of an iron-containing compound having an average particle size of 0.01 μm or more and less than 50 μm are added to the heated refractory aggregate, and kneaded or mixed to form a mixture. and evaporating water in the mixture to form a coating layer containing the water-soluble inorganic binder and the iron-containing compound powder on the surface of the refractory aggregate A method for producing a mold material, characterized by producing a dry coated sand having normal temperature fluidity. 10. The method of manufacturing a mold material according to claim 9 , wherein water is further added to prepare said admixture. After filling the mold material according to any one of claims 1 to 8 into a heated mold, water vapor is passed through the mold and held in the mold to solidify or harden. A method for producing a mold, characterized in that the desired mold is obtained by The mold manufacturing method according to claim 11 , wherein the mold is heated to a temperature of 80°C to 200°C. Water is added to the mold material according to any one of claims 1 to 8 to wet it, and after filling the wet mold material into a heated mold, the mold is A mold manufacturing method characterized by obtaining a desired mold by holding the mold inside and solidifying or hardening it. The mold manufacturing method according to claim 13 , wherein the mold is heated to a temperature of 80°C to 300°C. 15. The mold manufacturing method according to any one of claims 11 to 14 , wherein hot air or superheated steam is passed through the mold while the mold is being held. The water-soluble inorganic binder containing the powder of the iron-containing compound, which is obtained after casting using a mold made of the mold material according to any one of claims 1 to 8 , is adhered. A method for recycling recovered refractory aggregate containing refractory aggregate,
After the refractory aggregate is recovered, the recovered refractory aggregate is polished to scrape off the water-soluble inorganic binder adhering to the surface thereof, and then the refractory aggregate is The solid matter of the water-soluble inorganic binder scraped from the material is separated from the refractory aggregate by utilizing the action of attracting the powdered matter of the iron-containing compound contained in the solid matter to a magnet. A method for regenerating recovered refractory aggregate, characterized in that magnetic separation treatment is carried out. 17. The method for regenerating recovered refractory aggregate according to claim 16 , wherein the magnetic separation treatment is performed by a magnetic separator having a magnetic flux density within the range of 500 to 10000 gauss. 16. Firing treatment for the refractory aggregate is performed prior to the polishing treatment, between the polishing treatment and the magnetic separation treatment, and/or after the magnetic separation treatment, or The method for recycling recovered refractory aggregate according to claim 17 .

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