JPH08332547A - Casting method and mold and its production - Google Patents

Abstract

PURPOSE: To enable production of a precision casting similarer to a casting with a lost wax process than a general cast steel product and cheaper than the casting with the lost wax process by simplifying a complicated process in the lost wax process needing much cost and the long time in the casting. CONSTITUTION: A mold with a shell molding method formed by using coated sand consisting essentially of aggregate and organic binder, is used and inorganic binder 12 is impregnated on a casting skin forming surface to beforehand harden this surface. Molten metal is packed into the inner part of the shell mold forming the inorganic binder impregnating-hardened layer on the casting skin forming surface to produce the casting. Then, the shell mold is heated in the temp. range of almost 100-250 deg.C and the molten metal is rapidly poured by a dropping direct pouring method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a casting method using a novel mold similar to the shell mold, a novel mold similar to the shell mold used for the casting, and
The present invention relates to a new mold manufacturing method similar to the shell mold mold, and a new casting method using the shell mold mold.

[0002]

2. Description of the Related Art A shell mold used in a conventional sand mold casting method is manufactured and cast as described below. That is, conventionally, an aggregate such as silica sand, zircon, and alumina, and an organic binder or an inorganic binder are kneaded, and the kneaded product is blown with air into a heated mold to form an upper mold having a cavity and a lower mold. Mold each mold. Then, a mold coating agent in which graphite and silicon are mixed is applied to the cavity and the mold matching surface of each of the upper mold and the lower mold as needed. Then, the upper mold is placed on the lower mold, and the mold is dried.

After the molds have been dried in this way, the molds are piled up and then poured from the sprue part of the uppermost mold, and the molten metal flows through the side runners to the lowermost mold. Casting is performed by pouring (down-pouring) type pouring that sequentially fills the cavity above the cavity. Here, conventionally, the molten metal is poured into a mold at room temperature, and the molten metal is poured at a slow speed that is optimal so that the molten metal spreads well in each cavity, and the metal is pushed up (down-pour). The molten metal fills each cavity as a layered structure. After that, after cooling, the upper mold and the lower mold are collapsed to separate the molds to obtain a cast product.

As described above, the pouring method is generally a push-up method, but direct pouring (dropping) is performed by pouring the molten metal directly from the sprue of the uppermost mold to the runway where each cavity is connected to the side. There is also a method. However, this direct injection (drop-in) method is not usually used because gas defects are likely to occur. That is, since the casting defect caused by the fact that the mold at the sprue part is washed during pouring is escaped, the push-up method has been generally adopted conventionally.

By the way, the lost wax method is exclusively used as a precision casting method for obtaining a product which requires a highly precise and clean surface which cannot be obtained by the above general sand mold casting method. . The lost wax method is a method in which a refractory material is packed around the wax model or a layer made of the refractory material is formed, and the wax is poured out by heating to form a mold.The lost wax method includes a solid molding method and a ceramic shell method. There is a molding method, and each has a feature that a mother die (model) is made of wax.

9 and 10 show the steps of casting by the lost wax method (ceramic shell molding method). First, as shown in FIG. 9 (a), a wax model 91 corresponding to the product shape is formed. To do. Then, as shown in FIG. 9B, the wax models 92 of the sprue part and the runner part are joined onto the wax model 91 to assemble a tree,
By repeating coating, sanding and drying, as shown in FIG.
Forming a refractory layer 93 around the tree. Subsequently, as shown in FIG. 10A, the wax models 91 and 92 are melted and dewaxed by rapid heating, and then, in a furnace (not shown), for example, at 1000 ° C. to 1050 ° C.
After firing for about 0 minutes, as shown in FIG. 10B, the molten metal 95 is poured from the tribe 94 into the mold 96 for casting. After that, by collapsing the mold 96 with a vibration facility or the like, as shown in FIG.
The product 97 is taken out.

There is also a method of using a convert binder as a method of producing a mold which can withstand high temperatures without producing a wax matrix. This is, by the existing shell mold method, to make a mold with high strength at room temperature, after impregnating this with an inorganic conversion binder, in a heating furnace, first, by burning and removing the organic binder, This is a method of producing a mold bound by a heat-resistant inorganic sintered binder while keeping the temperature raised to a higher firing temperature. This method
Even if the mold is heated to a temperature at which the flowability of the molten metal becomes good, the strength is maintained to some extent, so that there is an advantage that a thin-wall cast product can be produced at low cost.

As another precision casting method, a shell mold method is used in which a thin shell-shaped mold is made by using sand mixed with 3 to 7% of carboxylic acid-based synthetic resin powder, and the molten metal is poured into the mold to make a cast product. There is. The sand is called resin sand, and there are mechanically mixed resin and sand, and coated sand in which sand particles are sprinkled with resin. As the shell mold method, the latter method requires a smaller amount of resin, so a method using coated sand with a thermosetting organic binder is generally used. Used for molding children.

[0009]

However, in the shell mold manufacturing method, which is the conventional general sand mold casting method as described above, the following methods are used in the case of using an organic binder and in the case of using an inorganic binder, respectively. There were some problems to mention.

(1) When an organic binder is used for molding First of all, most organic binders are thermosetting.
Although the productivity at the time of mold making is good, there are the following problems. It cannot be fired because the mold will collapse when fired. Gas is generated during casting, and defects such as gas entrapment defects and molten metal swirling are likely to occur. The mold coating agent hinders outgassing during casting and tends to cause gas defects and defective molten metal rotation. It is not suitable for precision casting (especially thin and thin) because the molten metal is poured into a mold at room temperature and cast.

(2) When an inorganic binder is used for molding Since the inorganic binder has fire resistance, gas generation during casting is small, but there are the following problems. Productivity is poor because the curing speed of the molding of the mold is relatively slow. A mold using an inorganic binder has difficulty in separating the mold after casting. Since it is cast at room temperature, it is not suitable for thin-walled products and precision cast products. Regeneration of sand is difficult and waste sand treatment is required.

Regarding the precision casting method, first of all, in the lost wax method, since the mother die is made of wax, as described above, the complex process of wax molding, coating and sanding and drying, dewaxing and firing is complicated. However, since the mold strength is too high even after casting, a large amount of equipment and labor are required for removing the mold, resulting in a high production cost and a long production period.

Further, according to the method using the convert binder, when the shell mold is heated, the temperature is from 500 ° C to 600 ° C.
Although the organic binder burns out at 0 ° C. and loses its binding force, the strength of the inorganic binder has not reached the strength obtained by sintering because the temperature is below the transformation point of SiO ₂ . Therefore, 500
The strength of the mold is low from 0 ° C to 600 ° C until the sintering temperature (800 ° C or higher) is reached, and the mold itself causes deformation. In order to prevent this, it is necessary to place the mold on a fire-resistant jig or the like to suppress deformation and fire it, and even if it can be used for making a mold with a relatively simple shape with a planar support part. However, there is a drawback that it cannot be applied to a mold having a complicated three-dimensional shape, or the dimensional accuracy is deteriorated even if it is applied. Further, since all of the organic binder is burnt off before pouring, there is also a drawback that the overall mold strength at the time of pouring is lowered and the precision of the cast product is lowered.

In the case of the shell mold method, 60
Since it decomposes at a high temperature of 0 ° C. or higher and loses its binding force, it is impossible to prevent the sand on the surface of the shell mold mold that comes into contact with the molten metal from collapsing and the casting surface to be roughened.

Therefore, an object of the present invention is to repeat wax forming, coating and sanding and drying, dewaxing, in the costly and time-consuming lost wax method.
It is an object of the present invention to provide a casting method that simplifies a complicated process such as firing and that enables production of a precision cast product that is cheaper than the lost wax method and closer to the lost wax method than a general cast steel product. Another object of the present invention is to provide a casting method that is more clean than general cast steel products and sand casting products and that has a casting surface close to that of lost wax casting products. Then, the present invention is a casting method which is cheaper than the lost wax method as described above and is capable of producing a precision casting product closer to the lost wax method than a general cast steel product and a casting surface close to the lost wax casting product is obtained. Apply to
Another object is to provide a mold that withstands the temperature and pressure of the molten metal during pouring and has good disintegration after cooling, and a manufacturing method thereof.

[0016]

In order to solve the above-mentioned problems, the invention according to claim 1 uses a shell mold mold formed by using a coated sand containing an aggregate and an organic binder as main components. , The inorganic surface of the casting mold forming surface is impregnated with an inorganic binder or an inorganic binder containing a refractory powder and hardened, and an inorganic binder-impregnated cured layer is formed on the surface of the casting surface to form a metal inside the shell mold. It is characterized by a casting method in which a molten product is filled to produce a cast product.

Further, the invention of claim 2 is the same as claim 1.
In the casting method described above, the inorganic binder-impregnated hardened layer is in a state in which the shell mold mold formed on the casting surface forming surface is heated therein, so that the molten metal is rapidly poured by a direct injection method. It is characterized by having done.

According to the third aspect of the present invention, a shell mold mold formed by using a coated sand containing an aggregate and an organic binder as a main component is used, and the shell mold mold is heated inside the shell mold mold. The casting method is characterized by rapidly pouring molten metal into a casting by a direct pouring method.

The invention according to claim 4 is the same as claim 2
Alternatively, in the casting method described in 3, the heating temperature of the mold is in the temperature range of approximately 100 ° C to 250 ° C.

The invention according to claim 5 is a shell mold mold formed by using a coated sand containing an aggregate and an organic binder as a main component, and the casting surface forming surface of the shell mold mold comprises: It is characterized by the constitution of a mold formed by forming an inorganic binder-impregnated cured layer by impregnating an inorganic binder or an inorganic binder containing refractory powder and curing the same.

[0021] According to the invention of claim 6, a shell mold is formed by using a coated sand containing an aggregate and an organic binder as main components, and an inorganic binder or an inorganic binder is formed on a casting surface of the shell mold. It is characterized by a method for producing a mold in which an inorganic binder-impregnated cured layer is formed by impregnating an inorganic binder containing refractory powder and curing it.

Further, the invention according to claim 7 is the invention according to claim 6.
In the method for producing a mold as described above, the inorganic binder is cured by (a) spraying or applying an alkaline atmosphere gas after impregnating the inorganic binder to accelerate curing.
(B) spraying an alkaline solution after impregnation with an inorganic binder or coating to accelerate curing, (c) substituting an alkaline atmosphere gas for impregnating an inorganic binder to promote curing, (d) spraying an alkaline solution,
Alternatively, after coating and drying, an inorganic binder is impregnated and cured, (e) an inorganic binder is mixed with an alkaline solution and impregnated by coating to accelerate curing, and (f) an inorganic binder and an alkaline solution are impregnated and cured by simultaneous spraying. Yes, (g) after being impregnated with an inorganic binder, it is placed in an acidic environment to gradually cure, and (h) it is impregnated with an inorganic binder to be humidified or placed in a dehumidifying environment to be cured.
It is characterized by either (i) impregnating with an inorganic binder and curing in an environment of humidification and dehumidification, or (j) impregnating with an inorganic binder and naturally curing.

[0023]

According to the first aspect of the present invention, the molten metal is filled by using a shell mold mold in which an inorganic binder or an inorganic binder containing a refractory powder has been impregnated and cured on the casting surface forming surface in advance. Then, a cast product having a beautiful casting surface can be obtained by the inorganic binder-impregnated cured layer formed on the casting surface forming surface of the mold. In this way, since the process is simplified as compared with the lost wax method, the product can be obtained at a lower cost than the lost wax method, and the casting surface of the thin portion is beautiful,
It enables the production of precision cast products that are closer to the lost wax method than general cast steel products. Further, in particular, in the thin portion, a cast product which is cleaner than a general cast steel product or a sand cast product and has a casting surface close to that of a lost wax cast product can be obtained.

Further, according to the second aspect of the present invention, the shell mold mold having the casting surface forming surface on which the inorganic binder-impregnated hardened layer is formed is heated, and a molten metal is dropped into the shell mold directly. Since it is a casting method in which the molten metal is rapidly poured by the shell mold, the molten metal can be easily poured by pouring it in the heated state of the shell mold, and since the rapid pouring is performed by the direct pouring method, the molten metal pressure in the cavity of the mold is instantly increased. Therefore, the influence of the gas generated from the mold can be minimized. Therefore, also from this, it becomes possible to produce a precision cast product closer to the lost wax method than a general cast steel product.

According to the third aspect of the invention, since the shell mold is a casting method in which the molten metal is rapidly poured into the inside in a heated state by a direct injection method, the shell mold is heated. Since the molten metal can be poured around in a good condition and the direct pouring method is used for rapid pouring, the molten metal pressure in the mold cavity can be instantly increased, minimizing the effect of gas generated from the mold. It can be suppressed to the limit. In this way, since the process is simplified as compared with the lost wax method, products can be obtained at a lower cost than the lost wax method, and in particular, because the hot water around the thin portion is good, the lost wax method is more suitable than general cast steel products. It is possible to produce close precision castings.

According to the invention as set forth in claim 4, at the time of the rapid pouring by the direct pouring method, approximately 100 ° C to
Since the shell mold is heated in the temperature range of 250 ° C., the organic binder is prevented from decomposing, the mold is not adversely affected by heat, the hot water flow is improved, and the water that causes gas defects is removed. A cast product with few surface defects can be obtained.

Further, according to the invention of claim 5, since it is a shell mold mold in which an inorganic binder-impregnated hardened layer is formed on the casting surface forming surface, the inorganic binder-impregnated hardening layer formed on the casting surface forming surface is The mold strength that can withstand the temperature and pressure of the molten metal during rapid pouring by such a direct pouring method can be maintained, and since the inside of the mold is a normal coated sand, the disintegration after cooling is good.

According to the sixth aspect of the present invention, the casting surface of the shell mold mold is impregnated with an inorganic binder or an inorganic binder containing refractory powder to cure the mold. A shell mold mold having an inorganic binder-impregnated hardened layer for securing strength during rapid pouring by a pouring method on a surface for forming a casting surface can be obtained.

Further, according to the invention of claim 7,
(A) spraying or applying an alkaline atmosphere gas after impregnating the inorganic binder to accelerate curing, (b) spraying or applying an alkaline solution after impregnating the inorganic binder to accelerate curing, or (c) applying an alkaline atmosphere gas. After substitution, impregnation with an inorganic binder to accelerate curing, (d) spraying or coating with an alkaline solution, followed by drying to impregnate and cure the inorganic binder,
(E) An inorganic binder is mixed with an alkaline solution to be impregnated by coating to accelerate curing, and (f) An inorganic binder and an alkaline solution are impregnated and cured by simultaneous spraying,
(G) After impregnating an inorganic binder, it is placed in an acidic environment to gradually cure, (h) Impregnated with an inorganic binder to be humidified, or placed in a dehumidified environment to be cured, (i) Impregnated with an inorganic binder to be humidified. And (c) by impregnating with an inorganic binder and naturally curing by impregnating with an inorganic binder, the inorganic binder impregnated on the casting surface of the shell mold is cured. A cured layer impregnated with an inorganic binder can be formed.

[0030]

Embodiments of the casting method, mold and manufacturing method thereof according to the present invention will be described below with reference to FIGS. 1 to 8. First, FIGS. 1 to 4 show, in order, an example of a mold manufacturing process to a casting process to which the present invention is applied.

First, in this embodiment, a method of manufacturing a thin stainless steel machine part will be described. FIG. 1 (a) shows a die manufacturing process, in which the upper die 1 and the lower die 2 are provided with molding portions 3 and 4 corresponding to the shape of the die on the mating surfaces thereof. A sand feeding port 5 is formed at 1. The upper die 1 and the lower die 2 described above are joined at their mating surfaces as shown in the drawing. The shape of the mold to be produced has a uniform thickness (for example, a wall thickness of several mm to 10 mm) that follows the shape of the cast product.
Several mm). Also, a divided mold is produced which is appropriately divided so that it can be die-cut, and can be assembled and joined accurately including the core.

Then, a mold is prepared. FIG. 1 (b) shows a molding process, in which a sand feeding pipe 6 is connected to the sand feeding port 5, and a coated sand 7 which is shell sand is fed into the molding portions 3 and 4 by a blow method to be filled. Here, the sand for shells is silica sand having heat resistance and air permeability necessary as an aggregate,
Cerabeads, zircon sand, fused quartz sand, alumina sand, etc. alone or mixed with refractory sand, in the same manner as in general shell mold coated sand, a binder mainly composed of phenolic resin (organic binder,
(See reference numeral 21 in FIG. 5).
The amount of the phenolic resin added is about 1% by weight, which is low enough to maintain the room temperature strength of the molded product. this is,
This is to reduce shrinkage of the mold during casting and to reduce combustion gas.

The above-mentioned sand mold is molded by a generally used shell-type automatic molding machine, that is, generally by the above-mentioned blow method. At that time, the thickness of the layer to be heat-cured is several meters as described above.
The thickness of the cured layer has sufficient strength in the range of m to 10 mm. If there is uncured sand outside the center, the shell sand mold is tilted and discharged after molding and hardening. This is to save the used coated sand and improve the outgassing. After the heating and curing by the above, the upper mold 1 and the lower mold 2 are opened, and the shell sand mold is taken out. FIG. 2 (a) shows a state in which the mold is taken out, and this shell sand mold 8 has a joint recess 9 on the peripheral mating surface and a runner 10 near the center.

Next, a hydrolyzed liquid of ethyl silicate (inorganic binder) is applied by a brush or a spray to the surface of the shell sand mold 8 on which the casting surface is formed, that is, the surface of the shell sand which is in contact with the casting surface of the casting. FIG. 2B shows impregnation with an inorganic binder, and as shown in the figure, the surface of the shell sand mold 8 on which the casting surface is formed is sprayed with a hydrolyzed liquid of ethyl silicate (inorganic binder) 12 by a spray 11 so that the runner portion 10 is also blown. Including the inorganic binder impregnated layer 13 is formed. Here, the ethyl silicate hydrolyzed liquid (inorganic binder) 12 penetrates into the sand mold 8 due to a capillary phenomenon, and the impregnation depth is deep, and the silica concentration in the surface layer is low. The treatment is repeated several times to form the required inorganic binder impregnated layer 13. And in an Example, the process which accelerates | stimulates hardening of this inorganic binder impregnation layer 13 is performed.

FIG. 2 (c) shows a hardening accelerating treatment of an inorganic binder, in which a shell sand mold 8 having an inorganic binder impregnated layer 13 formed on a casting surface is placed in an ammonia gas box 14 as shown in the figure, and gas is supplied. Opening and closing cock 16 for pipe 15
Open to fill the box 14 with ammonia gas. Reference numeral 18 is a gas exhaust pipe, and 19 is an opening / closing cock thereof. By exposing the inorganic binder impregnated layer 13 to the ammonia gas atmosphere in this way, the condensation reaction of the impregnated ethyl silicate hydrolyzed liquid is promoted, that is, the gelation of the inorganic binder impregnated layer 13 is promoted.
Then, after several minutes, the shell sand mold 8 is taken out from the box 14 and dried in the same manner as in the lost wax method of the ethyl silicate binder method. That is, natural drying or ammonia drying is performed.

The above-mentioned impregnation, gelation and drying are repeated 1 to 3 times in order to obtain the required mold surface strength. As a result, the inorganic binder-impregnated hardened layer 20 (see FIG. 5) in which the solidified SiO ₂ layer or the solidified particles mixed with the slurry are distributed between the sand particles is formed on the casting surface of the shell sand mold 8. In this case, sufficient voids are left between the sand particles so that the gas generated during casting escapes. For this reason, it becomes difficult for the defective molten metal flow due to the gas to occur.

That is, FIG. 5 shows the structure of the casting surface forming surface of the shell sand mold 8. As shown in FIG. 5A, the shell sand mold 8 has a wall thickness N (several mm to several tens of mm). On the other hand, the depth n of the inorganic binder-impregnated hardened layer 20 from the surface of the casting surface forming surface is reinforced by setting it to 3 mm to 5 mm. Therefore, it is possible to prevent the mold from collapsing at the time of casting and facilitate the mold separation after casting. That is, as shown in an enlarged view in FIG. 5B, the surface of the sand 7 is coated with the organic binder 21 to form a shell sand mold casting surface on which the inorganic binder is impregnated and dried to impregnate the inorganic binder. Hardened layer 2
The crystal 22 of the inorganic binder is SiO ₂
It is superior in breathability as compared with the type-coating agent because of the crystals. And even if the organic binder 21 evaporates due to the heat of pouring,
The crystal 22 of the inorganic binder holds the shape of the template.

As described above, the shell sand mold 8 having the inorganic binder-impregnated hardened layer 20 formed on the casting surface forming surface and the similar inorganic binder-impregnated hardened layer formed on the casting surface forming surface in parallel with this Join the shell sand mold and assemble the mold. FIG. 3 (a) shows the assembly of the mold, and the divided shell sand mold 23 corresponding to the shell sand mold 8 has the joining convex portion 24 on the peripheral mold matching surface, and the sprue sand mold 25 is prepared. Then assemble these. Figure 3 (b) shows the joining of the molds, the upper and lower shell sand molds 8,2.
The adhesive 26 used for the shell mold is applied to the mold matching surface around 5 and the mold matching surfaces are bonded to each other while fitting the bonding protrusions 24 to the bonding recesses 9.
Then, the sprue sand mold 25 is similarly bonded with the adhesive 26.

In this way, the mold shape is completed. further,
If necessary, a refractory mortar 27 is applied to the outer surface of the joint to reinforce the mold. Then, it is heated to complete the mold. FIG. 3 (c) shows the heating of the mold, in which the blower pipe 28 is connected to the sprue sand mold 25, and as shown by the arrow, 15
Hot air 29 at 0 ° C. to 300 ° C. is blown in for 1 to 3 hours to dry. Alternatively, the mold may be placed in a heating furnace (not shown) and the same drying process may be performed. The shell mold 30 thus assembled and joined is simply referred to as a shell mold 30 in the following examples.

Here, since the shell mold 30 produced according to the present invention uses an organic binder and an inorganic binder in combination, it has a higher high temperature strength than a mold having only an organic binder, but is baked like a lost wax mold. Since the binder is not sintered, it has lower high temperature strength than the lost wax mold. Therefore, the sprue and runner exposed to a high temperature for a longer time may be formed of a cheaper and highly fire-resistant material, and may be used by being joined to the shell mold 30 according to the present invention. Further, the completed shell mold 30 may be reinforced by binding with a wire or the like as necessary so that the joint portion does not float up due to the pressure of the hot water at the time of pouring.

Then, as described above, after holding at 150 ° C. to 300 ° C. for 1 to 3 hours to dry, the shell mold 30 is taken out and heated in the temperature range of 100 ° C. to 250 ° C., and the direct injection method is used. Rapid pouring. FIG. 4A shows a pouring state, in which the tribe 3 is placed above the shell mold 30.
The molten metal 35 of stainless steel is dropped from 4 into the sprue 31 at once, and the cavity 33 is filled with the molten metal through the runner 32. After that, if the cooling time has elapsed, the shell mold 30
Is collapsed to obtain a cast product. FIG. 4 (b) shows the mold variation, and the shell mold 30 becomes the collapsed sand 36 and becomes the cast product 37.
Can be taken out.

In the above, the mold temperature during pouring has some influence on the fluidity of the molten metal, but it is not critical. That is, when the mold temperature is close to the room temperature, the cooling of the hot water is faster, the mold surface is less likely to be collapsed, and the gas generation is gentle, so that a cleaner casting surface may be obtained in some cases.
Therefore, both the heating temperature and the mold temperature at the time of pouring should be appropriately selected depending on the shapes, weights, heat radiation properties, etc. of the cast product and the mold. However, since the present invention also utilizes the mold strength due to the binding force of the organic binder during pouring, heating is carried out within a range in which the strength of the organic binder does not decrease so much. The heating temperature range is 100 as described above.
C to 250C.

The shell mold 30 produced according to the present invention is covered with a thin organic binder on the surface of the refractory sand until the organic binder is burned, decomposed and volatilized by pouring the molten metal, and silica (SiO ₂ ) Is a structure surrounded by a film or solidified refractory layer, sufficient voids also remain. Therefore, the surface of the refractory sand is hardly in contact with the inorganic binder, and the refractory sand is only partially bonded at the portion where the organic binder is burned out only after pouring. Further, this SiO ₂ is only partially transformed, and the bonding strength is low. On the contrary, the SiO ₂ particles and the film interposed between the refractory sands suppress the movement of the sands and maintain the strength as a mold. Furthermore, the organic binder in the part away from the molten metal surface is not completely decomposed by heat, and holds the mold strength to some extent with the coexisting inorganic binder.
The backup effect of this layer helps to reduce the collapse of the mold surface in contact with the casting surface.

Further, since the porosity is higher than that of the lost wax mold, it is difficult for the gas to obstruct the flow of the molten metal, and it is possible to flow into the thin portion even at a lower molten metal temperature. Because of the viscosity that cannot flow into the gap, it is possible to obtain a fine cast surface that is far more beautiful than the roughness of the shell surface. That is, the casting surface becomes more clean as the portion cools faster in the thin portion. Due to the above mold characteristics, the mold disintegration is good, and it is not necessary to remove the mold by a knockout machine or alkali treatment, which contributes to cost reduction. The cutting and finishing of the cast product after removing the mold are the same as those for the general lost wax cast product.

As described above, according to the present invention, the point that the casting surface of the shell mold mold containing the organic binder is impregnated with the inorganic binder and hardened, and then the binder is not heated to be cristobaliteized by firing. is there.
That is, the method of using a conversion binder that converts an organic binder template into an inorganic binder template by heating and firing after impregnation curing has the above-mentioned drawbacks. But,
In the present invention, at the time of pouring, the SiO ₂ partly becomes cristobalite at the time of pouring, but since the heating time is short,
Most of them are not cristobalite, and the disintegration after casting is improved. In other words, even if SiO ₂ is not cristobaliteized, it does not burn as an inorganic substance, so that it does not lose its binding force like an organic binder.

Next, the reason why the present invention makes it possible to obtain a casting product which is more accurate than the sand casting and has a clean surface. (1) As is known, the shell mold method can make a mold with higher precision than a sand mold casting.

(2) The strength of the casting mold after pouring is determined by the high temperature strength (heat resistance) of the cavity surface layer and the strength of the backup portion connected to the cavity portion. In the shell molding method, it is possible to produce a mold having a shape that gives the backup portion necessary strength with a smaller amount of sand than the sand mold. Further, in the present invention, since the amount of sand (weight) is smaller than that of the normal sand mold, the heat capacity is small, the temperature drop of the hot water during pouring is small, the pouring fluidity is good, and the degassing is good. Therefore, it is easy for hot water to go around the thin wall. Therefore, a thinner and more precise cast product can be obtained.

(3) The mold is thin (compared to the normal sand mold)
Therefore, the heat dissipation is good. In the present invention, the hot water is cooled more quickly because the heat dissipation after the hot water is filled in the cavity is good. Therefore, the temperature of the cavity portion also drops rapidly, and the refractory sand is less likely to be damaged by heat. In addition, the temperature of the molten metal itself drops rapidly, and the fluidity of the molten metal decreases rapidly, making it difficult for the molten metal to flow into the heat-damaged mold. Therefore, a casting with a clean surface can be produced.

As described above, according to the present invention, by taking advantage of the characteristics of the shell mold template, the shell is reinforced with an inorganic binder having high strength at high temperature, and the cavity surface layer (casting surface forming surface) is coated with refractory powder, It enables the production of castings with beautiful casting surfaces.

By the way, in the above embodiment, FIG.
As shown in FIG. 2B, after the impregnation with the inorganic binder, a curing acceleration treatment with ammonia gas was performed.
On the contrary, as shown in FIG. 6, processing in the reverse order may be performed. That is, first, as shown in FIG. 6A, the shell sand mold 8 is put in the ammonia gas box 14 and the discharge pipe 1
The opening / closing cock 19 of 8 is opened to evacuate, and the opening / closing cock 16 of the gas supply pipe 15 is opened to open the box 14
By filling the inside with ammonia gas, the air inside the shell sand mold 8 is replaced with ammonia gas. Then, the shell sand mold 8 is taken out from the box 14 and
As shown in (b), spray 1 on the surface where the casting surface is formed.
1, the ethyl silicate hydrolyzed liquid (inorganic binder) 12 is sprayed to form the inorganic binder impregnated layer 13 including the runner portion 10.

According to the above gas replacement method, the inorganic binder did not penetrate deeply and gelled at the surface layer of shell sand,
Silica formation occurs. The shell replaced with ammonia gas is subjected to an operation of lowering the ammonia gas concentration in the surface layer. This is because the impregnation depth of the binder can be adjusted by the concentration of ammonia gas in the surface layer, but when the concentration is high, silica cannot be formed between the particles of the shell and the silica is formed on the surface, and the silica fixation stability is poor. Therefore, by lowering or reducing the concentration of ammonia gas in the surface layer to zero, the binder can be impregnated into the surface layer portion, and silica is formed between the shell particles. In this way, the permeation of the binder gels in the surface layer portion, so that the amount of silica in the surface layer portion increases. Further, the depth of silica impregnation can be adjusted, that is, it can be shallow.

By the way, FIG. 7 schematically shows an example of the rapid pouring method by the direct pouring method according to the present invention. As shown in the figure, a large sprue 38 above the shell mold 30 and also a large pouring water. A passage 39 is provided and a large metal spout 38 is provided with a molten metal 35 of stainless steel from the trolley 34.
Is dropped all at once, and the cavity 33 is also filled with molten metal through the large runner 39. As a result, the molten metal can be quickly filled up to every corner of the cavity 33 including the thin portion. Then, after the elapse of the cooling time, the shell mold 30 is collapsed to obtain a cast product 37, which is a thin-walled machine component made of stainless steel, as shown in FIG. It should be noted that FIG. 7 merely shows an example of the method of rapid pouring, and the specific method of rapid pouring is not limited to this, and an appropriate method may be adopted.

As described above, according to the embodiment of the present invention, a hydrolyzed binder of ethyl silicate is applied to the casting surface forming surface of the shell mold which is formed by using the coated sand containing the phenol resin as the main component. After impregnation and aeration with ammonia gas, (or after replacing the air inside the mold with ammonia gas and then impregnating the casting surface forming surface with a hydrolyzed binder of ethyl silicate), dry and remove silica. To make a casting product by gelling and making a mold in which the outside of the organic binder is solidified with an inorganic binder, and rapidly pouring the molten metal into the mold heated within the range where the organic binder does not decompose by the direct injection method at once. Therefore, the following effects can be obtained.

(1) From the complicated steps of wax molding such as the lost wax method, repeating coating and sanding and drying, dewaxing and firing, molds can be formed by simple steps of organic mold molding, inorganic binder impregnation and curing. In particular, the casting surface of the thin portion has a smoothness close to that of the lost wax casting, and the casting has less distortion than the lost wax method. Therefore, according to the present invention, a part of the cast product which has hitherto relied only on the lost wax method can be replaced, and the cost can be significantly reduced.

While the mold is being handled, the strength of the shell mold is high, the mold is not deformed or deformed easily, and it is easy to handle, and even after the binding force of the organic binder is lost.
Since the action of the inorganic binder can alleviate the collapse of the mold, a clean casting surface can be obtained.

SiO ₂ impregnated with ethyl silicate
Since it is a method of precipitating, it does not block the void of the shell mold and has sufficient voids, so gas is released well, the risk of gas obstructing the flow of hot water is reduced, You can make less castings. In addition, roughening of the surface due to the reaction between the molten metal and the gas is also reduced, which has the effect of improving the casting surface.

Because of good gas release, the flowability of hot water is good,
The pouring temperature can be lowered. As a result, the surface tension of the molten metal becomes high, and the molten metal does not reach the narrow gap portion of the mold, so that a smooth casting surface can be obtained due to the roughness of the mold surface (excluding the thick portion).

Compared with the lost wax mold in which the mold is cracked or deformed due to shrinkage or thermal deformation of the wax model, only the deformation of the shell mold is expected, and the structure of the shell structure can be improved. , For example, 1
It is possible to improve the accuracy of medium-sized castings of about 00 mm to 300 mm.

Since the organic binder is also used, the mold disintegration after casting is good and the mold removing work becomes easy.

(2) In a casting product requiring a hollow core, by utilizing the present invention, a core which is stronger than the shell core during pouring, is less likely to be deformed, and has good disintegration property is obtained. Therefore, it is possible to produce a hollow casting material that is inexpensive and has a high wall thickness accuracy. In this way, a core that replaces the soluble wax used in the lost wax method can be manufactured without using wax.

By the way, in the above-mentioned embodiment, ammonia gas was used for curing ethyl silicate,
As is known, ethyl silicate is sufficiently cured by hydrolysis alone in a short time. Moreover, the use of ammonia is not an absolute condition, because a denser SiO ₂ solid layer can be formed by gradually hardening it in an acidic environment over time. Note that examples of substitutes for ammonia gas as a curing agent (catalyst) that accelerates the curing of ethyl silicate include ammonium carbonate, amine compounds, aqueous ammonia solutions, and calcined magnesium oxide.

Further, in the above-mentioned embodiment, the case where ethyl silicate is used as the inorganic binder has been described.
A similar template can be prepared by using an aqueous colloidal silica. However, in that case, since water has a higher surface tension than alcohol, it is difficult to sufficiently impregnate the binder only by brushing or spraying. Therefore, the impregnation is performed after adding the surfactant to the colloidal silica solution. The selection of the silica concentration when using colloidal silica and the drying method are basically similar to those performed by the lost wax method, and it is necessary to make an appropriate selection according to the conditions. . As described above, colloidal silica, water glass (cured with CO _{2 in} this case) and the like can be cited as alternatives to ethyl silicate as an inorganic binder.

Furthermore, in the above-mentioned examples, the method of impregnating and curing only the inorganic binder was described. However, a small amount of fine refractory powder (for example, finer powder than zircon flour) was added to the inorganic binder solution, There is also a method of impregnating a coating material having a much lower concentration than the slurry in the lost wax method. In that case, it is necessary to set the mixing ratio of the refractory powder to such an extent that the air permeability, which is an advantage of the present invention, is not significantly impaired. In addition, if the particle size of the powder is large, it may flow only to the surface layer of the shell, and the air permeability may be worse than the effect of improving the mold strength and the desired effect may not be obtained, so the condition setting is sufficient. It is necessary to do it after conducting various experiments. For example,
A small amount of refractory powder is mixed in a silica sol (ethyl silicate or colloidal silica) solution so that the air permeability of the mold remains at least half that of the shell mold method mold, and a mold with higher fire resistance and high temperature strength is produced. The molten metal may be poured under the same conditions as in the above embodiment.

In short, the curing of the inorganic binder is
(A) spraying or applying an alkaline atmosphere gas after impregnating the inorganic binder to accelerate curing, (b) spraying or applying an alkaline solution after impregnating the inorganic binder to accelerate curing, or (c) applying an alkaline atmosphere gas. After substitution, impregnation with an inorganic binder to accelerate curing, (d) spraying or coating with an alkaline solution, followed by drying to impregnate and cure the inorganic binder,
(E) An inorganic binder is mixed with an alkaline solution to be impregnated by coating to accelerate curing, and (f) An inorganic binder and an alkaline solution are impregnated and cured by simultaneous spraying,
(G) After impregnating an inorganic binder, it is placed in an acidic environment to gradually cure, (h) Impregnated with an inorganic binder to be humidified, or placed in a dehumidified environment to be cured, (i) Impregnated with an inorganic binder to be humidified. And curing in an environment of dehumidification, or (j) impregnation with an inorganic binder and natural curing.

The present invention is also applied to the production of cores in the case of producing a hollow cast product at a lower cost by the lost wax method to produce a product having an excellent strength to weight ratio. Furthermore, if the present invention is applied to small cast iron products, it is also possible to make cast iron products with a more beautiful casting surface that could not be obtained by the conventional sand mold casting method, and to cast products of the same purpose in nonferrous metals such as aluminum. Can also be applied.

By the way, in the above-mentioned embodiment, the rapid casting is performed in the shell mold having the surface impregnated with the inorganic binder, but the present invention is not limited to this.
The surface may not be impregnated with the inorganic binder, and the molten metal may be rapidly poured into a shell mold just bonded with the organic binder. Further, the aggregate used and the types of the organic binder and the inorganic binder are optional, and examples of the organic binder include furan and the like in addition to the phenol resin of the examples. In addition, it goes without saying that the target of the product to be cast, the specific detailed structure, and the like can be appropriately changed.

[0067]

As described above, according to the casting method of the first aspect of the present invention, since the shell mold mold having the inorganic binder-impregnated hardened layer on the casting surface forming surface is used, the inorganic binder-impregnated hardened layer is used. It is possible to obtain a cast product with a beautiful casting surface. Therefore, the process can be simplified as compared with the lost wax method, and the product can be obtained at a lower cost than the lost wax method. In addition, it is possible to obtain a cast product having a casting surface that is cleaner than a general cast steel product or a sand casting product and has a casting surface close to that of a lost wax cast product, particularly in the thin portion.

Furthermore, according to the casting method of the second aspect of the present invention, the molten metal is directly poured into the shell mold mold, in which the inorganic binder-impregnated hardened layer is formed on the casting surface forming surface, in a heated state. Since the rapid pouring is performed by the method, first the molten metal is poured in the heated state of the shell mold, and the direct pouring method is used for rapid pouring. Therefore, the influence of the gas generated from the mold can be minimized. Therefore, also from this, it is possible to produce a precision cast product that is closer to the lost wax method than a general cast steel product.

According to the casting method of the third aspect of the present invention, since the molten metal is rapidly poured into the shell mold by the direct pouring method of dropping the shell mold in the heated state, Since the molten metal can be poured around in a heated state well and the direct pouring method is used for rapid pouring, the molten metal pressure in the mold cavity can be instantly increased. Can be kept to a minimum. Therefore, the process can be simplified as compared with the lost wax method, and the product can be obtained at a lower cost than the lost wax method. Moreover, in particular, since the thin-walled part has good hot water circulation, it is possible to produce a precision cast product that is closer to the lost wax method than a general cast steel product.

According to the casting method of the fourth aspect of the present invention, since the shell mold is heated in the temperature range of about 100 ° C. to 250 ° C., the organic binder is prevented from decomposing and the adverse effect of heat is exerted on the mold. Therefore, it is possible to obtain a cast product with few surface defects, since the hot water flow is improved and the water that causes gas defects is removed.

Further, according to the mold of the invention of claim 5, since the inorganic binder-impregnated cured layer is formed on the casting surface forming surface of the shell mold mold, the direct injection method is performed by the inorganic binder-impregnated cured layer. The strength to withstand the temperature and pressure of the molten metal during rapid pouring can be maintained. Moreover, since the inside is a normal coated sand, it also has an advantage that the disintegration after cooling is good.

Further, according to the method for producing a mold according to the sixth aspect of the present invention, the casting surface of the shell mold is impregnated with an inorganic binder or an inorganic binder containing refractory powder to be cured. It is possible to obtain a shell mold mold having an inorganic binder-impregnated cured layer for securing strength during rapid pouring by the pouring method on the surface on which the casting surface is formed.

Furthermore, according to the method for producing a mold according to the invention of claim 7, the above-mentioned (a), (b), (c),
An inorganic binder-impregnated cured layer is formed on the casting surface forming surface of the shell mold template by any of (d), (e), (f), (g), (h), (i) or (j). be able to.

[Brief description of drawings]

1A and 1B show a mold manufacturing process as an example to which the present invention is applied, in which FIG. 1A is a vertical sectional side view showing a mold manufacturing process;
(B) is a vertical sectional side view showing molding.

FIG. 2 shows a mold manufacturing process following FIG. 1 (b),
(A) is a vertical sectional side view showing a state in which a mold is taken out,
(B) is a partially broken side view showing the impregnation of an inorganic binder, and (c) is a vertical sectional side view showing a curing acceleration treatment of the inorganic binder.

FIG. 3 shows a mold manufacturing process following FIG. 2 (c),
(A) is a vertical side view of a disassembled state showing assembly of a mold, (b) is a vertical side view showing joining of molds, and (c) is a vertical side view showing heating of the molds.

FIG. 4 shows the casting process following FIG. 3 (c),
(A) is a vertical sectional side view showing a pouring state, and (b) is a vertical sectional side view showing mold variation.

5A and 5B show a structure of a casting surface of a mold according to the present invention, in which FIG. 5A is an enlarged sectional view showing an inorganic binder impregnated layer, and FIG. 5B is an enlarged view of a main part of FIG. is there.

FIG. 6 shows another embodiment of the curing acceleration treatment of the inorganic binder, (a) is a vertical sectional side view showing the gas replacement treatment,
(B) is a partially broken side view showing the impregnation with an inorganic binder.

FIG. 7 is a vertical cross-sectional side view schematically showing an example of a method of rapid pouring by a direct pouring method according to the present invention.

FIG. 8 is a vertical sectional side view showing an example of a cast product obtained according to the present invention.

9A and 9B show a casting process by the lost wax method (ceramic shell molding method), in which (a) is a vertical sectional view showing molding of a wax model, (b) is a vertical sectional view showing tree assembly, c) is a vertical cross-sectional view showing the formation of the refractory layer.

FIG. 10 shows a step that follows FIG. 9C,
(A) is a vertical cross-sectional view showing dewaxing, (b) is a vertical cross-sectional view showing casting, and (c) is a vertical cross-sectional view showing mold variation.

[Explanation of symbols]

 7 Coated Sand 13 Inorganic Binder Impregnated Layer 20 Inorganic Binder Impregnated Hardened Layer 21 Organic Binder 22 Crystal of Inorganic Binder 30 Template 35 Molten Metal 36 Collapsed Sand 37 Casting

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ishiaki Etsuaki Fukushima Prefecture Shima-gun Shiokawa-cho Ogune character No. 75 Omi within Juki Aizu Precision Co., Ltd. Omi 75 Juki Aizu Precision Co., Ltd.

Claims (7)

[Claims] 1. A shell mold mold formed by using a coated sand containing an aggregate and an organic binder as a main component is used, and an inorganic binder or an inorganic binder containing a refractory powder is impregnated in advance on a surface on which the casting surface is formed. The casting method is characterized in that an inorganic binder-impregnated hardened layer is filled with a molten metal into the shell mold mold formed on the surface for forming a casting surface to produce a cast product. 2. Rapidly pouring the molten metal into the shell mold mold, in which the inorganic binder-impregnated hardened layer is formed on the casting surface forming surface, in a heated state by a direct pouring method of dropping the molten metal. The casting method according to claim 1, wherein: 3. A shell mold mold formed by using a coated sand containing an aggregate and an organic binder as a main component, and the shell mold mold is heated inside the shell mold mold,
A casting method characterized in that a cast product is manufactured by rapidly pouring a molten metal by a direct pouring method. 4. The heating temperature of the mold is approximately 100.degree.
The casting method according to claim 2 or 3, wherein the temperature range is 250 ° C. 5. A shell mold mold formed by using a coated sand containing an aggregate and an organic binder as main components, wherein a casting surface forming surface of the shell mold mold contains an inorganic binder or refractory powder. A mold comprising an inorganic binder-impregnated cured layer formed by impregnating and curing an inorganic binder. 6. A shell mold mold is formed using a coated sand containing an aggregate and an organic binder as main components, and an inorganic binder or an inorganic binder containing a refractory powder is formed on the casting surface of the shell mold mold. A method for producing a mold, which comprises forming an inorganic binder-impregnated cured layer by impregnating and curing. 7. The inorganic binder is cured by (a) spraying an alkaline atmosphere gas after impregnating the inorganic binder or coating to accelerate curing, and (b) spraying or coating an alkaline solution after impregnating the inorganic binder. To accelerate the curing, (c) to accelerate the curing by impregnating with an inorganic binder after substituting with an alkaline atmosphere gas, (d) to spray or apply an alkaline solution, and then dry to impregnate and cure the inorganic binder. e)
An inorganic binder is mixed with an alkaline solution to impregnate it by coating to accelerate curing, (f) an inorganic binder and an alkaline solution are impregnated and cured by simultaneous spraying, (g)
After being impregnated with an inorganic binder, it is gradually cured by being placed in an acidic environment, (h) impregnated with an inorganic binder to be moistened or cured in a dehumidified environment, and (i) being impregnated with an inorganic binder to be humidified and dehumidified. 7. The method for producing a mold according to claim 6, wherein the method is performed by placing in an environment and curing, or (j) impregnating an inorganic binder and naturally curing.