JP6765868B2 - Mold manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a mold, and more particularly to a method capable of advantageously manufacturing a mold while improving workability at a molding site, which is a manufacturing site for a mold.

Conventionally, as one of the methods for manufacturing a mold used for casting a molten metal, a coated sand made by coating a mold sand made of a fire-resistant aggregate with a predetermined binder is used to obtain a desired shape. A method of molding a mold is adopted, and as a binder used there, for example, in "Casting Engineering Handbook" edited by the Japan Foundry Engineering Society, pp. 78-90, an inorganic type such as water glass is used. In addition to binders, organic binders using resins such as phenol resin, furan resin, and urethane resin have been clarified, and there, self-hardening molds are molded using these binders. The method has also been clarified.

Then, using water glass, which is one of the inorganic binders among these binders, a coated sand formed by covering a predetermined refractory aggregate (mold sand) is formed, and then molding of the mold is performed. Various methods have been proposed as methods for performing the above. For example, in Japanese Patent Application Laid-Open No. 2008-511447, a fire-resistant molding base material (fire-resistant aggregate), water glass, and particulate metal oxide are used. A molding material mixture for the production of a mold containing the above has been clarified. Further, there, at the molding site of the mold, the refractory molding base material, water glass and particulate metal oxide are kneaded, and wet water glass is adhered to the surface of the refractory molding base material. A mixture of molding materials (coated sand) in a wet form (wet state) is formed, and the mixture is filled in a predetermined molding mold to form a mold having a desired shape.

However, such a wet coated sand reacts with carbon dioxide in the air and gradually hardens, so that the pot life is short and the storage stability is not sufficient. Generally, the coated sand in such a wet state is manufactured at the molding site of the mold and then filled in the molding mold as it is to mold the target mold. However, it is quite difficult to transport finely powdered refractory aggregate and water glass to the molding site and knead them with a mixer to obtain a wet coated sand because of the high viscosity of the water glass. In addition to the difficulty of mixing with refractory aggregate due to the viscosity of water glass, the mixer for mixing and the molding mold for molding are easily soiled. There is an inherent problem of poor molding workability. Moreover, since the work is performed at the molding site, there is a high risk that the worker will be injured by the strongly alkaline water glass.

Further, in the wet coated sand produced by kneading at such a molding site, the coating layer made of water glass covering the surface of the aggregate is viscous, so that it becomes fluid and moldable. In addition to problems such as poor filling property and poor mold releasability from the molding die, when the molding die is heated when filling the molding die with such a wet coated sand via a blow head, the molding die is heated. Since the blow head is also heated, it becomes difficult to maintain the wet state of the coated sand contained in the blow head, and there is an inherent problem that the molding work cannot be continued.

On the other hand, unlike the wet coated sand as described above, water glass is used as a binder to form a dried coating layer of such a binder on the surface of the refractory aggregate. A dry coated sand having room temperature fluidity is disclosed in the publication of International Publication No. WO2014 / 98129. There, such dry coated sand is adjusted to have a moisture content of 0.5% by mass or less, filled into the molding cavity of the molding mold for molding, and then steamed. It has been clarified that the coated sand is solidified or hardened by aeration to obtain the desired mold. However, in such a molding method, a dry coated sand is used. In order to allow steam to be aerated through all the coated sand filled in the molding mold after filling, it is necessary to provide a special steam blowing device, and it is necessary to spread the steam throughout the mold. There are inherent problems such as complicated design of the position of the vent hole of the mold and restrictions on the shape of the mold.

Moreover, since it is necessary to wet the dry coated sand filled in the mold with steam, a step of blowing steam is added, and as a result, the mold is filled to dry solidify or hardened. There is also an inherent problem that the molding cycle leading to this becomes longer and the productivity of the mold decreases.

Japanese Patent Application Laid-Open No. 2008-511447 WO2014 / 98129

"Handbook of Casting Engineering", pp. 78-90

Here, the present invention has been made against the background of such circumstances, and the problem to be solved thereof is to provide a method for manufacturing a mold capable of effectively improving workability at a molding site. Another challenge is to provide a method that can advantageously manufacture the desired mold without complicating the design of the mold and without limiting the mold shape. It is in.

The present invention can be preferably carried out in various aspects as listed below in order to solve the above-mentioned problems, and each of the following aspects is adopted in any combination. It is possible. The aspects or technical features of the present invention are not limited to those described below, and can be recognized based on the invention idea that can be grasped from the description of the entire specification and the accompanying drawings. That should be understood.

(1) A step of preparing a dry coated sand obtained by coating the surface of a refractory aggregate with water glass, and a step of adding water to the coated sand to moisten it. , A method for producing a mold, which comprises a step of filling a molding mold with the obtained moistened coated sand and molding the mold.
(2) The method for producing a mold according to the above aspect (1), wherein the water is added at a ratio of 1 to 5 parts by mass with respect to 100 parts by mass of the dry coated sand.
(3) The method for producing a mold according to the above aspect (1) or the above-mentioned aspect (2), wherein the molding die is heated to a temperature of 40 to 250 ° C.
(4) The method for producing a mold according to any one of the above-described embodiments (1) to (3), wherein the moistened coated sand filled in the molding mold is heated by microwaves.
(5) Manufacture of the mold according to any one of the above-described embodiments (1) to (4), wherein heated air or dry air is ventilated in the molding mold filled with the moistened coated sand. How to make.
(6) The method for producing a mold according to any one of the above-described embodiments (1) to (5), wherein the inside of the molding mold filled with the moistened coated sand is dried under reduced pressure.
(7) The method for producing a mold according to any one of the above-described embodiments (1) to (6), wherein carbon dioxide gas is further ventilated in the molding mold filled with the moistened coated sand. (8) The method for producing a mold according to any one of the above-mentioned conditions (1) to (7), wherein the molar ratio of SiO ₂ / Na ₂ O in the water glass is 1.9 or more.
(9) The mode (1) in which the moistened coated sand is housed in a sand storage hopper, then supplied to a blow head from the sand storage hopper, and then filled into the molding die from the blow head. ) To the method for producing a mold according to any one of the above aspects (8).
(10) The embodiment (10), wherein a water supply means for supplying water to the inside of the blow head and / or the sand storage hopper to suppress or prevent the drying of the moistened coated sand is provided. 9) The method for producing a mold according to the above method.
(11) The method for producing a mold according to the above aspect (10), wherein the water supply means includes a steam or mist generator.
(12) The method for producing a mold according to any one of the above aspects (9) to (11), wherein the blow head is provided with a cooling means.
(13) The method for producing a mold according to the above aspect (12), wherein the blow head is cooled to a temperature of 40 ° C. or lower by the cooling means.
(14) When the moistened coated sand contained in the blow head and / or the sand storage hopper has a water content of 1% by mass or less, water is further added to the moistened coated sand. The method for producing a mold according to any one of the above-described embodiments (9) to (13), wherein the molding is performed after adding and moistening the mold.

As described above, in the present invention, using water glass as a binder, first, a dry coated sand is prepared and then brought to the molding site, while it is applied at the molding site. Since it is possible to mold the target mold simply by preparing water to moisten the dry coated sand, viscous water glass is used as a refractory aggregate in a molding site where the working environment is poor. It is not necessary to knead the glass, and therefore, the workability at the molding site is significantly improved. Moreover, even if water is added to the dry coated sand in the mixer to moisten it, it rarely adheres to the inside of the mixer or to a molding mold such as a mold used for molding, so that the apparatus can be used. In addition to being hard to get dirty, since water glass is not handled at the molding site, there is no risk of chemical damage to workers with such water glass.

Further, in the present invention, the dry coated sand prepared in advance hardly changes with time due to carbon dioxide in the air unless water is added, and is excellent in storage stability. Therefore, the dry state is excellent. It has a practical advantage that it is possible to prepare a large amount of the coated sand in advance, add water to moisten a part of the coated sand, and then mold the target mold. At the same time, the moistened dry coated sand has better filling property into the molding mold than the wet coated sand produced at the molding site as in the conventional case, and is molded. It exhibits a special feature that the mold can be easily released from the mold.

Further, according to the method for producing a mold according to the present invention, at a molding site, water is evaporated and dried, solidified or cured simply by filling a molded mold with moistened coated sand and heating it. Since it is a thing, there is no need to newly install special equipment such as a steam generator and a steam ventilation mechanism as in the case of using a dry coated sand as it is, and the design of the molding mold is complicated. There is no need to do anything or limit the mold shape, which avoids an increase in equipment cost and thus in mold manufacturing cost, and does not require the addition of a steam blowing process. It was also possible to advantageously avoid the lengthening of the molding cycle.

FIG. 5 is a schematic cross-sectional explanatory view of a molding apparatus showing a standby state before filling a molding mold of a moistened coated sand in an example of a mold manufacturing method according to the present invention. FIG. 5 is a schematic cross-sectional explanatory view showing a state in which the blow head is moved from the standby state of FIG. 1 and set in the molding die (state before blowing). FIG. 5 is a schematic cross-sectional explanatory view showing a state in which a gassing box is set in a molding die and gassing is performed in a step after the step shown in FIG. FIG. 3 is a schematic cross-sectional explanatory view showing a state in which a molding die is opened and a molded mold is taken out in a step after the step shown in FIG. It is sectional drawing which shows the state of the blowing (sand filling) of the moistened coated sand in another example of the manufacturing method of the mold according to this invention. FIG. 5 is a schematic cross-sectional explanatory view showing a state in which a molding mold filled with moistened coated sand is housed in a vacuum suction device and vacuum suction is performed. FIG. 5 is a schematic cross-sectional explanatory view showing an example of a vacuum / CO ₂ gas gassing step instead of the step of FIG. FIG. 5 is a schematic cross-sectional explanatory view showing a state in which a molding die is opened after the step of FIG. 7 and the molded mold is taken out.

By the way, in the method for producing a mold according to the present invention, a dry coated sand prepared in advance is generally prepared by mixing a refractory aggregate with water glass in an aqueous solution state as a binder, and then mixing the refractory aggregate with water glass. A dry coating layer made of solids of water glass, which is produced and is a binder, is produced by evaporating water from the mixture, in other words, by evaporating the water content of water glass in an aqueous solution, which is refractory bone. It is a dry material formed on the surface of the material and has good room temperature fluidity. In particular, in the present invention, such a coated sand has a water content of 0.1 to 0.8% by mass, preferably 0.15 to 0.75% by mass, and more preferably 0.2 to 0. It is adjusted to be 0.6% by mass. When this water content is smaller than 0.1% by mass, the water glass is vitrified, and even if water is added again, it does not return to the solution state, while when it is larger than 0.8% by mass, it is in a dry state. The problem arises that it does not become. As described above, by using the coated sand as described above, the pot life can be extended and the storage stability can be advantageously improved. Therefore, a large amount of such dry coated sand is previously produced in the factory. It will be possible to prepare a part of it and transport it to the molding site so that it can be used for molding the target mold, which can greatly contribute to the efficiency of the molding work. It becomes.

The refractory aggregate constituting the coated sand as described above is a refractory substance that functions as a base material of the mold, and is a variety of refractory granular or powdery materials that have been conventionally used for the mold. Can be used, specifically, special sands such as alumina sand, olivine sand, zircon sand, and chromate sand, as well as silica sand and recycled silica sand, ferrochrome slag, ferronickel slag, and refractory slag. Such as slag-based particles; artificial particles such as alumina-based particles and murite-based particles and their regenerated particles; alumina balls, magnesia clinker and the like. It should be noted that these refractory aggregates may be fresh sand, or recycled sand or recovered sand that has been used once or multiple times as casting sand for molding a mold, and further, such regeneration. There is no problem even if it is mixed sand made by adding new sand to sand or recovered sand and mixing them. Then, such a refractory aggregate is generally used as having a particle size of about 40 to 130 in AFS index, preferably having a particle size of about 60 to 110.

Further, in the present invention, the water glass used as a binder for obtaining a dry coated sand is an aqueous solution of a soluble silicic acid compound, and such a silicic acid compound is, for example, sodium silicate. , Potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, ammonium silicate, colloidal silica, alkyl silicate, etc., but in particular, in the present invention, sodium silicate (sodium silicate) can be mentioned. ) Will be used advantageously. In addition, such sodium silicate is usually classified into the types of Nos. 1 to 5 according to the molar ratio of SiO ₂ / Na ₂ O and used. Specifically, sodium silicate No. 1 has a molar ratio of SiO ₂ / Na ₂ O of 2.0 to 2.3, and sodium silicate No. 2 has a molar ratio of SiO ₂ / Na ₂ O. The molar ratio is 2.4 to 2.5, and sodium silicate No. 3 has a molar ratio of SiO ₂ / Na ₂ O of 3.1 to 3.3. In addition, sodium silicate No. 4 has a molar ratio of SiO ₂ / Na ₂ O of 3.3 to 3.5, and sodium silicate No. 5 has a molar ratio of SiO ₂ / Na ₂ O. Is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also specified in JIS-K-1408. Then, these sodium silicates may be used alone or in a mixed manner, and the molar ratio of SiO ₂ / Na ₂ O can be adjusted by mixing them.

Sodium silicate, which constitutes water glass used as a binder, preferably has a molar ratio of SiO ₂ / Na ₂ O of 1.9 or more in order to advantageously obtain the dry coated sand used in the present invention. Is preferably 2.0 or more, more preferably 2.2 or more, and sodium silicate corresponding to Nos. 1 and 2 is used particularly advantageously in the above-mentioned classification of sodium silicate. Such sodium silicate No. 1 and No. 2 respectively provide a dry coated sandwich having stable and good characteristics even in a wide range of sodium silicate concentration in water glass. Further, the upper limit of the molar ratio of SiO ₂ / Na ₂ O in such sodium silicate is appropriately selected according to the characteristics of 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 molar ratio of SiO ₂ / Na ₂ O is smaller than 1.9, the viscosity of the water glass becomes low, and it becomes difficult to dry the water unless the water content is considerably low. On the other hand, if it is larger than 3.5, the solubility in water is lowered, the adhesive area cannot be increased, and the mold strength is lowered.

The water glass used in the present invention means a solution of a silicic acid compound in a state of being dissolved in water, and is used in the state of a stock solution as purchased on the market, or water is added to such a stock solution. It will be used in a diluted state after being added. The solid content (water glass component) obtained by removing volatile substances such as water and solvent from such water glass is called a non-volatile content, and this corresponds to the above-mentioned soluble silicic acid compound such as sodium silicate. It is something to do. Further, the higher the ratio of such non-volatile content (solid content), the higher the concentration of the silicic acid compound in the water glass. Therefore, the non-volatile content of the water glass used in the present invention corresponds to the ratio excluding the amount of water in the stock solution when it is composed only of the stock solution, while the stock solution is made into water. When a diluted solution obtained by diluting is used, the ratio excluding the amount of water in the stock solution and the amount of water used for dilution corresponds to the non-volatile content of the water glass used. It becomes.

Further, the non-volatile content in such water glass is set to an appropriate ratio depending on the type of the water glass component (soluble silicic acid compound) and the like, but is preferably a ratio of 20 to 45% by mass. It is desirable that it is contained in. By appropriately allowing the water glass component corresponding to this non-volatile component to be present in the aqueous solution, the water glass component is evenly and uniformly applied to the refractory aggregate when mixed (kneaded) with the refractory aggregate. Can be coated, whereby the desired mold can be advantageously molded according to the present invention. If the concentration of the water glass component in the water glass becomes too low and the total amount of non-volatile components is less than 20% by mass, the heating temperature is raised or the heating time is lengthened for drying the coated sand. It is necessary to do so, which causes problems such as energy loss. Further, if the proportion of the non-volatile content in the water glass becomes too high, it becomes difficult to uniformly cover the surface of the refractory aggregate with the water glass component, which also causes a problem in improving the characteristics of the target mold. From the point of view, it is desirable to adjust the water glass in the form of an aqueous solution so that the non-volatile content is 45% by mass or less, and therefore the water content is 55% by mass or more.

Further, it is desirable that water glass is used at a ratio of 0.1 to 2.5 parts by mass in terms of solid content when considering only the non-volatile content with respect to 100 parts by mass of the refractory aggregate. A ratio of 0.2 to 2.0 parts by mass is particularly advantageously adopted to form a coating layer of water glass on the surface of the refractory aggregate. Here, the measurement of the solid content is carried out as follows. That is, 10 g of the sample was weighed and contained in an aluminum foil dish (length: 90 mm, width: 90 mm, height: 15 mm), placed on a heating plate held at 180 ± 1 ° C., and left for 20 minutes. The sample dish 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 (mass%) is calculated by the following formula.
Solid content (mass%) = [mass after drying (g) / mass before drying (g)] × 100
If the amount of water glass used is too small, it becomes difficult to form an effective coating layer of water glass on the surface of the refractory aggregate, and it becomes difficult for the coated sand to be sufficiently solidified or hardened. Causes problems. In addition, even if the amount of water glass used is too large, extra water glass adheres to the surface of the refractory aggregate, making it difficult to form a uniform coating layer, and the coated sands adhere to each other. As a result, there is a risk of agglomerating (composite particles), which adversely affects the physical properties of the mold and also causes a problem that it is difficult to remove sand from the core after casting the metal.

Then, in the present invention, a dry coated sandwich formed by forming a coating layer by using the above-mentioned water glass on the surface of a refractory aggregate is targeted. Such a coating layer may appropriately contain a known additive, if necessary. In order to include such an additive in the coating layer, a method of pre-blending a predetermined additive in water glass and then kneading or mixing it with a refractory aggregate, or a method of kneading or mixing the water glass separately from the water glass is specified. A method is adopted in which the additive of the above is added to the refractory aggregate to uniformly knead or mix the whole.

As one of such additives, solid oxides and salts will be advantageously used in the present invention. The inclusion of these solid oxides and salts can advantageously improve the moisture resistance of the coated sand. Among them, as the solid oxide, for example, the use of oxides of silicon, zinc, magnesium, aluminum, calcium, lead and boron is effective. In particular, among them, it is desirable to use silicon dioxide, zinc oxide, aluminum oxide, and boron oxide. Further, among silicon dioxide, precipitated silicic acid and exothermic silicic acid are preferably used. On the other hand, as salts, there are siliceous salts, silicates, phosphates, borates, tetraborates, carbonates, etc., among which zinc carbonate, potassium metaborate, sodium tetraborate, tetraborate, etc. The use of potassium acid is desirable. Then, these solid oxides and salts are used in a proportion of 100% by mass or less, preferably about 0.5 to 5% by mass, based on the non-volatile content in the water glass.

Further, as other additives, it is also effective to include a coupling agent that strengthens the bond between the refractory aggregate and water glass (binder). For example, a silane coupling agent, a zircon coupling agent, and a titanium cup. A ring agent or the like can be used. It is also effective to include a lubricant that contributes to improving the fluidity of the coated sand. For example, waxes such as paraffin wax, synthetic polyethylene wax and montanic acid wax; stearic acid amide, oleic acid amide, erucic acid amide and the like. Fatty acid amides; alkylene fatty acid amides such as methylene bisstearic acid amide and ethylene bisstearic acid amide; stearic acid, stearyl alcohol, metal stearate, lead stearate, zinc stearate, calcium stearate, magnesium stearate, stearic acid It is possible to use monoglyceride, stearyl stearate, hardened oil and the like. Furthermore, as mold release agents, paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, graphite fine particles, mica, 蛭 葉, fluorine-based mold release agent, silicone-based mold release agent. Agents and the like can also be used. Each of these other additives is contained in a proportion of 5% by mass or less, preferably 3% by mass or less, based on the non-volatile component in the water glass.

By the way, in the present invention, when producing a dry coated sand prepared in advance, generally, water glass as a binder is kneaded or kneaded with an additive, if necessary, with respect to the fire-resistant aggregate. A dry powder having room temperature fluidity by mixing and uniformly mixing to cover the surface of the fire resistant aggregate with water glass and evaporating the water content of such water glass. A method of obtaining a state-coated sand will be adopted, but the evaporation of water in the water glass (coating layer) at that time needs to be performed quickly before the water glass solidifies or hardens. Therefore, in the present invention, the water content is added to the fire-resistant aggregate within 5 minutes, more preferably within 3 minutes after the water glass in the form of an aqueous solution is added (mixed). It is desirable to skip it to make a dry powdered coated sand. If the evaporation time is long, the mixing (kneading) cycle is long, the productivity is lowered, and the water glass is exposed to CO ₂ in the air for a long time, which may cause problems such as deactivation. Because it will be expensive. The dry powdered coated sand thus obtained is generally 0.1 to 0.8% by mass, preferably 0.15 to 0.75% by mass, and more preferably 0.2 to 0. It will be obtained as a product adjusted to a water content of 6% by mass.

Further, in the manufacturing process of such a dry coated sand, as one of the effective means for rapidly evaporating the water content in the water glass, the refractory aggregate is preheated and then an aqueous solution is used. A method is adopted in which the water glass in the form of is kneaded or mixed so as to be mixed. By kneading or mixing water glass with this preheated refractory aggregate, the water in the water glass is vaporized extremely quickly by the heat of such refractory aggregate. Therefore, the moisture content of the obtained coated sand can be effectively reduced, and a dry powder having room temperature fluidity can be advantageously obtained. The preheating temperature of the refractory aggregate will be appropriately selected according to the water content of the water glass, the blending amount thereof, etc., but is generally about 100 to 150 ° C., preferably 100 to 120. It is desirable to heat the refractory aggregate to a temperature of about ° C. If the preheating temperature becomes too low, it will not be possible to effectively evaporate the water and it will take time to dry. Therefore, it is desirable to adopt a temperature of 100 ° C. or higher. If the preheating temperature becomes too high, the water glass component will harden when the obtained coated sand is cooled, and in addition, composite particles will progress. Therefore, the function as a coated sand, especially the physical properties such as strength, will be improved. It will cause problems.

Then, in the present invention, the dry coated sand obtained as described above is used, transported to a molding site, which is a mold manufacturing site, and then water is added at the molding site. After moisturizing, the obtained moistened coated sand is filled in a molding die to mold a target mold, in which water is added to the dry coated sand. The process of moistening is extremely simple because it is sufficient to moisten the coated sand by simply adding a predetermined amount of water and a dry coated sand to an appropriate mixer and mixing them. It can be carried out in a simple and easy manner even in a molding site where the working environment is bad.

Moreover, in order to moisten such a dry coated sand, it is only necessary to add water, and the viscous water glass is not kneaded into the refractory aggregate, so that the workability is extremely good. Therefore, the moistened coated sand does not easily adhere to the mixer, molding mold, etc., so that the equipment is not easily soiled, and water glass is not handled at the molding site. Therefore, there is an advantage that the worker is not likely to be injured.

The purpose of moistening the dry coated sand is to add a predetermined amount of water to the dry coated sand and mix it with a normal mixer at the molding site of the mold. The moistened coated sand is formed, and the amount of water used therein is appropriately determined according to the type and amount of the water glass component constituting the coated sand, and is generally determined. It is appropriately determined at a ratio of 1 to 5 parts by mass, preferably 1.5 to 4 parts by mass, and more preferably 2 to 3 parts by mass with respect to 100 parts by mass of the coated sand. It becomes. If the amount of this water added is too small, it is not possible to sufficiently moisten the coated sand in a dry state, and as a result, the mutual adhesion between the coated sands becomes weak, and the coated sand also becomes weak. As a result of the deterioration of the fluidity of the mold and the poor filling property of the mold, there is a problem that the strength of the obtained mold is lowered. On the other hand, if the amount of water added is too large, in addition to the problem that the filling operation to the molding die becomes difficult, the drying operation after filling the molding die takes time, and the molding time becomes long. Causes problems. In this way, the moistened coated sand obtained by adding water to the dry coated sand generally has a water content of more than 1% by mass.

Then, in the present invention, the moistened product of the dry coated sand obtained as described above is used, and the molded product is filled in a predetermined molding mold, specifically, the molding cavity thereof. By drying the moistened coated sand, a mold of the desired shape is formed. At that time, the moistened coated sand used is directly fire resistant to water glass. Compared to the wet coated sand obtained by kneading with aggregate, the fluidity is better, and the adhesion and adhesive strength between the sands are reduced, so the filling property is effectively improved and further molding is performed. Since the adhesion to the mold can be effectively reduced, the stain on the mold can be advantageously suppressed, and the mold releasability from the mold can also be advantageously improved.

By drying, solidifying, or curing the moistened coated sand filled in the molding mold in this way, it is advantageous to dry the moistened coated sand when molding the target mold. In order to achieve this, it is desirable to preheat the molding die, which is recommended in the present invention. By using this heated molding die, the drying of the filled moistened coated sand can be effectively advanced, so that the molding time can be advantageously shortened. As the heating temperature of such a molding mold, a temperature in the range of 40 to 250 ° C., preferably 70 to 200 ° C., and more preferably 100 to 175 ° C. is generally adopted. If the heating temperature is less than 40 ° C, it is difficult to sufficiently exert the drying promoting effect by heating, and there is a problem that the molding time becomes long. If the heating temperature is higher than 250 ° C, the mold is moistened. The coated sand solidifies too quickly and its filling property deteriorates, and the moistened coated sand becomes too dry and loses its adhesiveness, the adhesive effect becomes low, and the strength of the obtained mold decreases. Problems such as casting will also be caused.

Further, in order to accelerate the drying of the moistened coated sand filled in the molding die, it is also effective to heat the filled moistened coated sand with microwaves, and in particular, the molding die is made of resin. In the case of a mold, it is preferably adopted. Further, by aerating heated air or dry air into the mold filled with the moistened coated sand and passing it through the packed layer of the moistened coated sand, drying is promoted and the molding is filled more quickly. It is also effective to try to solidify or harden the moistened coated sand. In addition, it is also one of the effective drying means to dry the inside of the molding mold under reduced pressure by sucking the molding mold filled with the moistened coated sand under reduced pressure, and in particular, it is affected by heat such as a resin mold. It is being used advantageously in molds made of easily acceptable materials.

By removing the water from the moistened coated sand filled in the molding mold in this way, the target mold is molded, and at that time, the surface coating of the coated sand is formed. The water glass that constitutes the layer is usually solidified by evaporation to dryness of water unless any additives are added, and is cured if oxides, salts, etc. are added as a curing agent. It becomes. Then, in order to cure the water glass, it is possible to further aerate carbon dioxide gas in the molding mold filled with the moistened coated sand, whereby the water glass can be further aerated as in the conventional case. It can be cured quickly to advantageously increase the molding speed.

By the way, according to the present invention, various molding methods using known coated sand can be appropriately adopted as a method of filling a molding with moistened coated sand to form a molding. In the present invention, the moistened coated sand is housed in a hopper for sand storage, then supplied to a blow head from the sand storage hopper, blow-filled in a predetermined molding mold from the blow head, and dried. A blow molding method in which solidification or curing is performed is preferably adopted, and a typical embodiment thereof is shown in the attached drawings.

That is, FIG. 1 is a schematic cross-sectional explanatory view of a molding apparatus showing a standby state before filling a molding of a moistened coated sand in an example of a mold manufacturing method according to the present invention. Here, reference numeral 10 denotes a molding device provided with a molding chamber 12 composed of a space closed from the outside, which has an effective structure when a mold is used as the molding mold. Specifically, the molding apparatus 10 is provided with a hopper 16 accommodating the moistened coated sand 14 as described above in a form mounted on the ceiling wall, while the lower surface of the ceiling wall is provided with a hopper 16. , Two guide rails 18, 18 (only one is shown here) are arranged parallel to each other. A blow head 22 and a gassing box 24 having the same structure as those of the conventional one are detachably attached to the holding body 20 which is guided and moved in the left-right direction in the drawings by the guide rails 18 and 18. ing.

Further, in the standby state of the holding body 20 shown in FIG. 1, the hopper 16 and the blow head 22 are configured to be able to communicate with each other, and the hopper is opened and closed by opening and closing the valve body 26 provided at the lower part of the hopper 16. The moistened coated sand 14 housed in the 16 is guided into the blow head 22. Further, an introduction pipe 28 is inserted and arranged in the communication portion between the hopper 16 and the blow head 22, and the steam (steam) or water mist generated by the steam / mist generator 30 is introduced through the introduction pipe 28. Therefore, the moistened coated sand 14 housed in the blow head 22 is wetted, and the state of the moistened sand is maintained.

Further, the lower portion of the blow head 22 is closed by the blow plate 32, and the refrigerant supplied from the cooling device 34 arranged outside with respect to the refrigerant passage (not shown) formed in the blow plate 32. Is now available for distribution. As a result, the blow plate 32 is cooled to prevent its heating, thereby effectively suppressing the progress of drying (solidification) of the moistened coated sand (14) in the blow head 22 by heating. Is supposed to be blocked. By adopting such a cooling structure, the blow head 22 is generally cooled to 40 ° C. or lower, preferably about 5 to 35 ° C., and more preferably about 10 to 30 ° C. A compressed air introduction pipe (not shown) similar to the conventional one is attached to the blow head 22, and the wet state in the blow head 22 is caused by the action of the compressed air introduced through the compressed air introduction pipe. The coated sand 14 is blown into a molding mold described later through a plurality of blow nozzles 36 provided so as to penetrate the blow plate 32.

Further, in the standby state shown in FIG. 1, a steam / mist box 38 is arranged below the blow head 22, a steam / mist generator 40 is arranged inside the steam / mist box 38, and the outer cylinder 42 is provided. Is movable in the vertical direction, and by its rise, it is placed close to the blow plate 32 of the blow head 22, so that the space around the blow nozzle 36 is substantially closed in the steam / mist generator 40. By introducing the generated steam or water mist into the enclosed space, the drying of the wet sand in the blow nozzle 36 is suppressed or prevented.

On the other hand, in FIG. 1, a vertical movement cylinder 44 is arranged so as to penetrate the ceiling wall portion corresponding to the moving position of the gassing box 24, and the blow head 22 or the gassing box 24 is arranged in the vertical movement cylinder 44. Is attached and detached so that it can be moved up and down. The mold 46 as a molding mold is composed of the upper mold 46a and the lower mold 46b and is arranged on the mold mounting table 48 so as to be located below the gassing box 24. Further, the mold mounting table 48 can be moved in the vertical direction by the table moving cylinder 50, and is molded in the molding cavity of the mold 46 by the extrusion pin 52 and the pin moving cylinder 54. The mold is projected from the lower mold 46b.

Further, a hot air device 56 is arranged in the molding chamber 12 of the molding device 10 so that air taken in from the outside can be heated and supplied to the gassing box 24. Then, in the gassing box 24, the hot air supplied from the hot air device 56 is blown into the mold 46 through the gassing plate 25, as will be described later.

Then, from the standby state shown in FIG. 1, the holding body 20 is guided by the guide rail 18 and moved to the right, and after the blow head 22 is positioned above the mold 46, the blow head While the tip of the piston rod of the vertical movement cylinder 44 is connected to 22, the holding of the blow head 22 by the holding body 20 is released, and then the blow head 22 is released by the downward operation of the vertical movement cylinder 44. In the state shown in FIG. 2 in which the blow nozzle 36 is inserted into the mold 46 and set, compressed air is introduced into the blow head 22 through a compressed air supply pipe (not shown) as in the conventional case. By doing so, the moistened coated sand 14 in the blow head 22 is blown (blown into the sand) into the molding cavity formed in the mold 46 through the blow nozzle 36 so as to be filled. It has become.

Then, after the blowing (blow filling) of the moistened coated sand 14 is completed, the blow head 22 is held again by the holding body 20 and moved onto the steam / mist box 38, and then the valve is released from the hopper 16. The moistened coated sand 14 is accommodated through the body 26 and is put into a standby state as shown in FIG. On the other hand, with respect to the mold 46 filled with the moistened coated sand 14, the gassing box 24 is removed from the holding body 20 and attached to the tip of the piston rod of the vertical movement cylinder 44, so that the vertical movement is such. It is lowered by the operation of the moving cylinder 44, and in the set state, the hot air supplied from the hot air device 56 is blown into the mold 46 through the gassing plate 25 and ventilated (as shown in FIG. 3). Gashing) is done. As a result, the moistened coated sand 14 filled in the mold 46 is dried and solidified, whereby the target mold is formed.

In the molding step, the mold 60 obtained by solidifying or curing the moistened coated sand 14 is held by raising the gassing box 24 by the vertical movement cylinder 44 as shown in FIG. While the body 20 is held, the table moving cylinder 50 and the pin protruding cylinder 54 are lowered to open the upper mold 46a and the lower mold 46b constituting the mold 46, and the mold 60 is formed by the extrusion pin 52. As a result, it is projected from the lower mold 46b and taken out of the mold 46.

Therefore, according to the molding operation using such a molding device 10, the moistened coated sandwich 14 housed in the blow head 22 is dried by the steam and mist supplied from the steam / mist generators 30 and 40. The solidification can be effectively suppressed or prevented, and the blowing into the mold 46 can be advantageously performed, and the blow head 22 is provided with a blow plate 32 to be cooled and there. Since it is possible to avoid heating the moistened coated sandwich 14 housed in the blow head, the influence of the heating action from the mold 46, which is affected by the repeated molding operation, can be seen in the blow head. 22 is not subject to this, and in this respect as well, the problem caused by heating the moistened coated sand 14 housed in the blow head 22 can be advantageously avoided. It is. Moreover, hot air is blown into the mold 46 through the gassing plate 25 of the gassing box 24, so that the moistened coated sand 14 filled in the molding cavity of the mold 46 is quickly dried and solidified. It can be done. Further, there, it is also possible to advantageously adopt the heating of the mold 46 by an appropriate heating means, thereby making it possible to advantageously contribute to the drying and solidification of the moistened coated sand 14. ing.

By the way, as the molding die used in the method for producing a mold according to the present invention, a mold as in the above example can be often used, and a known mold such as a resin mold or a wooden mold can also be used. FIG. ~ FIG. 8 shows one molding example of a mold using a molding mold made of such a resin mold or a wooden mold.

Specifically, FIG. 5 shows a blowing (sand filling) form of the moistened coated sand 14 in a molding example using the resin mold 70, and the upper mold 70a and the lower mold 70b of the resin material are shown, respectively. The blow head 72 and the hopper 74 in which the moistened coated sand 14 is housed are placed and fixed on the resin mold 70 made of the resin, and the moistened coated sand 14 is made of resin by the same blowing operation as before. The mold 70 can be blow-filled. The blow plate 76 is provided with a flow path (not shown) for the refrigerant supplied from the cooling device 78, as in the above-described embodiment, thereby cooling the blow plate 76 and the blow head 72. At the very least, the heating of the moistened coated sand 14 contained therein can be suppressed or prevented. Further, in the hopper 74, the steam (steam) or water mist generated by the steam / mist generator 80 is introduced through the supply pipe 81, and the moistened coated sand 14 housed therein is introduced. , It is designed not to dry.

Then, the resin mold 70 in which the moistened coated sand 14 is blow-filled in FIG. 5 is then arranged in the vacuum suction device 82 and sucked under reduced pressure by the vacuum pump 84 as shown in FIG. As a result, the moistened coated sand 14 filled in the resin mold 70 is dried under reduced pressure and solidified to form a target mold.

Further, as shown in FIG. 7, the resin mold 70 formed by blow-filling the moistened coated sand 14 in FIG. 5 is subjected to a vacuum drying operation and carbon dioxide gas (CO ₂ gas) in a sealed gassing device 86. It is also possible to allow the cured mold to form by undergoing aeration treatment. There, the resin mold 70 in which the moistened coated sand 14 is blow-filled is fixed by the fixed cylinder 88, and the vacuum tank 90 is first communicated with the gassing device 86 to perform gassing. After the inside of the device 86 is evacuated and the resin mold 70 is subjected to the action to reduce the pressure, the carbon dioxide gas tank 92 is communicated with the gassing device 86 (at this time, the vacuum tank 90 is not). The carbon dioxide gas is introduced into the gassing device 86 (which is considered to be in a communication state). As a result, carbon dioxide gas also enters the resin mold 70, thereby accelerating the drying and curing of the filled wetted coated sand 14.

Further, in order to dry, solidify or harden the moistened coated sand 14 filled in the resin mold 70, although not shown, the moistened coated sand 14 is selectively heated by using microwaves. That is also effective. By utilizing this heating action by microwaves, there is an advantage that it is not necessary to prepare a strictly airtight processing space (chamber).

Then, as described above, the mold 94 having the desired shape obtained by drying, solidifying, or curing the filled moistened coated sand 14 (filler) in the resin mold 70 is shown in FIG. As shown in 8, the resin mold 70 (upper mold 70a and lower mold 46b) is manually or mechanically opened and taken out.

As described above, according to the molding method shown in FIGS. 5 to 8, the filled moistened coated sandwich 14 is dried, solidified, or cured without heating the resin mold 70 itself as a molding mold. Therefore, it can be said that it is preferably adopted in molding using a molding mold made of a material such as a resin mold or a wooden mold in which it is desirable to avoid heating.

As described above, the moistened coated sand 14 is housed in the sand storage hoppers 16 and 74, then supplied to the blow heads 22 and 72 from the sand storage hoppers, and then from the blow head to the molding die 46. In the step of filling the sand into the blow heads 22, 72 and / or the sand storage hoppers 16 and 74, the moistened coated sand 14 is stored for a long time or is subjected to some heating action to obtain such moisture. When the water content of the conditioned coated sand 14 is 1% by mass or less, the molding work becomes difficult and the physical properties such as the strength of the obtained mold are lowered. Therefore, such 1% by mass or less. Moisture Moisture Coated Sand 14 was allowed to moisten well and knead as needed in or out of a blowhead or sand storage hopper, with additional water added. Later, it will be advantageous to use it for molding again.

Further, as a method of moistening a dry coated sand according to the present invention and molding it by a predetermined molding mold, the above-exemplified molding method is preferably adopted, but other known molding methods are also known. It is also possible to manufacture a mold by adopting various molding methods of the above, and further, the present invention can be carried out in a mode in which various changes, modifications, improvements, etc. are made based on the knowledge of those skilled in the art. Therefore, it should be understood that all such embodiments belong to the scope of the present invention as long as they do not deviate from the gist of the present invention.

Hereinafter, the present invention will be clarified more concretely by using some examples, but the present invention shall not be construed in any way by the description of such examples. Should be understood. In the following examples and comparative examples, "%" and "part" are all shown on a mass basis unless otherwise specified. In addition, the moisture content, filling rate, and mold releasability of the coated sand (CS) obtained in Examples and Comparative Examples were evaluated as follows.

-Measurement of moisture content (%)-
10 g of each CS is weighed and stored in a crucible that has been air-baked and weighed, and the mass loss rate (%) (= moisture content) after heating at 900 ° C. for 1 hour is calculated using the following formula. did. The weighing was measured to the fourth decimal place.
Moisture content (%) = [(total mass of crucible and CS before firing)
-(Total mass of crucible and CS after firing)] / Mass of CS before firing x 100

-Measurement of filling rate (%)-
A mold having a size of width: 2.54 cm × height: 2.54 cm × length: 20 cm obtained by molding in each Example or each Comparative Example was used as a test piece, and the true aggregate was used. The ratio of the specific gravity of each test piece (calculated by dividing the mass by the volume of the test piece) to the specific gravity is calculated as a percentage.
Filling rate (%) = [Mass (g) / Volume (cm ³ ) of each test piece]
/ True specific gravity of aggregate (g / cm ³ ) x 100

-Evaluation of releasability-
After filling the molding mold with each CS and molding the mold, when the obtained mold is taken out from the molding mold, deposits are present on the molding mold surface (molding cavity surface). Whether or not it was present was visually observed and evaluated according to the following criteria.
◯: There was no deposit on the surface of the mold, and the mold could be taken out.
Δ: Although deposits were observed on the surface of the mold, the mold could be taken out.
X: The CS filled in the mold surface was stuck, and the mold collapsed when the mold was taken out.

− Production example of dry CS 1-
As a refractory aggregate, Lunamos # 80 (trade name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, is prepared, and as a water glass, which is a binder, a commercially available product: sodium silicate (No. 2) Product name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.5, solid content: 41.3%) was prepared.

Next, the above-mentioned Lunamos # 80 heated to a temperature of about 120 ° C. was put into a Shinagawa type universal stirrer (5DM-r type) (manufactured by Dalton Corporation), and the water glass was further added to 100 parts of Lunamos # 80. On the other hand, it is added at a ratio of 1.82 parts (solid content: 0.75 parts) and kneaded for 3 minutes to evaporate the water, while stirring and mixing until the sand granules collapse and then taking out. As a result, a dry coated sand (CS) 1 having free fluidity at room temperature was obtained. Then, when the water content (%) of the obtained CS1 was measured, it was 0.2%.

− Production example of dry CS 2-
The procedure is the same as in Production Example 1 above, except that the amount of water glass added as a binder is 4.12 parts (solid content: 2.00 parts) with respect to 100 parts of Lunamos # 80. Therefore, dry CS2 was obtained. The water content of the obtained CS2 was 0.5%.

− Production example of dry CS 3-
As water glass as a binder, a commercially available product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.1, solid content: 48.5%) The procedure was the same as in Production Example 1 above, except that the amount of water glass added was 1.55 parts (solid content: 0.75 parts) with respect to 100 parts of Lunamos # 80. , A dry CS3 was obtained. The water content of this CS3 was 0.2%.

− Production example of dry CS 4-
As a water glass as a binder, a commercially available product: No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 3.2, solid content: 38%) was prepared. , The amount of this water glass added was 1.97 parts (solid content: 0.75 parts) with respect to 100 parts of Lunamos # 80, but it was dried according to the same procedure as in Production Example 1 above. Obtained CS4 of the state. The water content of this CS4 was 0.2%.

-Mold manufacturing example-
(Example 1)
Using the dry CS1 obtained in Production Example 1 above, it is put into a Shinagawa universal stirrer (5DM-r type) (manufactured by Dalton Corporation), and water is further added to 100 parts of CS1. Then, the mixture was added in a ratio of 2 parts and stirred for 1 minute to moisten the dry CS1. Next, the obtained moistened CS1 was housed in a blow tank and blown into a molding die (mold) heated to 125 ° C. at a gauge pressure of 0.3 MPa to fill the mold. Then, by holding in that state for 90 seconds, the filled CS1 is dried and solidified, and a molded mold having a size of 2.54 cm × 2.54 cm × 20 cm is taken out from the molding mold and taken out as a test piece. And said.

(Example 2)
The procedure was the same as in Example 1 except that the amount of water added was 3 parts with respect to 100 parts of CS1 and the holding time of the molding mold filled with the moistened CS1 was 105 seconds. , A mold (test piece) was prepared.

(Example 3)
The procedure was the same as in Example 1 except that the amount of water added was 4 parts with respect to 100 parts of CS1 and the holding time of the molding mold after filling the moistened CS1 was 120 seconds. A mold (test piece) was prepared according to the above.

(Example 4)
A mold (test piece) was prepared according to the same procedure as in Example 1 except that the heating temperature of the mold was 75 ° C. and the holding time of the mold was 180 seconds.

(Example 5)
A mold (test piece) was prepared according to the same procedure as in Example 1 except that the heating temperature of the mold was 200 ° C. and the holding time of the mold filled with the moistened CS1 was 60 seconds.

(Example 6)
After the moistened CS1 is filled in the mold, it is held for 60 seconds, and 40 seconds after the start of the holding, heated air at a temperature of 150 ° C. is aerated for 20 seconds under a gauge pressure of 0.03 MPa. A mold (test piece) was prepared according to the same procedure as in Example 1 except for the above.

(Example 7)
A template (test piece) was prepared according to the same procedure as in Example 1 except that the dry CS1 was replaced with the dry CS2.

(Example 8)
A mold (test piece) was prepared according to the same procedure as in Example 1 except that the dry CS1 was replaced with the dry CS3.

(Example 9)
A mold (test piece) was prepared according to the same procedure as in Example 1 except that the dry CS1 was replaced with the dry CS4.

− Production example of wet CS 1-
As a refractory aggregate, Lunamos # 80 (trade name: manufactured by Kao Quaker Co., Ltd.), which is a commercially available artificial sand for casting, is prepared, and as a water glass as a binder, the above-mentioned commercially available product: No. 2 silicate is prepared. Sodium (trade name: manufactured by Fuji Chemical Co., Ltd.) was prepared. Next, the above-mentioned Lunamos # 80 in a normal temperature state was put into a Shinagawa type universal stirrer (5DM-r type) (manufactured by Dalton Corporation), and the water glass was further added to 100 parts of Lunamos # 80. 1.82 parts (solid content: 0.75 parts) was added and kneaded for 3 minutes to obtain wet CS11. The water content (%) of CS11 in this wet state was measured and found to be 1.1%.

− Production example of wet CS 2-
As the water glass as a binder, the above-mentioned commercial product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd.) was prepared, and the amount of this water glass added was 100 parts of Lunamos # 80. , 1.55 parts (solid content: 0.75 parts), and a wet CS12 was obtained according to the same procedure as in Production Example 1 of the wet CS described above. The water content of CS12 in the obtained wet state was 0.9%.

− Production example of wet CS 3-
As the water glass as a binder, prepare the above-mentioned commercial product: No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd.), and add the amount of this water glass to 100 parts of Lunamos # 80. A wet CS13 was obtained according to the same procedure as in Production Example 1 of the wet CS except that the amount was 1.97 parts (solid content: 0.75 parts). The water content of CS13 in the obtained wet state was 1.2%.

(Comparative Example 1)
Using the wet CS11 obtained above, this was placed in a blow tank and blown into a molding mold heated to a temperature of 125 ° C. at a gauge pressure of 0.3 MPa to fill the mold. Then, the mold was held for 90 seconds to form a mold having a size of 2.54 cm × 2.54 cm × 20 cm, which was then taken out from the mold and used as a test piece.

(Comparative Example 2)
A mold (test piece) was prepared according to the same procedure as in Comparative Example 1 except that the heating temperature of the mold was 75 ° C. and the holding time of the mold was 180 seconds.

(Comparative Example 3)
A mold (test piece) was prepared according to the same procedure as in Comparative Example 1 except that the heating temperature of the mold was 200 ° C. and the holding time of the mold was 60 seconds.

(Comparative Example 4)
After filling the mold with wet CS11, it is held for 60 seconds, and 40 seconds after the start of the holding, heated air at a temperature of 150 ° C. is aerated for 20 seconds under a gauge pressure of 0.03 MPa. Except for the above, a mold (test piece) was prepared according to the same procedure as in Comparative Example 1.

(Comparative Example 5)
A mold (test piece) was prepared according to the same procedure as in Comparative Example 1 except that the wet state CS11 was replaced with CS12.

(Comparative Example 6)
A mold (test piece) was prepared according to the same procedure as in Comparative Example 1 except that the wet state CS11 was replaced with CS13.

-Evaluation of mold characteristics-
With respect to the various molds (test pieces) obtained in Examples 1 to 9 and Comparative Examples 1 to 6 above, the filling rate was measured and the releasability was evaluated according to the above-mentioned measuring method or evaluation method. The results are shown in Tables 1 and 2 below.

As is clear from the results of Tables 1 and 2, the molds (test pieces) molded in Comparative Examples 1 to 6 obtained by using CS11 to 13 in a wet state having a water content of more than 0.8%. In the case of the above, while the releasability is poor, water is added to each of the dry CS1 to CS1 to 4 having a water content of 0.8% or less to moisten them, and then molding is performed. It is recognized that each of the molds (test pieces) according to Examples 1 to 9 thus obtained shows good releasability.

Further, the molds (test pieces) obtained in Examples 1 to 9 have an improved filling rate of CS1 to CS4 as compared with the molds (test pieces) obtained by using the wet CS11 to 13. Further, as in Example 5, the temperature of the mold is heated to 200 ° C. or higher, or as in Example 6, heated air is aerated in the mold to hold the mold for a holding time. It can be acknowledged that (dry solidification time) can be shortened and good mold characteristics can be realized.

10 Molding equipment 12 Molding chamber 14 Moisturized coated sand 16 Hopper 22 Blow head 24 Gashing box 25 Gushing plate 26 Valve body 30, 40 Steam / mist generator 32 Blow plate 34 Cooling device 36 Blow nozzle 38 Steam / mist box 42 Exterior cylinder 44 Vertical movement cylinder 46 Mold 48 Mold mounting table 50 Table moving cylinder 52 Extruding pin 54 Pin moving cylinder 56 Hot air device 60 Mold 70 Resin mold 72 Blow head 74 Hopper 76 Blow plate 78 Cooling device 80 Steam / mist Generator 81 Supply pipe 82 Vacuum suction device 84 Vacuum pump 86 Gassing device 88 Fixed cylinder 90 Vacuum tank 92 Carbon dioxide gas tank 94 Mold

Claims (15)

A step of preparing in advance a dry coated sand having a moisture content of 0.1 to 0.8% by mass, which is obtained by coating the surface of a fire-resistant aggregate with water glass , and for the coated sand. , Water is added to moisten the sand, and the moisturized coated sand having a water content of more than 1% by mass (however, the mold prepared by using the alkali silicate binder is disintegrated, and the waste sand is sieved and watered. It was added, in advance a step Ru give the excluded) those aged at room temperature, to fill the resulting Shimetai of coated sand in a mold, the manufacture of molds, characterized by a step of molding Method. The method for producing a mold according to claim 1, wherein the water is added at a ratio of 1 to 5 parts by mass with respect to 100 parts by mass of the dry coated sand. The method for producing a mold according to claim 1 or 2, wherein the molding mold is heated to a temperature of 40 to 250 ° C. The method for producing a mold according to any one of claims 1 to 3, wherein the moistened coated sand filled in the molding mold is heated by microwaves. The method for producing a mold according to any one of claims 1 to 4, wherein heated air or dry air is aerated in the molding mold filled with the moistened coated sand. The method for producing a mold according to any one of claims 1 to 5, wherein the inside of the molding mold filled with the moistened coated sand is dried under reduced pressure. The method for producing a mold according to any one of claims 1 to 6, wherein carbon dioxide gas is further aerated in the molding mold filled with the moistened coated sand. The method for producing a mold according to any one of claims 1 to 7, wherein the molar ratio of SiO ₂ / Na ₂ O in the water glass is 1.9 or more. Claims 1 to 8 in which the moistened coated sand is housed in a sand storage hopper, then supplied to a blow head from the sand storage hopper, and then filled into the molding die from the blow head. The method for producing a mold according to any one of the above. The mold according to claim 9, wherein a water supply means for supplying water into the blow head and / or the sand storage hopper to suppress or prevent the drying of the moistened coated sand is provided. Production method. The method for producing a mold according to claim 10, wherein the water supply means includes a steam or mist generator. The method for manufacturing a mold according to any one of claims 9 to 11, wherein the blow head is provided with a cooling means. The method for producing a mold according to claim 12, wherein the blow head is cooled to a temperature of 40 ° C. or lower by the cooling means. When the moistened coated sand contained in the blow head and / or the sand storage hopper has a water content of 1% by mass or less, water is further added to the moistened coated sand. The method for producing a mold according to any one of claims 9 to 13, wherein the molding is performed after moistening the mold. A claim that includes a step of transporting the prepared dry coated sand to a molding site different from the manufacturing site, in which the moistening step and the molding step are carried out. The method for producing a mold according to any one of items 1 to 14.

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