JPH09253792A - Paper core for casting and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core capable of casting a parts having a small hole or narrow gap with excellent accuracy and excellent-workability by providing a casting core in which cellulose fiber is the essential composition, and adding inorganic powder or inorganic fiber thereto. SOLUTION: A core to be used in manufacturing a casting of hollow shape or of undercut shape is formed of a material in which cellulose fiber is the essential composition, and the inorganic product and/or inorganic fiber is contained. In the paper core for casting, the content of the inorganic powder or inorganic fiber is preferably in the range of about 20-70wt.%. Talc powder, alumina powder, etc., is used for the inorganic powder. Alumina fiber is used for the inorganic fiber. The core is manufactured by adding cellulose fiber and inorganic powder and/or inorganic fiber to the solvent such as water to make the sluny, pouring the slurry into a mold, pressing the slurry, removing the solvent, and performing the drying. The pressure is preferably 10-30kgf/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting core, and particularly to a casting having a shape suitable for casting using a core such as a hollow shape or an undercut shape, for example, a thin hole or a narrow hole. The present invention relates to a casting paper core suitable for use in molding a cast product having a gap or the like by casting, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, forming a hole using a casting core is extremely inexpensive as compared with machining and has a high degree of freedom in its shape, so that it is applied to many parts. For this reason, a core for casting is used to form a hole that does not require particularly high dimensional accuracy, and a predetermined hole is formed during casting.

The required performance of the casting core is that it must withstand the heat during casting, that there is little generation of gas that causes defects, and that it can be easily taken out after casting. Is an essential condition.

Therefore, generally, a sand core (disintegrating core) obtained by hardening sand with a binder such as a resin is often used. And a narrow hole with a diameter of 5 mm or less, or a width of 5 m
When casting a narrow gap of m or less by casting, since the collapsible sand core is not elastic and brittle, the core may break and the hole or gap may be formed into a predetermined shape. There was a problem that it could not be done. Further, even if molding is possible, there is a problem in that it is difficult to take out sand after casting, especially when a thin long hole or a gap is formed.

Therefore, when a narrow gap is to be formed by casting, for example, there is a casting method disclosed in Japanese Patent Laid-Open No. 52-93820 in which paper is used as a core material for casting. The method disclosed here is that the exhaust port liner made of refractory metal is wrapped from the outer periphery with a separately prepared paper core, and is cast into the exhaust port of the engine when casting. Is a method of forming a narrow gap of 1 to 2 mm around the exhaust port liner. According to this manufacturing method, the used paper core becomes a relatively small amount of powder due to carbonization after casting, and is easily taken out. Even if it remains in the casting, there is no problem because it is a small amount.

[0006]

However, in the above-described method for manufacturing the exhaust port of the engine, the separately prepared paper core is cast while being wrapped from the outer periphery, and the paper core is used. It does not form a thin hole. Then, the present inventors have conducted various investigations for forming a fine hole in a casting using a paper core, and as a result of experiments, it has become clear that there are some problems.

That is, when trying to form a thin hole having a diameter of less than 5 mm by using a rod-shaped paper core, the first problem is that gas generated from the core due to heat during casting. , Not producing a sound casting due to gas defects. Secondly, a tar-like polymer compound is generated to deteriorate the workability of casting, and also to improve the workability of the core after casting. Difficult to discharge, third
As a problem of the above, various problems have arisen such that, when a rod-shaped core is formed by a so-called papermaking method, the core is significantly contracted and deformed during drying and does not have an intended shape. Therefore, it has been a problem to solve these problems.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is possible to form a part having a fine shape and a narrow hole or a narrow gap with good workability by casting. It is intended to provide a casting paper core.

[0009]

A casting paper core according to the present invention has a shape suitable for casting using a core such as a hollow shape or an undercut shape as described in claim 1. In a casting core used for producing a cast product having, the core is characterized in that it has a constitution in which an inorganic powder and / or an inorganic fiber are contained in addition to cellulose fiber as an essential component. There is.

In an embodiment of the casting paper core according to the present invention, as described in claim 2, the content of the inorganic powder and / or the inorganic fiber is within the range of 20 to 70% by weight. It is more preferable that the inorganic powder contained in the core is talc powder and / or alumina powder as described in claim 3, It is more preferable that the inorganic fiber contained in the core is an alumina fiber, as described in (1).

Further, the casting paper core manufacturing method according to the present invention, as described in claim 5, is suitable for manufacturing the casting paper core according to any one of claims 1 to 4. Cellulose fibers and inorganic powder and / or inorganic fibers are added to the solvent of (1) to appropriately stir to form a slurry, and the slurry is poured into a predetermined mold and pressurized to remove the solvent, and then dried. .

Further, in the embodiment of the method for producing a core for casting paper according to the present invention, the solvent may be water as described in claim 6, and
As described in claim 7, the pressure at the time of pressurization is 10
More preferably, it is set to be about 30 kgf / cm ² .

[0013]

INDUSTRIAL APPLICABILITY The casting paper core according to the present invention is a casting core used when manufacturing a cast product having a shape suitable for casting using a core having a hollow shape or an undercut shape. Since the core contains cellulose fiber as an essential component and contains inorganic powder and / or inorganic fiber in addition to this, it is an inorganic powder having excellent heat resistance or an inorganic powder having excellent heat resistance. By mixing the required amount of fibers, it is possible to suppress the generation of gas and tar from the core due to heat during casting, and parts with fine holes with a diameter of less than 5 mm and narrow gaps with an interval of less than 5 mm. Has a remarkable effect that it can be simultaneously molded at the time of casting, and by mixing the inorganic substance in the form of inorganic fiber, the moldability of the core is deteriorated even when the amount of the inorganic substance is increased. Having Chodai Naru effect that it is possible to prevent.

Furthermore, since inorganic powder and / or inorganic fibers are contained in addition to the cellulose fibers, a predetermined pressure is applied at the time of production to remove the solvent such as water, so that the shrinkage deformation occurs during drying. It is possible to obtain a product having a predetermined casting shape having a small hole with a diameter of less than 5 mm and a narrow gap with an interval of less than 5 mm, since it is possible to suppress the above and to form a paper core having elasticity. That is a great effect.

And, as described in claim 2,
By setting the content of the inorganic powder and / or the inorganic fiber within the range of 20 to 70% by weight, shrinkage deformation can be further prevented from occurring during molding and drying of the core.
This has a great effect that the shape accuracy of the core can be made more reliable.

Further, as described in claim 3, the inorganic powder contained in the core is talc powder and / or alumina powder, so that the core generated by the heat during casting is The extremely excellent effect that it is possible to suppress the generation of gas and tar is obtained.

Further, as described in claim 4, when the inorganic fiber contained in the core is an alumina fiber, generation of gas or tar from the core due to heat during casting is suppressed. Is possible with inorganic powder and /
Alternatively, when the content of the inorganic fibers is increased, the use of a larger amount of the inorganic fibers than the inorganic powder brings about a remarkable effect that it is possible to prevent the moldability of the core from being deteriorated.

In the method for producing a core for casting paper according to the present invention, when the core for casting paper according to any one of claims 1 to 4 is produced, cellulose fiber and inorganic powder and / or inorganic fiber are added to an appropriate amount of a solvent. In addition, it is made into a slurry, and this slurry is poured into a predetermined mold and pressurized to remove the solvent, and then dried, so that it is possible to suppress shrinkage deformation that occurs during drying, and casting with high shape accuracy A great effect that a paper core can be manufactured with good workability is brought about.

Then, as described in claim 6,
The use of water as the solvent brings about a remarkably excellent effect that it is possible to easily prepare a slurry containing the cellulose fiber and the inorganic powder and / or the inorganic fiber, and As described above, by setting the pressure at the time of pressurization to 10 to 30 kgf / cm ² , it is possible to manufacture a core made of cast paper which is excellent in shape accuracy without cracking or deformation. Remarkably excellent effect is brought about.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The casting paper core according to the present invention is
Cellulose fiber as an essential component and, in addition to this, contains inorganic powder and / or inorganic fiber,
In this case, as the inorganic powder and / or the inorganic fiber contained in the paper core together with the cellulose fiber, any one can be used as long as it has heat resistance and does not generate gas or tar during casting.

It is more preferable that the content range is 20 to 70% by weight. When the content is less than 20% by weight, the content of the cellulose fibers becomes small, so that when the rod-shaped core is formed and dried. Shrinkage deformation tends to occur, making it difficult to obtain a predetermined shape. Further, if the content exceeds 70% by weight, the core strength tends to be low, and as a result, cracks or the like may occur during molding and drying of the rod-shaped core. Because it comes out.

Then, as the proportion of the inorganic powder contained in the cellulose fibers is increased, the fluidity of the slurry injected into the mold becomes poor, and as a result, the moldability of the core deteriorates. In this case, deterioration of the moldability of the core can be prevented by using less inorganic powder and more inorganic fiber.

On the other hand, in a core made of only cellulose fibers, gas is generated from the core due to heat during casting.
Casting defects occur. Moreover, since a tar-like polymer compound is generated, handling and elimination of the generated tar after casting become a problem. Then, the amount of gas generated from the core decreases with an increase in the blending amount of the inorganic powder and / or the inorganic fiber. The compounding amount in the present invention is preferably in the range of 20 to 70% by weight, but the larger the compounding amount, the longer the fine holes that can be formed during casting can be made.

Further, in the method for producing a core for casting paper of the present invention, cellulose fiber and inorganic powder and / or inorganic fiber are added to an appropriate amount of a solvent such as water, and the mixture is stirred to form a slurry.
Then, the slurry is poured into a predetermined mold, pressurized with a punch and a die at a pressure of 10 to 30 kgf / cm ² , the solvent such as water is removed, and then the slurry is dried to produce a stick-shaped paper core. it can.

In this case, 1 by punching and dies.
Pressing at a pressure of 0 to 30 kgf / cm ² is a more preferable blending amount of the inorganic powder and / or the inorganic fiber 2
This is because the most suitable pressing force at which 0% to 70% by weight does not cause deformation or cracking. When the applied pressure is less than 10 kgf / cm ² , dehydration and molding of the core tend to be insufficient, and deformation may occur. On the other hand, if it exceeds 30 kgf / cm ² , cracks may occur during molding of the core.

[0026]

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to such Examples.

Example 1 To 1 liter of water, as shown in the column of Example 1 in the table, 10 g of old newspaper and 4.29 g of talc (average particle size 5.0 μm) were added as cellulosic fibers for about 1 minute. A slurry was prepared by stirring with a mixer. Then, FIG.
A punch 1 having a punch 1 and a die 2 as shown in FIG. 2 is used, and a predetermined amount of the slurry 4 is poured into the rectangular hole 2a of the die 2 using a pressure die in which a net 3 is arranged below the die 2. after drying under pressure of ^2, carried out for 15 minutes drying at 80 ° C., talc content of 30 wt% as shown in FIG. 2, one side rod-like paper core 5 of example 1 is 3mm Was produced. And Example 1
The transverse rupture strength of the rod-shaped paper core 5 was measured to be 5.6MP.
a.

FIG. 3 shows a mold 6 for casting a casting using the paper core of the present invention.
It has a cavity 7, a sprue 8, a runner 9, and a frying 10. Then, the paper core 5 obtained in Example 1 was placed in the cavity 7 of the mold 6, and the molten aluminum was poured from the pouring spout 8 to cast an aluminum casting.

FIG. 4 shows an aluminum casting 11 obtained by using the paper core 5 of Example 1 and having a thin rod-shaped casting hole 11a with a side of 3 mm.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 2 As shown in the column of Example 2 in the table, the content of talc was 50% by weight in the same manner as in Example 1 except that the talc was changed to 10 g. The rod-shaped paper core 5 of Example 2 was prepared. Then, the bending strength of the rod-shaped paper core 5 of Example 2 was measured and found to be 4.9 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 3 As shown in the column of Example 3 in the table, the content of talc was 70% by weight in the same manner as in Example 1 except that the talc was 23.3 g. The stick-shaped paper core 5 of Example 3 was prepared. Then, the third embodiment
The bending strength of the rod-shaped paper core 5 of No. 3 was measured to be 3.2MP.
a.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 4 As shown in the column of Example 4 in the table, Example 4 was changed except that 4.29 g of alumina fiber (length about 20 μm, average diameter 2 μm) was added in place of talc. In the same manner as in 1, a rod-shaped paper core 5 of Example 4 was prepared in which the content of alumina fibers was 30% by weight. When the transverse rupture strength of the bar-shaped paper core 5 of Example 4 was measured,
It was 5.2 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 5 As shown in the column of Example 5 in the table, the same as Example 1 except that 10 g of alumina fiber (length about 20 μm, average diameter 2 μm) was added in place of talc in Example 1. Similarly, a rod-shaped paper core 5 of Example 5 was produced in which the content of alumina fibers was 50% by weight. Then, the bending strength of the rod-shaped paper core 5 of Example 5 was measured.
It was 7 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 6 As shown in the column of Example 6 in the table, Example 2 was repeated except that 23.3 g of alumina fiber (length about 20 μm, average diameter 2 μm) was added in place of talc. In the same manner as in 1, the rod-shaped paper core 5 of Example 6 was prepared so that the content of alumina fibers was 70% by weight. Then, the bending strength of the rod-shaped paper core 5 of Example 6 was measured,
It was 2.5 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized to form a small amount of fine powder, which could be easily removed by air blow. .

Example 7 As shown in the column of Example 7 in the table, except that in Example 1, 4.29 g of talc was added and 5.71 g of alumina powder (average particle size 5.0 μm) was added. In the same manner as in Example 1, a rod-shaped paper core 5 of Example 7 was produced in which the total content of talc and alumina powder was 50% by weight. Then, the transverse rupture strength of the rod-shaped paper core 5 of Example 7 was measured and found to be 5.3 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Example 8 As shown in the column of Example 8 in the table, in Example 1, 4.29 g of alumina powder (average particle size: 5.0 μm) was used instead of talc, and alumina fiber (length: about 20 μm, Average diameter 2
[mu] m) was added in the same manner as in Example 1 to produce a rod-shaped paper core 5 of Example 8 in which the total content of talc and alumina fibers was 70% by weight. Then, the bending strength of the rod-shaped paper core 5 of Example 8 was measured and found to be 2.3 MPa.

Next, when the core portion of the cast product was confirmed after the completion of casting, the cellulose fibers were carbonized into a small amount of fine powder, which could be easily removed by air blow. .

Comparative Example 1 As shown in the column of Comparative Example 1 in the table, the content of talc was 10% by weight in the same manner as in Example 1 except that talc was 1.11 g. A bar-shaped paper core 5 of Comparative Example 1 was prepared.

In Comparative Example 1, although a slight improvement was observed as compared with the core made of only talc-free paper, tar and gas were remarkably generated during casting, and a casting hole having a predetermined shape was formed. It was not possible to solve the problem of the formation of the core and the subsequent handling of the core material residue.

Comparative Example 2 As shown in the column of Comparative Example 2 in the table, the content of talc was 80% by weight in the same manner as in Example 1 except that 40 g of talc was used. The rod-shaped paper core 5 of Comparative Example 2 was prepared.

In Comparative Example 2, the viscosity of the slurry increased during the production of the rod-shaped paper core 5 to make it difficult to handle, and the core was not formed into a predetermined core shape. Therefore, the subsequent casting was not carried out.

Comparative Example 3 As shown in the column of Comparative Example 3 in the table, the same as Example 1 except that 40 g of alumina fiber (length about 20 μm, average diameter 5 μm) was added in place of talc in Example 1. Similarly, a rod-shaped paper core 5 of Comparative Example 3 was prepared in which the content of alumina fibers was 80% by weight.

In Comparative Example 3, the rod-shaped paper core 5 did not have sufficient shape and strength and could not be handled or supported by the mold, so that the subsequent casting was not performed.

Comparative Example 4 As shown in the column of Comparative Example 4 in the table, Comparative Example 1 was repeated except that talc was not used and the content of the cellulose fibers was 100% by weight. A stick-shaped paper core 5 of Example 4 was produced.

In Comparative Example 4, the rod-shaped paper core 5 was deformed, but when the subsequent casting was carried out and the core portion of the cast product was confirmed after the completion of casting, the tar-like product was not adhered. It was confirmed, and a large blow was generated in the casting hole 11a due to gas generation, and the shape of the core could not be reflected in the cast product.

[0053]

[Table 1]

[Brief description of drawings]

FIG. 1 is a perspective view ((a) of FIG. 1) and a cross-sectional view ((b) of FIG. 1) showing a mold used for producing a core of a casting paper according to an example of the present invention.

FIG. 2 is an explanatory view of a slope showing a core of a casting paper produced in an example of the present invention.

FIG. 3 is a cross-sectional explanatory view showing a mold for casting using a casting paper core produced in an example of the present invention.

FIG. 4 is an explanatory view of an inclined surface showing the shape of a cast article cast using the casting paper core produced in the example of the present invention.

[Explanation of Codes] 1 Punch 2 Die 3 Mesh 4 Slurry 5 Paper Core 6 Mold 7 Cavity 8 Gate 9 Runner 10 Lifting 11 Casting 11a Casting Hole

Claims (7)

[Claims] 1. A core for casting, which is used for producing a cast product having a shape suitable for casting using a core such as a hollow shape or an undercut shape, wherein the core contains cellulose fiber as an essential component. And, in addition to this, a casting paper core characterized by containing inorganic powder and / or inorganic fiber. 2. The casting paper core according to claim 1, wherein the content of the inorganic powder and / or the inorganic fiber is within the range of 20 to 70% by weight. 3. The core for casting paper according to claim 1, wherein the inorganic powder contained in the core is talc powder and / or alumina powder. 4. The core for casting paper according to claim 1, wherein the inorganic fiber contained in the core is an alumina fiber. 5. When manufacturing the casting paper core according to any one of claims 1 to 4, cellulose fibers and inorganic powder and / or inorganic fibers are added to an appropriate amount of a solvent to form a slurry, and the slurry is prepared in a predetermined amount. A method for producing a core for a casting paper, which comprises pouring into a mold, pressurizing to remove a solvent, and then drying. 6. The method of manufacturing a casting paper core according to claim 5, wherein the solvent is water. 7. The pressure during pressurization is 10 to 30 kgf / c.
The casting paper core manufacturing method according to claim 5, wherein the casting paper core is m ² .