JPH0523791A - Method for treating wax pattern for precision casting and this treating liquid and this mold - Google Patents

Abstract

PURPOSE:To prevent peeling and crack of mold by forming a film having hydrophilic property higher than that of a wax on wax pattern surface. CONSTITUTION:At the time of executing the lost wax precision casting, after brining the pattern into contact with liquid forming the film having the hydrophilic property higher than that of the wax or easy-to-wet to alcohol, a base material in the treating liquid is removed to form the film having good stickness to slurry on the wax pattern surface. By this method, in manufacturing process for the mold, the peeling and crack on the coating layer, are not developed, and rapid drying can be executed and the manufacturing process for the mold can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lost wax precision casting method, and more particularly to a wax model treating solution and method, and a mold and a method for manufacturing the mold.

[0002]

2. Description of the Related Art In the lost wax precision casting method, a wax model is washed. The mainstream of the lost wax precision casting method is a ceramic shell precision casting method using a ceramic shell mold in which slurry and stucco are alternately coated and dried and solidified. Since the wax model is molded by injecting wax into a mold in which a mold release agent is sprayed, the oil and fat content of the mold release agent adheres to the surface of the wax model. Before coating the model surface with the slurry, a cleaning process is performed to remove the oil and fat and activate the model surface. If the washing process of the wax model is insufficient, the slurry will not adhere sufficiently to the model surface,
At the time of drying and solidification, peeling of the coating layer or cracking of the coating layer occurs, and the quality of the mold becomes a problem. Conventionally, as described in JP-A-58-196142 and JP-A-2-307648, a cleaning liquid for a wax model removes oils and fats to expose a fresh surface of the wax and activate trichloroethylene,
Chlorinated hydrocarbon-based organic solvents such as trichlorethane, chlorinated fluorinated hydrocarbon-based organic solvents such as trichlorotrifluoroethane (fluorocarbon), and ketone-based organic solvents such as acetone and methyl ethyl ketone are generally used.
Alcohol and aqueous detergent (having a surfactant added to water) with a small activation of the wax surface have been used as a highly safe cleaning liquid with insufficient cleaning ability.

[0003]

[Problems to be Solved by the Invention] In any cleaning process,
Adhesion to the slurry is not sufficient, and peeling or significant cracking occurs in the coating layer when rapidly dried, so the 1- and 2-layer coatings are slowly dried for at least 2 hours or longer. However, even in this case, cracks in the coating layer could not be completely prevented.

The object of the present invention is to provide a wax casting model treatment method for precision casting, which is capable of shortening the mold making process without peeling or cracking of the coating layer by making the wax casting surface having good adhesion to the slurry, and its treating solution and To provide a mold and a manufacturing method thereof.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a method of treating a wax model for precision casting, which comprises the step of forming on the surface of a wax model a film which is more hydrophilic than the wax or which is more wettable by alcohol.

The present invention is carried out by contacting the surface of the wax model with a composition capable of forming a hydrophilic film or a film that is easily wetted by alcohol, but it may be immersed in a liquid, applied or sprayed with a liquid. It can be carried out, and immersion is particularly preferable.

According to the present invention, after the hydrophilic film or the film that is easily wetted by alcohol is formed, the wax film type surface on which the film is formed is coated with a slurry containing a refractory and solidified to form a wax. A method for producing a wax model for precision casting, comprising: a step of forming a mold on the surface of the model; and a step of dewaxing the wax model on which the mold is formed.

The present invention is characterized by including a step of washing a wax model with an organic solvent or an aqueous solution containing a surfactant, and a step of bringing the washed wax model into contact with a composition containing the above-mentioned film forming agent. To do.

The present invention comprises a wax containing a substance capable of forming a hydrophilic film or a film that is easily wet with alcohol on the surface when dried, and a step of molding a model using the wax, or the model. The method is characterized by including a step of contacting with a liquid medium having compatibility with a substance capable of forming a hydrophilic film or a film that is easily wet with alcohol when dried.

The present invention resides in a precision casting wax or a wax model, which comprises a substance capable of forming a hydrophilic film or a film that is easily wet with alcohol when dried.

The present invention uses an initial layer consisting of one or two layers, which is a template surface, formed of zircon flour and zircon sand using colloidal silica as a binder, and colloidal silica formed on the initial layer as a binder. A precision casting mold having a plurality of layers of zircon flour and chamotte sand.

In the present invention, a step of bringing a composition capable of forming a film which is more hydrophilic or more wettable with alcohol than the wax onto the surface of the wax model, and a colloidal silica binder as a binder on the surface of the wax model on which the film is formed. And a step of forming an initial layer consisting of two layers by alternately depositing and solidifying a slurry having zircon filler and zircon sand, and a slurry having zircon filler as a binder and chamotte on the initial layer. The mold has a step of alternately repeating sand and a plurality of times to adhere and solidify to form a plurality of refractory layers, and a step of dewaxing from a mold formed on the wax model, and a mold baked after the dewaxing. A method for producing a precision casting mold or a casting method, characterized in that molten metal is cast into.

[0013]

In the present invention, "a hydrophilic film or a film that is easily wet with alcohol" means that this film has an affinity for a water slurry containing a refractory or an alcohol slurry containing a refractory as compared with a wax, It refers to the property that the slurry can be applied uniformly on this film. Preferably, the contact angle of the above slurry with wax to this film is 9
It is a film with an angle of 0 ° or less. As a result of the high affinity between this film and the above-mentioned slurry, the adhesive force between this film and the solidified slurry layer is greater than the adhesive force between the solidified slurry layer and the wax surface.

The film-forming agent is a thermoplastic synthetic resin, a thermosetting synthetic resin, an oxygen-curing synthetic resin, a thermoplastic natural resin,
These are thermosetting natural resins and oxygen-curing natural resins.

Specific examples thereof are polyvinyl acetate, polyvinyl chloride, polyvinyl acetal, polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl ether, polystyrene, polyethylene, nylon, ethyl cellulose, acetyl cellulose, propionate cellulose. , Cellulose acetate, nitrile rubber, neoprene rubber, butadiene rubber, acrylic resin, furan resin, urea resin, phenol resin, starch,
One or more of casein, a mixture or copolymer thereof.

The liquid medium is preferably an inorganic or organic volatile liquid having a boiling point of 100 ° C. or lower and a heat of vaporization of 540 cal / g or lower. When the liquid medium is water, it is preferable to add a polyhydric alcohol such as alcohol or glycol or a surfactant in order to increase the dispersion of the film forming agent and the wettability with the wax.

As the surfactant, fatty acid monocarboxylic acid salt, N-acryloylglutamate, alkylbenzene sulfonate, sulfosuccinic acid dialkyl ester,
Alkyl sulfate, alkyl polyoxyethylene sulfate,
Anionic type such as alkyl phosphate salt, cationic type such as alkylamine salt, alkyltrimethylammonium salt, alkyldimethylbenzylammonium salt, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxy Nonionic surfactants such as ethylene alkyl ether, polyethylene glycol fatty acid ester and fatty acid alkanolamide, and amphoteric surfactants such as lauryldimethyl acetic acid betaine.

When the liquid medium of the composition is an organic solvent, hydrocarbons such as benzene, hexane, octane, petroleum ether, petroleum benzene, kerosene, toluene and xylene,
Trichloroethane, trichloroethylene, carbon tetrachloride,
Halogenated hydrocarbons such as trichlorotrifluoroethane, alcohols such as ethanol, propanol and butanol, ethers such as ethyl ether and isopropyl ether, ketones such as acetone and methyl ethyl ketone, and esters such as methyl acetate and butyl acetate. A simple substance or a mixture of fatty acids such as formic acid and acetic acid, various gresols, and various nitrogen compounds can be used.

It is preferable to add pigments, dyes and the like to the composition so that the state of adhesion to the wax model surface can be visually observed. The color is preferably light red.

The method of bringing the composition containing the film-forming agent into contact with the wax model may be any of coating, dipping and spraying, and can be selected depending on the condition of the model and the properties of the composition.

The method of removing the liquid medium containing the film-forming agent from the surface of the model does not damage the formed film, does not apply extra stress to the model, and is less than the softening point of the wax by natural drying, ventilation drying, etc. It is better to evaporate the liquid medium at temperature.
In order to form a uniform film in the initial stage of evaporation of the base material,
It is desirable to rotate or flip the model.

When an excessive amount of oil and fat is used during the model formation, it is effective to reduce this oil and fat in advance for subsequent film formation. Therefore, the organic solvent effective for degreasing,
It can be lightly pretreated with an aqueous detergent.

It is also possible to form a thin film on the surface of the model by bringing the model formed of wax mixed with the film forming agent powder into contact with the liquid medium of the film forming agent. In this case, since the film forming agent powder is often covered with wax, the liquid medium in this case is effective to dissolve the wax.

If the film formed on the surface of the wax model is too thin, it cannot contain fats and oils, and if it is too thick, the size of the model becomes large. The amount of the film forming agent applied to the wax model is 3 to 50% by weight, preferably 30 to 50% by weight. The concentration of the film-forming agent is 0.1 for 1 liter of liquid medium.
It is preferably about 5 to 100 g, but can be determined according to the viscosity of the liquid, the shape of the model, and the required dimensional accuracy of the precision casting.

The treatment liquid used in the present invention is 1 to 10 parts of polyvinyl butyral per 1 liter of isopropyl alcohol.
g and red pigment 0.0005 to 0.05 g; acrylic resin 5 to 15 g per 1 liter of methyl ethyl ketone and red pigment 0.0005 to 0.05 g; styrene resin 1 to 10 g and red pigment 0.0005 to 0.05 per liter of toluene.
g; 0.2 to 1 liter of styrene-butadiene copolymer latex having a solid content of 20 to 60% by weight, 0.5 to 5 liters of a sodium alkylbenzene sulfonate aqueous solution of 5 to 20% by weight, and 5 to 20 liters of water are preferable.

In the conventional mold making method, it took a long time to remove the coating layer from the model, to generate cracks in the coating layer, and to make the mold. The reason for this is that when a slurry refractory mixed with binder and refractory powder is applied to the surface of the model, and further granular refractory is applied and drying begins, the temperature of the model decreases and the model shrinks due to evaporation of the solvent in the binder. Start. As the drying progresses, the evaporation amount of the solvent decreases, the temperature of the model rises toward the dry atmosphere temperature, and the model moves to the expansion process. Up to this point, the coating layer is still insufficiently solidified and can follow the contraction and expansion of the model. However, as the drying progresses further, the coating layer solidifies while shrinking due to drying, fails to follow the expansion of the model and is separated from the model surface, and cracks occur in the coating layer. If the drying speed is high, the evaporation rate of the solvent will be high, and the temperature decrease of the model in the early stage of drying will also be large,
The amount of expansion in the subsequent temperature recovery process also becomes large, and peeling and cracking are likely to occur.

In particular, when the first coating layer is dried and solidified and the second coating layer is applied on the first coating layer, the binder permeates into the first coating layer, the amount of solvent evaporation increases, and the model shrinks greatly. Since the dried and solidified initial coating layer does not soften due to the penetration of the binder, the coating layer is compressed and bent when the model contracts, and peels from the model. When the temperature of the model is restored to the expansion stage as the second coating layer is dried, the first coating layer is stretched while being bent, so that cracks occur.
The same phenomenon occurs in the coating layer after 3 times, but the shrinkage and expansion of the model is 2 because the drying speed becomes small.
Smaller than the first coating.

In order to prevent peeling and cracking of the initial coating layer, it is effective to reduce the evaporation amount of the solvent and reduce the drying speed to suppress the contraction and expansion of the model, and to avoid excessive drying. However, in the precision casting method, which is characterized by the manufacture of complicated shaped products, the size and shape of the casted products are widely varied. If the amount of the binder is reduced, the viscosity of the slurry-like refractory increases, and it is not possible to coat the narrow portion of the model and the coating with a uniform thickness, and the adhesion thickness increases, so the reduction in the evaporation amount of the solvent cannot be expected so much. In addition, the speed of dry solidification of each part of the model having a complicated shape is not uniform, and when the pores and concave portions are dry solidified, the flat surfaces and the convex portions become excessively dry.

The present inventor has found that the contraction and expansion of the model and the excessive drying cause peeling of the coating layer, which in turn causes cracks in the coating layer. In addition, the surface of the wax model has poor adhesion to the coating layer, and we believe that if this adhesion is improved, peeling and cracking of the coating layer can be prevented, and a thin film with good adhesion to the coating layer is applied to the wax model surface. We have found a wax model treatment method that is highly practical and that can prevent peeling and cracking of the coating layer.

The wax model treatment method according to the present invention is characterized in that a new film is formed on the surface of the wax model, and the coating layer formed on this film remains as a model even after the coating layer is dried and solidified. Since it has excellent adhesion and does not peel from the model, cracks do not occur in the coating layer. Since the peeling from the model does not occur even if the drying speed is increased, the mold manufacturing time can be significantly reduced.

The present invention is directed to steam turbine blades (moving blades, stationary blades) made of 12% Cr heat-resistant steel, gas turbine compressor blades, gas turbine moving blades (Ni-base superalloy), stationary blades (Co-base). It is used for lost wax precision castings of various products such as superalloys or Ni-based superalloys) and reactor fuel supports (18-8 series cast stainless steel).

As the above Ni-base superalloy, C by weight
0.15% or less, Si1% or less, Mn1% or less, Cr5
-15%, Al3-10%, Ti1.5-5%, Ta
5% or less, 5% or less of Re, 10% or less of W, 10% or less of Mo, 5% or less of Zr, 5% or less of V5 and an alloy having 45% or more of the balance of Ni, and a Co-based superalloy of C0.15- 0.3%, Si 1% or less, Mn 2%, C
r15-25%, W10% or less, Mo10% or less, N
An alloy having at least one of b, Zr, V, Ta, and Ti and the balance of Co of 45% or more is applied.

[0033]

【Example】

Example 1 10 l of methyl ethyl ketone and 100 acrylic resin
g A wax model with silicone oil used to facilitate mold release in a dissolved liquid is immersed for 10 seconds, air-dried for 30 seconds and air-dried for 2 hours, then slurry and stucco are prepared under the conditions shown in Table 1. Was coated and dried and solidified. This was dewaxed by steam in an autoclave and baked at 900 ° C., and then the first layer surface of the mold was observed. As a result, no crack was generated in the first coating layer. For comparison, the same wax model was added to 30% by volume trichloroethane / ethanol mixed solution and ethanol, 30 times each.
It was dipped for 2 seconds, naturally dried for 2 hours, coated with the same mold material, and dried and solidified. As a result, cracks were generated in the first coating layer.

Conventionally, the wax model is etched with trichloroethane, trichlorethylene, acetone, ketone or the like before coating the mold material in order to clean the surface of the silicone oil and roughen the surface to improve the sanding. However, in the present invention, these are no longer necessary.
The latter process is unnecessary, but the former process may be performed. Freon, alcohol + trichlorethane, soapy water, etc. are used for cleaning.

[0035]

[Table 1]

Example 2 A solution of 4 g of styrene resin dissolved in 1 liter of toluene was brush coated on the surface of a wax model, and naturally dried for 2 hours.
The slurry and the stucco template material were coated under the conditions described in 1. and dried and solidified. This was removed from the autoclave by steam and baked at 900 ° C., and the first layer surface of the mold was observed. As a result, no crack was generated in the coating layer. For comparison, the same wax model was immersed in trichlorotrifluoroethane for 15 seconds, naturally dried for 2 hours, coated with the same mold material, and dried and solidified. As a result, cracks were generated in the initial coating layer.

Example 3 A wax model surface was brushed with an aqueous solution prepared by mixing 0.5 liter of a styrene-butadiene copolymer rubber latex having a solid content of 40% by weight and 1.0 liter of a 16% by weight sodium alkylbenzenesulfonate aqueous solution and 10 liters of water. After air-drying for 12 hours, the slurry and stucco template material were coated and dried and solidified under the conditions shown in Table 1. After dewaxing in an autoclave and firing at 900 ° C., the surface of the first layer of the mold was observed. As a result, no crack was generated in the coating layer. For comparison, the same wax model was immersed in a commercially available 5% by volume mixed water of a neutral detergent containing 30% by weight of a surfactant for 3 minutes, naturally dried for 12 hours, and then coated with the same casting material and dried and solidified. As a result, cracks were generated in the initial coating layer.

Example 4 A model was molded using a wax in which acrylic resin powder was mixed at a weight ratio of 1: 1, the wax model was dipped in methyl ethyl ketone for 10 seconds, and naturally dried for 2 hours. The slurry and stucco template material were coated and dried and solidified. After dewaxing in an autoclave and firing at 900 ° C., the surface of the first layer of the mold was observed. As a result, no crack was generated in the first coating layer.

Example 5 Polyvinyl butyral resin (5 g) and red pigment (0.003 g) dissolved in 1 liter of isopropyl alcohol, the wax model was dipped in the solution for 3 seconds, air-dried for 5 hours, and then coated with the template material shown in Table 1 and dried and solidified. . After dewaxing in an autoclave and firing at 900 ° C., the surface of the first layer of the mold was observed. As a result, no crack was generated in the coating layer.

Next, using this template, SCM415 (C
r-Mo steel), SCS13 (austenitic steel) as an internal reactor structure, AC4C (Al-12% Si alloy)
Was cast in the atmosphere, and a Ni-based superalloy as a gas turbine blade and a Co-based superalloy having one blade as a nozzle were cast in a vacuum. In all cases, good castings could be obtained.

Example 6 10 g of polyvinyl butyral resin and 0.003 g of red pigment dissolved in 1 liter of isopropyl alcohol, 10 g of acrylic resin in 1 liter of methyl ethyl ketone and 0.003 g of pigment dissolved solution and 5 g of styrene resin in 1 liter of toluene and pigment. 0.003g Soak the wax model in each of the dissolved liquids for 3 seconds, let it air dry for 2 hours,
The first layer mold material in Table 1 was coated and dried and solidified for 2 hours. Cellophane tape was applied to the surface of this coating, and then the tape was peeled off. As a result, the cellophane tape had no adhered coating surface. This means that the adhesive strength between the coating surface and the coating is greater than that between the cellophane tape and the coating surface in the coating formed by any of the above three types of liquids. For comparison, the same wax model was immersed in tricolor trifluoroethane for 15 seconds, dried for 2 hours, coated with the first-layer mold material shown in Table 1, and dried and solidified for 2 hours. Cellophane tape was applied to the surface of this coating, and then the tape was peeled off. As a result, the coating layer adhered to the entire surface of the portion where the cellophane tape was in contact with the coating surface.

Example 7 (part name; with an outer diameter of 30 mm, an inner diameter of 280 mm and a length of 200 mm)
Water receiver, one side has a flange, and the other side has a side plate with a hole with a diameter of 70 mm.) A cylindrical wax model is dissolved in 1 liter of isopropyl alcohol, 5 g of polyvinyl butyral resin and 0.003 g of red pigment. After dipping for 2 seconds and naturally drying for 12 hours, each layer was coated with the template material shown in Table 1 and dried and solidified for 3 hours. The coating layer was not peeled off when the mold was manufactured. The same model was soaked and washed with a mixture of trivolethane 30 vol% isopropyl alcohol and isopropyl alcohol for 30 seconds each, and 1
After air-drying for 2 hours, the template material of Table 1 was used for each layer, and each layer was dried and solidified for 3 hours. At the time of coating the fourth layer, peeling occurred in the lower part of the coating layer, and it fell off from the first coating layer. In order to prevent this, it was necessary to attach eight extra wax protrusions with a diameter of 3 mm and a height of 10 mm on both sides of the model. These protrusions are used when finishing the surface of the casting.
Remove and flatten.

Styrene: Eslen beads Sekisui Chemical Co., Ltd. Acrylic: CLAREX (Nitto) Resin Co., Ltd. Polyvinyl butyral: # 3000 Denki Kagaku Co., Ltd. Styrene butadiene copolymer: JSR2801, Nippon Synthetic Chemical Co., Ltd. Pigment: Orient Oil Red 5B, Orient Chemical Co., Ltd. Dye: Ink manufactured by Pilot

[0044]

The wax model treatment liquid of the present invention forms a thin film on the model surface, and the slurry adheres firmly to it, so that there is no peeling of the coating layer or cracks after drying, and the mold production time is long. Can be shortened.

This treatment liquid hardly deteriorates even if it is used many times, and there is no problem of liquid exchange and waste liquid treatment unlike the conventional cleaning liquid.

Claims (15)

[Claims] 1. A method of treating a wax model for precision casting, which comprises the step of forming a hydrophilic film or a film more easily wetted with alcohol than the wax on the surface of the wax model. 2. A method of treating a wax model for precision casting, comprising the step of bringing a composition capable of forming a hydrophilic film or a film more easily wetted with alcohol than the wax into contact with the surface of the wax model. . 3. A wax model is dipped in a liquid of a composition capable of forming the hydrophilic film or the film that is more easily wet with alcohol than the wax, and the composition is applied or sprinkled on the surface of the wax model. The liquid medium in the formed composition comprises a step of removing the liquid medium from the surface of the wax model by natural drying or forced drying at a temperature lower than the softening point of the wax. Processing method. 4. A step of washing a wax model with an organic solvent or an aqueous solution containing a surfactant, and a film forming agent for forming a film of the washed wax model which is more hydrophilic or more wettable with alcohol than the wax. A method for treating a wax model for precision casting, comprising the step of bringing the wax model into contact with a composition containing. 5. A step of molding a model using a wax containing a substance capable of forming a film which is more hydrophilic than a wax or a film which is more easily wetted by alcohol, and the model is made a film or alcohol which is more hydrophilic than the wax. A method for treating a wax model for precision casting, comprising the step of bringing into contact with a liquid medium having compatibility with a substance capable of forming a film that is easily wettable. 6. At least one liquid medium selected from the group consisting of water and an organic solvent, and at least one film forming agent selected from a resin, the film forming agent being a hydrophilic film or alcohol as compared with a wax. A composition for treating a wax model for precision casting, which comprises forming a film which is easily wetted by a wax. 7. The resin is at least one selected from the group consisting of thermoplastic synthetic resins, thermosetting synthetic resins, oxygen-curing synthetic resins, thermoplastic natural resins, thermosetting natural resins and oxygen-curing natural resins. The composition for processing a wax model for precision casting according to claim 6, which is the resin according to claim 6. 8. The liquid medium comprises an inorganic liquid having a boiling point of 100 ° C. or less and an evaporation heat of 540 cal / g or less, and a boiling point of 10 or less.
7. At least one liquid selected from the group consisting of organic liquids having a heat of vaporization of 540 cal / g or less at 0 ° C. or less.
Or the composition for treating a wax model for precision casting according to item 7. 9. At least one liquid medium selected from the group consisting of water and organic solvents, a dye or pigment, and at least one film-forming agent selected from a resin, the film-forming agent being hydrophilic as compared with wax. Alternatively, a composition for processing a wax model for precision casting, which is for forming a film that is easily wetted by alcohol. 10. A precision casting wax comprising a substance that forms a film that is more hydrophilic or easier to wet with alcohol than a wax. 11. A wax model for precision casting, comprising a substance which forms a film which is more hydrophilic or more wettable with alcohol than wax. 12. An initial layer consisting of one or two layers, which is a template surface and is formed of zircon flour and zircon sand containing colloidal silica as a binder, and zircon containing colloidal silica formed as a binder on the initial layer. A precision casting mold having a plurality of layers of flowers and chamotte sand. 13. A step of bringing a composition capable of forming a hydrophilic film or an alcohol-wettable film into contact with the surface of a wax model, wherein a refractory material is formed on the surface of the wax model on which the film is formed. A method for producing a precision casting mold, comprising: a step of forming a mold on the surface of a wax model by applying and solidifying the containing slurry; and a step of dewaxing the wax model on which the mold is formed. 14. A step of bringing a composition capable of forming a film which is more hydrophilic or more wettable with alcohol than the wax onto the surface of the wax model, wherein colloidal silica is used as a binder on the surface of the wax model on which the film is formed. A step of alternately depositing and solidifying a slurry having zircon filler and zircon sand to form an initial layer consisting of two layers; a slurry having zircon filler as a binder and colloidal silica and chamotte sand on the initial layer; A method for producing a precision casting mold, comprising: a step of alternately repeating a plurality of times to adhere and solidify to form a plurality of refractory layers, and a step of dewaxing from a mold formed on the wax model. . 15. A step of bringing a composition capable of forming a film which is more hydrophilic or more wettable with alcohol than the wax onto the surface of the wax model, wherein colloidal silica is used as a binder on the surface of the wax model on which the film is formed. A step of alternately depositing and solidifying a slurry having zircon filler and zircon sand to form an initial layer consisting of two layers; a slurry having zircon filler as a binder and colloidal silica and chamotte sand on the initial layer; Steps for alternately repeating and adhering and solidifying a plurality of layers to form a refractory layer, and dewaxing from the mold formed on the wax model, casting molten metal in the mold baked after the dewaxing A precision casting method comprising a step of inserting.