JP2002219551A - Dissipating core and casting method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dissipating core without using core sand, thereby capable of solving the problem of waste sand in casting as industrial waste based on the increase of molding sand caused by mixing the core sand. SOLUTION: The dissipating core comprises a core body 4 made of a high polymeric material foam, and a heat resisting coat-and-covering film layer 6 formed at least on the surface of the core body 4 making contact with a molten metal and the core body 4 is made dissipatable caused by the heat of the molten metal in the casting process of the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vanishable core and a casting method using the vane core, and more particularly to a vanishable core which disappears after completion of a casting operation to solve the problem of core sand treatment. The present invention relates to a method of advantageously casting a target hollow cast product from a molten metal by using the above method.

[0002]

2. Description of the Related Art Conventionally, in producing a cast product having a hollow shape or a complex shape, a core having a desired hollow shape or the like is used, and such a core is placed in a casting cavity of a predetermined mold. After performing the casting operation of the molten metal, while taking out the formed casting from the mold,
By removing the core held by such a casting by physical or chemical means, a casting (casting product) having a desired shape such as a hollow portion has been manufactured.

[0003] In order to obtain a cast product having such a hollow shape, most of the cores used in the casting industry are made of core sand made of phenolic resin, furan resin or water glass. And a core formed by using a combination of CO ₂ and CO ₂ , and molded into a desired shape, and such a core is subjected to vibration and vibration when the casting is completed and the casting is removed from the mold. By being collapsed by applying an impact or the like, a hollow portion or the like is formed in the obtained cast product.

[0004] For this reason, the molding sand generated by the collapse of the mold after the end of the casting operation is inevitably added with the core sand generated by the collapse of the core. The problem is inherent. Although it is considered that the casting sand recovered after casting is subjected to a treatment such as sand separation, there is a problem in that the processing cost is high. In order to use as sand, high regeneration quality is required, and there is also a problem that the cost of regeneration treatment is increased.Therefore, foundry sand discharged from the casting process is treated as industrial waste. However, such treatment as industrial waste is not easy due to the problem of disposal sites, and such disposal has already reached its limits.

[0005] Further, since the core itself obtained by solidifying the core sand is also heavy, the work of setting it in a mold is an overburdened labor and makes the casting operation severe. Even if such a core setting operation is to be further automated, the mechanical device for this purpose must be large in view of the weight of the core.

[0006]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to eliminate the use of core sand, and thus to mix core sand. Can solve the problem of foundry sand as industrial waste based on the increase of foundry sand caused by
It is an object of the present invention to provide a vanishable core and a casting method using the core so that a casting operation can be easily performed.

[0007]

According to the present invention, in order to solve such a problem, a core body made of a foam of a polymer material is formed on at least a surface of the core body which comes into contact with a molten metal. A heat-resistant coating film layer that has been subjected to, the core of the core can be eliminated by the heat of the molten metal during the casting process of the molten metal, the vanishing core, characterized in that, This is the gist.

As described above, in the vanishable core according to the present invention, the heat-resistant coating film layer provided on the surface temporarily blocks the high-temperature action of the high-temperature molten metal, so that the metal is removed. Until the molten metal is cooled and solidified (solidified) and shaped, it does not deform and temporarily retains the shape of the core body made of a foam of a polymer material to allow the casting operation to proceed. By allowing such a core body to be eliminated by melting, decomposition, combustion, and the like, the core function can be advantageously performed without using a conventional core sand. There, therefore, from such vanishable cores, except for inorganic powder components such as heat-resistant aggregates that constitute the heat-resistant coating film layer, particles that become casting waste sand are converted into molding sand. There is no contamination at all and therefore the casting process Eliminating the emissions of al of waste casting sand, it's a fact that the industrial waste may be made effectively zero.

Moreover, such a vanishable core is mainly composed of a core body made of foam,
Compared to the conventional core sand, the weight is significantly reduced, and the core setting work is facilitated. Therefore, the size of the mechanical device can be advantageously reduced.

[0010] According to one preferred embodiment of the vanishable core according to the present invention, a foam of a polymer material that provides a core body constituting such a core includes:
Expanded polystyrene is advantageously used from the viewpoints of easy realization of the core shape and low occurrence of problems at the time of disappearance.

According to another preferred embodiment of the vanishable core according to the present invention, the heat-resistant coating film layer is formed of a coating material containing at least a heat-resistant aggregate and a binder. It is preferable that the heat-resistant aggregate contains the heat-resistant aggregate, whereby the shape of the coating film layer is maintained from the instantaneous high heat action at the time of contact with the high-temperature molten metal, and the binder is contained. By doing so, the heat-resistant aggregate is bonded and solidified at room temperature, and a hard coating film of a predetermined thickness can be effectively formed on the surface of the core body, and the shape of the coating film layer is advantageous. You can keep it.

In another preferred embodiment of the present invention, it is preferable that the coating material for providing the heat-resistant coating film layer further contains a fire / heat-resistant agent. Thereby, the coating film layer can be more effectively protected from the instantaneous high heat action at the time of contact with the high-temperature molten metal.

[0013] In addition, it is desirable that such a coating material is further blended with at least one of a vitrifying agent, a coating film layer reinforcing material and a plasticizer. Features such as promoting the formation of a solidified layer of the surrounding molten metal, enhancing the retention of the shape of the coating film layer, and facilitating the formation of the coating film layer.

Further, in the vanishable core according to the present invention, the heat-resistant coating film layer formed on the surface of the core body is advantageously formed in a thickness of 0.1 to 5 mm, Temporary protection of the molten metal of the core body from the high heat action by such a coating film layer can be effectively performed.

Further, in the present invention, as a casting method using the above-mentioned vanishable core, after setting such a core in a casting cavity of a predetermined mold, a predetermined molten metal is formed. And casting a solidified layer of the molten metal at a portion of the molten metal that is in contact with the core surface to withstand the pressure of the molten metal. The gist of the invention is also a casting method characterized by being made to disappear.

[0016] In such a casting method, the core body is advantageously provided before the casting operation is completed.
That is, the heat is lost by the heat of the molten metal.

According to the casting method according to the present invention, since the vanishable core becomes extremely light, various problems caused in the conventional casting operation for handling a heavy core are completely eliminated. Therefore, the casting operation can be facilitated, the casting operation can be automated easily, and the increase in the amount of casting sand recovered can be substantially avoided, so that the regeneration process can be facilitated. It is.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the configuration of the present invention will be described more specifically with reference to the drawings.

First, FIG. 1 shows an example of a vanishing core 2 according to the present invention in a partially cutaway sectional view.
In this case, as will be described later, the rectangular main body 4
And the heat-resistant coating film layer 6 formed on at least the surface in contact with the molten metal, to form the disappearing core 2 having a rectangular shape as a whole. Then, as shown in FIG. 2, such a vanishable core 2 is formed into a casting cavity 14 formed in a mold 12 comprising an upper mold 12a and a lower mold 12b formed of the same molding sand as in the prior art. At a predetermined position, so that a casting cavity 14 corresponding to a target hollow rectangular product shape is formed. A predetermined molten metal is guided to such a casting cavity 14 through a gate 16 and a runner 18 in the same manner as in the prior art, and a desired casting operation is performed.

Incidentally, the vanishable core 2 according to the present invention used in such a casting operation has a square tubular core body made of a foam of a predetermined polymer material, and at least the molten metal is used. As shown in FIGS. 1 and 2, a heat-resistant coating film layer 6 having a predetermined thickness is formed on the entire outer peripheral surface (four surfaces) including the surface in contact with the substrate. In addition, except for the thickness of the coating film layer 6, the core body 4 is a hollow body or a solid body having a shape substantially corresponding to the hollow shape of a target casting product, It is made of a foam of a polymer material so that it can be easily eliminated by the action of the high heat of the molten metal in the casting process of the molten metal due to the action of melting, decomposition, combustion, etc., and is lightweight. Will be done. Among them, expanded polystyrene is advantageously used as such a foam,
As a result, the desired core body 4 can be formed with good moldability, and can be advantageously eliminated while avoiding generation of harmful gas. In addition, such a foam is desirably a flame-retardant or heat-resistant one. However, even if it is untreated, it can be used as long as it functions as a core in the present invention. Needless to say,

The coating material used to form the predetermined heat-resistant coating film layer 6 on at least the surface of the core body 4 which is in contact with the molten metal is a coating material used when the high-temperature molten metal is in contact. Protects the core body 4 from momentary high heat action,
In order to maintain the shape of the coating film layer 6, it contains a heat-resistant aggregate in powder form, and also binds such heat-resistant aggregate,
It hardens at room temperature, forms a hard coating film of a predetermined thickness on the surface of the core body 4, and contains a binder so as to maintain the shape of the coating film layer 6. Further, such a coating material contains an aqueous solution of an acid such as water or phosphoric acid as a liquid medium in order to make it possible to coat the surface of the core body 4.
Thus, the coating material is in a fluid state that can be coated.

Examples of the heat-resistant aggregate include alumina, silica (including silica gel and colloidal silica), natural minerals containing silica as a main component, zirconia and natural minerals containing zirconia as a main component, Natural minerals mainly composed of calcium carbonate and calcium carbonate, magnesia and natural minerals mainly composed of magnesia can be used, and as a binder, sodium silicate, sodium metasilicate, calcium sulfate, calcium oxide, Calcium hydroxide, various siloxane compounds and the like can be used.

Further, the coating material used in the present invention does not undergo physical or chemical change such that the shape immediately changes even when it comes into contact with the molten metal. Has heat and fire resistance,
After cooling and solidifying the molten metal, it is desirable that heat be quickly transmitted to the core body 4 so that the core body 4 can be eliminated, and therefore, a fire / heat resistant agent is further required. In the same manner, a vitrifying agent and a coating film layer reinforcing material are further compounded. Among these compounding agents, the refractory / heat-resistant agent suppresses heat transfer, particularly when contacting with a high-temperature molten metal, so that the coating film layer 6 and the core body 4 can be instantaneously heated. Used to avoid destruction or contribute to protection,
For example, a substance mainly containing a carbon component such as graphite (earth-like, flake-like, etc.), coke, gilsonite, and coal powder is used.
Further, the vitrifying agent is melted in the coating material at the time of contact with the molten metal, and the endothermic action at that time promotes cooling and solidification (solidification) of the molten metal on the surface of the coating film layer 6, and 6, which temporarily promotes the mutual bonding of the constituent substances, for example, a glass-based substance such as boric acid, borax, glass powder, glass fiber, or the like is used. In addition, the coating film layer reinforcing material contributes to holding and strengthening the shape of the coating film layer 6, and for example, ceramic fibers such as glass fiber and alumina fiber are used.

Further, the coating material is given plasticity at the time of its preparation, so that the coating film layer 6 having a predetermined thickness can be easily formed. A plasticizer such as kaolin, bentonite, water glass, silicone resin, carboxymethyl cellulose or the like is further compounded so as to contribute to curing.

By the way, the various components constituting the above-mentioned coating material are used as the coating material so that the object of the present invention can be achieved well and the mixing effect of each component can be sufficiently exhibited. At an appropriate ratio.

The coating material such as the core body 4
Coating, at least on the surface in contact with the molten metal,
Coating is performed according to a conventional method such as dipping, brushing, spraying, ironing, and the like, and a desired coating film layer 6 is formed on a predetermined surface of the core body 4. In addition, if such a coating film layer 6 is integrally formed while being held on the surface of the core body 4,
It can be formed by any other method. For example, a layer having a predetermined thickness of a coating material formed on a molding cavity surface of a molding die of the core body 4 can be formed on the surface of the core body 4 molded in the molding die. To form a desired coating film layer 6 on the surface of the core body 4.
Here, when such a coating film layer 6 is formed, an appropriate thickness is selected as the thickness so that the object of the present invention can be satisfactorily achieved.
Desirably, it is formed in a thickness of 0.1 to 5 mm. If the thickness of the coating film layer 6 is too thin, it is difficult to sufficiently block or avoid the instantaneous high heat action of the molten metal, and if it is too thick, the formation of the coating film becomes troublesome. This causes problems such as difficulty in effectively removing the core body 4.

The thus obtained vanishing core 2 having the structure as shown in FIG. 1 is, for example, as shown in FIG.
The casting cavity 14 is set in a casting cavity 14 of a predetermined mold 12 and the casting cavity 14 corresponding to the shape of a casting (casting product) having a desired hollow shape or the like is formed in such a casting mold 12. At that time, the casting cavity 14
As shown in FIG. 2, the surface of the core 2 that is exposed to the outside is formed of the coating film layer 6 having a predetermined thickness. Even if the molten metal is cast, guided into the casting cavity 14 and brought into contact with the core 2, such instantaneous high heat action of the molten metal is temporarily blocked or applied by the coating film layer 6. Is avoided, and the core body 4 constituting the core 2 is prevented from disappearing due to melting, decomposition, combustion and the like.

Then, the casting (pouring) of the molten metal proceeds, and the inside of the casting cavity 14 is filled with the molten metal. On the other hand, cooling, solidification or solidification of the molten metal starts around the vanishing core 2. After a solidified layer of the molten metal that can withstand the pressure of the molten metal is formed at a portion in contact with the surface of the molten metal core 2, the vanishable core 2 passes through the coating film layer 6, Is applied, the core body 4 melts, decomposes or burns, etc., and disappears. In addition, even if the disappearing core 2 disappears, since the solidified layer of the solid molten metal is formed around the disappearing core 2, the shape given by the disappearing core 2 does not change. The casting operation continues.

As described above, in the method for casting a molten metal using the vanishable core according to the present invention, such a core 2
It is desirable that the core body 4 that constitutes the core body 4 be melted, decomposed, burned, or the like by the heat of the molten metal before the casting operation is completed. Although it can be easily done, it is also possible to make such a core body 4 disappear after the end of casting.

Next, when the casting operation is completed, the mold 12
The intended casting (casting product) will be taken out by the mold release.
Since the core body 4 has already been eliminated, the inorganic component constituting the coating film layer 6 is present only in powder form. There is substantially no particulate matter mixed in the molding sand of the present invention, and even in the case of the inorganic powder generated from the coating film layer 6, it can be easily separated from the molding sand. In addition to eliminating the need for processing costs such as sand separation, there is no need to increase the amount of foundry sand, and it is also unnecessary to treat it as industrial waste as foundry sand. As a result, it has become possible to achieve zero emission and to improve resource productivity effectively.

[0031]

Hereinafter, typical examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes no restrictions on the description of such examples. It is needless to say that it is not something to receive.
In addition, in addition to the following examples, the present invention may further include various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention. , Improvements and the like can be added. In addition, in the following examples, parts are based on weight.

Preparation of Coating Material A Graphite (earth): 20 parts, bentonite: 5 parts, silica:
30 parts, borax (hydrous): 20 parts, sodium metasilicate: 25 parts were mixed and pulverized, and water: 25 parts and No. 1 water glass: 8 parts were added to 100 parts of the obtained mixture. Then, by stirring, a mud-like coating material was prepared.

Preparation of Coating Material B Graphite (earth): 20 parts, kaolin: 5 parts, alumina: 3
0 parts, borax (hydrated): 20 parts, sodium silicate powder:
25 parts were mixed and pulverized, and 1 part of the obtained mixture was mixed.
25 parts of water and 10 parts of No. 1 water glass were added to 00 parts and stirred to prepare a mud-like coating material.

Preparation of Coating Material C Graphite (earth): 20 parts, bentonite: 5 parts, silica:
30 parts, borax (hydrous): 20 parts, glass fiber: 5 parts,
10 parts of calcium sulfate (0.5 hydrate) and 10 parts of sodium silicate powder were mixed and pulverized. Based on 100 parts of the obtained mixture, 43 parts of water and 1st water glass were used.
By adding 0 parts and stirring, a mud-like coating material was prepared.

Example of Casting First, a block-shaped flame-retardant expanded polystyrene base material (rectangular body) having a size of 50 mm × 50 mm × 20 mm was prepared as a core body 4. A coating material layer A having a thickness of 0.5 mm is formed by coating the coating material A, B or C prepared as described above on the entire outer peripheral surface by the ironing method, drying and solidifying the coating material. Thus, the intended core 2 was produced.

Next, as shown in FIG. 2, the obtained core 2 is arranged in a casting cavity 14 of a mold 12 so that a casting cavity 14 having a desired shape is formed. Then, by pouring the molten spheroidal graphite cast iron and casting, the outer dimensions are 40 mm × 67 mm ×
A casting having a rectangular hollow body shape with a thickness of 37 mm and a thickness of 8 mm was cast. After the completion of the casting operation, the mold 1
After performing the mold release of No. 2 and taking out the cast product, the coated cores 2 of any of the coating materials A to C were coated.
However, although it disappears due to the high heat action of the molten metal added at the time of casting and its disappearance is recognized, the hollow shape provided by such a core 2 has a constant shape similar to the conventional core. And it was recognized that a good cast product could be obtained.

[0037]

As is apparent from the above description, the core of the present invention is significantly reduced in weight due to the use of the core body made of foam, thereby facilitating the casting operation. In addition to the fact that the size of the machinery for automation can be effectively reduced, the increase in the amount of foundry sand in the casting process is advantageously avoided, thereby eliminating the waste as foundry sand and eliminating industrial waste. It is possible to achieve excellent effects such as realizing zero emission and zero emission, and effectively improving resource productivity.

[Brief description of the drawings]

FIG. 1 is a partially cutaway explanatory view showing an example of a vanishable core according to the present invention.

FIG. 2 is an explanatory sectional view showing a state in which the disappearing core shown in FIG. 1 is set in a casting cavity of a mold.

[Explanation of symbols]

2 core 4 core body 6 coating film layer 12a upper mold 12b lower mold 12 mold 14 casting cavity 16 gate 18 runner

Claims (8)

[Claims] 1. A casting of a molten metal, comprising: a core body made of a foam of a polymer material; and a heat-resistant coating film layer formed on at least a surface of the core body in contact with the molten metal. A vanishable core, wherein the core body can be vanished by the heat of the molten metal in the process. 2. The vanishable core according to claim 1, wherein the polymer foam is expanded polystyrene. 3. The heat-resistant coating film layer is formed of a coating material containing at least a heat-resistant aggregate and a binder.
Or the vanishable core according to claim 2. 4. The core according to claim 3, wherein a fire / heat resistant agent is further added to the coating material. 5. The disappearing mold according to claim 3, wherein the coating material further contains at least one of a vitrifying agent, a coating film layer reinforcing material, and a plasticizer. Nakako. 6. The core according to claim 1, wherein the coating layer has a thickness of 0.1 to 5 mm. 7. After the core is set in a casting cavity of a predetermined mold using the disappearing core according to claim 1, casting of a predetermined molten metal is performed. And forming a solidified layer of the molten metal at a portion of the molten metal that is in contact with the core surface, which can withstand the pressure of the molten metal, and further, causes the core body constituting the core to disappear. A casting method characterized in that: 8. The casting method according to claim 7, wherein the core body is eliminated by the heat of the molten metal by the time the casting operation is completed.