JP2024041481A - Structures for casting manufacturing - Google Patents

Abstract

[Problem] To provide a structure for manufacturing castings that provides good molten metal flow during casting. [Solution] The structure for manufacturing castings (3) has a cylindrical main body (31) and a coating layer (32) that coats the inner surface of the main body (31), and the main body (31) has electrical insulation properties. It is preferable that both the main body (31) and the coating layer (32) have electrical insulation properties. It is preferable that the evaluated electrical resistance 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 evaluated electrical resistance value measured in the thickness direction of the main body (31) is 200 kΩ/mm or more. [Selected Figure] Figure 1

Description

The present invention relates to a structure for manufacturing castings.

As a conventional technique related to a structure for manufacturing castings, the present applicant has previously proposed a structure having a main body containing inorganic fibers such as organic fibers and carbon fibers, inorganic particles, and a binder, and a coating layer formed on the inner surface of the main body. A structure for manufacturing castings was proposed (see Patent Document 1). According to the structure described in this document, since the coating layer shields the pyrolysis gas generated from the organic fibers contained in the main body during casting, there is an advantage that gas defects in the casting are reduced compared to the conventional structure.

JP2012-24841A

Casting defects such as molten metal wrinkles, cracks, and cavities are caused in part by poor molten metal flow that occurs as the pouring temperature decreases. As the quality of castings has improved in recent years, there has been a demand for further improvements in the flow of molten metal during pouring in structures for manufacturing castings. There was also room for improvement in the structure described in Patent Document 1 in terms of improving the flow of molten metal during casting.
Therefore, an object of the present invention is to provide a structure for manufacturing castings that has good flow during casting.

The present invention provides a structure for manufacturing castings, which has a cylindrical main body and a coating layer that covers the inner surface of the main body, and the main body has electrical insulation properties.

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

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

The present invention will be described below based on preferred embodiments thereof with reference to the drawings.
The casting manufacturing structure 3 of the present invention shown in FIGS. 1 and 2 (hereinafter also simply referred to as "casting structure") 3 is suitably used as a runner or lifting runner used in casting, for example. be. As will be described later, the casting structure 3 of the present invention is particularly suitably used as a runner or lifting runner in the production of cast steel.

As shown in FIGS. 1 and 2, the casting structure 3 includes a cylindrical main body 31 and a coating layer 32 that covers at least a 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 structure having a longitudinal direction and a width direction perpendicular to the longitudinal direction, and having a hollow interior. The shape of the cavity in the main 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 one in which a part of the longitudinal direction of the casting structure 3 has a bent part as shown in FIG. 2(a), and one in which the casting structure 3 has a bent part as shown in FIG. Examples include those whose entire longitudinal direction is curved in an arc shape, and those where the casting structure 3 has one or more branch portions as shown in FIGS. 2(c) and (d).
Since the main body portion 31 is cylindrical, the casting structure 3 is also cylindrical.

The casting structure 3 has a coating layer 32 on the inner surface through which 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. The term "membrane-like part" as used herein refers to a part where the particles constituting the coating layer 32 exist in the form of microscopic aggregated particles.
If the main body part 31 is not covered with the coating layer 32 and is in an exposed state, the components contained in the main body part 31 will be burned when the molten metal comes into contact with the main body part 31 during casting, and gas will be mixed in or dissolved in the molten metal. There is. In particular, when casting steel whose molten metal temperature is higher than that of cast iron, the amount of gas dissolved in the molten metal is large, so the gas generated from the components contained in the main body 31 during casting is larger than that of cast iron. It becomes easy to dissolve inside. In contrast, in the casting structure 3 of this embodiment, the inner surface of the main body 31 is covered with the coating layer 32, so that it is possible to prevent the molten metal from coming into contact with the main body 31, and as a result, during casting. Even if the components contained in the main body portion 31 burn and generate gas, the gas can be prevented from dissolving into the molten metal. This advantage is particularly advantageous in the case of cast steel, where gas is easily dissolved in the molten metal.
From the viewpoint of suppressing the mixing of gas into the molten metal during casting and improving the flow of the molten metal during casting as described later, the surface area of the coating layer 32 on the side of the main body 31 that comes into contact with the molten metal is The inner surface area of the portion 31 is preferably 50% or more, more preferably 80% or more, even more preferably 90% or more, and even more preferably 100%.

The main body portion 31 is configured to have electrical insulation properties.
As used herein, "electrical insulation" means a property that does not conduct any current at all or a property that substantially does not conduct any current.
The property of substantially not passing current means that the electrical resistance evaluation value measured in the thickness direction or on the surface is equal to or higher than a predetermined value. Specifically, if the electrical resistance evaluation value measured in the thickness direction is 200 kΩ/mm or more, or if the electrical resistance evaluation value measured on the surface is 200 kΩ/mm or more, the property is considered to be substantially non-current-passing. , that is, it becomes electrically insulating.

Generally, the movement of free electrons within an object is known as one form of heat transfer within the object. That is, the more free electrons there are, in other words, the lower the electrical resistivity of an object, the higher the thermal conductivity. In some conventional casting structures, the main body portion 31 may have electrical conductivity due to the components contained in the casting structure 3. Such a casting structure 3 has 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 to the outside of the casting structure 3 via the main body portion 31. As a result, the temperature of the molten metal flowing inside the casting structure 3 decreases, and as the casting temperature decreases, the flow of the molten metal deteriorates, and defects such as wrinkles, cracks, and cavities may occur. On the other hand, in the casting structure 3 of this embodiment, the main body part 31, which is the main part, has electrical insulation properties, or 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 outside the casting structure 3 via the main body portion 31. As a result, in the foundry structure 3 of the present invention, the temperature of the molten metal within the foundry structure 3 is less likely to drop than in conventional foundry structures, and the flow of the molten metal during pouring can be maintained at a good level. I can do it. Thereby, the occurrence of casting defects such as creases, cracks, and cavities can be suppressed.

From the viewpoint of further achieving the above-mentioned 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 portion 31, and/ Alternatively, it is preferable that the electrical resistance evaluation value measured in the thickness direction of the main 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 main body portion 31 is more preferably 300 kΩ/mm or more, even more preferably 500 kΩ/mm or more. The upper limit of the electrical resistance evaluation value measured at a position 60 mm away from the outer surface of the main body portion 31 is not particularly limited, but is realistically, for example, 1×10 ¹⁰ kΩ/mm or less.
More specifically, the electrical resistance evaluation value measured in the thickness direction of the main body portion 31 is more preferably 1000 kΩ/mm or more, and still more preferably 1×10 ⁴ kΩ/mm or more. The upper limit of the electrical resistance evaluation value measured in the thickness direction of the main body portion 31 is not particularly limited, but is realistically, for example, 1×10 ¹⁰ kΩ/mm or less.
In the casting structure 3 of this embodiment, only the electrical resistance evaluation value measured at a position 60 mm away from the outer surface of the main body 31 may satisfy the above-mentioned numerical range, and in the thickness direction of the main body 31. Only the electrical resistance evaluation value measured in may satisfy the above-mentioned numerical range, or may satisfy both of these values.

The electrical resistance evaluation value in the thickness direction of the main 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 blade such as a cutter or a file. Only the separated main body part 31 is collected, and the wall thickness of the main body part 31 and the electrical resistance value in the thickness direction are measured for the collected main body part 31. Specifically, after short-circuiting the test leads of the digital tester and performing zero adjustment, the test leads are attached to the surface of the main body 31 at opposing positions in the thickness direction of the main body 31 so as to sandwich the main body 31. Make contact and measure the electrical resistance value. The wall thickness at the position where the electrical resistance value was measured is measured using a dial caliper gauge, 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 8 different locations, and the average value of the 8 electrical resistance evaluation values is calculated. The digital tester used was an MCD-008 pocket multimeter manufactured by Multi Instruments Co., Ltd., and the dial caliper gauge was manufactured by Mitutoyo Co., Ltd., code No. 209-611, using the code DCGO-50RL.

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

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

From the viewpoint of further achieving the above-mentioned effects, in the casting structure 3 of this embodiment, the electrical 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, or And/or it is preferable that the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 is 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. The upper limit of the electrical resistance evaluation value measured at a position 60 mm away from the inner surface 32S of the coating layer 32 is not particularly limited, but is realistically, for example, 1×10 ¹⁰ kΩ/mm or less.
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. The upper limit of the electrical resistance evaluation value measured in the thickness direction of the coating layer 32 is not particularly limited, but is realistically, for example, 1×10 ¹⁰ kΩ/mm or less.
In the casting structure 3 of this 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-mentioned numerical range, and the thickness of the coating layer 32 may be Only the electrical resistance evaluation value measured in the direction may satisfy the above-mentioned numerical range, or both of these may be satisfied.

The electrical resistance evaluation value in the thickness direction of the coating layer 32 can be measured by the following "method for measuring the electrical resistance evaluation value in the thickness direction of the coating layer".
[Method for measuring 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 blade such as a cutter or a file. Only the separated coating layer 32 is collected, and the thickness of the coating layer 32 and the electrical resistance value in the thickness direction are measured for the collected coating layer 32. Specifically, after performing zero adjustment by short-circuiting the test leads of the digital tester, the test leads are attached to the surface of the coating layer 32 at opposing positions in the thickness direction of the coating layer 32 so as to sandwich the coating layer 32. Make contact and measure the electrical resistance value. The wall thickness at the position where the electrical resistance value was measured is measured using a dial caliper gauge, 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 8 different locations, and the average value of the 8 electrical resistance evaluation values is calculated.

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

The electrical resistance evaluation value on the inner surface 32S of the coating layer 32 can be measured by the following method.
Specifically, when applying the test leads of the digital tester to the coating layer 32 in the above-mentioned method for measuring the "electrical resistance evaluation value in the thickness direction of the coating layer", the length in the circumferential direction between the test leads is 60 mm. It is measured by measuring the electrical resistance value and dividing the electrical resistance value by 60 mm. The positional relationship of the test leads is not particularly limited, and for example, the test leads may be applied along the longitudinal direction of the coating layer 32 or may be applied along the circumferential direction of the coating layer 32.

As described above, the casting structure 3 of the present embodiment is preferably constructed so that the entire structure has electrical insulation properties, from the viewpoint of improving the flow of the metal during casting. In particular, by suppressing the heat of the molten metal that has flowed into the casting structure 3 during pouring from moving to the main body 31 via the coating layer 32 and further transferring the heat to the outside of the casting structure 3. From the viewpoint of improving the flow of the molten metal 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. Furthermore, the upper limit of the electrical resistance evaluation value measured in the thickness direction through the main body portion 31 and the coating layer 32 is not particularly limited, but is realistically, for example, 1×10 ¹⁰ kΩ/mm or less.

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

In the casting structure 3 of this embodiment, 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 both 200 kΩ/mm or more. It is preferable that According to the casting structure 3 having such a configuration, in each of the layers 31 and 32, the heat of the molten metal that has flowed into the casting structure 3 during casting is transferred to the main body 31 via the coating layer 32. , and the transfer of the heat to the outside of the casting structure 3 can be suppressed, and the flow of the molten metal during casting can be made even better.
From the same viewpoint, 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. Further, the upper limit of 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 is not particularly limited, but is, for example, 1×10 ¹⁰ kΩ/ mm or less is realistic.

It is preferable that the main body part 31 contains an electrically insulating material from the viewpoint of having an electrically insulating property and improving the flow of the molten metal during casting. As described later, the main body portion 31 of this embodiment mainly contains an inorganic compound and an organic component, and it is preferable that both of these components contain an electrically insulating material.

As the electrically insulating material, the main body portion 31 preferably contains an inorganic compound, and more preferably contains an inorganic fiber as the inorganic compound. By containing an electrically insulating inorganic compound in the casting structure 3, the flow of the metal during casting is improved, and the heat resistance of the casting structure 3 is improved, so that the structure during casting is improved. The strength, dimensional stability and shape retention of the material can be improved.
The inorganic fiber is a fibrous material that mainly forms the skeleton of the foundry structure 3 before it is used for casting, and maintains its shape without being burned by the heat of molten metal during casting.
Examples of the inorganic fibers include electrically insulating fibers such as artificial mineral fibers, ceramic fibers, glass fibers, and natural mineral fibers, which may be used alone or in combination of two or more.
The artificial mineral fiber includes, 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, the main body 31 can be configured to have electrically insulating properties. As a result, as described above, the flow of the molten metal during casting can be maintained at a good level. Furthermore, the hot strength of the main body portion 31 can be ensured.

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

The average fiber length of the inorganic fibers is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 2 mm or more. If the average fiber length of the inorganic fibers is equal to or greater than this lower limit, the heat during casting will suppress thermal shrinkage caused by thermal decomposition of the organic binder, which will be described later, and the casting structure 3 will easily maintain its shape. Become.
On the other hand, the average fiber length of the 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 main body part 31 preferably contains inorganic fibers in an amount of 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, based on the mass of the entire main body part 31. , it is even more preferable to contain 2% by mass or more. If the content of inorganic fibers is at least this lower limit, the strength of the casting structure 3 during casting can be ensured. This effect is particularly noticeable when the main 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 portion 31, peeling of the coating layer 32, etc. due to carbonization of the organic binder caused by heat during casting.
Further, the main body portion 31 preferably contains inorganic fibers in an amount of 80% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less, and 20% by mass or less, based on the total mass of the main body portion 31. It is even more preferable that the content is less than % by mass. If the content of inorganic fiber is below this upper limit, the formability of the main body part 31 will be particularly good during the papermaking and dewatering steps in the method for manufacturing the casting structure 3 described later, and the main body part 31 will have a uniform wall thickness. 31 becomes easier to obtain.

From the viewpoint of improving the hot strength of the foundry structure 3 and the formability of the foundry structure 3, the inorganic fibers have a long axis/short axis ratio of preferably 10 or more and 2000 or less, and even more preferably 50 or more and 1000 or less. It is as follows.

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

The above-mentioned 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 alone or in combination of two or more.
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, economic efficiency, etc. It is preferable that it contains silica, and it is more preferable that it contains silica.

The shape of the first inorganic particles can be independently spherical, polyhedral, scale-like, layered, spindle-like, 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, it is preferable that the average particle size of the first inorganic particles is within a specific range.
Specifically, the average particle diameter 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 size of the first inorganic particles within this upper limit, the density of the first inorganic particles in the main body 31 can be increased, and the strength of the main body 31 can be improved. Moreover, since the surface roughness of the main body part 31 can be reduced, when manufacturing the casting structure 3, the coating composition described below can be uniformly applied to the inner surface of the main body part 31. Specifically, it is possible to prevent the coating layer 32 formed by coating the inner surface of the main body portion 31 with a coating composition described below from being extremely thin.

From the viewpoint of improving the moldability of the main body portion 31, the average particle size of the first inorganic particles is preferably more than 1 μm, more preferably 5 μm or more, and even more preferably 10 μm or more. By setting the average particle size of the first inorganic particles within this lower limit, when manufacturing the intermediate molded body of the main body portion 31 by paper-making, the first inorganic particles will pass through the paper-making net, reducing the yield. Since this can be prevented, the moldability of the main body portion 31 can be improved. Moreover, since the freeness of the intermediate molded body of the main body part 31 can be improved, dehydration and drying can be easily performed, and the moldability of the main body part 31 can be improved.
These lower limits may be combined with any of the above-mentioned upper limits.

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

From the viewpoint of improving hot strength, the main body part 31 preferably contains the first inorganic particles in a content of 40% by mass or more, more preferably 45% by mass or more, based on the entire mass of the main body part 31. It is more preferable to contain 50% by mass or more.
Further, it is preferably contained in an amount of 80% by mass or less, more preferably contained in an amount of 75% by mass or less, still more preferably contained in an amount of 70% by mass or less, and particularly preferably contained in an amount of 68% by mass or less.

From the viewpoint of the main body 31 having electrical insulation properties and good melt flow during casting, the content of inorganic fibers relative to the mass of the entire main body 31 and the content of the first inorganic particles relative to the mass of the entire main body 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, More preferably, it is 5 or more.
Further, the content of the first inorganic particles relative 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 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 main body 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.
Further, 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 main body portion 31 is preferably 87% by mass or less, more preferably 85% by mass or less, and 80% by mass. It is more preferable that it is the following.

As an electrically insulating material, the main body portion 31 preferably contains an organic component, and more preferably further contains organic fibers as the organic component. The organic fiber forms the skeleton of the main body part 31 before being used for casting, and during casting, part or all of it is burned by the heat of the molten metal, forming voids inside the main body part 31 after the casting is produced. It is a fibrous material.
In the main body part 31, the organic fibers are entangled with each other, and voids are created in the main body part 31. As a result, the heat insulation properties of the casting structure 3 having the main body portion 31 are improved. Further, when some or all of the organic fibers are burned by the heat of the molten metal during casting, voids are created in the main body portion 31 by the burned organic fibers. As a result, the heat insulation properties of the casting structure 3 are further improved.
From the viewpoint of further achieving the above-mentioned effects, the organic fibers are preferably present in a dispersed manner on at least the surface of the main body part 31, and more preferably in the surface and inside of the main body part 31.

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

Whether or not the foundry structure 3 contains an organic component is determined based on the presence or absence of peaks corresponding to C=C bonds, C-H bonds, C=O bonds, and O-H bonds obtained by solid-state NMR. It can be determined by If at least a CH bond or a C═O bond exists among these bonds, it is determined that the material to be measured contains an organic component.
Whether or not the foundry structure 3 contains organic fibers can be determined by not only the solid-state NMR but also an FT-IR microscope (manufactured by Keyence Corporation, model no. : VHX-500, all microscopes in this specification are this type). Specifically, the position where a functional group derived from an organic substance is mapped is confirmed using a microscope FT-IR, and if a fibrous substance is observed under a microscope at that position, it is determined that organic fibers are contained. .

The organic fibers can include paper fibers such as wood pulp, fibrillated synthetic fibers, recycled fibers (for example, rayon fibers), and can include them alone or in combination of two or more types. 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 shapes by paper making, the wet strength of the dehydrated and dried molded product is excellent, paper fibers are easily available, stable, and economical. This is because it is the target.
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 (recovered product) can be used alone or in combination of two or more. From the viewpoints of ease of availability, environmental protection, reduction in manufacturing costs, etc., it is preferable to include waste paper pulp. The organic fiber preferably contains waste paper (newspaper, etc.) from the viewpoint of improving the moldability of the casting structure 3 and from the viewpoint of supplyability and economic efficiency.

The average fiber length of the organic fibers is preferably 0.8 mm or more, more preferably 0.9 mm or more. If the average fiber length of the organic fibers is equal to or greater than this lower limit, the organic fibers are likely to intertwine with each other, and as a result, it is easy to form a skeleton in a state before being used for casting.
Further, 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, surface smoothness of the casting structure 3 can be easily ensured.

From the viewpoint of improving toughness and usability, the main body part 31 preferably contains 8% by mass or more of organic fibers, more preferably 9% by mass or more, and 10% by mass or more of organic fibers based on the entire mass of the main body part 31. It is more preferable that the content is at least % by mass.
The upper limit of the organic fiber content in the main body portion 31 can be, for example, 30% by mass or less, particularly 25% by mass or less, and even 20% by mass or less.
In this specification, "usability" means that it is unlikely to crack due to the force applied during cutting when cutting to desired dimensions before use, or to be unlikely to be damaged by the weight of sand during casting. .

In addition to the main body portion 31, the covering layer 32 preferably also contains an electrically insulating material from the viewpoint of having electrically insulating properties and improving the flow of the molten metal during casting. As described later, the coating layer 32 of this embodiment mainly contains an inorganic compound, and it is preferable that the inorganic compound contains an electrically insulating inorganic compound. It is preferable that

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. When the coating layer 32 contains the second inorganic particles, the hot strength of the coating layer 32 can be improved.
When the coating layer 32 includes 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, particles 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 alone or in combination of two or more.
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 the electrically conductive material include particles of various metals. The metal preferably includes one or more selected from, for example, titanium, vanadium, iron, nickel, and chromium.
Preferably, titanium and vanadium include titanium hydroxide and vanadium hydroxide, respectively. These decompose thermally during casting and change into titanium and vanadium, respectively.
The iron is preferably treated with iron oxide for the purpose of preventing oxidation due to contact with an aqueous solvent.

The shape of the second inorganic particles can be independently spherical, polyhedral, scale-like, layered, spindle-like, 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 sealing properties on the surface of the main body 31, adhesion between the main body 31 and the coating layer 32, the average particle size 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, particularly preferably 15 μm or more.
Further, from the viewpoint of suppressing the transfer of pyrolysis gas generated from the main body 31 during casting to the molten metal side, the average particle diameter of the second inorganic particles is 100 μm or less, preferably 80 μm or less, and more preferably 70 μm or less. , more preferably 50 μm or less, particularly preferably 35 μm or less, 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 described above.

From the viewpoint of further achieving the above-mentioned effects, the coating layer 32 preferably contains the second inorganic particles in the entire coating layer 32 in an amount of 40% by mass or more and 94% by mass or less, and preferably contains 60% by mass or more and 90% by mass or less. is more preferable, and it is even more preferable that the content is 70% by mass or more and 89% by mass or less.

As the electrically insulating material, the covering layer 32 preferably contains clay mineral, which is one of the inorganic compounds.
Examples of clay minerals include layered clay minerals and multi-chain structure minerals, regardless of whether they are natural or synthetic.
Examples of layered clay minerals include clay minerals belonging to the genus smectite, genus kaolin, and genus illite, such as bentonite, smectite, hectorite, activated clay, kibushi clay, and zeolite.
Examples of the double-chain structure mineral include attapulgite, sepiolite, palygorskite, and the like.
The above-mentioned clay mineral may be in the form of granules or fine powder.
Since the coating layer 32 contains a layered clay mineral or a double-chain structure type 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 suppressed. , movement outside the casting structure 3 is suppressed. As a result, the temperature of the molten metal within the casting structure 3 becomes less likely to drop, and the flow of the molten metal during pouring can be maintained even better. In particular, when the coating layer 32 contains a double-chain structure type mineral, the above-mentioned effect becomes remarkable, so it is preferable that the coating layer 32 contains a double-chain structure type mineral.
From the viewpoint of further achieving the above-mentioned effects, it is more preferable that the coating layer 32 contains one or more selected from attapulgite, sepiolite, bentonite, and smectite.
Note that clay minerals are distinguished from the second inorganic particles, which mainly include, for example, a hexagonal close-packed structure, in that they have a layered structure or a multi-chain structure, and generally do not have a layered structure or a multi-chain structure. That is, the second inorganic particles do not have a layered structure and do not have a multi-chain structure.

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

The casting structure 3 preferably includes a binder, and the binder preferably includes at least one of an organic binder and an inorganic binder.
The main body portion 31 may contain both an organic binder and an inorganic binder from the viewpoint of having electrical insulation properties and ensuring good flow of the molten metal during casting and excellent removability after casting. Preferably, it is more preferable that only an organic binder is included.
From the viewpoint of sealing 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. When the sealing properties of the surface of the coating layer 32 are improved, even if the components contained in the main body part 31 are burned and gas is generated during casting, for example, it is possible to suppress the gas from being mixed into the molten metal.

Examples of the organic binder include thermosetting resins such as phenol resins, epoxy resins, and furan resins, which can be used alone or in combination of two or more. Among these, it is preferable to include a phenol resin because it generates less combustible gas, has a combustion suppressing effect, and has a high residual carbon percentage after thermal decomposition (carbonization).

Examples of the phenol resin include novolak phenol resin, resol type phenol resin, and modified phenol resin modified with urea, melamine, epoxy, and the like. In particular, by including a resol type phenolic resin, curing agents such as acids and amines are not required, and odor during molding of the main body 31 and casting defects when the main body 31 is used as a mold can be reduced. This is preferable because it can be done.

When a novolak 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 it is dehydrated when manufacturing the structure. The curing agent preferably includes, for example, hexamethylenetetramine.

Examples of the inorganic binder include phosphoric acid binders, water glasses such as silicates, gypsum, sulfates, silica binders, and silicon binders, which may be used alone or in combination of two or more.
It is preferable to include a silica-based binder as the inorganic binder, from the viewpoint of enabling the use of water as a dispersion medium and from the viewpoint of increasing the strength when hot.

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

The main body part 31 preferably contains a binder in an amount of 5% by mass or more, and preferably contains a binder in an amount of 10% by mass or more based on the entire mass of the main body part 31, from the viewpoint of improving the strength and further exerting the effect of suppressing the amount of gas generated. More preferably, it is contained in an amount of 15% by mass or more.
In addition, the main body portion 31 is designed to improve heat resistance, and to improve shape retention by preventing stickiness during molding and reducing the content of skeletal components 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, based on the entire mass of the main body portion 31. In particular, when the binder contains an organic binder, the effect of improving heat resistance is more significantly achieved by controlling the content of the binder within the above-mentioned range.

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

In addition to the above-mentioned components, the casting structure 3 may contain other components such as paper strength agents such as polyvinyl alcohol, carboxymethyl cellulose, and polyamidoamine epichlorohydrin resin, and polyvinyl alcohol, as long as they do not impair the effects of the present invention. It may contain a flocculant such as acrylamide, a coloring agent, and the like.

When the wall thickness of the main body portion 31 is defined as the wall thickness A, the wall 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.
Further, the wall thickness A is preferably 5 mm or less, more preferably 3.5 mm or less, and still more preferably 3 mm or less.
By setting the wall thickness A to be equal to or greater than the above-mentioned lower limit, the strength of the main body portion 31 is improved, and the handling of the casting structure 3 is improved. Furthermore, the movement of current and heat in the thickness direction of the main 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 within the casting structure 3 becomes less likely to drop, and the flow of the molten metal during pouring can be maintained even better.
By setting the wall thickness A to be less than or equal to the above-mentioned upper limit, the casting structure 3 can be made lighter, and in addition to improved portability, it is also economically advantageous. The wall thickness A can be measured by the method described in Examples below.

When the thickness of the coating layer 32 is defined as the 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.
Further, the wall thickness B is preferably 1000 μm or less, more preferably 900 μm or less, and still more preferably 800 μm or less.
By setting the wall thickness B to be equal to or greater than the above-mentioned lower limit, the strength of the coating layer 32 is improved, and the handling 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 within the casting structure 3 becomes less likely to drop, and the flow of the molten metal during pouring can be maintained even better.
By setting the wall thickness B to be less than or equal to the above-mentioned upper limit, it is possible to prevent cracks that may occur in the coating layer 32 after the drying step in the method for manufacturing the casting structure 3 described later. The wall thickness B, like the wall thickness A, can be measured by the method described in Examples below.

From the viewpoint of further achieving the above-mentioned effects, the total thickness of the main body portion 31 and the coating layer 32, that is, the total of the thickness A and the thickness 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.
Further, the total of wall thickness A and wall thickness B is preferably 6 mm or less, more preferably 4.5 mm or less, and still more preferably 4 mm or less.
By making the sum of the wall thickness A and the wall thickness B equal to or greater than the above-mentioned lower limit, the strength of the casting structure 3 is improved, and the handleability is improved.
By setting the sum of the wall thickness A and the wall thickness B to be less than or equal to the above-mentioned upper limit, the casting structure 3 can be made lighter, and in addition to improved portability, it is also economically advantageous.

From the viewpoint of further achieving the above-mentioned effects, the ratio B/A of the wall thickness B to the wall thickness A is preferably 0.001 or more, more preferably 0.01 or more, and still more preferably 0.1 or more.
Further, the ratio B/A of the wall thickness B to the wall 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 be equal to or greater than the above-mentioned lower limit, the shielding properties of pyrolysis gas generated during casting are improved.
By setting the ratio B/A of the wall thickness B to the wall thickness A to be equal to or less than the above-mentioned upper limit, 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 main body 31 and then forming the coating layer 32 on the inner surface of the manufactured main body 31. Hereinafter, a method for manufacturing the main body portion 31 will be described.

The main body portion 31 can be manufactured by a molding method that includes a papermaking process. Such a molding method is described, for example, in JP-A No. 2012-024841 [0052] to [0071].
The casting structure 3 can be manufactured by forming the coating layer 32 on the surface of the main body portion 31 manufactured by the above manufacturing method.

Examples of methods for forming the coating layer 32 include coating using a coating composition, such as brush coating, spray coating, electrostatic coating, baking coating, splash coating, dip coating, and tampon coating. After careful consideration of the uniformity of the thickness of the layer 32, efficiency, and economy, dip coating is most preferred. When forming the coating layer 32 on the inner surface of the hollow main body part 31 by dip coating, the coating layer 32 is formed by filling the hollow part of the main body part 31 with a coating composition and bringing it into contact with the coating composition (hereinafter referred to as " method 1). When method 1 is performed on the main body 31 in which the hollow portion is in an open state, for example, at least a portion of the open portion of the hollow portion is sealed so that the coating composition can be held in the hollow portion. The coating layer 32 can be formed by pouring the coating liquid composition into the cavity, preferably so that the coating liquid composition fills the hollow space, and preferably by discharging the coating liquid composition after allowing it to stand for a predetermined period of time. In either coating method, the temperature of the coating composition is preferably in the range of 5°C or more and 40°C or less, more preferably 15°C or more and 30°C or less, even more preferably 20°C or more and 30°C or less, and kept at a constant temperature. It is most preferable to set up the equipment so that Further, in dip coating, especially in Method 1, the standing time is preferably in the range of 1 second to 60 seconds from the viewpoint of productivity, and can be carried out batchwise or continuously. In either method, in order to adjust the thickness of the coating layer 32, the main body 31 coated with the coating composition can be vibrated using a vibration table or the like. In order to more firmly adhere the metal element to the surface of the main body 31, it is preferable to perform a drying process. Examples of the drying method include, but are not limited to, hot air drying using a heater, far infrared drying, microwave drying, superheated steam drying, vacuum drying, and the like. When drying using a hot air dryer, the drying temperature at the center of the drying oven is preferably in the range of 100°C or more and 500°C or less, and furthermore, from the viewpoint of reducing the effects of thermal decomposition of the binder and ensuring safety from ignition. From this point of view, the most preferable temperature range is 105°C or higher and 300°C or lower. In addition, examples of the dispersion medium of the coating composition include water, alcohol, etc., and water is preferable. Further, the dispersion medium is used in the range of 5 parts by mass to 100 parts by mass, furthermore 10 parts by mass to 80 parts by mass, and even more preferably 10 parts by mass to 50 parts by mass, based on 100 parts by mass of solids in the coating composition. It is preferable that

The casting structure 3 of the present invention can be used, for example, in manufacturing castings in the following manner.
As shown in FIG. 3, first, a cavity 5 is provided in at least one of the openings 33 of the foundry structure 3, and the foundry structure 3 is buried at a predetermined position in foundry sand to form a sand mold. form 6. When forming the sand mold 6, the foundry structure 3 is buried leaving a portion of the openings 33 (ie, at least one opening 33) of the foundry structure 3. At this time, the entire area of the unburied opening 33 may be outside the foundry sand, or a part of the unburied opening 33 may be inside the foundry sand. As the foundry sand for the sand mold 6, any ordinary foundry that has been conventionally used in the manufacture of this type of casting can be used without any restriction.
Next, a funnel-shaped pouring spout 7 for pouring molten metal into the casting structure 3 is installed at one end of the opening 33 that is not buried. As shown in FIG. 3, the outer diameter of the pouring port 7 on the side that is in contact with the opening 33 that is not buried is smaller than the inner diameter of the opening 33, so the pouring port 7 is fitted into the opening 33. It is attached. There is no particular restriction on the constituent material of the spout 7, and any conventionally known material can be used as long as it is not dissolved by molten metal.
There are no particular restrictions on the method of burying the foundry structure 3; for example, after the foundry structure 3 is placed in a predetermined position, molding sand may be placed, or after the foundry structure 3 is placed in a predetermined condition, , the casting structure 3 may be arranged. In this way, the casting mold 4 is manufactured.

After forming the foundry mold 4, molten metal is poured from the pouring port 7 of the foundry mold 4, and the molten metal is supplied into the cavity 5 to perform casting. After the casting is finished, the casting is cooled to a predetermined temperature, the casting mold 4 is dismantled to remove the foundry sand, and the casting structure 3 is removed by blasting to expose the casting. Thereafter, the casting may be subjected to post-treatment such as trimming treatment, if necessary. In this way, a casting is manufactured.

As described above, in the casting structure 3 of this embodiment, the main body part 31, which is the main part, has electrical insulating properties, so that the casting structure 3 can be easily poured into the casting structure 3 during casting. The heat of the molten metal is suppressed from moving outside the casting structure 3 via the main body portion 31. As a result, when the foundry mold 4 of this embodiment is used, the temperature of the molten metal in the foundry structure 3 is less likely to drop than in conventional foundry structures, and the flow of the molten metal during pouring is maintained at a good level. can be kept. Therefore, according to the casting mold 4 of this embodiment, a casting can be produced in which the occurrence of casting defects such as creases, cracks, and cavities is suppressed. In particular, when casting steel whose molten metal temperature is higher than that of cast iron, the above-mentioned effect becomes remarkable, so the casting mold 4 of this embodiment can be suitably used as a casting mold for steel casting. Further, by using the steel casting mold, a cast steel casting can be manufactured.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention.
For example, the above-mentioned foundry structure 3 has a two-layer structure including the main body 31 and the covering layer 32, but instead of this, the foundry structure 3 has other parts in addition to the main body 31 and the covering layer 32. It may be a three-layer structure having a layered structure. 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 31 and the coating layer 32 It may be in between.

Regarding each of the embodiments described above, the following casting structure 3 will be further disclosed.

<1>
A structure for manufacturing castings, comprising a cylindrical main body and a coating layer covering an inner surface of the main body, the main body having electrical insulation properties.

<2>
The coating layer is present as a film-like part on the inner surface of the main body,
The casting manufacturing structure according to <1>, wherein the film-like portion is a portion in which the particles constituting the coating layer exist in the form of microscopic aggregated particles.
<3>
The casting manufacturing structure according to <1> or <2>, wherein both the main body portion and the coating layer have electrical insulation properties.
<4>
The electrical insulation property is such that no current passes through it at all, or the electrical resistance evaluation value measured in the thickness direction is 200 kΩ/mm or more, or the electrical resistance evaluation value measured on the surface is 200 kΩ/mm or more. The casting manufacturing structure according to any one of <1> to <3>.
<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 casting manufacturing structure according to any one of <1> to <4> above.

<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, and more preferably 1×10 ⁴ kΩ/mm or more. , the casting manufacturing structure according to any one of <1> to <5>.
<7>
The electrical resistance evaluation value measured at a position 60 mm away from 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, and more preferably 1×10 ⁴ kΩ/mm or more. , the casting manufacturing structure according to <3>.
<9>
The electrical resistance evaluation value measured in the thickness direction through the main body portion 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 has a resistance of ⁴ kΩ/mm or more.
<10>
The electrical resistance evaluation value measured in the thickness direction of the main body portion and the electrical resistance evaluation value measured in the thickness direction of the coating layer are both 200 kΩ/mm or more, <1> to <9> above. The structure for manufacturing castings according to any one of the above.

<11>
The casting manufacturing structure according to any one of <1> to <10>, wherein the main body portion includes inorganic fibers, and the inorganic fibers are made only of electrically insulating inorganic fibers.
<12>
The casting manufacturing structure according to <11>, wherein the main body does not contain an electrically conductive material.
<13>
The casting manufacturing structure according to <12>, wherein the main body contains the electrically conductive material in a range of 0% by mass or more and 1% by mass or less, preferably 0.5% by mass or less.
<14>
The casting manufacturing structure according to any one of <1> to <13>, wherein the main body portion includes inorganic particles, and the inorganic particles are made only of electrically insulating inorganic particles.
<15>
The casting manufacturing structure according to <14>, wherein the main body further contains organic fibers.

<16>
The casting manufacturing structure according to any one of <1> to <15>, wherein the coating layer contains an inorganic compound, and the inorganic compound is composed only of an electrically insulating inorganic compound.
<17>
The casting manufacturing structure according to any one of <1> to <16>, wherein the coating layer contains a double-chain mineral.
<18>
The structure for manufacturing castings according to any one of <1> to <17>, wherein the main body has a wall thickness of 0.3 mm or more, preferably 0.5 mm or more, and more preferably 0.8 mm or more.
<19>
The casting manufacturing structure according to any one of <1> to <18>, wherein the main body has a wall thickness of 5 mm or less, preferably 3.5 mm or less, and 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 manufacturing a casting 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, and more preferably 800 μm or less.
<22>
According to any one of <1> to <21> above, the total thickness of the main body portion and the coating layer is 0.305 mm or more, preferably 0.5 mm or more, more preferably 0.8 mm or more. Structures for manufacturing castings.
<23>
The casting product 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> above, wherein the ratio B/A of the thickness B of the coating layer to the thickness A of the main body portion is 0.001 or more, preferably 0.01 or more, more preferably 0.1 or more. The structure for manufacturing castings according to any one of the above.
<25>
Any one of <1> to <24> above, 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. The structure for manufacturing castings described in .

<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. 1> to <25>. The structure for manufacturing castings according to any one of items 1> to <25>.
<27>
The structure for producing a casting according to any one of <1> to <26>, which is a structure for producing a casting for cast steel.
<28>
A method of using the casting manufacturing structure according to any one of <1> to <27> as a runner or lifting runner in casting steel.
<29>
burying the foundry manufacturing structure according to any one of <1> to <27> in foundry sand, leaving some of the openings of the foundry manufacturing structure; A method for manufacturing a casting mold for cast steel.
<30>
The foundry manufacturing structure according to any one of <1> to <27> is buried in foundry sand leaving some of the openings of the foundry manufacturing structure, and a mold is formed. a mold manufacturing process for manufacturing;
A method for manufacturing a steel casting, comprising a casting step of pouring molten metal into the mold.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the scope of the invention is not limited to such examples.

[Example 1]
After forming a fiber laminate using the raw material slurry described below, the fiber laminate was dehydrated and dried to obtain a structure for casting. 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>
After dispersing the organic fibers and inorganic fibers shown below in water to prepare an aqueous slurry of approximately 1% by mass (the total mass of organic fibers and inorganic fibers is 1% by mass with respect to the aqueous slurry), a 1 Inorganic particles, a binder, a coagulant, and a paper strength agent were blended to prepare a raw material slurry. The blending amounts of organic fibers, inorganic fibers, first inorganic particles, and binder in the raw material slurry were such that the content ratio of each component in the intended main body portion was as shown in Table 1. Note that when the total amount of organic fibers, inorganic fibers, first inorganic particles, and binder is 100 parts by mass (solid content equivalent), the amount of flocculant in the raw material slurry is 0.625 parts by mass. The paper strength strengthening agent was blended into the raw material slurry in an amount of 0.025 parts by mass (in terms of solid content). The respective components shown in Table 1 are as follows.

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

<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>
・Phenol resin (resol type): Weight loss rate 44% at 1000°C in nitrogen atmosphere (TG thermal analysis measurement)

<Flocculant>
・Flocculant: Polyamide epichlorohydrin

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

<Dispersion medium>
・Dispersion medium: water

<Paper making/dehydration process>
As the papermaking mold, a mold having a cavity forming surface corresponding to the above-mentioned 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. Note that the mold consists of a pair of split molds. The raw material slurry was circulated by a pump and a predetermined amount of the slurry was injected into the papermaking mold under pressure, while water in the slurry was removed through the communication holes and a predetermined fiber laminate was deposited 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 the 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 above-described main body (straight tube and elbow tube) was used. A large number of communication holes are formed in the mold to communicate the cavity forming surface with the outside. Note that the mold consists of a pair of split molds. The fiber laminate was taken out of the papermaking mold and transferred to a drying mold heated to 200°C. Then, a bag-shaped elastic core is inserted through the upper opening of the drying mold, and pressurized air (0.2 MPa) is injected into the elastic core inside the sealed drying mold. An elastic core was inflated, and the fiber laminate was pressed against the inner surface of the drying mold using 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 drying under pressure (for 60 seconds), the pressurized air inside the elastic core is removed to shrink the elastic core and taken out from the drying mold.The molded body is taken out from the drying mold, cooled, and heated. A hardened main 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 solid materials were stirred with water for 15 minutes using a stirrer to obtain a coating composition containing the second inorganic particles as a main component. The amounts of the second inorganic particles, clay mineral, and binder in the coating liquid composition were such that the content ratio of each component in the intended coating layer was as shown in Table 1. The amount of water in the coating composition was adjusted so that the solid content concentration of the coating composition was 85% by mass.

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

<Clay minerals>
・Atapulgite: manufactured by Hayashi Kasei Co., Ltd., product 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 main bodies (straight tube and elbow tube) was sealed, and the coating composition prepared above was poured into them up to the upper end, and after standing still for 10 seconds. , turn it upside down and drain the coating composition. After air drying, it was dried in a hot air dryer at 200° C. for 30 minutes to obtain a casting structure on which a coating layer was formed.

[Example 2]
A casting structure was obtained in the same manner as in Example 1 by mixing each material in the proportions 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
A casting structure was obtained in the same manner as in Example 1, except that carbon fibers (average fiber length: 3 mm, fiber width: 11 μm (major axis/minor axis ratio: 273)) were used instead of alumina fibers as the inorganic fibers contained in the main body, and the materials were mixed in the ratios shown in Table 1 below.

[Comparative example 2]
Examples except that carbon fiber was used instead of alumina fiber as the inorganic fiber contained in the main body, zircon was used as the second inorganic particle contained in the coating layer, and each material was mixed in the proportions shown in Table 1 below. A casting structure was obtained in the same manner as in Example 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 included in the main body, and each material was mixed in the proportions shown in Table 1 below.

〔evaluation〕
In the casting structures obtained in Examples and Comparative Examples, the wall thickness of the main body (wall thickness A) and the wall thickness of the coating layer (wall thickness B) were measured according to the following method.
In addition, according to the above method, the electrical resistance evaluation value in the thickness direction of the main body, the electrical resistance evaluation value on the outer surface of the main body, the electrical resistance evaluation value in the thickness direction of the coating layer, and the electrical resistance evaluation value on the inner surface of the coating layer. The resistance evaluation value was measured to evaluate whether the main body portion or the coating layer had electrical conductivity.
If the electrical resistance evaluation value of a casting structure is low, in other words, if the thermal conductivity is low, the flow of the molten metal during casting will be good, and poor molten metal flow that occurs as the casting temperature decreases is one of the causes It is less likely that hot water wrinkles, which are a common casting defect, will occur.
The results obtained are shown in Table 1.

<Measurement of the wall thickness of the main body (thickness A)>
The thickness of the main body part 31 is measured using a dial caliper gauge [manufactured by Mitutoyo Co., Ltd., 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 taken.

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

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

3 Structure for manufacturing castings 31 Main body 32 Covering layer 32S Inner surface of coating layer 33 Opening 4 Casting mold 5 Cavity 6 Sand mold 7 Pouring spout

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

Claims (11)

A structure for manufacturing castings, comprising a cylindrical main body and a coating layer covering an inner surface of the main body, the main body having electrical insulation properties. The casting manufacturing structure according to claim 1, wherein both the main body portion and the coating layer have electrical insulation properties. An 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/or an electrical resistance evaluation value measured in the thickness direction of the main body is 200 kΩ/mm. The casting manufacturing structure according to claim 1 or 2, which is the above. The structure for manufacturing castings according to claim 3, wherein an electrical resistance evaluation value measured in the thickness direction through the main body portion and the coating layer is 200 kΩ/mm or more. Any one of claims 1 to 4, wherein the electrical resistance evaluation value measured in the thickness direction of the main body portion and the electrical resistance evaluation value measured in the thickness direction of the coating layer are both 200 kΩ/mm or more. A structure for manufacturing castings as described in . The casting manufacturing structure according to any one of claims 1 to 5, wherein the main body portion contains inorganic fibers, and the inorganic fibers are made only of electrically insulating inorganic fibers. The casting manufacturing structure according to claim 6, wherein the main body further contains organic fibers. The casting manufacturing structure according to any one of claims 1 to 7, wherein the coating layer contains a double-stranded mineral. A method of using the casting manufacturing structure according to any one of claims 1 to 8 as a runner or lifting runner in casting steel. burying the foundry manufacturing structure according to any one of claims 1 to 8 in foundry sand, leaving some of the openings of the foundry manufacturing structure; A method of manufacturing a mold for casting steel. Manufacturing a mold by burying the foundry manufacturing structure according to any one of claims 1 to 8 in foundry sand, leaving some of the openings of the foundry manufacturing structure. The mold manufacturing process,
A method for manufacturing a steel casting, comprising a casting step of pouring molten metal into the mold.

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