Cast-manufacturing structure

Abstract

A cast-manufacturing structure (1) is cylindrical and is provided with a cylindrical body part (20) having: a trunk section (11); and a female fitting section (12) that is connected to the trunk section (11) and has an inner diameter greater than or equal to the outer diameter of the trunk section (11). The cast-manufacturing structure (1) has: a trunk section inner surface covering layer (31) that covers the inner surface of the trunk section (11); and an outer surface covering layer (32) that covers the outer surface of the female fitting section (12). The outer surface covering layer (32) preferably covers the entire outer surface of the female fitting section (12).

Description

Casting manufacturing structures

[0001] The present invention relates to a structure for producing castings.

[0002] In the production of castings, a mold having an internal cavity is generally formed using molding sand, and a receiving port, a sprue, a runner, and a weir are formed to communicate with the cavity to supply molten metal to the cavity. Furthermore, a gas vent, a riser, and a riser are also formed to communicate with the outside. A core may also be disposed within the cavity. The present applicant has previously proposed a casting manufacturing structure that can be used as a runner or a riser (Patent Documents 1 and 2). The casting manufacturing structures described in Patent Documents 1 and 2 have a cylindrical main body and a coating layer formed on the inner surface of the main body. Patent Document 3 also describes a runner in which a refractory material is fixed to the inner or outer surface of a cardboard tube.

[0003] Japanese Patent Application Laid-Open No. 2021-70052 Japanese Patent Application Laid-Open No. 2012-24841 Japanese Utility Model Publication No. 56-34834

[0004] The present invention relates to a cylindrical casting structure. In one embodiment, the structure preferably includes a cylindrical main body having a barrel portion and a female fitting portion connected to the barrel portion and having an inner diameter equal to or greater than the outer diameter of the barrel portion. In one embodiment, the structure preferably includes a barrel inner surface coating layer that coats the inner surface of the barrel portion and an outer surface coating layer that coats the outer surface of the female fitting portion.

[0005] In one embodiment, it is preferable that the device has a cylindrical main body at one end of a barrel having a male fitting portion that fits into a female fitting portion. In one embodiment, it is preferable that the outer diameter of the male fitting portion is equal to or smaller than the inner diameter of the female fitting portion. In one embodiment, it is preferable that the device has a barrel inner surface coating layer that coats the inner surface of the barrel and an outer surface coating layer that coats the outer surface of the male fitting portion.

[0006] The present invention also relates to a method for manufacturing a cylindrical structure for casting. In one embodiment, the structure for casting preferably includes a cylindrical main body having a barrel and a female fitting portion connected to the barrel and having an inner diameter equal to or greater than the outer diameter of the barrel. In one embodiment, the method preferably includes a barrel coating step of applying a coating liquid to the inner surface of the barrel to form a barrel inner surface coating layer that covers the inner surface of the barrel. In one embodiment, the method preferably includes a female fitting coating step of applying a coating liquid to the outer surface of the female fitting portion around the entire circumference of the female fitting portion to form an outer surface coating layer that covers the outer surface of the female fitting portion.

[0007] FIG. 1 is a perspective view schematically illustrating a preferred embodiment of a structure for casting according to the present invention. FIG. 2(a) is a cross-sectional view taken along line IIa-IIa in FIG. 1, FIG. 2(b) is a cross-sectional view taken along line IIb-IIb in FIG. 1, and FIG. 2(c) is a cross-sectional view taken along line IIc-IIc in FIG. 1. FIG. 3 is a perspective view schematically illustrating two structures for casting shown in FIG. 1 connected to each other. FIG. 4 is an enlarged cross-sectional view of a main portion of FIG. 3. FIG. 5 is a schematic cross-sectional view of a mold containing the structure for casting shown in FIG. 1. FIG. 6(a) is a cross-sectional view schematically illustrating another preferred embodiment of a structure for casting according to the present invention, which corresponds to FIG. 2(a). FIG. 6(b) is an enlarged cross-sectional view of a main portion of the structures for casting shown in FIG. 6(a) connected to each other, which corresponds to FIG. 4. Fig. 7(a) is a cross-sectional view schematically showing yet another preferred embodiment of the structure for casting according to the present invention, and corresponds to Fig. 2(a). Fig. 7(b) is an enlarged cross-sectional view of a main portion of the structure for casting according to Fig. 7(a) in a connected state, and corresponds to Fig. 4. Fig. 8(a) is a cross-sectional view schematically showing yet another preferred embodiment of the structure for casting according to the present invention, and corresponds to Fig. 2(a). Fig. 8(b) is an enlarged cross-sectional view of a main portion of the structure for casting according to Fig. 8(a) in a connected state, and corresponds to Fig. 4. Fig. 9(a) is a cross-sectional view schematically showing yet another preferred embodiment of the structure for casting according to the present invention, and corresponds to Fig. 2(a). Fig. 9(b) is an enlarged cross-sectional view of a main portion of the structure for casting according to Fig. 9(a) in a connected state, and corresponds to Fig. 4. Fig. 10(a) is a cross-sectional view, equivalent to Fig. 2(a), showing a still further preferred embodiment of the structure for casting according to the present invention. Fig. 10(b) is an enlarged cross-sectional view, equivalent to Fig. 4, showing a state in which the structures for casting according to Fig. 9(a) are connected to each other. Fig. 11 is an enlarged cross-sectional view, equivalent to Fig. 1, showing a still further preferred embodiment of the structure for casting according to the present invention. Fig. 12 is a perspective view, equivalent to Fig. 1, showing a still further preferred embodiment of the structure for casting according to the present invention. Fig. 13(a) is a cross-sectional view taken along line XIIIa-XIIIa in Fig. 12, and Fig. 13(b) is a cross-sectional view taken along line XIIIb-XIIIb in Fig. 12.FIG. 14 is a perspective view, equivalent to FIG. 3, showing a state in which the structures for casting shown in FIG. 12 are connected to each other. FIG. 15 is an enlarged cross-sectional view of a main portion of FIG. 14. FIG. 16(a) is a cross-sectional view, equivalent to FIG. 13(a), showing a still further preferred embodiment of the structure for casting according to the present invention. FIG. 16(b) is an enlarged cross-sectional view, equivalent to FIG. 15, showing a state in which the structures for casting shown in FIG. 16(a) are connected to each other. FIGS. 17(a) to 17(d) are perspective views, equivalent to FIG. 2(a), showing a modified example of the structure for casting according to the present invention. FIGS. 18(a) to 18(e) are schematic cross-sectional views illustrating a preferred embodiment of the method for manufacturing a structure for casting according to the present invention. FIGS. 19(a) to 19(e) are schematic cross-sectional views illustrating a modified example of a preferred embodiment of the method for manufacturing a structure for casting according to the present invention. Detailed Description of the Invention

[0008] The casting structure of Patent Document 1 includes a cylindrical body portion and a fitting portion connected to the body portion. The casting structure of Patent Document 1 can connect multiple casting structures by inserting and fitting one end of the body portion of one adjacent casting structure, the end farthest from the fitting portion, into the fitting portion of the other casting structure. The casting structure of Patent Document 1 has an inner diameter of one end of the body portion that is 1.0 mm or more smaller than the inner diameter of the other end, thereby suppressing peeling of the coating layer during pouring at the portion where adjacent casting structures are fitted together. However, there is room for improvement in the possibility of molten metal seeping out of the casting structure during pouring, especially when the pressure of the molten metal inside the casting structure is high. This molten metal seepage is particularly likely to occur at the portion where adjacent casting structures are fitted together. The casting structure of Patent Document 2 also has room for improvement. Patent Document 3 does not describe at all the use of a plurality of cylindrical casting structures fitted together as a runner, nor does it consider at all how to prevent molten metal from seeping out at the portion where adjacent casting structures fit together. The present invention relates to a casting structure that can prevent molten metal from seeping out during pouring.

[0009] The present invention will be described below based on preferred embodiments. FIG. 1 shows a structure for casting production (hereinafter, simply referred to as "structure") 1 according to a first preferred embodiment of the structure for casting production of the present invention. The structure 1 is typically cylindrical. The term "cylindrical" as used herein includes a straight structure as shown in FIG. 1 , a structure having a bent portion 17 in a partial axial direction as shown in FIG. 17( a), a structure curved in an arc shape entirely in the axial direction as shown in FIG. 17( b), and a structure in which a cylindrical first portion 18 branches off from a cylindrical second portion 19 as shown in FIGS. 17( c) and 17( d). Furthermore, the term "cylindrical" includes not only a cylindrical structure with a circular cross section, i.e., a cylindrical shape, but also a cylindrical structure with a polygonal cross section, i.e., a rectangular cylindrical shape. The cross-sectional shape perpendicular to the axial direction of a cylindrical structure is typically circular but may be elliptical. The cross-sectional shape perpendicular to the axial direction of a rectangular cylindrical structure is typically square but may be triangular, rectangular, or polygonal with pentagons or more, or may be a polygon with rounded corners.

[0010] The structure 1 has a cylindrical main body 20. The main body 20 typically contains organic fibers, inorganic fibers, inorganic particles, and a binder. The components contained in the main body 20 will be described later. The main body 20 is the main part of the structure 1. The main body 20 preferably has a trunk 11 and a female fitting 12 connected to the trunk 11 and having an inner diameter equal to or greater than the outer diameter of the trunk 11. The female fitting 12 may be formed at one axial end 1a of the trunk 11. An example of this is shown in FIG. 2. In the example of the structure 1 shown in FIG. 2, the main body 20 preferably has an inner diameter larger at one end 1a in the axial direction Z than at the other end 1b.

[0011] The female fitting portion 12 may also be formed by branching off from the body portion 11. An example of this is shown in FIG. 17( d ). In the example of the structure 1 shown in FIG. 17( d ), it is preferable that the inner diameters of the ends 1 c and 1 d of the structure 1 other than the female fitting portion 12 are equal to or smaller than the inner diameter of the female fitting portion 12. In the example of the structure 1 shown in FIG. 17( d ), the inner diameter of the end 1 c of the structure 1 and the inner diameter of the end 1 d of the structure 1 may be the same as or different from each other. Alternatively, the inner diameter of only one of the ends 1 c and 1 d of the structure 1 may be equal to or smaller than the inner diameter of the female fitting portion 12.

[0012] The female fitting portion 12 preferably has a larger inner diameter and an outer diameter than the body portion 11. In the example of the structure 1 shown in Figure 2, a step portion 15 that protrudes radially outward from the body portion 11 is formed at the end portion on the side of one end 1a in the axial direction Z of the body portion 11, and the female fitting portion 12 is connected to the body portion 11 via the step portion 15.

[0013] Preferably, the structure 1 is capable of connecting multiple identical or similar structures. In the example of the structure 1 shown in FIG. 1 , both ends of the main body 20 in the axial direction Z are open. The outer diameter D1 of the end of the structure 1 other than the female fitting portion 12 is preferably equal to or smaller than the inner diameter D2 of the female fitting portion 12. In the example of the structure 1 shown in FIGS. 1 and 2 , the end of the structure 1 other than the female fitting portion 12 is the end 1b of the body 11 opposite to the one end 1a in the axial direction Z. In the example of the structure 1 shown in FIG. 17( d ), the end of the structure 1 other than the female fitting portion 12 is the end 1c, 1d of the first portion 18. If the outer diameter D11 of the end 1c of the first portion 18 and the outer diameter D12 of the end 1d of the first portion 18 are different, the outer diameter D1 is the smaller of the outer diameter D11 and the outer diameter D12. Although only one of the outer diameter D11 of the end 1c of the first portion 18 and the outer diameter D12 of the end 1d of the first portion 18 may be equal to or less than the inner diameter D2 of the female fitting portion 12, it is more preferable that both the outer diameter D11 and the outer diameter D12 are equal to or less than the inner diameter D2. In this specification, unless otherwise specified, the inner diameter and the outer diameter refer to the inner diameter and the outer diameter of the entire structure 1, including both the main body portion and the coating layer that coats the surface of the main body portion.

[0014] Preferably, the structures 1 can be connected to each other by inserting and fitting an end of one structure 1 other than the female fitting portion 12 into the female fitting portion 12 of another structure 1. By connecting a desired number of structures 1, a long cylindrical body 10 of a desired length can be formed (see FIG. 3 ). The end of the structure 1 other than the female fitting portion 12 preferably forms a male fitting portion 13 that fits into a female fitting portion whose inner diameter is equal to or greater than the outer diameter of the body portion 11. In the example of the structure 1 shown in FIG. 17( d ), either the outer diameter D11 of the end 1c of the first portion 18 or the end 1d of the first portion 18 may be a male fitting portion 13, but it is more preferable that both the end 1c and the end 1d are male fitting portions 13.

[0015] The male fitting portion 13 refers to the portion that is inserted into the female fitting portion 12 when an end of the structure 1 other than the female fitting portion 12 is internally fitted into the female fitting portion 12 of the same or similar structure 1. Specifically, the length L1 of the male fitting portion 13 is the same as the depth L2 of the female fitting portion 12. Here, "same" not only refers to the case where the length L1 of the male fitting portion 13 and the depth L2 of the female fitting portion 12 are the same, but also includes the case where the lengths L1 and L2 are so similar that they can be considered to be roughly the same. Specifically, when the ratio of the length L1 of the male fitting portion 13 to the depth L2 of the female fitting portion 12 is preferably 80% or more and 120% or less, more preferably 90% or more and 110% or less, and even more preferably 95% or more and 105% or less, the depth L2 and the length L1 are considered to be the same. Examples of the length L1 and the depth L2 are shown in Figure 2(a) and Figure 17(d). The length L1 of the male fitting portion 13 is the length of the male fitting portion 13 along the axial direction Z of the body portion 11 in the example of the structure 1 shown in Figure 2(a) and is the length of the male fitting portion 13 along the axial direction Zx of the first portion 18 in the example of the structure 1 shown in Figure 17(d).

[0016] In the example of the structure 1 shown in Fig. 2, it is preferable that the length L3 of the body 11 in the axial direction Z is longer than the depth L2 of the female fitting portion 12. In the example of the structure 1 shown in Fig. 2, when the length L3 of the body 11 in the axial direction Z is shorter than the depth L2 of the female fitting portion 12, or when the length L3 of the body 11 and the depth L2 of the female fitting portion 12 are the same, substantially the entire body 11 becomes the male fitting portion 13.

[0017] The structure 1 preferably has a barrel inner surface coating layer 31 that coats the inner surface of the barrel 11, and an outer surface coating layer 32 that coats the outer surface of the female fitting portion 12 (hereinafter also referred to as the "female fitting portion outer surface coating layer"). An example of this is shown in Figure 2(a). The barrel inner surface coating layer 31 and the outer surface coating layer 32 preferably contain refractory inorganic particles selected from the group consisting of metal oxides and metal silicates, a binder, and a clay mineral. The components contained in both coating layers 31, 32 will be described later.

[0018] The barrel inner surface coating layer 31 is preferably continuous over the entire circumferential direction of the structure 1. An example of this is shown in Fig. 2(b). The barrel inner surface coating layer 31 is also preferably continuous over the entire area of ​​the barrel 11 in the axial direction Z. In other words, the barrel inner surface coating layer 31 preferably covers the entire area of ​​the inner surface of the barrel 11. An example of this is shown in Fig. 2(a).

[0019] When high-temperature molten metal flows into the structure 1, gas is generated when the organic fibers, binders, etc. contained in the main body 20 are thermally decomposed, or from the molding sand. The structure 1 has the barrel inner surface coating layer 31, which can prevent gas from entering the structure 1. This makes it difficult for gas to be mixed into the molten metal flowing through the structure 1. From the viewpoint of achieving this effect more significantly, the barrel inner surface coating layer 31 is preferably continuous around the entire circumferential direction of the structure 1, and more preferably covers the entire inner surface of the barrel 11.

[0020] It is preferable that the outer surface coating layer 32 of the female fitting portion 12 is continuous over the entire circumferential direction of the structure 1. An example of this is shown in Figure 2(c). It is also preferable that the outer surface coating layer 32 is continuous over the entire outer surface of the female fitting portion 12 in the axial direction Z. In other words, it is preferable that the outer surface coating layer 32 covers the entire outer surface of the female fitting portion 12. An example of this is shown in Figure 2(a).

[0021] The structure 1 can be used, for example, in the production of a casting as follows. First, the structures 1 are connected together to form a cylindrical body 10. Then, as shown in FIG. 5 , the cylindrical body 10 is embedded at a predetermined position in molding sand to form a mold 40. In the example shown in FIG. 5 , the mold 40 is a sand mold. The structures are typically embedded, leaving some openings. Specifically, of the multiple structures 1 connected to form the cylindrical body 10, the structure 1 located most upstream is preferably embedded with its upstream opening exposed to the outside of the molding sand. There are no particular limitations on the method of embedding the cylindrical body 10. For example, the cylindrical body 10 may be placed at a predetermined position and then molding sand may be added, or the molding sand may be placed in a predetermined state and then the cylindrical body 10 may be placed. The molding sand for the sand mold 40 may be any ordinary molding sand that has been conventionally used in the production of this type of casting, without any limitations.

[0022] Molten metal is then poured into the mold 40 for casting. Specifically, the molten metal is poured into the cavity 42 through a pouring port 41 provided at one end of the cylindrical body 10, and casting is performed. During this process, the structure 1 maintains its hot strength and experiences minimal thermal contraction due to thermal decomposition, thereby preventing cracking of each structure 1 and damage to the structure 1 itself. Furthermore, the molten metal is less likely to penetrate the structure 1 or to adhere to the molding sand. After casting, the structure is cooled to a predetermined temperature, the molding flask is dismantled to remove the molding sand, and the casting structure is removed by blasting to expose the casting. The casting is then subjected to post-processing, such as trimming, as needed, to complete the production of the casting. The structure 1 is suitable for use as, for example, a runner or lifting runner used in casting. Furthermore, the structure 1 is particularly suitable for use as a runner or lifting runner in the production of cast steel. This is because cast steel has a higher melting point than cast iron, so the temperature of the molten metal when poured is high and the dynamic viscosity tends to be low.

[0023] The structure 1 has an outer surface coating layer 32 on the female fitting portion 12, which prevents molten metal from seeping out during pouring. This point will be described in detail below. When connecting structures 1 to each other, it is difficult to achieve a tight fit between the end face 11e of one structure 1 at the end other than the female fitting portion 12, i.e., the end face 11e of the male fitting portion 13 of one structure 1, and the end face 12e located inside the female fitting portion 12 of the other structure 1. As a result, a gap may be formed between the end face 11e of one structure 1 and the end face 12e of the other structure 1 (see FIG. 4 ). In the illustrated example, the end face 12e of the female fitting portion 12 is the upper surface 12e of the step portion 15. During pouring, the molten metal that has entered the gap may come into contact with the corner formed by the inner peripheral surface 12a of the female fitting portion 12 and the upper surface 12e of the step portion 15 (hereinafter also referred to as the "corner of the female fitting portion"). This may damage the corner, resulting in the formation of minute holes that penetrate the female fitting portion 12. There is a risk that the molten metal flowing within the structure 1 may seep out to the outside of the structure 1 through such holes. However, by covering the outer surface of the female fitting portion 12 with the outer surface coating layer 32, the molten metal can be prevented from penetrating the female fitting portion 12 and seeping out to the outside of the structure 1. Because the outer surface coating layer 32 covers the outer surface of the female fitting portion 12 as described above, there is no risk of the outer surface coating layer 32 peeling off when the male fitting portion 13 is fitted into the female fitting portion 12. This ensures that the effect of preventing the seepage of the molten metal can be achieved. From the viewpoint of more effectively preventing seepage of the molten metal, it is preferable to have a female fitting portion inner surface coating layer 33 that coats the inner surface of the female fitting portion 12 in addition to the outer surface coating layer 32. The female fitting portion inner surface coating layer 33 will be described later.

[0024] If the molten metal seeps out of the structure 1, it will come into contact with the molding sand, resulting in the mixing of the molding sand into the molten metal, a phenomenon known as "burn-on." Generally, when producing a casting, the molten metal in the cavity of the sand mold solidifies to form a product portion, and the molten metal in the runner tube solidifies to form a non-product portion. By preventing the mixing of molding sand into the molten metal, the non-product portion can be more easily reused. Furthermore, the process of removing the molding sand from the molten metal obtained by remelting the non-product portion can be omitted, thereby reducing costs and stabilizing the quality of the molten metal obtained by remelting the non-product portion.

[0025] The effect of preventing seepage of molten metal from the structure 1 during pouring is more pronounced when the inner diameter D3 of the body 11 of the structure 1 is large. Generally, seepage of molten metal during pouring is more likely to occur when the pressure of the molten metal in the structure 1 is high. When the cavity 42 of the mold 40 used for casting is large, the amount of molten metal poured increases. To prevent the temperature of the molten metal from dropping during pouring when a large amount of molten metal is poured, a structure 1 constituting the cylindrical body 10 embedded in the mold 40 with a large inner diameter D3 of the body 11 is preferred, as this allows for a large flow rate of the molten metal to be poured. Furthermore, when the cavity 42 is large, the mold 40 also becomes larger accordingly, and the vertical height of the cylindrical body 10 also tends to increase. Therefore, when the inner diameter D3 of the body 11 of the structure 1 is large, it is often used under conditions where the pressure of the molten metal is high. Specifically, when the inner diameter D3 of the other end of the body 11 opposite to the one end 1a in the axial direction Z, i.e., the male fitting portion 13, is 45 mm or more, it is expected that the structure will be used under conditions of high molten metal pressure. In the structure 1 of the present invention, even when the inner diameter D3 of the body 11 in the structure 1 is large and the pressure of the molten metal in the body 11 is high, it is possible to prevent oozing of the molten metal during pouring. From the viewpoint of more significantly achieving the effect of preventing oozing of the molten metal during pouring, the inner diameter D3 of the male fitting portion 13 is preferably 65 mm or more, more preferably 90 mm or more. Furthermore, from the viewpoint of handleability, the inner diameter D3 of the male fitting portion 13 is preferably 700 mm or less, more preferably 550 mm or less, and even more preferably 350 mm.

[0026] The outer surface coating layer 32 of the female fitting portion 12 may be discontinuous in the circumferential direction of the structure 1, but from the viewpoint of effectively preventing the seepage of molten metal, it is preferable that it be continuous over the entire circumferential direction of the structure 1. Furthermore, the outer surface coating layer 32 of the female fitting portion 12 may cover only a portion of the outer surface of the female fitting portion 12 in the axial direction Z, but from the viewpoint of effectively preventing the seepage of molten metal, it is preferable that it cover the entire outer surface of the female fitting portion 12 in the axial direction Z. It is more preferable that the outer surface coating layer 32 be continuous over the entire circumferential direction of the structure 1 and cover the entire outer surface of the female fitting portion 12 in the axial direction Z. In other words, it is more preferable that the outer surface coating layer 32 cover the entire outer surface of the female fitting portion 12.

[0027] As described above, in the structure 1, the outer diameter D1 of the end portion of the structure 1 other than the female fitting portion 12 is preferably equal to or smaller than the inner diameter D2 of the female fitting portion 12. This makes it easier to insert the end portion of the structure 1 other than the female fitting portion 12 into the female fitting portion 12 of the other structure 1, making it easier to fit the two together. From the viewpoint of making it easier to insert the end portion 13 of the structure 1 other than the female fitting portion 12, i.e., the male fitting portion 13 of the structure 1, into the female fitting portion 12 of the other structure 1, the ratio D1 / D2 of the outer diameter D1 to the inner diameter D2 is preferably equal to or smaller than 1, more preferably equal to or smaller than 0.9999, and even more preferably equal to or smaller than 0.9995. Furthermore, from the viewpoint of preventing the gap between the outer surface of the male fitting portion 13 and the inner surface of the female fitting portion 12 from becoming too large when the male fitting portion 13 of one structure 1 is fitted with the female fitting portion 12 of another structure 1 and further stabilizing the fitted state between them, the ratio D1 / D2 is preferably 0.9 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. From the viewpoint of achieving both of these, the ratio D2 / D1 is preferably 0.9 or more and less than 1, more preferably 0.95 or more and 0.9999 or less, and even more preferably 0.99 or more and 0.9995 or less.

[0028] Of the outer diameters of the structure 1, it is preferable that the outer diameter D4 of the female fitting portion 12 is the largest. This makes it possible to ensure a smooth flow of molten metal when pouring molten metal into a state where a plurality of structures 1 are connected together. It is also preferable that of the inner diameters of the structure 1, the inner diameter D2 of the female fitting portion 12 is the largest. This makes it possible to ensure a smooth flow of molten metal when pouring molten metal into a state where a plurality of structures 1 are connected together.

[0029] Next, preferred embodiments of the structure 1 of the present invention will be described. For the second to ninth embodiments, differences from the first embodiment will be described, and the description of the first embodiment will be applied as appropriate to points not specifically described.

[0030] Figure 6 shows a structure 1 of a second embodiment. The structure 1 preferably has a female fitting inner surface coating layer 33 that coats the inner surface of the female fitting portion 12. The inner surface of the female fitting portion 12 includes the inner peripheral surface 12a of the female fitting portion 12 and the upper surface 12e of the step portion 15. The female fitting inner surface coating layer 33 preferably coats both the inner peripheral surface 12a and the upper surface 12e. In other words, the female fitting inner surface coating layer 33 coats the entire inner surface of the female fitting portion 12. An example of this is shown in Figure 6.

[0031] The female fitting portion inner surface coating layer 33 in the structure 1 can more effectively prevent seepage of molten metal during pouring. This point will be described in detail below. When connecting structures 1, as described above, a gap may occur between the end surface 11e of one structure 1 and the end surface 12e disposed inside the other structure 1. The female fitting portion inner surface coating layer 33 can reduce the size of the gap, making it less likely to form. Furthermore, even if a gap does occur and molten metal penetrates into the gap, the female fitting portion 12 can be protected. This is because the inner surface of the female fitting portion 12, particularly the inner surface at the corners of the female fitting portion, is coated with the female fitting portion inner surface coating layer 33. An example of this is shown in FIG. 6.

[0032] The molten metal that has entered the gap may penetrate into the gap between the outer peripheral surface of the male fitting portion 13 of one structure 1 and the inner peripheral surface 12a of the female fitting portion 12 of the other structure 1. However, this penetration can be prevented because the inner peripheral surface 12a of the female fitting portion 12 is also covered with the female fitting portion inner surface coating layer 33. This is because the female fitting portion inner surface coating layer 33 is disposed between the outer peripheral surface of the male fitting portion 13 of one structure 1 and the inner peripheral surface 12a of the female fitting portion 12 of the other structure 1. Even if the molten metal penetrates between the two, the female fitting portion 12 can be protected. This is because the inner peripheral surface 12a of the female fitting portion 12 is covered with the female fitting portion inner surface coating layer 33. An example of this is shown in FIG. 6.

[0033] It is preferable that the structure 1 has not only the female fitting inner surface coating layer 33 but also the outer surface coating layer 32 of the female fitting portion 12. In other words, it is preferable that both the inner and outer surfaces of the female fitting portion 12 are coated. This also contributes to more effectively preventing the molten metal from seeping out of the structure 1 during pouring.

[0034] In order to more significantly achieve the effect of protecting the female fitting portion 12, it is preferable that the female fitting portion inner surface coating layer 33 be continuous around the entire circumferential direction of the structure 1, and that it cover the entire inner surface of the female fitting portion 12.

[0035] It is preferable that the female fitting portion inner surface coating layer 33 and the barrel portion inner surface coating layer 31 are continuous. This allows the inner surfaces of the female fitting portion 12 and the barrel portion 11 to be protected without any gaps. The female fitting portion inner surface coating layer 33 and the barrel portion inner surface coating layer 31 may be discontinuous. For example, the female fitting portion inner surface coating layer 33 and the barrel portion inner surface coating layer 31 may be separate bodies.

[0036] It is more preferable that the entire inner surface of the main body 20 be covered with the female fitting inner surface coating layer 33 and the trunk inner surface coating layer 31. This makes it possible to protect the entire inner surface of the main body 20, and more effectively prevent the molten metal from seeping out during pouring.

[0037] 7 shows a structure 1 according to a third embodiment. The structure 1 preferably has an end surface covering portion 34 (hereinafter also referred to as the "female fitting portion end surface covering portion") that covers the outermost end surface of the structure 1 at the female fitting portion 12. The end surface covering portion 34 may cover only a portion of the end surface of the female fitting portion 12, or may cover the entire end surface.

[0038] The end surface covering portion 34 of the female fitting portion 12 more effectively prevents the molten metal from seeping out of the structure 1 during pouring. This point will be described in detail below. When connecting structures 1 to each other, as described above, the molten metal may enter the gap formed between the end surface 11e of one structure 1 and the end surface 12e of the other structure 1. The molten metal may then enter between the inner surface of the female fitting portion 12 of one structure 1 and the outer surface of the male fitting portion 13 of the other structure 1. This may result in the molten metal seeping out of the structure 1 from the one end 1a of one structure 1, i.e., the end surface side of the female fitting portion 12 of the one structure 1. However, by covering the end surface of the female fitting portion 12 with the end surface covering portion 34, the molten metal can be prevented from seeping out of the structure 1 from the end surface side of the female fitting portion 12 of the structure 1. In order to make this effect even more pronounced, it is preferable that the end face covering portion 34 be continuous around the entire circumferential direction of the structure 1, and it is even more preferable that it cover the entire end face of the female fitting portion 12.

[0039] In the structure 1 having the outer surface coating layer 32 of the female fitting portion 12, the outer surface coating layer 32 and the end surface coating portion 34 of the female fitting portion 12 may be discontinuous. However, from the viewpoint of more effectively preventing seepage of the molten metal during pouring, it is preferable that the outer surface coating layer 32 and the end surface coating portion 34 are continuous, and preferably molded as a single unit.

[0040] Fig. 8 shows a structure 1 of a fourth embodiment. The structure 1 preferably has a body outer surface coating layer 35 that coats the outer surface of the body 11. The structure 1 also preferably has a body inner surface coating layer 31. It is more preferable that the structure 1 is coated on both the inner and outer surfaces of the body 11. An example of this is shown in Fig. 8.

[0041] The structure 1 has the barrel inner surface coating layer 31 and the barrel outer surface coating layer 35, which effectively prevents the molten metal from seeping out during pouring, particularly from penetrating the barrel 11. For example, even when the pressure of the molten metal inside the structure 1 is high, the molten metal can be prevented from seeping out. To make this effect even more pronounced, it is preferable that the barrel outer surface coating layer 35 be continuous around the entire circumferential direction of the structure 1.

[0042] In the structure 1 having the female fitting portion inner surface coating layer 33, from the viewpoint of protecting the inner surfaces of the female fitting portion 12 and the body portion 11 without any gaps, it is preferable that the female fitting portion inner surface coating layer 33 and the body portion inner surface coating layer 31 are continuous, and it is preferable that the two are molded as a single unit.

[0043] The outer surface coating layer 32 preferably extends through the end face of the female fitting portion 12 to the inner surface of the body 11. In other words, it is preferable that the outer surface coating layer 32 of the female fitting portion 12, the end face coating portion 34 of the female fitting portion 12, the female fitting portion inner surface coating layer 33, and the body inner surface coating layer 31 are continuous. It is also preferable that the body outer surface coating layer 35 extends through the outer surface and end face of the female fitting portion 12 to the inner surface of the body 11. In other words, the structure 1 of the fourth embodiment has the body outer surface coating layer 35, the outer surface coating layer 32 of the female fitting portion 12, the end face coating portion 34 of the female fitting portion 12, the female fitting portion inner surface coating layer 33, and the body inner surface coating layer 31, and it is preferable that these are continuous.

[0044] The body inner surface coating layer 31 and the female fitting portion inner surface coating layer 33 may be formed as separate bodies. In this case, it is preferable that the female fitting portion inner surface coating layer 33 extends to the inner surface of the body 11, with a portion of it overlapping with the body inner surface coating layer 31. By having a portion of the female fitting portion inner surface coating layer 33 overlap with the body inner surface coating layer 31, it is possible to suppress seepage of molten metal from the interface between the body inner surface coating layer 31 and the female fitting portion inner surface coating layer 33, which are formed as separate bodies. An example of this is shown in Figure 9.

[0045] When a portion of the female fitting portion inner surface coating layer 33 overlaps with the barrel portion inner surface coating layer 31, either may be located more inward in the radial direction of the structure 1. However, it is preferable that the female fitting portion inner surface coating layer 33 be located more inward in the radial direction of the structure 1 than the barrel portion inner surface coating layer 31. By positioning the female fitting portion inner surface coating layer 33 and the barrel portion inner surface coating layer 31 in this manner, it is possible to prevent the molten metal flowing from one end 1a toward the other end 1b inside the structure 1 from colliding with the end of the barrel portion inner surface coating layer 31 on the one end 1a side, and it is possible to suppress peeling of the barrel portion inner surface coating layer 31 starting from the end on the one end 1a side during pouring.

[0046] When a portion of the female fitting portion inner surface coating layer 33 overlaps with the barrel inner surface coating layer 31, the thickness T1 of the overlapping portion is preferably greater than both the thickness T2 of the thickest portion of the female fitting portion inner surface coating layer 33 (hereinafter also referred to as the "maximum thickness of the female fitting portion inner surface coating layer") and the thickness T3 of the thickest portion of the barrel inner surface coating layer 31 (hereinafter also referred to as the "maximum thickness of the barrel inner surface coating layer"). Examples of T1 to T3 are shown in Figure 9. The barrel inner surface coating layer 31 and the female fitting portion inner surface coating layer 33 preferably have a constant thickness. Here, "constant thickness" includes cases where slight unintended thickness variations occur, such as variations in thickness unavoidable during manufacturing.

[0047] The advantage of the thickness T1 being thicker than the thickness T2 is as follows. When connecting and pouring multiple structures 1, the flow of molten metal is likely to be disturbed at the connection between the structures 1. However, by making the thickness T1 thicker than the thickness T2, the flow of molten metal flowing within the structures 1 can be prevented from being disturbed at the connection. This prevents the molten metal from colliding with the corners of the female fitting portion 12, thereby protecting the corners of the female fitting portion 12. The advantage of the thickness T1 being thicker than the thickness T3 is as follows. Generally, when pouring, the molten metal flows from one end 1a of the structure 1, where the female fitting portion 12 is located, toward the other end 1b. By making the thickness T1 thicker than the thickness T3, the molten metal flowing within the structure 1 can be prevented from colliding with the end of the body inner surface coating layer 31 on the one end 1a side. This protects the body inner surface coating layer 31 during pouring.

[0048] The ratio T1 / T2 of the thickness T1 to the thickness T2 is preferably greater than 1, more preferably greater than 1.5, and even more preferably greater than 2, from the viewpoint of protecting the corners of the female fitting portion 12. Furthermore, from the viewpoint of protecting the female fitting portion inner surface coating layer 33 from friction when connecting the structures 1, the ratio T1 / T2 is preferably less than 15, more preferably less than 10, and even more preferably less than 5. From the viewpoint of achieving both of these, the ratio T1 / T2 is preferably greater than 1 and less than 15, more preferably greater than 1.5 and less than 10, and even more preferably greater than 2 and less than 5.

[0049] The ratio T1 / T3 of the thickness T1 to the thickness T3 is preferably greater than 1, more preferably greater than 1.1, and even more preferably greater than 1.2, from the viewpoint of protecting the barrel inner surface coating layer 31 during pouring. Moreover, the ratio T1 / T3 is preferably equal to or less than 5, more preferably equal to or less than 3, and even more preferably equal to or less than 2, from the viewpoint of smoothing the flow of molten metal at the connection portions between the structures 1 during pouring. From the viewpoint of achieving both of these, the ratio T1 / T2 is preferably greater than 1 and equal to or less than 5, more preferably equal to or greater than 1.1 and equal to or less than 3, and even more preferably equal to or less than 1.2 and equal to or less than 2.

[0050] The maximum thickness T2 of the female fitting portion inner surface coating layer 33 is preferably thinner than the maximum thickness T3 of the trunk portion inner surface coating layer 31. This makes it easier to insert and fit the end of the other end 1b of another structure 1 into the female fitting portion 12 of the structure 1. From the viewpoint of making it easier to fit the end of the other end 1b of another structure 1 into the female fitting portion 12 of the structure 1, the ratio T2 / T3 of the thickness T2 to the thickness T3 is preferably less than 1, more preferably 0.8 or less, and even more preferably 0.5 or less. Furthermore, from the viewpoint of protecting the main body portion 20 in the female fitting portion 12, the ratio T2 / T3 is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. From the viewpoint of achieving both of these, the ratio T2 / T3 is preferably 0.01 or more but less than 1, more preferably 0.05 or more but 0.8 or less, and even more preferably 0.1 or more but 0.5 or less.

[0051] The thicknesses of the body inner surface coating layer 31 and the female fitting inner surface coating layer 33 do not have to be uniform. Fig. 10 shows an example of a structure 1 in which the body inner surface coating layer 31 has a non-uniform thickness.

[0052] When the thickness of the barrel inner surface coating layer 31 is not constant, it is preferable that the barrel inner surface coating layer 31 have a portion that is thicker than the portion 31a of the barrel inner surface coating layer 31 located at the end portion on the one end 1a side of the barrel 11 in the axial direction Z. This makes it difficult for the molten metal flowing inside the cylindrical body 10 obtained by connecting structures 1 to each other to directly impinge on the surface of the barrel inner surface coating layer 31 that coats the inner surface of the end portion on the one end 1a side of the barrel 11 of the downstream structure 1 when the molten metal flows through the barrel 11 of the upstream structure 1 in the direction Z1 and enters the barrel 11 of the downstream structure 1 in the direction Z1. This prevents impact from being applied to the end portion on the one end 1a side of the barrel 11 of the downstream structure 1, thereby protecting the barrel inner surface coating layer 31. From the viewpoint of achieving this effect more significantly, it is preferable that the thickness of the portion 31a of the barrel inner surface coating layer 31 is the thinnest. It is preferable that the thickness of the barrel inner surface coating layer 31 gradually increases from one end 1a toward the other end 1b in the axial direction Z. An example of this is shown in FIG.

[0053] Furthermore, when the trunk inner surface coating layer 31 and the female fitting portion inner surface coating layer 33 are formed as separate bodies, the female fitting portion inner surface coating layer 33 and the outer surface coating layer 32 may or may not have the same position at the base end side edge in the connecting direction Y of the female fitting portion 12. From the viewpoint of easily manufacturing the structure 1 having the female fitting portion inner surface coating layer 33 and the outer surface coating layer 32, it is preferable that the position of the base end side edge 33b of the female fitting portion inner surface coating layer 33 and the position of the base end side edge 32b of the outer surface coating layer 32 coincide.

[0054] Here, the term "the positions of the edge 33b of the female fitting portion inner surface coating layer 33 and the edge 32b of the outer surface coating layer 32 being aligned" refers not only to the case where their positions are completely aligned in the connecting direction Y of the female fitting portion 12, but also to the case where their positions are so similar that they can be considered to be aligned. Specifically, the positions of the edge 33b of the female fitting portion inner surface coating layer 33 and the edge 32b of the outer surface coating layer 32 are considered to be aligned when the ratio of the distance L5 in the connecting direction Y between the edge 33b of the female fitting portion inner surface coating layer 33 and the edge 32b of the outer surface coating layer 32 to the length L4 of the outer surface of the female fitting portion 12 in the connecting direction Y is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. Examples of the length L4 and the distance L5 are shown in FIG. 11 .

[0055] Furthermore, among the coating layers that coat the surface of the main body 20 in the structure 1, the female fitting inner surface coating layer 33 is preferably the thinnest. In other words, the female fitting inner surface coating layer 33 is preferably thinner than the coating layers other than the female fitting inner surface coating layer 33. This makes it easier to insert the end of the structure 1 other than the female fitting portion 12 into the female fitting portion 12, making it easier to fit the two together. Furthermore, even if the coating layer peels off when the male fitting portion 13 is fitted into the female fitting portion 12, the amount of peeling can be reduced, minimizing the impact on product quality.

[0056] Figure 12 shows a structure 1B of the fifth embodiment. The structure 1B preferably includes a cylindrical main body 20. The main body 20 preferably has a male fitting 13 at one end of the barrel 11. The male fitting 13 is preferably adapted to fit internally into the female fitting. The outer diameter of the male fitting 13 is preferably equal to or smaller than the inner diameter of the female fitting. The structure 1B preferably has a female fitting 12, the inner diameter of which is equal to or larger than the outer diameter of the barrel 11, connected to the other end of the barrel 11.

[0057] The female fitting portion 12 preferably has both an inner diameter and an outer diameter larger than those of the body portion 11. Typically, a step 15 that projects radially outward from the body portion 11 is formed at the end of the body portion 11 on the female fitting portion 12 side, and the female fitting portion 12 is connected to the body portion 11 via the step 15.

[0058] It is preferable that the structure 1B can be connected to a plurality of identical or similar structures. In the structure 1B of the example shown in FIG. 12, both ends of the main body 20 in the axial direction Z are open. The inner diameter of the female fitting portion 12 is preferably equal to or greater than the outer diameter of the male fitting portion 13 of the trunk portion 11. It is preferable that the structures 1B can be connected to each other by inserting and fitting the male fitting portion 13 of one structure 1B into the female fitting portion 12 of another structure 1B. By connecting a desired number of structures 1B, it is possible to form a long cylindrical body 10 of a desired length. An example of this is shown in FIG. 14.

[0059] Structure 1B preferably has a barrel inner surface coating layer 31 and an outer surface coating layer 36 (hereinafter also referred to as "outer surface coating layer of male fitting portion") that coats the outer surface of male fitting portion 13. The outer surface coating layer 36 of male fitting portion 13 preferably contains refractory inorganic particles selected from the group consisting of metal oxides and metal silicates, a binder, and a clay mineral. The components contained in the outer surface coating layer 36 will be described later.

[0060] It is preferable that the barrel inner surface coating layer 31 be continuous over the entire circumferential circumference of the structure 1B. An example of this is shown in FIG. 13( b). It is preferable that the barrel inner surface coating layer 31 be continuous over the entire area of ​​the barrel 11 in the axial direction Z. That is, in the structure 1B as well, the barrel inner surface coating layer 31 covers the entire inner surface of the barrel 11. An example of this is shown in FIG. 13( a). By having the barrel inner surface coating layer 31, the structure 1B is less likely to contain gas in the molten metal flowing within the structure 1B. From the viewpoint of achieving this effect more significantly, it is preferable that the barrel inner surface coating layer 31 be continuous over the entire circumferential circumference of the structure 1B, and it is more preferable that the barrel inner surface coating layer 31 cover the entire inner surface of the barrel 11.

[0061] The outer surface coating layer 36 preferably covers the entire outer surface of the male fitting portion 13. The structure 1B of the fifth embodiment can also be used to manufacture castings in the same manner as the structure 1 of the first embodiment.

[0062] The structure 1B has an outer surface coating layer 36 on the male fitting portion 13, which prevents molten metal from seeping out of the structure 1B during pouring. This point will be described in detail below. When connecting structures 1B to each other, a gap may form between the end face 11e of the male fitting portion 13 of one structure 1B and the end face 12e located inside the female fitting portion 12 of the other structure 1B. Molten metal that seeps into this gap may penetrate between the outer peripheral surface 11b of the male fitting portion 13 of one structure 1B and the inner peripheral surface 12a of the female fitting portion 12 of the other structure 1B. However, the structure 1B can prevent molten metal from penetrating between the outer peripheral surface 11b and the inner peripheral surface 12a. This is because the outer peripheral surface 11b of the male fitting portion 13 is also coated with the outer surface coating layer 36. This is also because the outer surface coating layer 36 of the male fitting portion 13 is disposed between the outer peripheral surface 11b of the male fitting portion 13 of one structure 1 and the inner peripheral surface 12a of the female fitting portion 12 of the other structure 1B. Furthermore, structure 1B has the outer surface coating layer 36 of the male fitting portion 13 and the trunk inner surface coating layer 31, and it is preferable that the outer and inner surfaces of the male fitting portion 13 are coated. This effectively prevents the molten metal from seeping through the male fitting portion 13 during pouring.

[0063] The outer surface coating layer 36 of the male fitting portion 13 may be discontinuous in the circumferential direction of the structure 1B, but from the viewpoint of effectively preventing the seepage of molten metal, it is preferable that it be continuous around the entire circumferential direction of the structure 1B.

[0064] In the fifth embodiment, as described above, the barrel inner surface coating layer 31 covers the entire inner surface of the barrel 11. This makes it possible to protect the entire inner surface of the main body 20, and therefore makes it possible to more effectively prevent the molten metal from seeping out during pouring.

[0065] In the structure 1B of the fifth embodiment, as in the structure 1 of the first embodiment, when the inner diameter D3 of the body portion 11 of the structure 1 is large, the effect of being able to more effectively prevent the molten metal from seeping out during pouring is more pronounced. The preferred range of the inner diameter D3 of the male fitting portion 13 of the fifth embodiment is the same as that of the first embodiment.

[0066] 16 shows a structure 1B according to a sixth embodiment. The structure 1B preferably has an outer surface coating layer 36 of the male fitting portion 13 and an end surface coating portion 37 (hereinafter also referred to as the "male fitting portion end surface coating portion") that covers the end surface 11e of the male fitting portion 13. The end surface coating portion 37 may cover only a portion of the end surface of the male fitting portion 13, or may cover the entire end surface.

[0067] The end surface covering portion 37 of the male fitting portion 13 can more effectively prevent seepage of molten metal during pouring. This point will be described in detail below. When connecting structures 1B to each other, as described above, a gap may occur between the end surface 11e of the male fitting portion 13 of one structure 1B and the end surface 12e located inside the female fitting portion 12 of the other structure 1B. The end surface covering portion 37 of the male fitting portion 13 of structure 1B can reduce this gap, making it less likely to occur. An example of this is shown in Figure 16.

[0068] When the structure 1B has an outer surface coating layer 36 of the male fitting portion 13, the outer surface coating layer 36 and the end surface coating portion 37 of the male fitting portion 13 may be discontinuous. However, from the viewpoint of more effectively preventing the seepage of the molten metal during pouring, it is preferable that the outer surface coating layer 36 and the end surface coating portion 37 are continuous and are preferably molded as a single unit.

[0069] When the structure 1B has the trunk inner surface coating layer 31, the end surface coating portion 37 of the male fitting portion 13 is preferably continuous with the trunk inner surface coating layer 31, and these are preferably molded as a single unit. The outer surface coating layer 36 of the male fitting portion 13 preferably extends through the end surface of the male fitting portion 13 to the inner surface of the trunk portion 11.

[0070] The outer diameter D1 of the male fitting portion 13 is preferably equal to or smaller than the inner diameter D2 of the other end of the body 11 opposite to the one end in the axial direction Z, i.e., the female fitting portion 12. This makes it easier to insert the male fitting portion 13 of one structure 1B into the female fitting portion 12 of another structure 1B, making it easier to fit the two together. The preferred range of the ratio D1 / D2 of the outer diameter D1 to the inner diameter D2 is the same as the preferred range of the ratio D1 / D2 in the first embodiment.

[0071] The trunk inner surface coating layer 31 is preferably disposed on the radially innermost side of the structure 1, 1B in the portion where the trunk inner surface coating layer 31 is disposed. By doing so, the trunk inner surface coating layer 31 in the structure 1, 1B comes into contact with the molten metal passing through the inside of the structure 1, 1B, which makes it easier to protect the main body 20 of the structure 1, 1B. In the example of the structure 1 shown in Figure 1, the radial direction of the structure 1 in the portion where the trunk inner surface coating layer 31 is disposed is the radial direction in a cross section perpendicular to the axial direction Z of the structure 1. In addition, in the example of the structure 1 shown in Figure 17 (d), the radial direction of the structure 1 in the part where the trunk inner surface coating layer 31 is arranged is the radial direction in a cross section perpendicular to the axial direction Zx of the first part 18 in the case of the trunk inner surface coating layer 31 arranged in the first part 18, and is the radial direction in a cross section perpendicular to the axial direction Zy of the second part 19, i.e., the connecting direction Y of the female fitting part 12 in the case of the trunk inner surface coating layer 31 arranged in the female fitting part 12.

[0072] The outer surface coating layer 32 of the female fitting portion 12 is preferably disposed on the radially outermost side in a cross section perpendicular to the axial direction Z of the structure 1. This makes it possible to achieve both ease of manufacturing and protection of the main body portion 20.

[0073] The main body 20 may have a laminated structure in which two or more layers are stacked, but from the viewpoint of easy manufacturing, it is preferable that the main body 20 has a single-layer structure.

[0074] Preferably, the main body 20 is formed as a single unit in the circumferential direction. This configuration makes the main body 20 continuous around the entire circumferential direction, thereby preventing gaps and holes from forming in the main body 20 and effectively preventing molten metal from seeping out during pouring. Preferably, the structures 1 and 1B have a portion of the outer surface of the main body 20 that is not covered by the coating layers 32, 35, and 36. During pouring, gas is generated when the organic fibers, binders, and other materials contained in the main body 20 thermally decompose as the molten metal flows into the structure 1. By having a portion of the outer surface of the main body 20 that is not covered by the coating layers 32, 35, and 36, gas can be preferentially discharged from that portion to the casting sand, i.e., to the outside of the structures 1 and 1B.

[0075] The outer surfaces of any of the barrel 11, the male fitting portion 13, and the female fitting portion 12 of the main body 20 may have portions that are not covered by the coating layers 32, 35, and 36. From the viewpoint of effectively achieving the effect of preferentially discharging gas to the outside of the structure 1, 1B, it is preferable that the outer surface of the barrel 11 of the main body 20 has a portion that is not covered by the barrel outer surface coating layer 35. The uncovered area ratio, which is the ratio of the area of ​​the portion not covered by the barrel outer surface coating layer 35 to the total area S1 of the outer surface of the barrel 11, is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more, from the viewpoint of preferentially discharging gas to the outside of the structure 1, 1B. From the viewpoint of preventing the molten metal from seeping out of the structure 1 during pouring, the uncovered area ratio is preferably 100% or less, more preferably 95% or less, and even more preferably 90% or less. From the viewpoint of achieving both of these, the uncovered area ratio is preferably 30% or more and 100% or less, more preferably 50% or more and 95% or less, and even more preferably 70% or more and 90% or less.

[0076] Next, the constituent materials of structures 1 and 1B will be described. The main body portion 20 typically contains organic fibers, inorganic fibers, inorganic particles (hereinafter also referred to as first inorganic particles), and a binder (hereinafter also referred to as first binder). Such main body portion 20 is typically manufactured by the following means. First, a slurry composition (hereinafter referred to as raw material slurry) containing organic fibers, inorganic fibers, first inorganic particles, the first binder, and a dispersion medium is prepared. Next, an intermediate molded body of the main body portion 20, for example, a water-containing main body portion, is paper-formed using a mold for paper-forming and dehydration molding. Next, the intermediate molded body is heated and dried using a mold, thereby forming the main body portion 20.

[0077] The organic fibers are entangled with the inorganic fibers and inorganic particles in the main body 20 before being used for casting, thereby maintaining the shape of the structures 1 and 1B. During casting, some or all of the organic fibers are burned by the heat of the molten metal.

[0078] The organic fiber can be one or more types selected from pulp fiber, synthetic fiber, recycled fiber (e.g., rayon fiber), etc. Among these, pulp fiber is preferred. This is because it can be molded into a variety of shapes by papermaking, the strength properties of the dehydrated and dried molded body are excellent, and pulp fiber is readily and consistently available and economical. The pulp fiber can be one or more types selected from wood pulp, cotton pulp, linter pulp, bamboo, straw, and other non-wood pulps. Also, one or more types selected from virgin pulp or recycled paper pulp (recycled products) can be used. From the viewpoints of ease of availability, environmental protection, and reduced manufacturing costs, it is preferred to include recycled paper pulp such as recycled newspaper.

[0079] The inorganic fibers mainly improve the strength of the structure 1, 1B in the main body 20 before it is used for casting. They do not burn even when exposed to the heat of the molten metal during casting, and maintain their shape. In particular, when an organic binder (described later) is used, the inorganic fibers can suppress the combustion of the organic fibers due to the heat of the molten metal and the thermal shrinkage caused by the thermal decomposition of the organic binder.

[0080] The inorganic fiber may be one or more selected from carbon fiber, artificial mineral fiber such as rock wool, ceramic fiber, glass fiber, and natural mineral fiber. Among these, carbon fiber, which has high strength even at high temperatures at which metals melt, is preferred in terms of suppressing the thermal shrinkage. From the viewpoint of reducing production costs, it is preferred to include one or more selected from rock wool and glass fiber.

[0081] The first inorganic particles may be one or more types selected from refractory aggregate particles such as mullite, graphite, mica, silica, hollow ceramics, and fly ash.

[0082] The average particle diameter of the first inorganic particles is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of improving the breathability of the main body portion 20. Furthermore, the average particle diameter of the first inorganic particles is preferably 100 μm or less, from the viewpoint of improving the moldability of the main body portion 20. When the average particle diameter of the first inorganic particles is equal to or greater than the above-mentioned lower limit, the breathability of the main body portion 20 is improved, and the gas pressure in the mold during casting is appropriately reduced. Furthermore, the increased breathability of the main body portion 20 increases the voids between the materials of the main body portion 20, improving the permeability of the coating composition described below into the main body portion 20 and making it difficult for the coating layer to peel off from the main body portion 20. When the first inorganic particles are equal to or less than the above-mentioned upper limit, the inorganic particles are less likely to fall off from the surface of the main body portion 20 and improving moldability.

[0083] From the viewpoint of raw material dispersibility, the apparent specific gravity of the first inorganic particles is preferably 0.5 or more, more preferably 2.8 or more. Furthermore, from the viewpoint of weight reduction, the apparent specific gravity of the first inorganic particles is preferably 3 or less, more preferably 2.8 or less, and even more preferably 2.5 or less. The apparent specific gravity is the specific gravity of a hollow particle when the volume of the hollow portion inside the hollow particle is assumed to be a portion of the volume of the hollow particle. In the case of solid particles without an internal hollow portion, the apparent specific gravity is equal to the true specific gravity. Having the apparent specific gravity of the first inorganic particles within the above range improves raw material dispersibility in the papermaking process when water is used as the dispersion medium. Furthermore, the weight of the molded main body 20 can be reduced, improving handleability. The composition of the main body 20 can be determined by taking into account the apparent specific gravity of the first inorganic particles as well as the bulk specific gravity. The bulk specific gravity is calculated by measuring the amount of particles entering a container of a certain volume when the particles are placed in a certain state, and then calculating the mass per unit volume.

[0084] The first inorganic particles may be hollow. By using hollow particles, the apparent specific gravity of the first inorganic particles can be reduced.

[0085] In the present invention, the first binder may be one or more selected from organic binders and inorganic binders. It is preferable to include an organic binder from the viewpoint of excellent removability after casting. As the organic binder, one or more selected from thermosetting resins such as phenolic resins, epoxy resins, and furan resins may be used. Among these, it is preferable to include a phenolic resin from the viewpoints of low generation of flammable gases, combustion suppression effect, and high carbon residue rate after pyrolysis (carbonization).

[0086] The phenolic resin may be one or more selected from novolac phenolic resins, resol-type phenolic resins, modified phenolic resins modified with urea, melamine, epoxy, etc. Among these, the inclusion of a resol-type phenolic resin is preferred because it does not require a curing agent such as an acid or an amine and can reduce odors during molding of the main body 20 and casting defects when the main body 20 is used as a mold.

[0087] When novolac phenolic resin is used, it is preferable to use a curing agent in combination. Because the curing agent is easily soluble in water, it is preferable to apply it to the surface of the main body 20 after dehydration. Hexamethylenetetramine or the like is preferably used as the curing agent.

[0088] As the inorganic binder, one or more binders selected from phosphate binders, water glass such as silicates, gypsum, sulfates, silica binders, and silicon binders can be used.

[0089] The dispersion medium used in the raw material slurry can be one or more selected from solvents such as water, ethanol, methanol, dichloromethane, acetone, xylene, etc. Among these, it is preferable to contain water from the viewpoint of ease of handling.

[0090] The main body 20 may contain a paper reinforcing material in addition to the organic fibers, inorganic fibers, first inorganic particles, and first binder. The paper reinforcing material has the effect of maintaining the shape of the intermediate molded body. As the paper reinforcing material, one or more materials selected from latex, acrylic emulsion, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide resin, polyamide epichlorohydrin resin, etc. can be used.

[0091] The barrel inner surface coating layer 31, the outer surface coating layer 32 of the female fitting portion 12, the female fitting inner surface coating layer 33, the end surface coating portion 34 of the female fitting portion 12, the barrel outer surface coating layer 35, the outer surface coating layer 36 of the male fitting portion 13, and the end surface coating portion 37 of the male fitting portion 13 (hereinafter, these may be collectively referred to as "coating layers") can typically be formed by applying a coating composition containing refractory inorganic particles (hereinafter, also referred to as second inorganic particles) selected from the group consisting of metal oxides and metal silicates and having an average particle diameter of 1 μm or more and 100 μm or less, a binder (hereinafter, also referred to as second binder), and a clay mineral to the surface of the main body portion 20.

[0092] With respect to refractory inorganic particles, being refractory means that the melting point is 1500°C or higher, preferably 1600°C or higher, and more preferably 1700°C or higher. The second inorganic particles can be one or more selected from the group consisting of metal oxides and metal silicates. Specifically, one or more selected from mullite, zircon, zirconia, alumina, olivine, spinel, magnesia, chromite, etc. can be used. From the viewpoint of improving gas defects in castings, it is preferable to contain zircon. Cast steel, which has a lower carbon content than cast iron, preferably contains non-carbonaceous aggregate particles, and more preferably contains zircon, which has a high melting point and low wettability with molten metal.

[0093] From the viewpoints of the pore-sealing property on the surface of the main body 20 and the adhesion between the main body 20 and the coating layer, the average particle size of the second inorganic particles is preferably 1 μm or more, and more preferably 3 μm or more. The average particle size of the second inorganic particles is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 40 μm or less.

[0094] In Structures 1 and 1B, the ratio of the average particle size of the first inorganic particles contained in the main body 20 to the average particle size of the second inorganic particles contained in the coating layer, [average particle size of the first inorganic particles] / [average particle size of the second inorganic particles], is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.8 or more, from the viewpoint of the pore-sealing property on the surface of the main body 20. Furthermore, the ratio of the average particle size of the first inorganic particles contained in the main body 20 to the average particle size of the second inorganic particles contained in the coating layer, [average particle size of the first inorganic particles] / [average particle size of the second inorganic particles], is preferably 35 or less, more preferably 30 or less, even more preferably 20 or less, and particularly preferably 6 or less. In Structures 1 and 1B, the proportion of the second inorganic particles in the coating layer is preferably 50% by mass or more but less than 100% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 90% by mass or more.

[0095] The coating layer preferably contains a clay mineral from the viewpoints of improving hot strength and imparting viscosity during application. Adding a clay mineral to the dispersion (coating composition) for obtaining the coating layer imparts an appropriate viscosity to the dispersion, preventing sedimentation of raw materials in the dispersion and improving raw material dispersibility. As the clay mineral, one or more types selected from layered silicate minerals, double-chain structure minerals, etc. can be used. These can be natural or synthetic. As the layered silicate mineral, one or more types selected from clay minerals belonging to the smectite, kaolin, and illite groups, such as bentonite, smectite, hectorite, activated clay, kibushi clay, and zeolite, can be used. As the double-chain structure mineral, one or more types selected from attapulgite, sepiolite, palygorskite, etc. can be used. From the viewpoint of improving hot strength and ensuring viscosity during application, it is preferable to use one or more selected from attapulgite, sepiolite, bentonite, and smectite, and it is more preferable to use one or more selected from attapulgite and sepiolite. Clay minerals have a layered or double-chain structure, and are distinguished from refractory inorganic particles that, for example, mainly have a hexagonal close-packed structure and do not usually have a layered or double-chain structure. The clay mineral is preferably contained in an amount of 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the refractory inorganic particles. The clay mineral is preferably contained in an amount of 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the refractory inorganic particles. In this ratio, if the clay mineral is above the lower limit, it is possible to impart an appropriate viscosity to the dispersion and prevent the raw material from settling or floating in the dispersion.

[0096] The coating layer preferably further contains a second binder from the viewpoint of improving hot strength. Using a second binder when forming the coating layer is preferable from the viewpoint of improving the room-temperature strength and heat resistance of the structure for casting production. The second binder may be one or more binders selected from organic binders and inorganic binders, and preferably contains an inorganic binder. Examples of organic binders that can be used include one or more binders selected from phenolic resins, epoxy resins, furan resins, water-soluble alkyd resins, water-soluble butyral resins, polyvinyl alcohol, water-soluble acrylic resins, water-soluble polysaccharides, vinyl acetate resins, and copolymers thereof. Examples of inorganic binders that can be used include one or more binders selected from various sols such as sulfates, silicates, phosphates, lithium silicate, zirconia sol, colloidal silica, and alumina sol. Preferably, one or more binders selected from the group consisting of colloidal silica and aluminum phosphate are used, and colloidal silica is more preferably included. The second binder is preferably contained in an amount of 1 part by mass or more, more preferably 3 parts by mass or more, based on 100 parts by mass of the second inorganic particles, in terms of the active ingredient. The second binder is preferably contained in an amount of 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 7 parts by mass or less, based on 100 parts by mass of the second inorganic particles, in terms of the active ingredient.

[0097] A preferred embodiment of the method for manufacturing a structure for casting production of the present invention will be described using the method for manufacturing the structure 1 shown in Fig. 18 as an example. The manufacturing method of this embodiment typically includes a barrel coating step for forming a barrel inner surface coating layer 31, and a female fitting portion coating step for forming a female fitting portion outer surface coating layer 32. In the female fitting portion coating step of this embodiment, in addition to the female fitting portion outer surface coating layer 32, a female fitting portion inner surface coating layer 33 and a female fitting portion end surface coating portion 34 are also formed.

[0098] In the barrel coating step, it is preferable to coat the inner surface of the barrel 11 of the main body 20 with a coating liquid to form a barrel inner surface coating layer 31. Specifically, it is preferable to inject a coating composition 70 into the barrel 11 and fill the barrel 11 with the coating composition 70 (see FIGS. 18( a) and 18(b)). More specifically, a lid 60 is placed on the open end of the male fitting portion 13. The barrel 11 is then filled with the coating composition 70. When the upper surface of the coating composition 70 reaches a desired height, the filling of the coating composition 70 is completed. After a certain period of time has elapsed, the lid 60 is opened. The coating composition 70 is then discharged, leaving some of the coating composition 70 on the inner surface of the barrel 11.

[0099] Then, it is preferable to leave the barrel 11 with the remaining coating liquid composition 70 in a state where the axial direction Z of the barrel 11 is approximately parallel to the vertical direction Z1, and dry and solidify the coating liquid composition 70 remaining on the inner surface of the barrel 11, thereby forming a barrel inner surface coating layer 31 on the inner surface of the barrel 11 (see Figure 18 (c)).

[0100] The female fitting portion coating step is preferably performed after the body portion coating step. In the female fitting portion coating step, the coating composition is preferably applied to the inner and outer surfaces and end surfaces of the female fitting portion 12 of the main body portion 20 along the entire circumference of the female fitting portion 12. Specifically, the female fitting portion 12 of the main body portion 20 is preferably immersed in the coating composition 71. The coating composition 71 is then applied to the inner and outer surfaces and end surfaces of the female fitting portion 12 (see FIG. 18(d)). After a certain period of time has passed, the female fitting portion 12 is removed from the coating composition 71. The coating film, i.e., the coating composition 71 remaining on the inner and outer surfaces and end surfaces of the female fitting portion 12, is then dried and solidified to form the female fitting portion inner surface coating layer 33, the female fitting portion outer surface coating layer 32, and the female fitting portion end surface coating portion 34. In this manner, the structure 1 is manufactured, which has the body inner surface coating layer 31, the female fitting portion inner surface coating layer 33, the female fitting portion outer surface coating layer 32, and the female fitting portion end surface coating portion 34. According to the manufacturing method of this embodiment, the structure 1 can be manufactured efficiently.

[0101] In the barrel coating step, the coating composition 70 filled into the barrel 11 may reach the upper surface 12e of the step 15 (see FIG. 18(b)), or may not reach that extent (see FIG. 19(a)). Furthermore, the coating composition 70 filled into the barrel 11 may reach the female fitting portion 12 (see FIGS. 19(b) and 19(c)). When the coating composition 70 reaches the female fitting portion 12, the coating composition 70 may reach the open end of the female fitting portion 12 (see FIG. 19(b)), or may not reach that extent (see FIG. 19(c)).

[0102] In the barrel coating step, instead of filling the barrel 11 with the coating liquid composition 70, the coating liquid composition 70 may be applied to the inner surface of the barrel 11 by, for example, applying the coating liquid composition 70 to the inner surface of the barrel 11 with a brush or the like. From the viewpoint of making it possible to easily form the barrel inner surface coating layer 31 and to more efficiently manufacture the structure 1, it is preferable to apply the coating liquid composition 70 by filling the barrel 11 with the coating liquid composition 70.

[0103] In the female fitting portion coating process, the main body 20 may be immersed in the coating composition 70 up to the position of the underside 15a of the step 15 (see Figure 18(d)), or only the portion of the female fitting portion 12 on the one end 1a side of the underside 15a of the step 15 may be immersed in the coating composition 70 (see Figure 19(d)), or the main body 20 may be immersed in the coating composition 71 up to a position on the other end 1b side of the underside 15a of the step 15 (see Figure 19(e)).

[0104] In the female fitting portion coating step of this embodiment, the female fitting portion inner surface coating layer 33, the female fitting portion outer surface coating layer 32, and the female fitting portion end surface coating portion 34 are formed, but it is also possible to form only the female fitting portion outer surface coating layer 32 in the female fitting portion coating step. For example, the coating composition 71 may be applied to the outer surface of the female fitting portion 12 by applying the coating composition 71 with a brush or the like. From the viewpoint of easily forming the female fitting portion inner surface coating layer 33, the female fitting portion outer surface coating layer 32, and the female fitting portion end surface coating portion 34 and more efficiently manufacturing the structure 1, it is more preferable to apply the coating composition 71 by immersing the female fitting portion 12 of the main body portion 20 in the coating composition 71 (see FIG. 18(d)).

[0105] The order in which the female fitting portion coating step and the barrel portion coating step are performed is not particularly limited. For example, the barrel portion coating step may be performed after the female fitting portion coating step, or the female fitting portion coating step and the barrel portion coating step may be performed simultaneously. Furthermore, the coating composition 70 in the barrel portion coating step and the coating composition 71 in the female fitting portion coating step may be the same as or different from each other.

[0106] The main body 20 can be manufactured by, for example, the following method. <Method for Manufacturing the Main Body 20> The main body 20 can be manufactured by a molding method including a papermaking process. Such a molding method is described, for example, in paragraphs

[0052] to

[0071] of JP 2012-024841 A. Specifically, first, a raw material slurry containing organic fibers, inorganic fibers, first inorganic particles, and a first binder in a predetermined ratio is prepared. The raw material slurry is prepared by dispersing the organic fibers, inorganic fibers, first inorganic particles, and first binder in a predetermined dispersion medium. Note that the first binder may be impregnated into the main body 20 without being mixed into the raw material slurry.

[0107] As the dispersion medium, in addition to water, one or more solvents selected from ethanol, methanol, dichloromethane, acetone, xylene, etc. can be used. Among these, water is preferred from the viewpoint of ease of handling. The content ratios of the organic fibers, inorganic fibers, first inorganic particles, and the first binder in the raw material slurry are appropriately adjusted so as to obtain the desired composition of the main body portion 20. Additives such as paper strength agents, flocculants, and preservatives can be added to the raw material slurry as needed.

[0108] Next, the raw material slurry is used to form an intermediate molded body for the main body 20. In the process of forming the intermediate molded body, for example, a mold for papermaking and dehydration molding is used, in which a cavity having a shape corresponding to the outer shape of the intermediate molded body is formed inside by butting two split dies together. A predetermined amount of raw material slurry is then injected under pressure into the cavity through the upper opening of the mold. This pressurizes the cavity to a predetermined pressure. Each split die is provided with a plurality of communication holes connecting the outside with the cavity, and the inner surface of each split die is covered with a net having a predetermined mesh size. A pressure pump, for example, is used to pressurize and inject the raw material slurry. The pressure for pressurizing and injecting the raw material slurry is preferably 0.01 MPa or more and 5 MPa or less, more preferably 0.01 MPa or more and 3 MPa or less, and even more preferably 0.1 MPa or more and 0.5 MPa or less.

[0109] As described above, the cavity is pressurized, so the dispersion medium in the raw material slurry is discharged to the outside of the mold through the communicating holes. Meanwhile, the solid content of the raw material slurry is deposited on the net covering the cavity, and a fiber laminate is uniformly formed on the net. The fiber laminate obtained in this manner has organic fibers and inorganic fibers intricately entangled with a binder interposed between them. Therefore, even if the fiber laminate has a complex shape, it can maintain its shape even after drying and molding. Furthermore, because the cavity is pressurized, the raw material slurry flows within the cavity and is agitated, even when molding a hollow intermediate molded body. Therefore, the slurry concentration within the cavity is uniform, and the fiber laminate is uniformly deposited on the net.

[0110] After the fiber laminate is formed, the pressurized injection of the raw material slurry is stopped, and air is forced into the cavity to pressurize and dehydrate the fiber laminate. Thereafter, the air is stopped, the cavity is evacuated through the communicating holes, and an elastic, stretchable, hollow core (elastic core) is inserted into the cavity. The core is preferably made of urethane, fluororubber, silicone rubber, elastomer, or the like, which has excellent tensile strength, impact resilience, stretchability, etc.

[0111] Next, pressurized fluid is supplied into the elastic core inserted into the cavity to expand the elastic core, and the expanded elastic core presses the fiber laminate against the inner surface of the cavity, thereby transferring the shape of the inner surface of the cavity to the outer surface of the fiber laminate and promoting dewatering of the fiber laminate.

[0112] The pressurized fluid used to expand the elastic core may be, for example, compressed air (heated air), oil (heated oil), or any other liquid. The supply pressure of the pressurized fluid is preferably 0.01 MPa or more and 5 MPa or less, taking into consideration the production efficiency of the molded body, and more preferably 0.1 MPa or more and 3 MPa or less, and even more preferably 0.1 MPa or more and 0.5 MPa or less, from the viewpoint of efficient production. A pressure of 0.01 MPa or more provides good drying efficiency for the fiber laminate and sufficient surface properties and transferability, while a pressure of 5 MPa or less provides good effects and allows the device to be made smaller.

[0113] In this way, because the fiber laminate is pressed against the inner surface of the cavity from the inside, even if the inner surface of the cavity has a complex shape, the inner shape is accurately transferred to the outer surface of the fiber laminate. Furthermore, even if the molded product to be manufactured has a complex shape, the process of bonding each part is unnecessary, so the final part does not have any seams or thick parts due to bonding. In other words, the final main body 20 is molded as a single unit in the circumferential direction of the main body 20.

[0114] Once the inner surface shape of the cavity has been sufficiently transferred to the outer surface of the fiber laminate and the fiber laminate has been dehydrated to a predetermined moisture content, the pressurized fluid in the elastic core is released, causing the elastic core to automatically shrink to its original size. The shrunk elastic core is then removed from the cavity, and the mold is opened to remove the wet fiber laminate with the predetermined moisture content. The fiber laminate can also be dehydrated by omitting the pressing and dehydration of the fiber laminate using the elastic core, and by pressing and dehydrating only by injecting air into the cavity.

[0115] The dehydrated and molded fiber laminate is then transferred to a heating and drying process. In the heating and drying process, a mold for dry molding is used, which has a cavity formed in a shape corresponding to the outer shape of the intermediate molded body. The mold is then heated to a predetermined temperature, and the dehydrated and molded wet fiber laminate is loaded into the mold.

[0116] Next, an elastic core similar to the elastic core used in the papermaking process is inserted into the fiber laminate, and pressurized fluid is supplied into the elastic core to expand it, and the expanded elastic core presses the fiber laminate against the inner surface of the cavity. An elastic core whose surface has been modified with a fluorine-based resin, silicone-based resin, or the like is preferably used. The supply pressure of the pressurized fluid is preferably the same as that in the dewatering process. Under this condition, the fiber laminate is heated and dried, and the intermediate molded body is dry-molded.

[0117] The heating temperature (mold temperature) of the mold for dry molding is preferably 100°C or higher and 300°C or lower, more preferably 150°C or higher and 250°C or lower, and even more preferably 190°C or higher and 240°C or lower, from the viewpoint of improving surface properties and shortening drying time. The heat treatment time cannot be generalized because it varies depending on the heating temperature, but from the viewpoint of improving quality and productivity, it is preferably 0.5 minutes or higher and 30 minutes or lower, and more preferably 1 minute or higher and 10 minutes or lower. If the heating temperature is 300°C or lower, the surface properties of the intermediate molded body are good, and if it is 100°C or higher, the drying time of the intermediate molded body can be shortened.

[0118] Once the fiber laminate is sufficiently dried, the pressurized fluid in the elastic core is released, causing the core to shrink and be removed from the fiber laminate. The mold is then opened to remove the intermediate molded body. The thermosetting resin in this intermediate molded body is hardened by heat treatment and used as the main body 20.

[0119] The main body 20 thus obtained has highly smooth inner and outer surfaces because it is pressed by an elastic core. This results in high molding precision, and even when it has fittings or threads, a highly accurate structure can be obtained. Therefore, molten metal flows smoothly through the structure connected by these fittings or threads. Furthermore, the thermal shrinkage of the main body 20 during casting is less than 5%, so leakage of molten metal due to cracks or deformation of the structure can be easily prevented.

[0120] The obtained intermediate compact can be further partially or entirely impregnated with a first binder. On the other hand, if the first binder is impregnated into the intermediate compact but not contained in the raw material slurry, the processing of the raw material slurry and white water becomes easier. When a thermosetting binder is used as the first binder, the intermediate compact is heated and dried at a predetermined temperature to thermally cure the thermosetting binder, thereby completing the production of the main body 20.

[0121] While the present invention has been described above based on its preferred embodiments and implementations, the present invention is not limited to the above-described embodiments and implementations. The above-described embodiments and their modifications can be combined as long as the contents thereof are not contradictory. For example, the casting structure of the present invention may have both the outer surface coating layer 32 of the female fitting portion 12 and the outer surface coating layer 36 of the male fitting portion 13.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0123] Example 1 The structure 1 shown in Fig. 9 was manufactured by the manufacturing method described above to provide a structure for casting of Example 1. The configuration of the structure for casting of Example 1 is as shown in Table 1 and below. Specifically, the coating layer was blended with 100 parts by mass of zircon, 1.25 parts by mass of attapulgite, and 5 parts by mass of colloidal silica. The main body was blended with 100 parts by mass of all components in total, with 10.2 parts by mass of recycled newspaper, 8.5 parts by mass of carbon fiber, 66 parts by mass of spherical silica, and 15.3 parts by mass of phenolic resin. Zircon: Zircosil No. manufactured by Hakusui Tech Co., Ltd. 1 Attapulgite: Attagel 50 manufactured by Hayashi Kasei Co., Ltd. Colloidal silica: Snowtex 50 manufactured by Nissan Chemical Industries, Ltd. Carbon fiber: Torayca chopped fiber manufactured by Toray Industries, Inc. Spherical silica: S85-P manufactured by Micron Co., Ltd. Phenolic resin: Bellpearl S890 manufactured by Air Water Performance Chemicals Inc. The inner diameter of the male fitting portion was 99.4 mm and the outer diameter was 102.4 mm. The thickness T2 of the female fitting portion inner surface coating layer was 0.1 mm, the thickness T3 of the trunk inner surface coating layer was 0.3 mm, and the thickness T1 of the overlapping portion of the female fitting portion inner surface coating layer and the trunk inner surface coating layer was 0.4 mm.

[0124] 1 was produced by the above-described production method to provide a structure for casting of Example 2. In the female fitting portion coating step, the coating composition 70 was applied to the outer surface of the female fitting portion 12 with a brush or the like, thereby coating the outer surface of the female fitting portion 12 with the coating composition 70. The composition of the structure for casting of Example 2 was the same as that of the structure for casting of Example 1.

[0125] Comparative Example 1 A structure for casting was produced in the same manner as in Example 1, except that the female fitting portion coating step was not carried out.

[0126]

[0127] [Evaluation of the Presence or Absence of Molten Metal Oozing During Pouring] For each of the casting structures of Example 1 and Comparative Example 1, the casting structures were connected to form a cylindrical body. Molten metal was then poured into a sand mold having each cylindrical body as a runner to produce a casting. 5t of carbon cast steel SC450 (JIS classification) was used as the molten metal. The surfaces of each cylindrical body remaining after solidification of the molten metal were visually observed, and cross sections of the fitting portions were observed. A cylindrical body in which the molten metal did not ooze out and the metal inside the sand mold was separated was evaluated as "no oozing." A cylindrical body in which the molten metal oozed out and some of the molding sand in the sand mold was burned was evaluated as "oozed."

[0128] As shown in Table 1, seepage of the molten metal occurred in Comparative Example 1. In contrast, seepage of the molten metal did not occur in Example 1. Therefore, it is clear that the structure for casting of the present invention can suppress burn-on due to seepage from the fitting portion.

[0129] According to the structure for casting of the present invention, it is possible to prevent oozing of molten metal during pouring. According to the method for manufacturing a structure for casting of the present invention, it is possible to efficiently manufacture a structure for casting that can prevent oozing of molten metal during pouring.

Claims

1. A cylindrical casting structure comprising a cylindrical main body having a trunk and a female fitting portion connected to the trunk and having an inner diameter equal to or greater than the outer diameter of the trunk, a trunk inner surface coating layer that coats the inner surface of the trunk, and an outer surface coating layer that coats the outer surface of the female fitting portion.

2. The structure for casting production according to claim 1, wherein the outer surface coating layer covers the entire outer surface of the female fitting portion.

3. A structure for casting according to claim 1 or 2, further comprising a female fitting portion inner surface coating layer for coating the inner surface of the female fitting portion.

4. The structure for casting according to claim 3, wherein the female fitting portion inner surface coating layer and the body portion inner surface coating layer are continuous.

5. A structure for casting according to claim 3, wherein the female fitting portion inner surface coating layer extends to the inner surface of the body portion and partially overlaps the body portion inner surface coating layer.

6. A structure for manufacturing castings as described in claim 5, wherein in the portion where the female fitting portion inner surface coating layer and the body portion inner surface coating layer overlap, the female fitting portion inner surface coating layer is arranged radially inward of the structure for manufacturing castings relative to the body portion inner surface coating layer.

7. A structure for casting production as described in claim 5 or 6, wherein the thickness of the portion where the female fitting portion inner surface coating layer and the body portion inner surface coating layer overlap is greater than both the thickness of the thickest portion of the female fitting portion inner surface coating layer and the thickness of the thickest portion of the body portion inner surface coating layer.

8. A structure for casting production as described in any one of claims 3 to 7, wherein the female fitting portion inner surface coating layer covers the entire inner surface of the female fitting portion, and the body portion inner surface coating layer covers the entire inner surface of the body.

9. A structure for casting manufacturing described in any one of claims 3 to 8, wherein the female fitting portion inner surface coating layer and the outer surface coating layer have the same edge position on the base end side in the direction in which the female fitting portion is connected.

10. A structure for casting production according to any one of claims 1 to 9, further comprising an end face covering portion that covers an end face of the female fitting portion.

11. A structure for casting production as described in any one of claims 1 to 10, comprising a female fitting portion inner surface coating layer that coats the inner surface of the female fitting portion, and an end face coating portion that coats the end face of the female fitting portion, the end face coating portion and the female fitting portion inner surface coating layer being continuous.

12. A structure for casting production according to any one of claims 1 to 11, wherein the outer surface coating layer extends through an end face of the female fitting portion to an inner surface of the body portion.

13. A structure for casting production according to any one of claims 1 to 12, further comprising a female fitting portion inner surface coating layer that coats the inner surface of the female fitting portion, the female fitting portion inner surface coating layer being thinner than coating layers other than the female fitting portion inner surface coating layer.

14. A structure for casting manufacturing according to any one of claims 1 to 13, wherein the outer diameter of the end of the structure for casting manufacturing other than the female fitting portion is equal to or smaller than the inner diameter of the female fitting portion.

15. A structure for use in casting as described in claim 14, wherein the outer diameter of the female fitting portion is the largest among the outer diameters of the structure for use in casting, and the inner diameter of the female fitting portion is the largest among the inner diameters of the structure for use in casting.

16. A structure for casting according to any one of claims 1 to 15, wherein the inner diameter of the end of the structure for casting other than the female fitting portion is 100 mm or more.

17. A cylindrical casting manufacturing structure comprising: a cylindrical main body portion at one end of a body portion having a male fitting portion that is fitted into a female fitting portion, the outer diameter of the male fitting portion being equal to or smaller than the inner diameter of the female fitting portion; a body inner surface coating layer that covers the inner surface of the body portion; and an outer surface coating layer that covers the outer surface of the male fitting portion.

18. The structure for casting according to claim 17, further comprising an end face covering portion for covering an end face of the male fitting portion.

19. The structure for casting production according to claim 18, wherein the end surface coating portion and the outer surface coating layer are continuous.

20. A structure for manufacturing castings as described in any one of claims 17 to 19, wherein the main body portion has a female fitting portion connected to the trunk portion and an inner diameter equal to or greater than the outer diameter of the trunk portion, and the outer diameter of the male fitting portion is equal to or less than the inner diameter of the female fitting portion connected to the trunk portion.

21. A structure for use in casting as described in claim 20, wherein the outer diameter of the female fitting portion is the largest among the outer diameters of the structure for use in casting, and the inner diameter of the female fitting portion is the largest among the inner diameters of the structure for use in casting.

22. A structure for casting production according to any one of claims 17 to 21, wherein the body inner surface coating layer covers the entire inner surface of the body.

23. A structure for casting production according to any one of claims 17 to 22, wherein the inner diameter of the male fitting portion is 45 mm or more and 700 mm or less, preferably 65 mm or more and 550 mm or less, and more preferably 90 mm or more and 350 mm or less.

24. A structure for casting production according to any one of claims 1 to 23, wherein the barrel inner surface coating layer is arranged on the radially innermost side of the structure for casting production in the portion where the barrel inner surface coating layer is arranged.

25. A structure for casting production according to any one of claims 1 to 24, wherein the outer surface coating layer is disposed on the radially outermost side of the structure for casting production.

26. A structure for casting production according to any one of claims 1 to 25, wherein the main body portion has a single-layer structure.

27. A structure for casting manufacturing according to any one of claims 1 to 26, wherein the main body portion is integrally formed in the circumferential direction of the main body portion.

28. A structure for casting production according to any one of claims 1 to 27, further comprising a barrel outer surface coating layer that coats the outer surface of the barrel.

29. A structure for casting according to claim 28, wherein the body outer surface coating layer is continuous over the entire circumferential circumference of the structure for casting.

30. A method for manufacturing a cylindrical structure for use in casting, the structure for casting comprising a cylindrical main body having a trunk and a female fitting portion connected to the trunk in the axial direction and having an inner diameter equal to or greater than the outer diameter of the trunk, the method comprising: a trunk coating process for applying a coating liquid to the inner surface of the trunk to form a trunk inner surface coating layer that covers the inner surface of the trunk; and a female fitting coating process for applying a coating liquid to the outer surface of the female fitting portion around the entire circumference of the female fitting portion to form an outer surface coating layer that covers the outer surface of the female fitting portion.

31. A method for manufacturing a structure for casting production as described in claim 30, wherein in the body coating process, the coating liquid is applied by injecting the coating liquid into the body from an end side of the body other than the end side of the female fitting portion.

32. A method for manufacturing a structure for casting production as described in claim 30 or 31, wherein in the female fitting portion coating process, a coating liquid is applied to the inner surface of the female fitting portion around the entire circumference of the female fitting portion, thereby forming a female fitting portion inner surface coating layer that covers the inner surface of the female fitting portion.

33. A method for manufacturing a structure for casting production as set forth in claim 32, wherein in the female fitting portion coating step, the coating liquid is applied by immersing the female fitting portion in the coating liquid.

34. A method for manufacturing a structure for casting according to any one of claims 30 to 33, wherein the female fitting portion coating step is carried out after the body portion coating step.

35. A method for using a structure for casting production according to any one of claims 1 to 29 as a runner or lift runner in casting cast steel.

36. A method for manufacturing a mold for casting steel, comprising the step of embedding the structure for manufacturing castings according to any one of claims 1 to 29 in molding sand, leaving only some of the openings of the structure for manufacturing castings.

37. A method for producing steel castings, comprising: a mold production step of embedding a structure for producing castings according to any one of claims 1 to 29 in molding sand, leaving only some of the openings of the structure for producing castings, to produce a mold; and a casting step of pouring molten metal into the mold.

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