JP7249459B1 - Structures for casting manufacturing - Google Patents

Abstract

An object of the present invention is to provide a structure for manufacturing castings, in which molten metal flows well during casting. A casting manufacturing structure (3) has a cylindrical main body (31) and a coating layer (32) covering the inner surface of the main body (31), and the main body (31) has electrical insulation. Both the body portion 31 and the coating layer 32 preferably have electrical insulation. The electrical resistance evaluation value measured at a position 60 mm away on the outer surface of the main body 31 is 200 kΩ/mm or more, and/or the electrical resistance evaluation value measured in the thickness direction of the main body 31 is 200 kΩ/mm or more. is preferably [Selection drawing] Fig. 1

Description

The present invention relates to structures for manufacturing castings.

As a prior art related to a structure for manufacturing castings, the present applicant has previously proposed a main body containing organic fibers, inorganic fibers such as carbon fibers, inorganic particles, and a binder, and a coating layer formed on the inner surface of the main body. We have proposed a structure for casting (see Patent Document 1). According to the structure described in the same document, the coating layer shields the thermal decomposition gas generated from the organic fibers contained in the main body during casting, so there is an advantage that gas defects in the casting are reduced more than before.

JP 2012-24841 A

Casting defects such as wrinkles, cracks, cavities, etc. are caused by poor flow of molten metal caused by a decrease in casting temperature. As the quality of castings has improved in recent years, there has been a demand for further improvements in melt flow during casting in structures for manufacturing castings. Regarding the improvement of molten metal flow during casting, there is room for improvement in the structure described in Patent Document 1 as well.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a structure for manufacturing castings, which has good molten metal flow during casting.

SUMMARY OF THE INVENTION The present invention provides a casting manufacturing structure having a tubular main body and a coating layer covering the inner surface of the main body, wherein the main body has electrical insulation.

According to the present invention, it is possible to provide a structure for manufacturing castings, which has good fluidity during casting.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the structure for manufacturing castings of the present invention. FIGS. 2(a) to 2(d) are schematic cross-sectional views showing another embodiment of the structure for manufacturing castings of the present invention. FIG. 3 is a schematic cross-sectional view showing one embodiment of a mold manufactured using the structure for manufacturing castings of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on its preferred embodiments with reference to the drawings.
1 and 2, the structure for manufacturing castings of the present invention (hereinafter also simply referred to as "structure for castings") 3 is suitably used, for example, as runners used in casting or lifting runners. be. As will be described later, the casting structure 3 of the present invention is particularly suitable for use as a runner or lifting runner in the production of cast steel.

As shown in FIGS. 1 and 2 , the casting structure 3 has a tubular main body 31 and a coating layer 32 that covers at least part of the inner surface of the main body 31 . The “main body portion” in this specification is a portion that occupies most of the volume of the casting structure 3 . The term “cylindrical” as used herein means a hollow structure having a longitudinal direction and a width direction orthogonal to the longitudinal direction. The shape of the cavity in the body portion 31 is not limited, and the cross-sectional shape of the cavity may be, for example, circular, elliptical, or polygonal. Further, the “cylindrical shape” includes, as shown in FIG. It includes those whose entire longitudinal direction is curved in an arc shape, and those in which the casting structure 3 has one or more branches as shown in FIGS. 2(c) and 2(d).
Due to the tubular body portion 31, the casting structure 3 is also tubular.

The casting structure 3 has a coating layer 32 on the inner surface, which is the surface through which the molten metal flows into the main body 31 during casting. The “coating layer” in this specification typically exists as a film-like portion on the inner surface of the main body portion 31 . As used herein, the term “film-like portion” refers to a portion where particles constituting the coating layer 32 are microscopically present in the form of agglomerated particles.
If the main body portion 31 is not covered with the coating layer 32 and is exposed, the components contained in the main body portion 31 are burned when the molten metal comes into contact with the main body portion 31 during casting, and gas is mixed or dissolved in the molten metal. There is In particular, when cast steel having a higher molten metal temperature than cast iron is cast, the amount of gas dissolved in the molten metal is large. It becomes easy to dissolve in it. On the other hand, in the casting structure 3 of the present embodiment, the inner surface of the body portion 31 is covered with the coating layer 32, so that the body portion 31 can be prevented from coming into contact with the molten metal. Even if the components contained in the body portion 31 burn to generate gas, the gas can be prevented from dissolving in the molten metal. This advantage is particularly advantageous in the case of cast steel, in which gases tend to dissolve in the molten metal.
From the viewpoint of suppressing the gas from entering the molten metal during casting and improving the molten metal flow during casting as described later, the surface area of the coating layer 32 on the side of the main body 31 that contacts the molten metal is It is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more, and more preferably 100% of the inner surface area of the portion 31 .

The body portion 31 is configured to have electrical insulation.
As used herein, the term "electrically insulating" means a property that does not pass electric current at all or a property that does not substantially pass electric current.
The property of substantially impervious to current means that the electrical resistance evaluation value measured in the thickness direction or surface is equal to or greater than a predetermined value. Specifically, if the electric resistance evaluation value measured in the thickness direction is 200 kΩ / mm or more, or if the electric resistance evaluation value measured on the surface is 200 kΩ / mm or more, the property that does not pass current substantially , that is, it is electrically insulating.

Generally, the movement of free electrons within a body is known as one mode of heat movement in the body. That is, the more free electrons, in other words the lower the electrical resistivity of the object, the higher the thermal conductivity. In some conventionally known casting structures, the body portion 31 may have electrical conductivity due to the components contained in the casting structure 3 . Such a foundry structure 3 has a relatively high thermal conductivity. In such a casting structure 3 , part of the heat of the molten metal that has flowed into the casting structure 3 during casting moves out of the casting structure 3 via the main body portion 31 . As a result, the temperature of the molten metal flowing in the casting structure 3 decreases, and the flow of the molten metal deteriorates as the casting temperature decreases, which may cause defects such as wrinkles, cracks, and cavities. On the other hand, in the casting structure 3 of the present embodiment, the main body portion 31, which is the major part of the structure, has electrical insulation, in other words, has low thermal conductivity. The heat of the molten metal that has flowed into the casting structure 3 is suppressed from moving to the outside of the casting structure 3 via the body portion 31 . As a result, in the casting structure 3 of the present invention, the temperature of the molten metal in the casting structure 3 is less likely to decrease than in the conventional casting structure, and the molten metal flow during casting can be kept good. can be done. Thereby, generation of casting defects such as flow lines, cracks, and cavities can be suppressed.

From the viewpoint of further exerting the above effects, the casting structure 3 of the present embodiment has an electrical resistance evaluation value of 200 kΩ / mm or more measured at a position 60 mm away from the outer surface of the main body 31, and/ Alternatively, it is preferable that the electrical resistance evaluation value measured in the thickness direction of the body portion 31 is 200 kΩ/mm or more.
Specifically, the electrical resistance evaluation value measured at a position 60 mm away from the outer surface of the body portion 31 is more preferably 300 kΩ/mm or more, and still more preferably 500 kΩ/mm or more. Although the upper limit of the electric resistance evaluation value measured at a position 60 mm away from the outer surface of the main body 31 is not particularly limited, for example, 1×10 ¹⁰ kΩ/mm or less is realistic.
More specifically, the electrical resistance evaluation value measured in the thickness direction of the body portion 31 is more preferably 1000 kΩ/mm or more, and still more preferably 1×10 ⁴ kΩ/mm or more. Although the upper limit of the electrical resistance evaluation value measured in the thickness direction of the main body 31 is not particularly limited, for example, 1×10 ¹⁰ kΩ/mm or less is realistic.
In the casting structure 3 of the present embodiment, only the electrical resistance evaluation value measured at a position 60 mm away from the outer surface of the body portion 31 may satisfy the above-described numerical range, and the thickness direction of the body portion 31 may be Only the electrical resistance evaluation value measured in may satisfy the above numerical range, or both of them may be satisfied.

The electrical resistance evaluation value in the thickness direction of the body portion 31 can be measured by the following method.
First, a part of the coating layer 32 in the casting structure 3 is separated from the main body 31 using a knife such as a cutter or a file. Only the separated main body portion 31 is recovered, and the thickness of the recovered main body portion 31 and the electric resistance value in the thickness direction are measured. Specifically, after short-circuiting the test leads of the digital tester and performing zero adjustment, the test leads are placed on the surface of the body portion 31 at positions facing each other in the thickness direction of the body portion 31 so as to sandwich the body portion 31. Make contact and measure the electrical resistance. A dial caliper gauge is used to measure the wall thickness at the position where the electrical resistance value was measured, and the electrical resistance evaluation value is calculated by dividing the electrical resistance value by the wall thickness. The electrical resistance value and wall thickness are measured at eight different points, and the average value of the eight electrical resistance evaluation values is calculated. MCD-008 pocket multimeter manufactured by Multi Keiseki Co., Ltd. is used as the digital tester, and a code No. manufactured by Mitutoyo Co., Ltd. is used as the dial caliper gauge. 209-611, code DCGO-50RL.

The electrical resistance evaluation value on the outer surface of the body portion 31 can be measured by the following method.
Specifically, when the test leads of the digital tester are applied to the outer surface of the main body 31 in the above-described method for measuring the electric resistance evaluation value in the thickness direction of the main body 31, the circumferential length between the test leads is set to 60 mm. , and the electrical resistance is divided by 60 mm. The positional relationship of the test leads described above is not particularly limited.

In the casting structure 3 of the present embodiment, the molten metal that has flowed into the casting structure 3 comes into contact with the coating layer 32 . In such a casting structure 3, if the coating layer 32 in addition to the body portion 31 is also configured to have electrical insulation, the function of both the body portion 31 and the coating layer 32 will make the casting structure 3 during casting. The heat of the molten metal that has flowed into the body 3 is further suppressed from moving to the outside of the casting structure 3 . As a result, the temperature of the molten metal in the casting structure 3 is even less likely to drop, and the molten metal flow during casting can be maintained even better. From this point of view, it is preferable that only the body portion 31 in the casting structure 3 has electrical insulation, but it is more preferable that both the body portion 31 and the coating layer 32 have electrical insulation. That is, by configuring the casting structure 3 of the present embodiment having the main body portion 31 and the coating layer 32 so that the entire structure has electrical insulation, it is possible to improve the molten metal flow during casting. can.

From the viewpoint of further exerting the above effects, in the casting structure 3 of the present embodiment, the electric resistance evaluation value measured at a position 60 mm away from the inner surface 32S of the coating layer 32 is 200 kΩ / mm or more, And/or, the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 is preferably 200 kΩ/mm or more.
Specifically, the electrical resistance evaluation value measured at a position 60 mm away from the inner surface 32S of the coating layer 32 is more preferably 300 kΩ/mm or more, and still more preferably 500 kΩ/mm or more. Although the upper limit of the electric resistance evaluation value measured at a position 60 mm away from the inner surface 32S of the coating layer 32 is not particularly limited, for example, 1×10 ¹⁰ kΩ/mm or less is realistic.
More specifically, the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 is more preferably 1000 kΩ/mm or more, and still more preferably 1×10 ⁴ kΩ/mm or more. Although the upper limit of the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 is not particularly limited, for example, 1×10 ¹⁰ kΩ/mm or less is realistic.
In the casting structure 3 of the present embodiment, only the electrical resistance evaluation value measured at a position 60 mm away from the inner surface 32S of the coating layer 32 may satisfy the above numerical range, and the thickness of the coating layer 32 Only the electrical resistance rating measured in the direction may satisfy the above numerical ranges, or both.

The thickness direction electrical resistance evaluation value of the coating layer 32 can be measured by the following "Method for measuring the thickness direction electrical resistance evaluation value of the coating layer".
[Method of measuring the electrical resistance evaluation value in the thickness direction of the coating layer]
First, a part of the coating layer 32 in the casting structure 3 is separated from the main body 31 using a knife such as a cutter or a file. Only the separated coating layer 32 is recovered, and the thickness of the recovered coating layer 32 and the electric resistance value in the thickness direction are measured. Specifically, after short-circuiting the test leads of the digital tester and performing zero adjustment, the test leads are applied to the surface of the coating layer 32 at positions facing each other in the thickness direction of the coating layer 32 so as to sandwich the coating layer 32. Make contact and measure the electrical resistance. A dial caliper gauge is used to measure the wall thickness at the position where the electrical resistance value was measured, and the electrical resistance evaluation value is calculated by dividing the electrical resistance value by the wall thickness. The electrical resistance value and wall thickness are measured at eight different points, and the average value of the eight electrical resistance evaluation values is calculated.

The thickness of the coating layer 32 can also be measured by the following "method for measuring the thickness of the coating layer".
[Method for measuring thickness of coating layer]
First, the thickness of the body portion 31 before forming the coating layer 32 on the body portion 31 is measured. Next, the thickness of the casting structure 3 after forming the coating layer 32 on the body portion 31 is measured. After that, the thickness of the coating layer 32 is obtained by subtracting the thickness of the body portion 31 from the thickness of the casting structure 3 . Specifically, the thickness of the main body portion 31 before the coating layer 32 is formed on the main body portion 31 is determined by marking the outer peripheral surface of the main body portion 31 in advance and using a dial caliper gauge. Measure at position. The thickness of the casting structure 3 after forming the coating layer 32 on the main body 31 is measured at the position of the mark given to the main body 31 using a dial caliper gauge.

The electrical resistance evaluation value of the inner surface 32S of the coating layer 32 can be measured by the following method.
Specifically, when the test leads of the digital tester are applied to the coating layer 32 in the above-described method for measuring the "electric resistance evaluation value in the thickness direction of the coating layer", the length in the circumferential direction between the test leads is set to 60 mm. The electrical resistance value is measured and measured by dividing the electrical resistance value by 60 mm. The positional relationship of the test leads is not particularly limited.

As described above, the casting structure 3 of the present embodiment is preferably configured so as to have electrical insulation as a whole from the viewpoint of improving molten metal flow during casting. In particular, by suppressing the heat of the molten metal that has flowed into the casting structure 3 during casting from moving to the main body 31 through the coating layer 32, and further from the heat moving to the outside of the casting structure 3 , from the viewpoint of further improving the melt flow during casting, the electrical resistance evaluation value measured in the thickness direction through the main body 31 and the coating layer 32 is preferably 200 kΩ / mm or more, more preferably It is 1000 kΩ/mm or more, more preferably 1×10 ⁴ kΩ/mm or more. Also, the upper limit of the electrical resistance evaluation value measured in the thickness direction through the body portion 31 and the coating layer 32 is not particularly limited, but for example, 1×10 ¹⁰ kΩ/mm or less is realistic.

The electric resistance evaluation value in the thickness direction through the main body portion 31 and the coating layer 32 in the casting structure 3 can be measured by the following method.
After short-circuiting the test leads of the digital tester and performing zero adjustment, the body part 31 and the coating layer 32 in the casting structure 3 are aligned in the thickness direction so as to sandwich the body part 31 and the coating layer 32. The test leads are brought into contact with the surfaces of the body portion 31 and the coating layer 32 at the positions, and the electrical resistance values are measured. Using a dial caliper gauge at the position where the electrical resistance value was measured, the thickness at that position was measured in the same manner as the method for measuring the thickness of the main body described in the examples described later, and the electrical resistance value was measured. The electric resistance evaluation value is calculated by dividing by the wall thickness.

In the casting structure 3 of the present embodiment, the electric resistance evaluation value measured in the thickness direction of the main body portion 31 and the electric resistance evaluation value measured in the thickness direction of the coating layer 32 are both 200 kΩ / mm or more. is preferably According to the casting structure 3 having such a configuration, in each of the layers 31 and 32, the heat of the molten metal flowing into the casting structure 3 during casting is transferred to the main body 31 via the coating layer 32. , and its heat can be suppressed from moving out of the casting structure 3, and the melt flow during casting can be further improved.
From the same point of view, both the electrical resistance evaluation value measured in the thickness direction of the main body portion 31 and the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 are preferably 1000 kΩ / mm or more, more preferably It is 1×10 ⁴ kΩ/mm or more. Also, the upper limits of the electrical resistance evaluation value measured in the thickness direction of the body portion 31 and the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 are not particularly limited, but are, for example, 1×10 ¹⁰ kΩ/ mm or less is realistic.

From the viewpoint that the main body portion 31 has electrical insulation and good molten metal flow during casting, the main body portion 31 preferably contains an electrical insulating material. As will be described later, the body portion 31 of the present embodiment mainly contains an inorganic compound and an organic component, and both of them preferably contain an electrically insulating material.

As an electrically insulating material, the body portion 31 preferably contains an inorganic compound, and more preferably contains an inorganic fiber as the inorganic compound. By including an electrically insulating inorganic compound in the casting structure 3, the molten metal flow during casting is improved, and the heat resistance of the casting structure 3 is improved, so that the structure during casting. The strength, dimensional stability and shape retention of the resin can be enhanced.
Inorganic fibers are mainly fibrous materials that form the framework of the structure 3 for casting before being used for casting, and maintain their shape without being burned by the heat of the molten metal during casting.
Inorganic fibers can include, for example, electrically insulating fibers such as artificial mineral fibers, ceramic fibers, glass fibers, and natural mineral fibers, and they can be included singly or in combination of two or more thereof.
Man-made mineral fibers include, for example, rock wool.
Ceramic fibers include alumina fibers, silica fibers, mullite fibers, zirconia fibers, silicon carbide fibers, and the like.

It is preferable that the inorganic fibers used in this embodiment are only electrically insulating inorganic fibers. By including only electrically insulating inorganic fibers in the main body portion 31, the main body portion 31 can be configured to have electrical insulating properties. As a result, as described above, good molten metal flow can be maintained during casting. Furthermore, the hot strength of the body portion 31 can be ensured.

From the standpoint of good molten metal flow during casting, the main body 31 preferably does not contain an electrically conductive material. “Containing no electrically conductive material” means that the main body 31 is not intentionally made to contain an electrically conductive material, but, for example, microparticles derived from the material are inevitably mixed into the main body 31. means allow. Specifically, when the body portion 31 contains 0% by mass or more and 1% by mass or less, particularly 0.5% by mass or less of the electrically conductive material, it is said that the electrically conductive material is not contained. be able to.

The average fiber length of the inorganic fibers is preferably 0.2 mm or longer, more preferably 0.5 mm or longer, and still more preferably 2 mm or longer. If the average fiber length of the inorganic fibers is at least this lower limit value, thermal shrinkage due to thermal decomposition of the organic binder described later due to heat during casting is suppressed, and the casting structure 3 tends to exhibit shape retention. Become.
On the other hand, the average fiber length of inorganic fibers is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 4 mm or less. If the average fiber length of the inorganic fibers is equal to or less than this upper limit, it becomes easier to obtain the main body portion 31 with a uniform thickness.

The body portion 31 preferably contains 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more of the inorganic fiber with respect to the mass of the entire body portion 31. , more preferably 2% by mass or more. If the inorganic fiber content is at least this lower limit, the strength of the casting structure 3 during casting can be ensured. This effect is particularly remarkable when the body portion 31 contains an organic binder, which will be described later. In addition to this, it is possible to prevent shrinkage and cracking of the main body 31, peeling of the coating layer 32, and the like due to carbonization of the organic binder caused by heat during casting.
In addition, the body portion 31 preferably contains 80% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less of the inorganic fiber with respect to the mass of the entire body portion 31. 20 It is even more preferable to contain not more than mass %. If the content of the inorganic fibers is equal to or less than this upper limit, the moldability of the main body portion 31 in the papermaking and dehydration steps in the manufacturing method of the casting structure 3 described later is particularly good, and the main body has a uniform thickness. Part 31 is easily obtained.

From the viewpoint of improving the hot strength of the casting structure 3 and the moldability of the casting structure 3, the inorganic fiber has a long axis/short axis ratio of more preferably 10 or more and 2000 or less, more preferably 50 or more and 1000. It is below.

As an electrically insulating material, the body portion 31 preferably contains inorganic particles (hereinafter also referred to as “first inorganic particles”). By including the first inorganic particles in the body portion 31, the heat resistance of the casting structure 3 can be improved, and the strength of the casting structure 3 during casting can be increased. From the viewpoint of further exhibiting this effect, it is preferable that the first inorganic particles consist only of electrically insulating inorganic particles. In addition, the electrical resistivity of the first inorganic particles themselves, for example, is the first inorganic particles separated from the main body 31 of the casting structure 3, and the powder resistance measurement system MCP-PD51 manufactured by Nitto Seiko Analytic Co., Ltd. is used. It can be measured by using
When the body portion 31 contains the first inorganic particles, the first inorganic particles are preferably present at least on the surface of the body portion 31 , and more preferably present both on the surface and inside the body portion 31 .

The above first inorganic particles may include refractory aggregate particles such as mullite, obsidian, zirconia, zircon, mica, silica, hollow silica, hollow ceramics, fly ash and alumina. The first inorganic particles can contain these singly or by selecting two or more of them.
Hollow silica is silica particles having a hollow structure.
Hollow ceramics are hollow particles contained in fly ash, and can be obtained by flotation separation of fly ash using water.
Among the first inorganic particles described above, the main body 31 contains silica, hollow silica, obsidian, zircon, mica, silica, hollow ceramics, and fly ash from the viewpoint of low thermal conductivity, availability, economy, etc. is preferred, and silica is more preferred.

The shape of the first inorganic particles can each independently be spherical, polyhedral, scaly, layered, spindle-shaped, fibrous, amorphous, or a combination thereof.
The first inorganic particles may be used alone or in combination of two or more.

In the casting structure 3, the average particle size of the first inorganic particles is preferably within a specific range.
Specifically, the average particle size of the first inorganic particles is preferably 150 μm or less, more preferably 60 μm or less, even more preferably 30 μm or less, and particularly preferably 27 μm or less. By setting the average particle diameter of the first inorganic particles within this upper limit, the density of the first inorganic particles in the body portion 31 can be increased, and the strength of the body portion 31 can be improved. In addition, since the surface roughness of the body portion 31 can be reduced, the inner surface of the body portion 31 can be uniformly coated with a coating liquid composition, which will be described later, when manufacturing the casting structure 3 . Specifically, it is possible to prevent extremely thin portions from being formed in the coating layer 32 formed by coating the inner surface of the body portion 31 with a coating liquid composition, which will be described later.

From the viewpoint of improving the formability of the body portion 31, the average particle size of the first inorganic particles is preferably over 1 μm, more preferably 5 μm or more, and even more preferably 10 μm or more. By setting the average particle diameter of the first inorganic particles within this lower limit, when the intermediate molded body of the main body 31 is produced by papermaking, the first inorganic particles pass through the papermaking net, resulting in a decrease in yield. can be prevented, the formability of the body portion 31 can be improved. Moreover, since the freeness of the intermediate molded body of the body portion 31 can be improved, dehydration and drying can be easily performed, and the moldability of the body portion 31 can be improved.
These lower limits may be combined with any of the above upper limits.

The average particle size of the first inorganic particles can be measured by the following method.
[Method for measuring average particle size]
The average particle diameter of 50% volume cumulative measured using a laser diffraction particle size distribution analyzer (manufactured by Horiba, Ltd., LA-920) is defined as the average particle diameter in the present specification. Analysis conditions are as follows.
・Measurement method: Flow method ・Refractive index: Varies depending on various inorganic particles (refer to the manual attached to LA-920)
・Dispersion medium: Use one suitable for various inorganic particles ・Dispersion method: Stirring, built-in ultrasonic wave (22.5 kHz) for 3 minutes ・Sample concentration: 2 mg/100 cm ³

From the viewpoint of improving the hot strength, the body portion 31 preferably contains the first inorganic particles in an amount of 40% by mass or more, more preferably 45% by mass or more, relative to the mass of the entire body portion 31. It is more preferable to contain 50% by mass or more.
In addition, it preferably contains 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, and particularly preferably 68% by mass or less.

From the viewpoint that the body portion 31 has electrical insulation and good melt flow during casting, the content of the inorganic fibers relative to the mass of the entire body portion 31 and the amount of the first inorganic particles relative to the mass of the entire body portion 31 are determined. Provided that the content is within the above range, the content of the first inorganic particles relative to the content of the inorganic fibers is preferably 2.5 or more, more preferably 3 or more, It is more preferably 5 or more.
Also, the content of the first inorganic particles with respect to the content of the inorganic fibers is preferably 13 or less, more preferably 12 or less, and even more preferably 10 or less.

For the same reason as described above, the ratio of the sum of the mass of the inorganic fibers and the mass of the first inorganic particles to the mass of the entire body portion 31 is preferably 55% by mass or more, more preferably 60% by mass or more. It is preferably 70% by mass or more, and more preferably 70% by mass or more.
In addition, the ratio of the sum of the mass of the inorganic fibers and the mass of the first inorganic particles to the mass of the entire body portion 31 is preferably 87% by mass or less, more preferably 85% by mass or less, and 80% by mass. More preferably:

As an electrically insulating material, the body portion 31 preferably contains an organic component, and more preferably contains an organic fiber as the organic component. The organic fibers form the skeleton of the main body 31 before being used for casting, and part or all of them are burned by the heat of the molten metal during casting, forming voids inside the main body 31 after casting. It is a fibrous material that
In the body portion 31 , the organic fibers are entangled with each other, and voids are generated in the body portion 31 . As a result, the heat insulation of the casting structure 3 having the main body 31 is improved. Furthermore, if part or all of the organic fibers are burned by the heat of the molten metal during casting, voids are generated in the body portion 31 by the amount of the organic fibers that have been burned. As a result, the heat insulating property of the casting structure 3 is further improved.
From the viewpoint of further exhibiting the above effects, the organic fibers are preferably dispersed on at least the surface of the main body 31 , and more preferably dispersed on the surface and inside of the main body 31 .

As used herein, "organic component" refers to a natural product or compound having hydrocarbon groups in its molecular structure. Therefore, materials composed of only carbon elements or carbon and nitrogen elements, such as carbon fibers, do not constitute organic components and materials containing organic components in the present disclosure, and are classified as inorganic fibers as described above.

Whether or not the foundry structure 3 contains an organic component is based on the presence or absence of peaks corresponding to C=C bonds, C—H bonds, C=O bonds, and OH bonds obtained by solid-state NMR. can be determined by If at least a CH bond or a C═O bond is present among these bonds, it is determined that the material to be measured contains an organic component.
In addition, whether or not the casting structure 3 contains organic fibers can be determined by the solid-state NMR, and the surface and inside of the casting structure 3 can be examined with a microscopic FT-IR and a microscope (manufactured by KEYENCE CORPORATION, model number : VHX-500, which is the microscope of this specification). Specifically, confirm the position where the functional group derived from the organic substance is mapped in the microscopic FT-IR, and if a fibrous substance is observed with a microscope at the position, it is determined that the organic fiber is contained. .

Organic fibers can include paper fibers such as wood pulp, fibrillated synthetic fibers, regenerated fibers (for example, rayon fibers), and the like, and they can be used alone or in combination of two or more. Among these, it is preferable to include paper fibers. The reason for this is that when manufacturing the casting structure 3, it can be molded into various forms by papermaking, the wet strength characteristics of the dehydrated and dried molded product are excellent, the availability of paper fibers is easy and stable, and it is economical. because it is targeted.
Paper fibers can include wood pulp, as well as cotton pulp, linter pulp, bamboo, straw and other non-wood pulps. As the wood pulp, virgin pulp or waste paper pulp (recycled product) can be used alone or in combination of two or more. From the viewpoints of availability, environmental protection, reduction of production costs, etc., it is preferable to contain waste paper pulp. Organic fibers preferably contain used paper (newspaper, etc.) from the viewpoint of improving the moldability of the casting structure 3 and from the viewpoint of supply and economy.

The average fiber length of the organic fibers is preferably 0.8 mm or longer, more preferably 0.9 mm or longer. If the average fiber length of the organic fibers is at least this lower limit value, the organic fibers are likely to be entangled with each other, and as a result, it is easy to form a skeleton in a state before being used for casting.
Also, the average fiber length of the organic fibers is preferably 10 mm or less, more preferably 7 mm or less, and even more preferably 5 mm or less. If the average fiber length of the organic fibers is equal to or less than this upper limit, it becomes easier to ensure the surface smoothness of the casting structure 3 .

From the viewpoint of improving toughness and improving usability, the body portion 31 preferably contains 8% by mass or more, more preferably 9% by mass or more, of organic fibers with respect to the mass of the entire body portion 31. It is more preferable to contain more than mass %.
The upper limit of the content of the organic fibers in the body portion 31 can be, for example, 30% by mass or less, particularly 25% by mass or less, and further 20% by mass or less.
"Usability" as used herein means that when the material is cut to any size before use, it is less likely to crack due to the force applied during cutting or to be damaged by the weight of sand during casting. .

In addition to the body portion 31, the coating layer 32 has electrical insulation, and from the viewpoint of further improving the melt flow during casting, it is preferable that the coating layer 32 also contains an electrical insulation material. As described below, the coating layer 32 of the present embodiment mainly contains an inorganic compound, and the inorganic compound preferably contains an electrically insulating inorganic compound. It is preferable to be

As an electrically insulating material, the coating layer 32 preferably contains an inorganic compound, and preferably contains inorganic particles (hereinafter also referred to as “second inorganic particles”) as the inorganic compound. By including the second inorganic particles in the coating layer 32, the hot strength of the coating layer 32 can be improved.
When the coating layer 32 contains the second inorganic particles, the second inorganic particles are preferably present on the inner surface of the foundry structure 3 , and more preferably on both the surface and inside of the coating layer 32 .

The above-mentioned second inorganic particles can include, for example, those selected from the group consisting of metal oxides and metal silicates. Specifically, the second inorganic particles include refractory inorganic particles such as mullite, zircon, zirconia, alumina, olivine, magnesia, and chromite. The second inorganic particles can contain these singly or by selecting two or more of them.
From the viewpoint of excellent heat resistance and low wettability with molten metal, the coating layer 32 preferably contains zircon as the second inorganic particles.

An electrically conductive material can also be used as the second inorganic particles. Examples of electrically conductive materials include particles of various metals. The metal preferably contains one or more selected from, for example, titanium, vanadium, iron, nickel, and chromium.
Titanium and vanadium preferably comprise titanium hydroxide and vanadium hydroxide, respectively. These are thermally decomposed during casting and changed to titanium and vanadium, respectively.
Iron is preferably treated with iron oxide for the purpose of preventing oxidation due to contact with a water solvent.

The shape of the second inorganic particles can be independently spherical, polyhedral, scaly, layered, spindle-shaped, fibrous, amorphous, or a combination thereof.
The second inorganic particles may be used alone or in combination of two or more.

From the viewpoint of the sealing property of the surface of the body portion 31, the adhesion between the body portion 31 and the coating layer 32, and the like, the average particle diameter of the second inorganic particles is 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. , more preferably 10 μm or more, and particularly preferably 15 μm or more.
In addition, from the viewpoint of suppressing the transfer of thermal decomposition gas generated from the main body 31 to the molten metal during casting, the average particle size of the second inorganic particles is 100 μm or less, preferably 80 μm or less, and more preferably 70 μm or less. , is more preferably 50 μm or less, particularly preferably 35 μm or less, and particularly preferably 25 μm or less.
The average particle size of the second inorganic particles can be determined in the same manner as the method for measuring the average particle size of the first inorganic particles.

From the viewpoint of further exhibiting the above effects, the coating layer 32 preferably contains 40% by mass or more and 94% by mass or less of the second inorganic particles in the entire coating layer 32, and preferably contains 60% by mass or more and 90% by mass or less. is more preferable, and it is even more preferable to contain 70% by mass or more and 89% by mass or less.

As an electrically insulating material, the coating layer 32 preferably contains a clay mineral, which is one of inorganic compounds.
Clay minerals include layered clay minerals, double-strand structure minerals, and the like, and these may be natural or synthetic.
Layered clay minerals include clay minerals belonging to the genus smectite, kaolin, and illite, such as bentonite, smectite, hectorite, activated clay, kibushi clay, and zeolite.
Attapulgite, sepiolite, palygorskite and the like are examples of double-chain structure minerals.
The clay mineral described above may be in the form of granules or fine particle powder.
Since the coating layer 32 contains the layered clay mineral or the double-strand structure mineral, the movement of current and heat in the thickness direction of the coating layer 32 is suppressed, and the heat of the molten metal flowing into the casting structure 3 during casting is dissipated. , movement to the outside of the casting structure 3 is suppressed. As a result, the temperature of the molten metal in the casting structure 3 is even less likely to drop, and the molten metal flow during casting can be maintained even better. In particular, when the coating layer 32 contains a double-chain structure mineral, the above-described effects are remarkable, so the coating layer 32 preferably contains a double-chain structure mineral.
From the viewpoint of further achieving the above effects, the coating layer 32 more preferably contains one or more selected from attapulgite, sepiolite, bentonite, and smectite.
In addition, the clay mineral is distinguished from the second inorganic particles, which mainly contain a hexagonal close-packed structure and usually do not have a layered structure or a double chain structure, in that they have a layered structure or a double chain structure. That is, the second inorganic particles do not have a layered structure and do not have a double chain structure.

The coating layer 32 preferably contains 1.5% by mass or more, more preferably 2% by mass or more, of the clay mineral in the entire coating layer 32 from the viewpoint of improving the molten metal flow during casting. It is more preferable to contain 2.2% by mass or more.
In addition, from the viewpoint of good molten metal flow during casting, the clay mineral content in the entire coating layer 32 is preferably 50% by mass or less, more preferably 25% by mass or less, and 10% by mass or less. is more preferred.

The casting structure 3 preferably contains a binder, and preferably contains at least one of an organic binder and an inorganic binder as the binder.
The main body part 31 may contain both an organic binder and an inorganic binder from the viewpoints that the main body part 31 has electric insulation properties, and from the viewpoints of good molten metal flow during casting and excellent removability after casting. More preferably, it contains only an organic binder.
From the viewpoint of sealing properties of the surface of the coating layer 32, the coating layer 32 preferably contains both an organic binder and an inorganic binder, and more preferably contains only an inorganic binder. If the pore-sealing property of the surface of the coating layer 32 is improved, for example, even if the components contained in the body portion 31 are burned during casting to generate gas, the gas can be prevented from being mixed into the molten metal.

Examples of organic binders include thermosetting resins such as phenolic resins, epoxy resins, and furan resins, which can be used singly or in combination of two or more. Among these, it is preferable to contain a phenolic resin because it generates little combustible gas, has an effect of suppressing combustion, and has a high residual carbon content after thermal decomposition (carbonization).

Examples of phenolic resins include novolak phenolic resins, resol-type phenolic resins, and modified phenolic resins modified with urea, melamine, epoxy, and the like. Above all, by containing a resol-type phenolic resin, it is possible to reduce odors during molding of the main body 31 and casting defects when the main body 31 is used as a mold without the need for a curing agent such as acid or amine. It is preferable because it can be done.

When a novolac phenol resin is included, it is preferable to use a curing agent together. Since the curing agent is easily soluble in water, it is preferably applied to the surface of the main body 31 after dehydration when manufacturing the structure. The curing agent preferably contains, for example, hexamethylenetetramine.

Examples of inorganic binders include phosphoric acid-based binders, water glasses such as silicates, gypsum, sulfates, silica-based binders, and silicon-based binders.
From the standpoint of enabling the use of water as a dispersion medium and from the standpoint of increasing the strength when hot, it is preferable to include a silica-based binder as the inorganic binder.

When manufacturing the casting structure 3, the binder is used at 1000° C. in a nitrogen atmosphere from the viewpoint of firmly binding the organic fibers, inorganic fibers and inorganic particles when the parts made into paper before casting are dried and molded. It is desirable that the weight loss rate (measured by TG thermal analysis) is 50% by mass or less, particularly 45% by mass or less.

The main body 31 preferably contains 5% by mass or more, more preferably 10% by mass or more, of a binder with respect to the total mass of the main body 31 from the viewpoint of improving the strength and further expressing the effect of suppressing the amount of gas generated. More preferably, it contains 15% by mass or more.
In addition, the main body part 31 has a viewpoint of improving heat resistance, and a viewpoint of improving shape retention by preventing stickiness during molding and reducing the content of the skeleton component when manufacturing the casting structure 3. Therefore, the binder is preferably contained in an amount of 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, relative to the mass of the entire body portion 31 . In particular, when the binder contains an organic binder, the effect of improving the heat resistance is exhibited more significantly by setting the content of the binder within the above range.

The coating layer 32 preferably contains 5% by mass or more, more preferably 6% by mass or more, of a binder in the entire coating layer 32 from the viewpoint of sealing properties of the surface of the coating layer 32 and from the viewpoint of increasing the strength when hot. It is more preferable to contain 7% by mass or more, and it is particularly preferable to contain 8% by mass or more.
In addition, from the viewpoint of improving the hot strength, the coating layer 32 preferably contains 30% by mass or less of the binder in the entire coating layer 32, more preferably 20% by mass or less, and 15% by mass or less. is more preferable, and containing 12% by mass or less is particularly preferable. In particular, when the binder contains an inorganic binder, the effect of improving the heat resistance is exhibited more significantly by setting the content of the binder within the above range.

In addition to the above-described components, the casting structure 3 includes other components, such as polyvinyl alcohol, carboxymethyl cellulose, polyamidoamine epichlorohydrin resin, and other paper strength agents, as long as the effects of the present invention are not impaired. It may contain acrylamide-based coagulants, colorants, and the like.

The thickness A is preferably 0.3 mm or more, more preferably 0.5 mm or more, and even more preferably 0.8 mm or more.
Also, the thickness A is preferably 5 mm or less, more preferably 3.5 mm or less, and even more preferably 3 mm or less.
By setting the thickness A to the above lower limit value or more, the strength of the main body portion 31 is improved, and the handleability of the casting structure 3 is improved. Furthermore, the movement of current and heat in the thickness direction of the body portion 31 is suppressed, and the heat of the molten metal that has flowed into the casting structure 3 during casting is suppressed from moving outside the casting structure 3 . As a result, the temperature of the molten metal in the casting structure 3 is even less likely to drop, and the molten metal flow during casting can be maintained even better.
By making the thickness A equal to or less than the above upper limit value, the weight of the casting structure 3 can be reduced, and in addition to improving the portability, it is economically advantageous. The thickness A can be measured by the method described in Examples below.

When the coating layer 32 has a thickness B, the thickness B is preferably 5 μm or more, more preferably 20 μm or more, and still more preferably 100 μm or more.
Also, the thickness B is preferably 1000 μm or less, more preferably 900 μm or less, and even more preferably 800 μm or less.
By making the thickness B equal to or greater than the above lower limit value, the strength of the coating layer 32 is improved, and the handleability of the casting structure 3 is improved. Furthermore, the movement of current and heat in the thickness direction of the coating layer 32 is suppressed, and the heat of the molten metal that has flowed into the casting structure 3 during casting is suppressed from moving outside the casting structure 3 . As a result, the temperature of the molten metal in the casting structure 3 is even less likely to drop, and the molten metal flow during casting can be maintained even better.
By making the thickness B equal to or less than the above-described upper limit value, it is possible to prevent cracks that may occur in the coating layer 32 after the drying process in the manufacturing method of the structure 3 for casting, which will be described later. The thickness B, like the thickness A, can be measured by the method described in Examples below.

From the viewpoint of further exhibiting the above effects, the total thickness of the main body portion 31 and the coating layer 32, that is, the total thickness A and B is preferably 0.305 mm or more, more preferably 0.305 mm or more. It is 5 mm or more, more preferably 0.8 mm or more.
Also, the total thickness A and thickness B is preferably 6 mm or less, more preferably 4.5 mm or less, and even more preferably 4 mm or less.
By making the sum of the thickness A and the thickness B equal to or greater than the above lower limit value, the strength of the casting structure 3 is improved, and the handleability is improved.
By making the sum of the thickness A and the thickness B equal to or less than the above upper limit value, the weight of the casting structure 3 can be reduced, which is economically advantageous in addition to improving the portability.

From the viewpoint of further exhibiting the above effects, the ratio B/A of the thickness B to the thickness A is preferably 0.001 or more, more preferably 0.01 or more, and still more preferably 0.1 or more.
Also, the ratio B/A of the thickness B to the thickness A is preferably 3.4 or less, more preferably 2 or less, and still more preferably 1 or less.
By setting the ratio B/A of the wall thickness B to the wall thickness A to the above lower limit value or more, the shielding property against the thermal decomposition gas generated during casting is improved.
By setting the ratio B/A of the thickness B to the thickness A to the upper limit value or less, peeling of the coating layer 32 from the main body portion 31 is suppressed when an impact or the like is applied to the casting structure 3. can do.

Next, a method for manufacturing the casting structure 3 will be described. The casting structure 3 can be manufactured, for example, by manufacturing the body portion 31 and then forming the coating layer 32 on the inner surface of the manufactured body portion 31 . A method for manufacturing the body portion 31 will be described below.

The body portion 31 can be manufactured by a molding method including a papermaking process. Such a molding method is described, for example, in JP-A-2012-024841 [0052] to [0071].
By forming the coating layer 32 on the surface of the body portion 31 manufactured by the manufacturing method described above, the casting structure 3 can be manufactured.

Examples of the method for forming the coating layer 32 include methods such as coating using a coating liquid composition, such as brush coating, spray coating, electrostatic coating, baking coating, splash coating, dip coating, and tampo coating. Dip coating is most preferred as a result of careful consideration of layer 32 thickness uniformity, efficiency and economy. When the coating layer 32 is formed on the inner surface of the body portion 31 having a hollow interior by dip coating, the coating layer 32 is formed by filling and contacting the hollow portion of the body portion 31 with the coating liquid composition (hereinafter referred to as " Method 1”.) can be done. When method 1 is performed on the body portion 31 having an open hollow portion, for example, at least a part of the open portion of the hollow portion is closed so that the hollow portion can hold the coating composition. The coating layer 32 can be formed by pouring an object into the hollow portion preferably so that the coating liquid composition fills the hollow portion, preferably leaving the coating liquid composition for a predetermined period of time, and then discharging the coating liquid composition. In any coating method, the temperature of the coating liquid composition is preferably in the range of 5° C. to 40° C., more preferably 15° C. to 30° C., still more preferably 20° C. to 30° C. and at a constant temperature. It is most preferable to set up the equipment so that In addition, in dip coating, particularly in method 1, the standing time is preferably in the range of 1 second or more and 60 seconds or less from the viewpoint of productivity, and can be carried out batchwise or continuously. In any method, in order to adjust the film thickness of the coating layer 32, the body portion 31 coated with the coating liquid composition can be vibrated with a vibration table or the like. In order to make the metal element adhere to the surface of the main body part 31 more strongly, it is preferable to pass through a drying process. Drying methods include, but are not limited to, hot air drying using a heater, far-infrared drying, microwave drying, superheated steam drying, and vacuum drying. When drying using a hot air dryer, the drying temperature in the center of the drying furnace is preferably in the range of 100 ° C. or higher and 500 ° C. or lower, and furthermore, from the viewpoint of reducing the influence of thermal decomposition of the binder and ensuring safety due to ignition. From the point of view, the range of 105° C. or higher and 300° C. or lower is most preferable. The dispersion medium for the coating liquid composition includes water, alcohol, and the like, with water being preferred. Further, the dispersion medium is 5 parts by mass or more and 100 parts by mass or less, further 10 parts by mass or more and 80 parts by mass or less, and further 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content in the coating composition. preferably.

The casting structure 3 of the present invention can be used, for example, in the manufacture of castings as follows.
As shown in FIG. 3, first, a cavity 5 is provided in at least one of the openings 33 of the casting structure 3, and the casting structure 3 is buried at a predetermined position in casting sand to form a sand mold. 6 is formed. When the sand mold 6 is formed, the foundry structure 3 is buried leaving a part of the openings 33 (that is, at least one opening 33 ) of the foundry structure 3 . At this time, the entire opening 33 that is not embedded may be outside the foundry sand, or a part of the opening 33 that is not embedded may be inside the foundry sand. As the foundry sand for the sand mold 6, any ordinary sand conventionally used for manufacturing this type of casting can be used without limitation.
Next, a funnel-shaped pouring port 7 for pouring molten metal into the casting structure 3 is installed at one end of the opening 33 that is not embedded. As shown in FIG. 3, the outside diameter of the pouring port 7 on the side that contacts the opening 33 that is not embedded is smaller than the inside diameter of the opening 33, so the pouring port 7 fits into the opening 33 by fitting. It is attached. There is no particular limitation on the constituent material of the pouring port 7 as long as it is a material that does not dissolve in the molten metal, and conventionally known materials can be used.
The method of burying the foundry structure 3 is not particularly limited. , the casting structure 3 may be arranged. Thus, the casting mold 4 is manufactured.

After forming the casting mold 4, the molten metal is poured from the pouring port 7 of the casting mold 4, and the molten metal is supplied into the cavity 5 for casting. After casting, the casting mold 4 is dismantled to remove casting sand, and the casting structure 3 is removed by blasting to expose the casting. After that, if necessary, the casting may be subjected to post-treatment such as trimming. Thus, a casting is produced.

As described above, in the casting structure 3 of the present embodiment, the main body portion 31, which is a portion occupying the majority thereof, has electrical insulation. The heat of the molten metal is suppressed from moving out of the casting structure 3 via the body portion 31 . As a result, when the casting mold 4 of the present embodiment is used, the temperature of the molten metal in the casting structure 3 is less likely to decrease than in the conventional casting structure, and the molten metal flow during casting remains good. can keep. Therefore, according to the casting mold 4 of the present embodiment, it is possible to manufacture castings in which the occurrence of casting defects such as wrinkles, cracks, and cavities is suppressed. In particular, when cast steel having a higher molten metal temperature than cast iron is cast, the above effect becomes remarkable, so the casting mold 4 of the present embodiment can be suitably used as a casting mold for cast steel. Moreover, a cast steel casting can be produced by using the cast steel mold.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the present invention.
For example, the casting structure 3 described above has a two-layer structure including the body portion 31 and the coating layer 32, but instead of this, the casting structure 3 includes the body portion 31 and the coating layer 32 as well as other layers. A three-layer structure having a layer structure may be used. When the casting structure 3 has a three-layer structure, the other layer structure may be the outermost layer or the innermost layer of the casting structure 3, and the main body portion 31 and the coating layer 32 may be between

Further, the following casting structure 3 is disclosed for each of the above-described embodiments.

<1>
A structure for casting, comprising a cylindrical main body and a coating layer covering the inner surface of the main body, wherein the main body has electrical insulation.

<2>
The coating layer exists as a film-like portion on the inner surface of the main body,
The structure for manufacturing castings according to <1>, wherein the film-like portion is a portion in which the particles constituting the coating layer are microscopically present in the form of agglomerated particles.
<3>
The structure for manufacturing castings according to <1> or <2>, wherein both the main body and the coating layer have electrical insulation.
<4>
The electrical insulation is a property that does not pass current at all, or an electrical resistance evaluation value measured in the thickness direction is 200 kΩ / mm or more, or an electrical resistance evaluation value measured on the surface is 200 kΩ / mm or more. The structure for manufacturing castings according to any one of <1> to <3> above.
<5>
The electrical resistance evaluation value measured at a position 60 mm away from the outer surface of the main body is 200 kΩ/mm or more and 1×10 ¹⁰ kΩ/mm or less, preferably 300 kΩ/mm or more, and more preferably 500 kΩ/mm or more. The structure for manufacturing castings according to any one of <1> to <4>.

<6>
The electrical resistance evaluation value measured in the thickness direction of the main body is 200 kΩ/mm or more and 1×10 ¹⁰ kΩ/mm or less, preferably 1000 kΩ/mm or more, more preferably 1×10 ⁴ kΩ/mm or more. , the structure for manufacturing castings according to any one of <1> to <5>.
<7>
The electric resistance evaluation value measured at a position separated by 60 mm on the inner surface of the coating layer is 200 kΩ/mm or more and 1×10 ¹⁰ kΩ/mm or less, preferably 300 kΩ/mm or more, and more preferably 500 kΩ/mm or more. The structure for manufacturing castings according to <3>.

<8>
The electrical resistance evaluation value measured in the thickness direction of the coating layer is 200 kΩ/mm or more and 1×10 ¹⁰ kΩ/mm or less, preferably 1000 kΩ/mm or more, more preferably 1×10 ⁴ kΩ/mm or more. , the structure for manufacturing castings according to <3>.
<9>
The electrical resistance evaluation value measured in the thickness direction through the main body and the coating layer is 200 kΩ/mm or more and 1×10 ¹⁰ kΩ/mm or less, preferably 1000 kΩ/mm or more, more preferably 1×10. The structure for manufacturing castings according to <5> or <6> above, which is ⁴ kΩ/mm or more.
<10>
The above <1> to <9>, wherein the electric resistance evaluation value measured in the thickness direction of the main body and the electric resistance evaluation value measured in the thickness direction of the coating layer are both 200 kΩ / mm or more. A structure for manufacturing castings according to any one of the preceding claims.

<11>
The structure for producing castings according to any one of <1> to <10> above, wherein the main body contains inorganic fibers, and the inorganic fibers consist only of electrically insulating inorganic fibers.
<12>
The structure for manufacturing castings according to <11>, wherein the main body does not contain an electrically conductive material.
<13>
The structure for manufacturing castings according to <12> above, wherein the main body contains 0% by mass or more and 1% by mass or less, preferably 0.5% by mass or less of the electrically conductive material.
<14>
The structure for producing castings according to any one of <1> to <13> above, wherein the main body contains inorganic particles, and the inorganic particles consist only of electrically insulating inorganic particles.
<15>
The structure for producing castings according to <14>, wherein the main body further contains organic fibers.

<16>
The structure for producing castings according to any one of <1> to <15> above, wherein the coating layer contains an inorganic compound, and the inorganic compound consists only of an electrically insulating inorganic compound.
<17>
The structure for manufacturing castings according to any one of <1> to <16>, wherein the coating layer contains a double-strand structure mineral.
<18>
The structure for manufacturing castings according to any one of <1> to <17>, wherein the main body has a thickness of 0.3 mm or more, preferably 0.5 mm or more, and more preferably 0.8 mm or more.
<19>
The structure for manufacturing castings according to any one of <1> to <18>, wherein the main body has a thickness of 5 mm or less, preferably 3.5 mm or less, more preferably 3 mm or less.
<20>
The structure for manufacturing castings according to any one of <1> to <19>, wherein the coating layer has a thickness of 5 μm or more, preferably 20 μm or more, more preferably 100 μm or more.

<21>
The structure for producing castings according to any one of <1> to <20>, wherein the coating layer has a thickness of 1000 μm or less, preferably 900 μm or less, more preferably 800 μm or less.
<22>
Any one of <1> to <21> above, wherein the total thickness of the main body portion and the coating layer is 0.305 mm or more, preferably 0.5 mm or more, and more preferably 0.8 mm or more. casting manufacturing structures.
<23>
For manufacturing castings according to any one of <1> to <22>, wherein the total thickness of the main body portion and the coating layer is 6 mm or less, preferably 4.5 mm or less, more preferably 4 mm or less. Structure.
<24>
<1> to <23>, wherein the ratio B/A of the thickness B of the coating layer to the thickness A of the main body is 0.001 or more, preferably 0.01 or more, and more preferably 0.1 or more. A structure for manufacturing castings according to any one of the above.
<25>
Any one of <1> to <24>, wherein the ratio B/A of the thickness B of the coating layer to the thickness A of the main body is 3.4 or less, preferably 2 or less, more preferably 1 or less. A structure for manufacturing castings according to .

<26>
The surface area of the coating layer on the side in contact with the molten metal in the main body is 50% or more and 100% or less, preferably 80% or more, and more preferably 90% or more of the inner surface area of the main body. A structure for manufacturing castings according to any one of 1> to <25>.
<27>
The structure for producing castings according to any one of <1> to <26> above, which is a structure for producing castings for cast steel.
<28>
A method of using the structure for manufacturing castings according to any one of <1> to <27> as a runner or a lifting runner in casting of cast steel.
<29>
a step of burying the casting manufacturing structure according to any one of the above <1> to <27> in foundry sand leaving a part of the openings of the casting manufacturing structure A method for manufacturing a mold for cast steel.
<30>
The casting manufacturing structure according to any one of the above <1> to <27> is embedded in casting sand leaving a part of the openings of the casting manufacturing structure, leaving a part of the openings of the casting manufacturing structure, a mold manufacturing process for manufacturing the
and a casting step of pouring molten metal into the mold.

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the scope of the invention is not limited to such examples.

[Example 1]
After making a fiber laminate using the following raw material slurry, the fiber laminate was dehydrated and dried to obtain a casting structure. The casting structure includes a straight-shaped main body (see FIG. 1) and an elbow-shaped main body (see FIG. 2(a)). The composition of the main body was as shown in Table 1.

<Preparation of raw material slurry>
Organic fibers and inorganic fibers shown below are dispersed in water to prepare an aqueous slurry of about 1% by mass (the total mass of organic fibers and inorganic fibers is 1% by mass with respect to the aqueous slurry). 1 Inorganic particles, a binder, a flocculant and a paper strength agent were blended to prepare a raw material slurry. The amounts of the organic fibers, inorganic fibers, first inorganic particles, and binder in the raw material slurry were adjusted so that the content ratio of each component in the target main body portion was as shown in Table 1. When the total amount of the organic fiber, the inorganic fiber, the first inorganic particles, and the binder is 100 parts by mass (in terms of solid content), the amount of the flocculant in the raw material slurry is 0.625 parts by mass. was blended into the raw slurry, and the blending amount of the paper strength agent was blended into the raw slurry so as to be 0.025 parts by mass (in terms of solid content). Each component shown in Table 1 is as follows.

<Organic fiber>
・Organic fiber: waste newspaper (average fiber length 1 mm, freeness 150 mL)

<Inorganic fiber>
・ Inorganic fiber: alumina fiber [average fiber length 3 mm, fiber width 7 μm (long axis/short axis ratio = 429)]

<First inorganic particles>
・Silica: spherical particle shape, average particle size 26 μm

<Binder>
・Phenolic resin (resole type): 44% weight loss at 1000°C in nitrogen atmosphere (TG thermal analysis measurement)

<Flocculant>
・Flocculant: Polyamide epichlorohydrin

<Paper strength agent>
・ Paper strength agent: 1% by mass aqueous solution of carboxymethyl cellulose

<Dispersion medium>
・Dispersion medium: water

<Paper making/dehydration process>
As a papermaking mold, a mold having a cavity forming surface corresponding to the main body (straight tube and elbow tube) was used. A net with a predetermined opening is arranged on the cavity forming surface of the mold, and a large number of communication holes are formed to communicate the cavity forming surface with the outside. In addition, the mold consists of a pair of split molds. The raw material slurry was circulated by a pump, and a predetermined amount of slurry was pressurized and injected into the papermaking mold, while water in the slurry was removed through the communicating holes to deposit a predetermined fiber laminate on the surface of the net. After injection of a predetermined amount of raw material slurry was completed, pressurized air was injected into the papermaking mold to dehydrate the fiber laminate. The pressure of pressurized air was 0.2 MPa, and the time required for dehydration was about 30 seconds.

<Drying process>
As a drying mold, a mold having a cavity forming surface corresponding to the main body (straight pipe and elbow pipe) was used. A large number of communication holes are formed in the mold for communicating the cavity forming surface with the outside. The mold consists of a pair of split molds. The fiber laminate was removed from the papermaking mold and transferred to a drying mold heated to 200°C. Then, a bag-like elastic core is inserted from the upper opening of the dry mold, and pressurized air (0.2 MPa) is injected into the elastic core in the sealed dry mold to thereby The elastic core was inflated, and the fiber laminate was pressed against the inner surface of the drying mold by the elastic core, and the fiber laminate was dried while transferring the inner surface shape of the drying mold to the surface of the fiber laminate. After pressurized drying (60 seconds), the pressurized air in the elastic core is released, the elastic core is shrunk and removed from the drying mold. A hardened body portion 31 was obtained.

<Preparation of Coating Liquid Composition Containing Second Inorganic Particles as Main Component>
The second inorganic particles, clay mineral and binder shown below as the solid content materials, and water were stirred for 15 minutes with a stirrer to obtain a coating liquid composition containing the second inorganic particles as a main component. The amounts of the second inorganic particles, the clay mineral and the binder in the coating liquid composition were adjusted so that the content ratio of each component in the desired coating layer was as shown in Table 1. The amount of water in the coating liquid composition was adjusted so that the solid content concentration of the coating liquid composition was 85% by mass.

<Second inorganic particles>
・Titanium (average particle size 20 μm)

<Clay mineral>
・ Attapulgite: manufactured by Hayashi Kasei Co., Ltd., trade name “Atagel 50”

<Binder>
・ Colloidal silica: manufactured by Nissan Chemical Co., Ltd., product name “Snowtex 50-T”

<Formation of coating layer>
One open end of each of the heat-cured body portions (straight tube and elbow tube) is closed, and the coating liquid composition prepared above is poured into them to the upper end and allowed to stand for 10 seconds. , turned upside down, and discharged the coating liquid composition. After air-drying, it was dried with a hot air dryer at 200° C. for 30 minutes to obtain a casting structure having a coating layer formed thereon.

[Example 2]
A casting structure was obtained in the same manner as in Example 1 by mixing each material in the ratio shown in Table 1 below, except that the second inorganic particles contained in the coating layer were zircon (average particle size: 20 μm). .

[Comparative Example 1]
As inorganic fibers contained in the main body, carbon fibers (average fiber length 3 mm, fiber width 11 μm (long axis/short axis ratio = 273)) are used instead of alumina fibers, and each material is used in the ratio shown in Table 1 below. A casting structure was obtained in the same manner as in Example 1, except that the materials were mixed.

[Comparative Example 2]
Carbon fiber was used instead of alumina fiber as the inorganic fiber contained in the main body, zircon was used as the second inorganic particles contained in the coating layer, and each material was mixed in the ratio shown in Table 1 below. A casting structure was obtained in the same manner as in 1.
[Comparative Example 3]
A casting structure was obtained in the same manner as in Comparative Example 2, except that hollow silica was used instead of silica as the first inorganic particles contained in the main body, and the respective materials were mixed in the proportions shown in Table 1 below.

〔evaluation〕
In the structures for casting obtained in Examples and Comparative Examples, the thickness of the main body portion (thickness A) and the thickness of the coating layer (thickness B) were measured according to the following method.
Further, according to the above-described method, the electric resistance evaluation value in the thickness direction of the main body portion and the electric resistance evaluation value on the outer surface of the main body portion, the electric resistance evaluation value in the thickness direction of the coating layer and the electric resistance on the inner surface of the coating layer A resistance evaluation value was measured to evaluate whether or not the main body portion or the coating layer had electrical conductivity.
If the casting structure has a low electrical resistance evaluation value, in other words, if the thermal conductivity is low, the molten metal flow will be good during casting. This makes it difficult for hot water wrinkles, which are casting defects that occur together, to occur.
The results obtained are shown in Table 1.

<Measurement of wall thickness (thickness A) of main body>
The thickness of the body portion 31 is determined by a dial caliper gauge [manufactured by Mitutoyo Corporation, Code No. 209-611, code DCGO-50RL], measurements were taken at eight arbitrary points in the circumferential direction on the same plane, and the average value was obtained.

<Measurement of thickness of coating layer (thickness B)>
The thickness of the coating layer 32 is obtained by subtracting the thickness of the body portion 31 before the coating layer 32 is formed on the body portion 31 from the thickness of the casting structure 3 after the coating layer 32 is formed on the body portion 31. rice field. Specifically, the thickness of the main body portion 31 before the coating layer 32 is formed on the main body portion 31 is obtained by marking the outer peripheral surface of the main body portion 31 in advance at arbitrary eight points in the circumferential direction on the same plane. , was measured as described above. The thickness of the casting structure 3 after the coating layer 32 is formed on the main body 31 is measured at any eight positions marked on the outer peripheral surface of the main body 31 by a dial caliper gauge [manufactured by Mitutoyo Co., Ltd., code No. 209-611, code DCGO-50RL], and the average value was obtained.

As can be seen from the description in Table 1, the structures for casting of Examples 1 and 2, in which the main body has electrical insulation in the thickness direction, are different from those of Comparative Examples 1 to 3, in which the body has electrical conductivity in the thickness direction. Compared to the casting structure, the electrical resistance evaluation value increased and the difficulty of heat conduction improved.

3 casting manufacturing structure 31 main body 32 coating layer 32S inner surface of coating layer 33 opening 4 casting mold 5 cavity 6 sand mold 7 pouring port

Claims (11)

Having a cylindrical main body and a coating layer covering the inner surface of the main body, the main body having electrical insulation,
the main body contains inorganic fibers,
The main body is a single layer,
A structure for manufacturing castings , wherein the body portion is circumferentially integral . 2. The structure for casting production according to claim 1, wherein both said body portion and said coating layer have electrical insulation. The electrical resistance evaluation value measured at a position 60 mm away on the outer surface of the main body is 200 kΩ / mm or more, and / or the electrical resistance evaluation value measured in the thickness direction of the main body is 200 kΩ / mm. 2. The structure for manufacturing castings according to claim 1, wherein: 4. The structure for casting production according to claim 3, wherein the electrical resistance evaluation value measured in the thickness direction through the body portion and the coating layer is 200 kΩ/mm or more. 2. The structure for casting according to claim 1, wherein the main body has a thickness of 0.3 mm or more and 5 mm or less. The foundry manufacturing structure of claim 1, wherein the coating layer comprises inorganic particles. 2. The structure for casting according to claim 1, wherein the coating layer has a thickness of 1000 [mu]m or less. 2. The foundry manufacturing structure of claim 1 , wherein said body further comprises organic fibers. 9. A method of using the casting manufacturing structure according to any one of claims 1 to 8 as a runner or lifting runner in the casting of cast steel. A step of burying the casting manufacturing structure according to any one of claims 1 to 8 in casting sand, leaving a part of the openings of the casting manufacturing structure, A method for manufacturing a mold for cast steel. The structure for manufacturing castings according to any one of claims 1 to 8 is buried in casting sand leaving a part of the openings of the structure for manufacturing castings to manufacture a mold. a mold manufacturing process to
and a casting step of pouring molten metal into the mold.

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