JP2002143983A - Casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method where the casting process is simplificed, and by which a casting withstanding high casting temperature and having high quality is producible. SOLUTION: This casting method is composed of the following stages (a) a stage where a mold stock is molded by an aggregate and a first organic binder; (b) a stage where a second binder composed of an alcohol solution containing one or more kinds of metallic alkoxides selected from the metallic alkoxides of the group 4A or 4B (exclusive of carbon) and the group 3A or 3B in the periodic table and the partially hydrolyzed products thereof and an alkali compound of alkali metals or alkaline earth metals is applied to and/or impregnated into the mold stock molded by the above stage (a); and a stage (c) where, after the above (b) stage, the obtained mold stock is dried, and, (1) this mold stock is used as a core, the core is set in a die, and molten metal is poured therein, or (2) this mold stock is used as a mold, and molten metal is poured into the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an organic template element in which aggregates such as silica sand and alumina are bonded by a first organic binder, and a specific second binder is adhered to the surface of the organic template body. The present invention relates to a casting method for casting a casting, in which a molten metal is poured using a casting or a mold. As a result, a heat-resistant film of the second binder is formed on the surface of the casting mold body, thereby preventing the molten metal generated at the time of casting from sticking to the organic casting mold. In mold casting, an organic mold (core) set in a preheated mold prevents thermal deformation due to heat resistance of a second binder (organosilane compound) impregnated and formed on the mold surface. And a method for casting a casting.

[0002]

2. Description of the Related Art Conventionally, as a binder used for a casting mold, an organic binder has been used for excellent moldability and productivity. An organic mold using this organic binder has excellent moldability and room-temperature strength, but has low heat resistance, starts softening at about 200 ° C., and burns at about 400 ° C. Since this mold is instantaneously exposed to a high-temperature molten metal during casting, the mold surface is required to have severe impact resistance and heat resistance. For this reason, a so-called coating mold is used in which a refractory aggregate such as zircon is mixed with a dispersant and applied to the surface of a mold. However, although the conventional coating mold has a sealing effect, there is a limit in improving the heat resistance and thermal shock resistance of the organic mold.

On the other hand, a resin shell molding method is known as one of typical casting methods. This method has good flowability of the coated sand of the mold sand and can accurately mold a mold having a complicated shape. The coated sand can be stored for a long period of time. Can be mechanized, mold molding speed is fast,
The molded mold has characteristics such as excellent storage stability, and the mold is thermally decomposed at a high temperature and excellent in disintegration after casting. For this reason, it is widely used in many fields such as cast iron castings in the automobile industry and the like. Also, an appropriate amount of phenolic resin and polyisocyanate are added to silica sand, mixed and molded, and the mold is instantaneously cured by passing amine gas through the mold.After curing, air is blown to blow unreacted amine gas in the mold. Many cold box methods have also been used to create organic templates.

[0004] However, the organic mold in the resin shell mold method or the cold box method has an advantage of excellent productivity in molding the mold, but has poor heat resistance, and is used as a core in casting. Gas is generated by the combustion of the resin as a binder, and serious defects such as blowholes are generated. Further, when a thin mold (core) is used, there is a problem that the heat resistance of the mold is insufficient, so that the thickness cannot be sufficiently reduced.

Also, organic self-hardening binders (for example,
Casting methods using a phenolic resin, furan resin, urethane resin, etc.) to form a mold are also widely known, but a mold using this binder has the same casting defects as the resin shell mold method and the cold box method. And problems.

In recent years, a molded article body has been formed using an aggregate and a first binder, impregnated with, for example, alkoxysilanes, and then dried and fired at a high temperature to form a refractory. There has been proposed a method of obtaining a product and casting the casting using the product as a core or a mold (Japanese Patent Laid-Open No.
-232967). However, this method requires a high-temperature sintering step, and has a problem that the step is complicated.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for casting a casting to achieve the following objects. (a) The casting process can be simplified. (b) Since the mold (or the core) is exposed to a high temperature by pouring the molten metal, the heat resistance of the mold surface can be improved without impairing the characteristics (such as disintegration) of the organic mold. . (C) Since it can be used as a relatively high temperature mold (or core) at 200 to 300 ° C., it is possible to reduce the thickness of a cast product or the like. (E) Since it has strength in a wide temperature range from low to high temperatures, it can be used for casting from light alloys to cast steel products. (F) By the inclined impregnation of the second binder, the strength of the inner core of the mold (or the core) can be adjusted, and the disintegration property is improved.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a casting method comprising the following steps. (A) a step of forming a template body using an aggregate and a first organic binder; (b) a group 4A or group 4B (excluding carbon) and 3
A second binder comprising an alcohol solution containing one or more metal alkoxides selected from Group A or Group 3B metal alkoxides and partial hydrolysates thereof, and an alkali compound of an alkali metal or an alkaline earth metal; Is applied and / or impregnated to the mold body molded in the step (a); (c) after the step (b), the obtained mold body is dried;
Using this mold element as a core, setting the core in a mold and pouring molten metal, or pouring the molten metal into this mold using this mold element as a mold Process.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Step (a) In the step (a), an aggregate and a first organic binder are used.
This is a step of molding a core element or a mold element to be a mold. Here, the aggregate for forming the mold body is not particularly limited, and examples thereof include silica sand, alumina, quartz, zircon, fused silica, silica flower, mullite, synthetic mullite, chamotte, and synthetic chamotte. In actual use, one or more of these can be appropriately selected and used depending on the use of the template body to be manufactured.

The elementary binder (first organic binder) used together with these aggregates is, for example, a thermosetting resin such as a phenolic resin used in shell mold casting, or a self-hardening urethane-based resin. Organic binders such as resin, furan-based resin, and phenol-based resin are exemplified. Regarding the first organic binder, at the time of actual use, one or two or more thereof can be appropriately selected and used depending on the use of the casting to be produced. The amount of the first organic binder used is usually about 2.5% by weight or less, preferably about 1% by weight or less based on the aggregate.

[0011] The method of forming the template body with the aggregate and the organic binder is not particularly limited, and a conventionally known method can be employed.

Step (b) Step (b) is one or two kinds selected from metal alkoxides of Group 4A or 4B (excluding carbon) and Group 3A or 3B of the periodic table and partial hydrolysates thereof. A step of applying and / or impregnating the above-mentioned metal alkoxide and a second binder composed of an alcohol solution containing an alkali compound of an alkali metal or an alkaline earth metal to the mold element molded in the step (a). is there.

The second binder used in the step (b) is
As a binder component in an alcohol solvent, a compound represented by the general formula R _m
M ¹ (OR) _4-m or M ² (OR) ₃ (where wherein M ¹
Represents a metal of Group 4A or Group 4B other than carbon, M ² represents a metal of Group 3A or 3B of the periodic table,
R is the same as each other or different alkyl group of 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group alkoxyalkyl group or a C 7-12 having 2 to 6 carbon atoms, M ¹ M = 0 to 3 when is Si
Where M ¹ is other than Si, m = 0.) One or more metal alkoxides selected from alcohol-soluble metal alkoxides and partial hydrolysates thereof And 1 to 50% by weight in terms of a metal oxide, and the following general formula M ³ OR ′ or M ⁴ (OR) ₂ (where M ³ represents an alkali metal, M ⁴ represents an alkaline earth metal, R 'represents hydrogen or an alkyl group having 1 to 6 carbon atoms) and an alcohol-soluble alkali compound represented by the formula (1) to 16% by weight in terms of metal oxide.

In the present invention, the metal alkoxide constituting the second binder component is a metal alkoxide of a metal M ^{1 of} Group 4A or Group 4B other than carbon or a metal M ² of Group 3A or Group 3B of the periodic table. Or a partial hydrolyzate thereof. Here, the metal M ¹ forming the metal alkoxide is T 4 as a Group 4A metal in the periodic table.
i, Zr, etc., and other metals such as Si, Ge, Sn, and Pb as Group 4B metals other than carbon, and M ² as Periodic Table 3A
Sc, Y and the like can be mentioned as group metals, and B, Al, Ga and the like can be mentioned as group 3B metals.

Further, R which forms the metal alkoxide
Are the same or different alkyl groups having 1 to 6 carbon atoms, aryl groups having 6 to 8 carbon atoms, alkoxyalkyl groups having 2 to 6 carbon atoms, and aryloxyalkyl groups having 7 to 12 carbon atoms. Specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an amyl group, a hexyl group, a cyclohexyl group, a butyl group, an isobutyl group, a t-butyl group, and an s-butyl group. And aryl groups such as phenyl, tolyl, and xylyl groups, and alkoxyalkyl groups such as methoxyethyl, methoxyisopropyl, methoxypropyl, methoxybutyl, ethoxyethyl, ethoxypropyl, and ethoxy. Butyl group, etc., and as the aryloxyalkyl group, phenoxymethyl group, phenoxyethyl group, phenoxypropyl group, phenoxybutyl group, toloxymethyl group, toloxyethyl group, toloxypropyl group, toloxybutyl group, etc. Can be mentioned.

The partial hydrolyzate of such a metal alkoxide is not particularly limited as long as it has a hydrolysis rate of 55% or less and is dissolved in an alcohol solvent, and is a linear partial hydrolyzate. May also be a network partial hydrolyzate or a cyclic partial hydrolyzate. Further, these metal alkoxides composed of these metal alkoxides and partial hydrolysates thereof may be used alone, or may be used as a mixture of two or more.

In the present invention, the most preferred metal alkoxides are the components of the mold sand, and from the viewpoint that they are easily bonded to sand, the general formula R _m Si (O
R) _{4- m} (wherein R is the same or different, and is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an alkoxyalkyl group having 2 to 6 carbon atoms, or 7 to 12 carbon atoms) Wherein m is 0 to
And an alkyl silicate represented by formula (1), and one or more silicates selected from these partial hydrolysates.

Specifically, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane,
Tetraptoxysilane, methoxytriethoxysilane,
Dimethoxydiethoxysilane, ethoxytrimethoxysilane, methoxytriisopropoxysilane, dimethoxydiisopropoxysilane, methoxytryptoxysilane, and the like.Also, as the alkyltrialkoxysilane, methyltrimethoxysilane, methyltriethoxysilane , Methyltripropoxysilane, methyltriisopropoxysilane, methyltryptoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane and the like.

The dialkyldialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldiisopropoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldiisopropoxysilane And the like, and as the trialkylalkoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, trimethylisopropoxysilane, trimethylbutoxysilane, triethylmethoxysilane, triethylethoxysilane, triethylisopropoxysilane, etc. Can be mentioned.

Further, examples of the aryloxysilane include tetraphenoxysilane and tetratoloxysilane. Examples of the alkylaryloxysilane include methyltriphenoxysilane, ethyltriphenoxysilane, dimethyldiphenoxysilane, and diethyldisilane. Phenoxysilane, methyltritrioxysilane, and the like can be given.

Further, examples of the alkoxyalkylsilane include tetramethoxymethylsilane, tetramethoxyethylsilane, tetramethoxyisopropylsilane, tetraethoxymethylsilane, tetraethoxyethylsilane, tetraethoxyisopropylsilane, and the like. Examples of the oxyalkylsilane include tetraphenoxymethylsilane, tetraphenoxyethylsilane, tetraphenoxypropylsilane, tetraphenoxyisopropylsilane, and tetratrioxyethylsilane.

Other preferable metal alkoxides include trimethylborin, triethoxyborin, tetrabutoxytitanium, tetrabutoxyzircan,
And triisopropoxyaluminin.

The content of these metal alkoxides is 1 to 50% by weight, preferably 2 to 30% by weight in terms of metal oxide (for example, when the metal alkoxide is a silicate ester, in terms of SiO ₂ ). If the content is less than 1% by weight, the content of the metal oxide derived from the metal alkoxides becomes insufficient when used as a template body,
Desired strength required for handling during handling of mold (core) (for example, 10 kg / cm ² or more, preferably 30 kg / cm ² or more)
kg / cm ² or more), but if it exceeds 50% by weight, the amount of alkali compound dissolved becomes less than 0.5% by weight from the viewpoint of solubility, and the desired strength is obtained. I can't.

As for the alkali compound as another binder component, examples of the metal M ³ include lithium, sodium, and potassium, and preferably sodium and potassium. The substituent R 'forming the alkali metal alkoxide may be hydrogen or a carbon atom having 1 carbon atom such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy, cyclohexyloxy and the like. To 6, an alkyl group, a phenoxy group, a toloxy group, an alkoxyalkyl group or an aryloxyalkyl group. These alkali compounds may be used alone alone,
Moreover, you may use as a mixture of 2 or more types.

Regarding the content of the alkali compound,
Metal oxide conversion (e.g., in the case the metal of the alkali compound is sodium terms of Na ₂ O) 0.5 to 16% by weight,
Preferably it is in the range of 1 to 10% by weight. 0.5% by weight
If the amount is less than the above value, the content of the metal oxide derived from the alkali metal alkoxide becomes insufficient when used as a template body, and the desired strength (for example, 10 kg / cm ² or more, preferably 30 kg / cm ² or more,
(kg / cm ² or more) cannot be obtained. On the other hand, if it exceeds 16% by weight, the dissolved amount of SiO ₂ becomes less than 1% by weight from the viewpoint of solubility, and the desired strength cannot be obtained. .

Further, as the alcohol solvent for dissolving the metal alkoxides and the alkali compound of the binder component, for example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, amyl alcohol, hexyl alcohol, cyclohexyl alcohol , Ethylene glycol, diethylene glycol, propylene glycol, ethyl cellosolve, methyl cellosolve, propyl cellosolve, butyl cellosolve, phenylmethyl cellosolve, phenylethyl cellosolve and the like.

The thickness (dry film thickness) of the second binder is as follows:
It is about 2 to 5 mm, preferably about 2 to 3 mm. 5mm
If it exceeds, it is not economical and it is difficult to remove the mold.

In the second binder of the present invention, additives other than those described above can be added for various purposes.
Examples thereof include alkali or neutral surfactants such as sodium dodecylsulfonate and polyethylene glycol ethyl ether added for the purpose of improving impregnation.

Further, in addition to the above additives, inorganic fine particles (hereinafter, also simply referred to as “fine particles”) and a silane coupling agent can be added to the second binder of the present invention. Examples of the inorganic fine particles include silica fine particles such as fumed silica, mushrooms, and other ceramic fine particles. These fine particles are preferably dispersed and used using an organic solvent such as varnish or polyethylene glycol having a molecular weight of about 1,500 to 10,000. In this case, the solid content concentration of the fine particles is usually 8
About 30% by weight. In the present invention, by adding the fine particles to the second binder, it is possible to make the second binder permeate only into the surface layer (about 2 to 3 mm) of the template body obtained in the step (a). The smoothness of the template body can be obtained by the addition and the added fine particles. The compounding amount of these fine particles is usually about 1 to 5% by weight in terms of solid content in the second binder.

Examples of the silane coupling agent include amino silane, ureido silane, epoxy silane and the like. Here, when a silane coupling agent is used, it is preferable to dissolve or disperse the silane coupling agent in water and / or an organic solvent, and to add this to the second binder before use. Examples of the organic solvent used here include an alcohol solvent used for the second binder. By adding the silane coupling agent to the second binder, the silane coupling agent reacts with the organic binder and / or aggregate as the first binder in the template body obtained in the step (a). The second binder can be firmly adhered to the surface of the template body, and the heat resistance of the template body can be improved. The amount of the silane coupling agent used is usually about 1 to 5% by weight in the second binder.

The method of applying and / or impregnating the second binder of the present invention to the template element obtained in the step (a) is, for example, immersing the template element in the second binder, The method of "dipping → draining", in which the template body is pulled up from the binder and drained, or the method of "dipping → draining → drying" in which the alcohol solvent is removed by drying after this "dipping → draining" Or a method of repeating this step of “immersion → drainage → drying” a plurality of times as necessary, or a method of impregnating the above-described binder in a template body under reduced pressure as in a VRH process, A method of spraying the above binder in a shower shape on the mold body,
A method in which the binder is applied to the surface of the template body with a brush or the like can be used.

Step (c) In the step (c), after the step (b), the obtained template body is dried, and the template body is used as a core, and the core is set in a mold. This is a step of pouring the molten metal or pouring the molten metal into the mold using the mold body as a mold. The drying in the step (c) is performed at room temperature to 1
Usually, the heat treatment may be performed at a temperature of 00 ° C. for about 30 to 60 minutes. (B) After drying the template body obtained in the step,
When the molten metal is cast using a core or a mold, the high heat of the molten metal causes the second binder to melt instantly and alkalisilate, forming a heat-resistant film on the surface of the mold body, 1,200 ° C or higher, and 1,60 ° C
It is possible to form a film that can withstand a high-temperature molten metal of 0 ° C. or more. Conventionally, as described above, it has been considered that the mold body obtained in the step (b) is not suitable for casting unless it is fired at a high temperature, as proposed in JP-A-7-232967. However, surprisingly, it has been found in the present invention that the second binder can form a heat-resistant film due to the high temperature of the molten metal without such high-temperature sintering. .

The second binder used in the present invention is:
It is characterized in that an alkali compound such as sodium alcoholate or a hydroxide thereof is added to a partial hydrolyzate of an alkyl silicate or an allyl silicate in an alcohol solvent and used. Sodium alcoholate is a strong alkali, but can uniformly dissolve metal alkoxides such as alkyl silicate or allyl silicate without hydrolyzing them. The curing mechanism of the second binder according to the present invention is not clear, but is presumed as follows.

That is, when sodium alcoholate, for example, sodium ethylate (C ₂ H ₅ ONa), and alkyl silicate, for example, ethyl silicate, are mixed with alcohol in necessary amounts, for example, hydrolysis reaction is caused by the influence of water in the air. Occurs, and NaOH and S
iO ₂ is generated, and the generated NaOH and SiO ₂ are
Due to the high heat of the molten metal in step (c), Na ₂ O ·
It is presumed that SiO ₂ is generated to reinforce the high-temperature strength of the template body.

According to the present invention, since the second binder is an alcohol solution, the second binder is efficiently impregnated into the mold base formed by the aggregate and the base binder (first organic binder). Then, a metal oxide is generated from the metal alkoxides of the second binder component, and a metal oxide is also generated from the alkali compound. By the subsequent pouring of the molten metal, the metal alkoxides are generated. It is believed that the metal oxide and the metal oxide derived from the alkali compound form a composite fused alkali silica salt, which are mutually bonded to the aggregate, thereby achieving high strength in the template body as in the case of the firing treatment. Can be

Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 is a process flow chart of a preferred embodiment of the present invention. First, an alkali phenol resin as an organic binder (first binder) is kneaded with sand as a mold material (aggregate) (step 100). The amount of the binder is about 2.5% by weight or less, preferably 1% by weight or less, based on sand (aggregate). The molding sand (aggregate) used for this purpose is preferably a material that is less likely to expand and contract due to heat, such as mullite and fused quartz.

This kneaded material is pressed into a core mold. At this time, the kneaded material has good moldability since it has good fluidity, and the sand is hardened in the mold by the alkali phenol resin to form a core element faithful to the mold shape (step 102). ).

The core element is removed from the mold, and immediately thereafter, its surface is impregnated with the second binder (step 104). As a result, the second binder penetrates to an appropriate depth from the surface of the core element. Here, the impregnation of the second binder is performed by spraying or brushing,
An appropriate method such as immersion can be adopted. The second used here
Are as described above.

The second binder impregnated in the core element is immediately hydrolyzed (in about 30 seconds) by the water contained in the core element, and increases the green strength of the core element. This core element is heated at a temperature of room temperature to 100 ° C. for about 30 to 6 hours.
Dry for about 0 minutes (step 106). As a result, the water in the core element is almost completely removed to form a core.

Next, the core is set in a mold (step 108). Then, molten metal is poured into this mold (step 110). In addition, for organization adjustment,
Of course, the mold temperature is appropriately controlled. Also,
Instead of the mold, a cold-box mold of a room temperature curing type can be used.

As described above, when the molten metal poured at a high temperature, for example, at a temperature of 1600 ° C. or more, comes into contact with the core due to the pouring of the molten metal, the second binder becomes, for example, sodium oxide Forming a composite molten salt of silica,
By forming a film with high heat resistance and high strength, the core element can be protected.

After the poured molten metal is solidified, the product is taken out of the mold, cooled appropriately, and the mold is separated (step 112). This is because the core is removed by separating the mold, but the core is broken down by the high heat-resistant film made of the second binder without being converted into ceramics.

The core produced as described above can be used for casting aluminum alloy, cast iron, or the like. As the organic binder, an alkali phenol resin is optimal, but it can also be used for a furan resin, a phenol urethane resin and the like. Further, in this embodiment,
Although the core has been described as a template material, it goes without saying that the present invention can be applied to a template body. That is, in this case, the mold body obtained by the present invention may be used for, for example, an upper mold and a lower mold, and molten metal may be poured into the mold.

[0044]

As described above, according to the present invention, the second binder applied to the surface of the template body in the step (b) comprises:
In the step (c), the molten metal is poured into the mold body at a high temperature, for example, at a temperature of 1,000 ° C. or more by the pouring of the molten metal, and the second binder is made of, for example, sodium oxide and silica. It forms a composite molten salt and crystallizes into tridymite to form a film having high heat resistance and high strength, thereby protecting the template body. As a result, the process of further baking after applying the second binder is simplified, and the mold (or core) is exposed to a high temperature by pouring the molten metal. It can be used as a relatively high temperature mold (or core) at 200 to 300 ° C., which can improve the heat resistance of the mold surface without impairing the disintegration (such as disintegration). Since it has strength in a wide temperature range from low temperature to high temperature, it can be used for casting from light alloys to cast steel products. By means of inclined impregnation of the second binder, the strength of the inner core of the mold (or core) can be adjusted. It has many advantages such as improved disintegration.

[Brief description of the drawings]

FIG. 1 is a process flowchart of one embodiment of the present invention.

Claims (7)

[Claims] 1. A casting method comprising the following steps. (A) a step of forming a template body using an aggregate and a first organic binder; (b) a group 4A or group 4B (excluding carbon) and 3 of the periodic table
A second binder comprising an alcohol solution containing one or more metal alkoxides selected from Group A or Group 3B metal alkoxides and partial hydrolysates thereof, and an alkali compound of an alkali metal or an alkaline earth metal; Is applied and / or impregnated to the mold body molded in the step (a); (c) after the step (b), the obtained mold body is dried;
Using this mold element as a core, setting the core in a mold and pouring molten metal, or pouring the molten metal into this mold using this mold element as a mold Process. 2. An aggregate comprising silica sand, mullite, alumina,
The casting method according to claim 1, wherein the casting method is at least one selected from the group consisting of quartz, zircon, fused silica, silica flour, and chamotte. 3. The casting method according to claim 1, wherein the first organic binder is at least one organic binder selected from the group consisting of a phenol resin, a urethane resin and a furan resin. 4. The casting method according to claim 1, wherein inorganic fine particles are further added to the second binder. 5. The casting method according to claim 4, wherein the inorganic fine particles are fumed silica. 6. The casting method according to claim 4, wherein the inorganic fine particles contain, as a dispersant, at least one organic solvent selected from the group consisting of varnish, polyethylene glycol and polyethylene glycol ethyl ether. 7. The casting method according to claim 1, wherein a silane coupling agent is further added to the second binder.