Casting production structure

Abstract

A cylindrical production structure for a casting (1) is provided with: a cylindrical main body (20) having a body portion (11) and a female joint (12) connected consecutively to the body portion (11) and having an internal diameter greater than an external diameter of the body portion (11); wherein an inner body covering layer (31) covering the inner face of the body portion (11) and an outer covering layer (32) covering an external face of the female joint (12) are provided. The outer covering layer (32) preferably covers the entire region of the external face of the female joint (12).

Description

Title of the invention: Casting production structure

[0001] Technical domain The present invention relates to a production structure for a casting.

[0002] Prior art In the production of castings, a mold with an internal cavity is typically formed using casting sand. A receiving orifice, a pouring spout, a pouring channel, and a grid are formed to supply molten metal to the cavity. Additionally, a gas vent, a riser, and a pressure regulator are formed to communicate with the cavity. A core is sometimes arranged inside the cavity. The applicant has previously proposed casting production structures usable as a pouring channel or pressure regulator (Patent Literatures 1 and 2). The casting production structure described in each of Patent Literatures 1 and 2 has a cylindrical main body and a covering layer formed on the inner face of the main body. Patent literature 3 describes a casting channel obtained by fixing refractories to the inner or outer face of a paper tube.

[0003] List of citations Patent literature Literature Exam 1: JP 2021-70052 A Literature Exam 2: JP 2012-24841 A Literature Brevet 3: JP 1981-34834 Y

[0004] Summary of the invention The present invention relates to a cylindrical structure for the production of a casting. In one embodiment, it is preferable that a main cylindrical body is provided, which has a body part and a female joint connected consecutively to the body part and having an internal diameter equal to or greater than the external diameter of the body part. In one embodiment, it is preferable that an inner body cover layer covering the inner face of the body part and an outer cover layer covering the outer face of the female joint are provided. In one embodiment, it is preferable that an internal diameter of an end portion of the production structure of a casting other than the female joint is 100 mm or more.

[0005] In one embodiment, it is preferable that a cylindrical main body be provided, which has a body portion and a male joint, which is to be joined internally to the female joint, in an end portion of the body portion. In one embodiment, it is preferable that the male joint have an external diameter equal to or less than the internal diameter of the female joint. In one embodiment, it is preferable that an inner body cover layer covering the inner face of the body part and an outer cover layer covering the outer face of the male joint are provided.

[0006] The present invention also relates to a method for producing a cylindrical structure for producing a casting. In one aspect, it is preferable that the production structure of a casting be provided with a cylindrical main body having a body part and a female joint consecutively connected to the body part and having an internal diameter equal to or greater than the external diameter of the body part. In one aspect, it is preferable that a body part application step be provided, in which a coating composition is applied to the inner face of the body part to form an inner body cover layer covering the inner face of the body part. In one aspect, it is preferable that a female joint application step be provided, in which a coating composition is applied to the outer face of the female joint over the entire circumference of the female joint to form an outer covering layer covering the outer face of the female joint.

[0007] Brief description of the drawings [Fig.1] Fig.1 is a perspective view schematically showing a preferred embodiment of a production structure for a casting according to the present invention. [Fig.2] Fig.2(a) is a cross-sectional view along line lia-lia of [Fig.1], Fig.2(b) is a cross-sectional view along line Ilb-IIb of [Fig.1], and Fig.2(c) is a cross-sectional view along line IIc-IIc of [Fig.1]. [Fig.3] The [Fig.3] is a perspective view schematically showing a state in which the production structures of a casting shown on the [Fig.1] are coupled together. [Fig.4] The [Fig.4] is an enlarged cross-sectional view of a main part of the [Fig.3]. [Fig.5] The [Fig.5] is a schematic cross-sectional view of a mold housing the production structure of a casting shown in [Fig.1] inside. [Fig.6] [Fig.6](a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to [Fig.2](a), [Fig.6](b) is an enlarged cross-sectional view of a main part schematically showing a state in which the production structures of a casting shown in [Fig.6](a) are coupled to each other, and is an equivalent view to [Fig.4]. [Fig.7] [Fig.7](a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to [Fig.2](a), [Fig.7](b) is an enlarged cross-sectional view of a main part schematically showing a state in which the production structures of a casting shown in [Fig.7](a) are coupled to each other, and is an equivalent view to [Fig.4]. [Fig.8] Fig.8(a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to Fig.2(a). Fig.8(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the production structures of a casting shown in Fig.8(a) are coupled to each other, and is an equivalent view to Fig.4. [Fig.9] Fig.9(a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to Fig.2(a). Fig.9(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the production structures of a casting shown in Fig.9(a) are coupled to each other, and is an equivalent view to Fig.4. [Fig. 10] [Fig.10](a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to [Fig.2](a), [Fig.10](b) is an enlarged cross-sectional view of a main part schematically showing a state in which the production structures of a casting shown in [Fig.9](a) are coupled to each other, and is an equivalent view to [Fig.4]. [Fig.l 1] The [Fig.l 1] is an enlarged cross-sectional view of a main part schematically showing another preferable embodiment of the production structure of a casting according to the present invention. [Fig. 12] The [Fig. 12] is a perspective view schematically showing another preferable embodiment of the production structure of a casting according to the present invention, and is an equivalent view to the [Fig. 1]. [Fig. 13] The [Fig.13](a) is a cross-sectional view along line XlIIa-XIIIa of [Fig. 12], and the [Fig.13](b) is a cross-sectional view along line XlIIb-XIIIb of [Fig.12]. [Fig. 14] The [Fig. 14] is a perspective view schematically showing a state in which the production structures of a casting shown on the [Fig. 12] are coupled to each other, and is an equivalent view to the [Fig.3]. [Fig. 15] The [Fig. 15] is an enlarged cross-sectional view of a main part of the [Fig. 14], [Fig. 16] [Fig.16](a) is a schematic cross-sectional view showing another preferred embodiment of the production structure of a casting according to the present invention, and is an equivalent view to [Fig.13](a), [Fig.16](b) is an enlarged cross-sectional view of a main part schematically showing a state in which the production structures of a casting shown on [Fig.16](a) are coupled to each other, and is an equivalent view to [Fig. 15]. [Fig. 17] Figures 17(a) to 17(d) are perspective views schematically showing modifications to the production structure of a casting according to the present invention, and is an equivalent view to [Fig.2](a). [Fig. 18] Figures 18(a) to 18(e) are schematic cross-sectional views explaining a preferable aspect of a production process for a production structure of a casting according to the present invention. [Fig. 19] Figures 19(a) to 19(e) are schematic cross-sectional views explaining modifications to a preferable aspect of the production process of a production structure for a casting according to the present invention.

[0008] Description of embodiments A casting production structure described in patent literature 1 includes a cylindrical body portion and a joint connected to the body portion. Regarding the casting production structure described in the same literature, two or more casting production structures can be coupled together by inserting an end portion on the far side of a joint into the body portion of one of the adjacent casting production structures, and then inserting this joint into the joint of the other casting production structure.The production structure of a casting described in the same literature is designed to eliminate peeling of the cover layers during the pouring of molten metal in a section where adjacent structures are joined. This is achieved by ensuring that the internal diameter of one end portion of the body portion is 1.0 mm smaller than the internal diameter of the other end portion. However, the production structure of a casting has room for improvement in the event of molten metal leaking outwards. of the casting production structure when the molten metal pressure inside the casting production structure is high during the pouring process. Molten metal leakage is particularly likely to occur in a section where adjacent casting production structures are joined. The casting production structure described in patent literature also has a similar scope for improvement. The patent literature 3 describes nothing about the use of a plurality of cylindrical casting production structures joined together as a casting channel, and considers nothing about preventing leakage of molten metal in a portion where adjacent casting production structures are joined together. The present invention relates to a production structure for a casting adapted to prevent leakage of molten metal during the pouring of molten metal.

[0009] The present invention is described below on the basis of preferred embodiments thereof. Fig. 1 represents a production structure for a casting (hereafter also simply referred to as "structure") 1 according to a first preferred embodiment of the production structure for a casting of the present invention. Structure 1 is typically cylindrical. The term "cylindrical" used here includes one that is straight, as shown in [Fig. 1], one that has a curved portion 17 in the axial direction, as shown in [Fig. 17](a), one in which the entire structure in the axial direction is curved in an arc shape, as shown in [Fig. 17](b), one that has a second cylindrical portion 19 branching off from a first cylindrical portion 18, as shown in Figures 17(c) and 17(d), and similar structures. Furthermore, the term "cylindrical" includes not only a cylindrical shape with a circular cross-section, i.e., a circular cylindrical shape, but also a cylindrical shape with a polygonal cross-section, i.e., a square cylindrical shape. The cross-section of a circular cylindrical structure orthogonal to the axial direction is typically circular, and can also be oval.The cross-sectional shape orthogonal to the axial direction of a square cylindrical structure is typically a square shape, and can also be a triangular shape, a rectangular shape, or a polygonal shape of a pentagonal or more, or can be a shape in which the corners of the polygon are rounded.

[0010] Structure 1 has a cylindrical main body 20. The main body 20 typically contains organic fibers, inorganic fibers, inorganic particles, and a binder. Each component contained in the main body 20 is described further on. The main body 20 is a constituent portion of a main part of structure 1. The main body 20 preferably has a body part 11 and a female joint 12 connected consecutively to the body part 11 and having an internal diameter equal to or greater than the external diameter of the body part 11. The female joint 12 can be formed at one end 1a in the axial direction of the body part 11. This example is shown in [Fig. 2]. In an example of the structure 1 shown in [Fig. 2], the main body 20 preferably has a larger internal diameter at one end 1a in an axial direction Z than at the other end 1b.

[0011] The female joint 12 can be formed to bifurcate from the body part 11. This example is shown in [Fig. 17](d). In an example of structure 1 shown in [Fig. 17](d), the internal diameters of the end portions I and Id other than the female joint 12 in structure 1 are preferably equal to or less than the internal diameter of the female joint 12. In an example of structure 1 shown in [Fig. 17](d), the internal diameter of the end portion I of structure 1 and the internal diameter of the end portion Id of structure 1 may be the same or different. Only the internal diameter of either the end portion I and the end portion Id of structure 1 may be equal to or less than the internal diameter of the female joint 12.

[0012] The female joint 12 preferably has both the internal and external diameters greater than those of the body part 11. In an example of the structure 1 shown in [Fig.2], an end part of the side la an end la in the axial direction Z in the body part 11 is formed with a step part 15 projecting outwards in the radial direction of the body part 11, and the female joint 12 is connected consecutively to the body part 11 via the step part 15.

[0013] As structure 1, it is preferable that several structures of the same type or of a similar type can be coupled to each other. In an example of structure 1 shown in [Fig.1], both ends in the axial direction Z in the main body 20 are open. An external diameter DI of an end part of the structure 1 other than the female joint 12 is preferably equal to or less than an internal diameter D2 of the female joint 12. In an example of the structure 1 shown in figures 1 and 2, the end part of the structure 1 other than the female joint 12 denotes an end part of the other end 1b opposite the end la in the axial direction Z in the body part 11. In an example of the structure 1 shown in [Fig. 17](d), the end portion of structure 1 other than the female joint 12 refers to the end portions I and Id of a first portion 18. When an external diameter DI1 of the end portion I of the first portion 18 differs from an external diameter D12 of the end portion Id of the first portion 18, the external diameter DI1 is the smaller of the external diameter DI1 and the external diameter D12. Only one of the external diameter DI1 of the end portion I of the first portion 18 and the external diameter D12 of the end portion Id of the first portion 18 can be equal to or less than the internal diameter D2 of the female joint 12. Both the external diameter DI1 and the external diameter D12 are more preferably equal to or less than the internal diameter D2 of the female joint 12. In the patent memorandum of this application, the internal diameter and external diameter refer to the internal and external diameters of the entire structure 1, including both the main body and the covering layers overlying the surfaces of the main body, unless otherwise specified.

[0014] The structure 1 is preferably configured so that the structures 1 can be coupled together by inserting and joining the end portion of the structure 1 other than the female joint 12 to the female joint 12 of the other structure 1. By coupling a desired number of the structures 1, a long cylindrical body 10 having a desired length can be formed (see [Fig. 3]). The end portion of structure 1, other than the female joint 12, preferably serves as a male joint 13 joined internally to the female joint having an internal diameter equal to or greater than the external diameter of the body portion 11. In an example of structure 1 shown in [Fig. 17](d), only one of the external diameter DI 1 of the end portion le of the first part 18 and of the end portion Id of the first part 18 can serve as a male joint 13. Both the end portion le and the end portion Id more preferably serve as male joints 13.

[0015] The male joint 13 designates a portion inserted into the female joint 12 when the end portion of structure 1, other than the female joint 12, is joined internally to the female joint 12 of structure 1 of the same or a similar type.In detail, a length L1 of the male joint 13 is the same as a depth L2 of the female joint 12. Here, the term "same" means not only a case where the length L1 of the male joint 13 and the depth L2 of the female joint 12 are the same, but a case where the length L1 and the depth L2 are approximated to such an extent that the length L1 and the depth L2 are assumed to be substantially equal to each other. Specifically, when a ratio of the length L1 of the male joint 13 to the depth L2 of the female joint 12 is preferably 80% or more and 120% or more. 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 assumed to be the same. Examples of the length L1 and the depth L2 are shown in Figures 2(a) and 17(d). In an example of structure 1 shown in [Fig.2], the length L1 of the male joint 13 is the length of the male joint 13 along the axial direction Z of the body part 11. In an example of structure 1 shown in [Fig.17](d), the length L1 of the male joint 13 is the length of the male joint 13 along an axial direction Zx of a first part 18.

[0016] In an example of the structure 1 shown in [Fig.2], a length L3 in the axial direction Z of the body part 11 is preferably longer than the depth L2 of the female joint 12. In an example of the structure 1 shown in [Fig.2], when the length L3 in the axial direction Z of the body part 11 is shorter than the depth L2 of the female joint 12 or when the length L3 of the body part 11 and the depth L2 of the female joint 12 are the same, the entire region of the body part 11 essentially serves as a male joint 13.

[0017] The structure 1 preferably has an inner covering layer 31 covering the inner face of the body part 11 and an outer covering layer 32 covering the outer face of the female joint 12 (hereinafter also referred to as the "outer covering layer of the female joint"). This example is shown in [Fig.2](a). The inner body coating layer 31 and the outer coating layer 32 preferably contain refractory inorganic particles selected from the group consisting of metal oxides and metal silicates, a binder, and clay minerals. Each component contained in the two coating layers 31 and 32 is described later.

[0018] The inner covering layer of body 31 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. This example is shown in [Fig.2](b). In addition, the inner covering layer of body 31 is preferably continuous over the entire region of the body part 11 in the axial direction Z. More specifically, the inner covering layer of body 31 preferably covers the entire region of the inner face of the body part 11. This example is shown in [Fig.2](a).

[0019] Due to the flow of high-temperature molten metal in structure 1, gas is generated from the casting sand when the organic fibers, binder, and similar substances contained in the main body 20 are thermally decomposed. Structure 1 has an inner body covering layer 31, and can therefore prevent the entry of gas in structure 1. It is therefore difficult for the gas to mix with the molten metal flowing into structure 1. From the point of view of presenting this effect more remarkably, the inner covering layer of body 31 is preferably continuous over the entire circumference in the circumferential direction of structure 1 and more preferentially covers the entire region of the inner face of the body part 11.

[0020] The outer covering layer 32 of the female joint 12 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. This example is shown in [Fig.2](c). The outer covering layer 32 is preferably continuous over the entire region of the outer face of the female joint 12 in the axial direction Z. More specifically, the outer covering layer 32 preferably covers the entire region of the outer face of the female joint 12. This example is shown in [Fig.2](a).

[0021] Structure 1 can be used to produce a casting as follows, for example. First, the structures 1 are coupled together to form the cylindrical body 10. Then, as shown in [Fig. 5], the cylindrical body 10 is embedded in a predetermined position within casting sand to form a mold 40. In the example shown in [Fig. 5], the mold 40 is a sand mold. The structure is typically embedded, leaving some of its opening exposed. Specifically, the structure 1 positioned on the upstream side among the plurality of structures 1 coupled together to form the cylindrical body 10 is preferably embedded in such a way that the opening on the upstream side is exposed outside the casting sand. There are no particular limitations on a method of coating the cylindrical body 10; for example, casting sand may be arranged after the cylindrical body 10 is arranged in a predetermined position or the cylindrical body 10 may be arranged after casting sand is arranged in a predetermined position. For the casting sand of the sand mold 40, the common casting sand that has been classically used to produce the casting of this type is usable without limitations.

[0022] Next, molten metal is poured into the mold 40 for casting. Specifically, the molten metal is poured from a pouring hole 41 provided at one end of the cylindrical body 10, and the molten metal is brought into a cavity 42 for casting. At this point, the heat resistance is maintained and the thermal shrinkage due to thermal decomposition is low in the structure 1. Therefore, cracks in each structure 1 and damage to the structure 1 itself are prevented. and the insertion of molten metal into structure 1 or the adhesion of casting sand or similar to structure 1 also occurs with difficulty. After casting, the temperature is lowered to a predetermined level, the casting sand is removed by dismantling a frame, and the casting's production structure is removed by sandblasting, exposing the casting. The casting then undergoes post-processing, such as deburring, as needed, to finalize its production. Structure 1 is used appropriately as a pouring channel or depressurizer pouring channel used for casting, for example. Furthermore, structure 1 is particularly well-suited for use as a pouring channel or pressure-reducing channel in the production of cast steel. This is because cast steel has a higher melting point than pig iron, and consequently, the molten metal temperature during pouring is high, and the kinematic viscosity is likely to be lower.

[0023] Structure 1 has the outer covering layer 32 of the female joint 12, and can thus prevent leakage during the pouring of molten metal. This point is described in detail below. When structures 1 are coupled together, it is difficult to bring an end face 1 of the end portion other than the female joint 12 into a structure 1; that is, the end face 1 of the male joint 13 of one structure 1 and an end face 12e arranged inside the female joint 12 of the other structure 1 into close contact without any gap. Consequently, a gap is sometimes generated between the end face 1 of one structure 1 and the end face 12e of the other structure 1 (see [Fig. 4]). In the example shown in the figure, the end face 12e of the female joint 12 is the upper surface 12e of the tread portion 15. During the pouring of molten metal, the molten metal entering the gap comes into contact with a corner portion formed by an internal circumferential surface 12a of the female joint 12 and the upper surface 12e of the tread portion 15 (hereafter also referred to as the "corner portion of the female joint"). This sometimes damages the corner portion, leading to the formation of a pore through the female joint 12. The molten metal flowing into the structure 1 presents a risk of leakage to the outside of the structure 1 through such a pore. However, by covering the outer face of the female joint 12 with the outer covering layer 32, the molten metal can be prevented from passing through the female joint 12 and leaking out of the structure 1. The outer covering layer 32 covers the outer face of the female joint 12 as described above, and therefore presents no risk of peeling when the male joint 13 is attached to the female joint 12. Consequently, the effect of preventing molten metal leakage can be reliably ensured. To more effectively prevent molten metal leakage, an inner covering layer 33 covering the inner face of the female joint 12 is preferably provided in addition to the outer covering layer 32. The inner covering layer 33 is described later.

[0024] When the molten metal leaks out of structure 1, it comes into contact with the casting sand, leading to metal penetration in which the casting sand is mixed with the molten metal. Generally, during the production of the casting, a portion of the product is obtained by solidifying the molten metal in the cavity of the sand mold, and a non-product portion is obtained by solidifying the molten metal inside a casting channel pipe. By eliminating the mixing of casting sand with the molten metal, the non-product portion can be easily reused. Furthermore, a step of removing casting sand from the molten metal obtained by remelting the non-product portion can be omitted, and consequently, the cost can be reduced, and the quality of the molten metal obtained by remelting the non-product portion can be stabilized.

[0025] The effect of preventing leakage of molten metal from structure 1 during pouring is more remarkably achieved when the internal diameter D3 of the body portion 11 in structure 1 is large. In general, leakage of molten metal during pouring is likely to occur when the molten metal in structure 1 is under high pressure. When the cavity 42 of the mold 40 used for the casting is large, the quantity of molten metal to be poured becomes large. To prevent a decrease in the temperature of a large quantity of the molten metal during pouring, it is preferable that the structure 1 constituting the cylindrical body 10 embedded in the mold 40 is a structure in which the internal diameter D3 of the body portion 11 is large, capable of increasing the flow rate of the molten metal to be poured.When the cavity 42 is large, the mold 40 also becomes large in relation to this, and therefore the vertical height of the cylindrical body 10 is likely to be large. Consequently, when the internal diameter D3 of the body part 11 in structure 1 is large, structure 1 is used in conditions where the molten metal pressure is high in many cases. Specifically, when the internal diameter D3 of the other end part on the opposite side to the end in the axial direction Z in the body part 11, i.e., the male joint 13, is 45 mm or more, it is assumed that structure 1 is used in conditions where the molten metal is under high pressure. Structure 1 of the present invention can prevent leakage of molten metal during pouring of molten metal, even when the internal diameter D3 of the part of The body 11 in structure 1 is large, and the pressure of the molten metal in the body part 11 is high. To more effectively demonstrate the effect of preventing molten metal leakage during pouring, the internal diameter D3 of the male joint 13 is preferably 65 mm or more, and more preferably 90 mm or more. Furthermore, from the point of view of handling properties, the internal diameter D3 of the male joint 13 is preferably 700 mm or less, more preferably 550 mm or less, and even more preferably 350 mm or less.

[0026] The outer covering layer 32 of the female joint 12 may be discontinuous in the circumferential direction of the structure 1. However, from the point of view of effectively preventing leakage of molten metal, the outer covering layer 32 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. Furthermore, the outer covering layer 32 of the female joint 12 may only cover a part of the outer face of the female joint 12 in the axial direction Z. However, from the point of view of effectively preventing leakage of molten metal, the outer covering layer 32 preferably covers the entire region of the outer face of the female joint 12 in the axial direction Z. It is more preferable that the outer covering layer 32 be continuous around the circumference in the circumferential direction of the structure 1 and cover the entire region of the outer face of the female joint 12 in the axial direction Z. In other words, the outer covering layer 32 more preferentially covers the entire region of the outer face of the female joint 12.

[0027] In structure 1, the external diameter DI of the end portion of structure 1 other than the female joint 12 is preferably equal to or less than the internal diameter D2 of the female joint 12 as described above. This facilitates the insertion of the end portion of structure 1 other than the female joint 12 into the female joint 12 of the other structure 1, and thus the two structures can be easily joined together. From the point of view of considerably facilitating the insertion of the end part 13 of the structure 1 other than the female joint 12, i.e. the male joint 13 of the structure 1, into the female joint 12 of the other structure 1, a ratio D1 / D2 between the external diameter DI and the internal diameter D2 is preferably 1 or less, more preferably 0.9999 or less, and even more preferably 0.9995 or less. Furthermore, from the point of view of preventing the space between the external face of the male joint 13 and the internal face of the female joint 12 from becoming excessively large and of further stabilizing the junction state between them when the male joint 13 of structure 1 and the female joint 12 of the other structure 1 are joined together, 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 point of view of obtaining both, the D2 / D1 ratio 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] In structure 1, an external diameter D4 of the female joint 12 is preferably the largest among the external diameters of structure 1. Thus, when the molten metal is poured in the state where the plurality of structures 1 are coupled to each other, the flow of the molten metal can be smoothed. Furthermore, in structure 1, the internal diameter D2 of the female joint 12 is preferably the largest among the internal diameters of structure 1. Thus, when the molten metal is poured in the state where the plurality of structures 1 are coupled to each other, the flow of the molten metal can be smoothed.

[0029] Next, structures 1 of the second to ninth preferred embodiments of the present invention are described. The second to ninth embodiments are described with respect to the points different from the first embodiment, and the description of the first embodiment is applied as appropriate to the points that are not specifically described.

[0030] Fig. 6 shows structure 1 of the second embodiment. Structure 1 preferably has the inner cover layer of the female joint 33 covering the inner face of the female joint 12. The inner face of the female joint 12 includes the inner circumferential surface 12a of the female joint 12 and the upper surface 12e of the walking part 15. The inner covering layer of the female joint 33 preferably covers both the inner circumferential surface 12a and the upper surface 12e. In other words, the inner covering layer of the female joint 33 covers the entire region of the inner face of the female joint 12. This example is shown in [Fig. 6].

[0031] Structure 1 has the inner cover layer of the female joint 33, and can therefore more effectively prevent leakage of molten metal during pouring. This point is described in detail below. When structures 1 are coupled to each other, a gap is sometimes generated between the end face of one structure 1 and the end face 12e arranged inside the other structure 1, as described above. Since the internal cover layer of the female joint 33 is provided, this gap can be made smaller and therefore more difficult to generate. Furthermore, even when the gap is created and the molten metal enters the gap, the female joint 12 can be protected. This is because the inner face of the female joint 12, in particular the inner face of the corner portion of the female joint, is covered by the inner female joint cover layer 33. This example is shown in [Fig. 6].

[0032] Molten metal entering the gap may penetrate between the outer circumferential surface of the male joint 13 of one structure 1 and the inner circumferential surface 12a of the female joint 12 of the other structure 1. However, the inner circumferential surface 12a of the female joint 12 is also covered by the inner covering layer of the female joint 33, and therefore this entry can also be prevented. Indeed, the inner covering layer of the female joint 33 is arranged between the outer circumferential surface of the male joint 13 of one structure 1 and the inner circumferential surface 12a of the female joint 12 of the other structure 1. Even when molten metal penetrates between the two surfaces, the female joint 12 can be protected. This is because the internal circumferential surface 12a of the female joint 12 is covered by the internal female joint cover layer 33. This example is shown in [Fig. 6].

[0033] The structure 1 preferably has not only the inner covering layer of the female joint 33 but also the outer covering layer 32 of the female joint 12. More specifically, the inner and outer faces of the female joint 12 are preferably covered. This also helps to more effectively prevent molten metal from leaking out of the structure 1 during the pouring of the molten metal.

[0034] From the point of view of presenting more remarkably the protective effect of the female joint 12, the inner covering layer of the female joint 33 is preferably continuous over the entire circumference in the circumferential direction of the structure 1 and more preferably covers the entire region of the inner face of the female joint 12.

[0035] The inner cover layer of the female joint 33 and the inner cover layer of the body 31 are preferably continuous. This allows the inner faces of the female joint 12 and the body part 11 to be protected without any gaps. The inner cover layer of the female joint 33 and the inner cover layer of the body 31 may be discontinuous. For example, the inner cover layer of the female joint 33 and the inner cover layer of the body 31 may be separate bodies.

[0036] The entire region of the inner face of the main body 20 is more preferentially covered by the inner cover layer of the female joint 33 and by the inner cover layer of the body 31. This makes it possible to protect the entire region of the inner face of the main body 20, and thus to more effectively prevent the leakage of molten metal during the pouring of molten metal.

[0037] Figure 7 shows structure 1 of the third embodiment. The structure 1 preferably has an end face cover portion 34 covering the outermost end face of the structure 1 in the female joint 12 (hereafter also referred to as the "end face cover portion of the female joint"). The end face cover portion 34 may cover only part of the end face of the female joint 12 or may cover the entire end face region.

[0038] The end face cover portion 34 of the female joint 12 is provided, and thus leakage of molten metal from structure 1 during molten metal pouring can be more effectively prevented. This point is described in detail below. When the structures 1 are coupled together, molten metal sometimes enters the gap between the end face 1 of one structure 1 and the end face 12 of the other structure 1, as described above. Then, molten metal sometimes enters between the inner face of the female joint 12 of one structure 1 and the outer face of the male joint 13 of the other structure 1. Then, the molten metal presents a risk of leakage outward from structure 1 from the end face of one structure 1, that is, the end face of the female joint 12 of one structure 1.However, leakage of molten metal from the end face side of the female joint 12 of structure 1 to the outside of structure 1 can be prevented by covering the end face of the female joint 12 with the end face cover part 34. From the point of view of presenting this effect more remarkably, the end face cover part 34 is preferably continuous over the entire circumference in the circumferential direction of the structure 1, and more preferentially covers the entire region of the end face of the female joint 12.

[0039] In the structure 1 having the outer covering layer 32 of the female joint 12, the outer covering layer 32 and the end face covering portion 34 of the female joint 12 may be discontinuous. However, from the point of view of more effectively preventing leakage of molten metal during pouring, the outer covering layer 32 and the end face covering portion 34 are preferably continuous, and preferably molded integrally.

[0040] Figure [Fig.8] shows structure 1 of the fourth embodiment. Structure 1 preferably has an outer covering layer of body 35 covering the outside of the body part 11. In addition, structure 1 preferably has the inner body cover layer 31. In structure 1, both the inner and outer faces of body part 11 are more preferentially covered. This example is shown in [Fig. 8].

[0041] Structure 1 having an inner body cover layer 31 and an outer body cover layer 35, leakage of molten metal during pouring, particularly leakage of molten metal through body part 11, can be effectively prevented. For example, even when the molten metal in structure 1 is under high pressure, leakage of molten metal can be prevented. From the point of view of presenting this effect more remarkably, the outer covering layer of body 35 is preferably continuous over the entire circumference in the circumferential direction of structure 1.

[0042] In the structure 1 having the inner cover layer of the female joint 33, the inner cover layer of the female joint 33 and the inner cover layer of the body 31 are preferably continuous, and the two are more preferably molded together from the point of view of the protection of the female joint 12 and the inner face of the body part 11 without any gap.

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

[0044] The inner body cover layer 31 and the inner cover layer of the female joint 33 can be formed as separate bodies. In this case, it is preferable for the inner cover layer of the female joint 33 to extend to the inner face of the body part 11 and partially overlap. with the inner body cover layer 31. The inner cover layer of the female joint 33 partially overlaps the inner body cover layer 31, and thus the leakage of molten metal from the interface between the inner body cover layer 31 and the inner cover layer of the female joint 33, which are formed as separate bodies, can be suppressed. This example is shown in [Fig. 9].

[0045] When the inner cover layer of the female joint 33 partially overlaps the inner cover layer of the body 31, either one can be positioned on the inner side in the radial direction of the structure 1. However, the inner cover layer of the female joint 33 is preferably positioned on the inner side in the radial direction of the structure 1 relative to the inner cover layer of the body 31.By setting the position relationship between the inner cover layer of the female joint 33 and the inner cover layer of the body 31 to such a position relationship, the molten metal flowing into the structure 1 from one end side la to the other end side 1b can be prevented from colliding with the end part of the one end side la in the inner cover layer of the body 31, which prevents the inner cover layer of the body 31 from peeling with the end part of the one end side la as the starting point when pouring the molten metal.

[0046] When the inner cover layer of the female joint 33 partially overlaps the inner cover layer of the body 31, a thickness T1 of a portion where the two overlap is preferably greater than both the thickness of the portion having the greatest thickness in the inner cover layer of the female joint 33 (hereafter also referred to as the "maximum thickness of the inner cover layer of the female joint") T2 and the thickness of the portion having the greatest thickness in the inner cover layer of the body 31 (hereafter also referred to as the "maximum thickness of the inner cover layer of the body") T3. Figure 9 shows examples of T1 to T3. The inner cover layer of the body 31 and the inner cover layer of the female joint 33 preferably have a fixed thickness.Here, "fixed thickness" includes a case where slight, unintentional variations in thickness occur, such as variations in thickness that are unavoidable during production.

[0047] The advantage of having the thickness T1 greater than the thickness T2 is as follows. When the plurality of structures 1 are coupled together and the molten metal is poured, the flow of the molten metal is likely to be disturbed in the connecting parts between the structures 1. However, the thickness T1 is greater than the thickness T2, and therefore the flow of the molten metal can be prevented from being disturbed and the collision of the molten metal with the corner part can be eliminated. of the female joint 12, and consequently the corner part of the female joint 12 can be protected. The advantage of having a thickness Tl greater than thickness T3 is as follows. Generally, when molten metal is poured, it flows from one end of structure 1, where the female joint 12 is arranged, towards the other end 1b. Since the thickness Tl is greater than the thickness T3, the molten metal flowing into structure 1 can be prevented from colliding with the end of the inner coating layer of body 31. This protects the inner coating layer of body 31 during the pouring of the molten metal.

[0048] A ratio T1 / T2 between the thickness T1 and the thickness T2 is preferably greater than 1, more preferably 1.5 or more, and even more preferably 2 or more from the point of view of the protection of the corner part of the female joint 12. The ratio T1 / T2 is preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less from the point of view of the protection of the inner cover layer of the female joint 33 against friction when the structures 1 are connected together. From the point of view of accomplishing these two elements, the T1 / T2 ratio is preferably greater than 1 and 15 or less, more preferably 1.5 or more and 10 or less, and even more preferably 2 or more and 5 or less.

[0049] A ratio T1 / T3 between the thickness T1 and the thickness T3 is preferably greater than 1, more preferably 1.1 or more, and even more preferably 1.2 or more from the point of view of the protection of the inner covering layer of body 31 during the pouring of the molten metal. The T1 / T3 ratio is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less from the point of view of smoothing the flow of molten metal in the connecting pieces between structures 1 during the pouring of molten metal. From the point of view of accomplishing these two elements, the T1 / T3 ratio is preferably greater than 1 and 5 or less, more preferably 1.1 or more and 3 or less, and even more preferably 1.2 or more and 2 or less.

[0050] The maximum thickness T2 of the inner cover layer of the female joint 33 is preferably less than the maximum thickness T3 of the inner cover layer of the body 31. Thus, the end part of the other end side 1b of the other structure 1 can be easily inserted and joined to the female joint 12 of the structure 1. From the point of view of facilitating the joining of the end part on the other end side 1b of the other structure 1 to the female joint 12 of structure 1, a ratio The T2 / T3 ratio between thickness T2 and thickness T3 is preferably less than 1, more preferably 0.8 or less, and even more preferably 0.5 or less. Furthermore, from the point of view of protecting the main body 20 in the female joint 12, the T2 / T3 ratio is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. From the point of view of accomplishing these two elements, the T2 / T3 ratio is preferably 0.01 or more and less than 1, more preferably 0.05 or more and 0.8 or less, and even more preferably 0.1 or more and 0.5 or less.

[0051] The thicknesses of the inner body cover layer 31 and the inner female joint cover layer 33 need not be fixed. [Fig. 10] shows an example of the structure 1 in which the thickness of the inner body cover layer 31 is not fixed.

[0052] When the thickness of the inner cover layer of body 31 is not fixed, the inner cover layer of body 31 preferably has a portion having a thickness greater than that of a portion 31a arranged in the end part of the side an end la in the axial direction Z of the part of body 11 in the inner cover layer of body 31.Thus, when the molten metal flowing inside the cylindrical body 10 obtained by coupling the structures 1 passes through the interior of the upstream part of the body 11 of the structure 1 in a direction Z1, and then flows into the downstream part of the body 11 of the structure 1 in the direction Z1, the flow of molten metal is unlikely to directly collide with the surface of the inner body coating layer 31 covering the inner face of the end portion of the body part 11 in the downstream structure 1. This prevents the application of an impact to the end portion of the body part 11 of the downstream structure 1, and thus the inner body coating layer 31 is protected.From the point of view of presenting this effect more remarkably, portion 31a preferably has the smallest thickness in the inner covering layer of body 31. The thickness of the inner covering layer of body 31 increases preferably gradually from one end side to the other end side 1b in the axial direction Z. This example is shown in [Fig. 10].

[0053] When the inner body cover layer 31 and the inner female joint cover layer 33 are formed as separate bodies, the position of an edge on the proximal end side in a consecutive Y-connection direction of the female joint 12 of the inner female joint cover layer 33 may or may not coincide with the position of an edge on an end side proximal in the consecutive connection direction Y of the female joint 12 of the outer cover layer 32. From the point of view that the structure 1 having the inner cover layer of the female joint 33 and the outer cover layer 32 can be produced simply, the position of an edge 33b on the proximal end side in the inner cover layer of the female joint 33 and the position of an edge 32b on the proximal end side in the outer cover layer 32 preferably coincide with each other.

[0054] Here, the description "the position of the edge 33b of the inner cover layer of the female joint 33 and the position of the edge 32b of the outer cover layer 32 coincide with each other" includes not only a case where the two positions in the consecutive Y connection direction of the female joint 12 completely coincide with each other, but a case where the two positions are approximated to such an extent that the positions are assumed to substantially coincide with each other.Specifically, when the ratio between a distance L5 in the consecutive Y-direction between the edge 33b of the inner cover layer of the female joint 33 and the edge 32b of the outer cover layer 32 and a length L4 in the consecutive Y-direction of the outer face of the female joint 12 is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less, the position of the edge 33b of the inner cover layer of the female joint 33 and the position of the edge 32b of the outer cover layer 32 are assumed to coincide. Examples of the length L4 and the distance L5 are shown in [Fig. 11].

[0055] In structure 1, the thickness of the inner cover layer of the female joint 33 is preferably the smallest of the cover layers covering the surfaces of the main body 20. In other words, the thickness of the inner cover layer of the female joint 33 is preferably less than the thicknesses of the cover layers other than the inner cover layer of the female joint 33. Thus, the end portion of structure 1 other than the female joint 12 can be easily inserted into the female joint 12, and the two can be easily joined to each other. Even if the cover layers are peeled when the male joint 13 is joined to the female joint 12, the amount of peeling can be reduced and the impact on product quality can be minimized.

[0056] Figure 12 shows a structure IB of the fifth embodiment. The structure IB is preferably provided with the cylindrical main body 20. The main body 20 preferably has the male joint 13 in an end portion of the body portion 11. The male joint 13 is preferably joined internally to the female joint. The male joint 13 preferably has an external diameter equal to or less than the internal diameter of the female joint. In structure IB, the female joint 12 having an internal diameter equal to or greater than the external diameter of the body part 11 is coupled to the other end part of the body part 11.

[0057] The female joint 12 preferably has an internal diameter and an external diameter greater than those of the body part 11. Typically, the end part of the female joint side 12 in the body part 11 is formed with the tread part 15 projecting outwards in the radial direction of the body part 11, and the female joint 12 is connected consecutively to the body part 11 via the tread part 15.

[0058] As an IB structure, it is preferable that several structures of the same type or of a similar type can be coupled to each other. In the IB structure of the example shown in [Fig.12], both ends in the axial direction Z in the main body 20 are open. The internal diameter of the female joint 12 is preferably equal to or greater than the external diameter of the male joint side 13 of the body part 11. Structure IB is preferably configured so that IB structures can be coupled together by inserting and joining the male joint 13 of structure IB to the female joint 12 of the other IB structure. By coupling a desired number of IB structures, a long cylindrical body 10 of a desired length can be formed. This example is shown in [Fig. 14].

[0059] The structure IB preferably has the inner body cover layer 31 and an outer cover layer 36 covering the outer face of the male joint 13 (hereinafter also referred to as the "outer cover layer of the male joint"). The outer coating layer 36 of the male joint 13 preferably contains refractory inorganic particles selected from the group consisting of metal oxides and metal silicates, a binder, and clay minerals. Each component contained in the outer coating layer 36 is described later.

[0060] The inner coating layer of the body 31 is preferably continuous around its entire circumference in the circumferential direction of the structure IB. This example is shown in [Fig. 13](b). The inner covering layer of body 31 is preferably continuous over the entire region of the body part 11 in the axial direction Z. More specifically, the inner covering layer of body 31 covers the entire region of the inner face of the body part 11 also in the structure IB. This example is shown in [Fig.13](a). Structure IB exhibits the inner covering layer of body 31, and consequently, the gas mixes poorly with the molten metal flowing within structure IB. To more prominently demonstrate this effect, the inner covering layer of body 31 is preferably continuous around the entire circumference in the circumferential direction of structure IB and more preferentially covers the entire region of the inner face of body part 11.

[0061] The outer covering layer 36 preferably covers the entire region of the outer face of the male joint 13. Structure IB of the fifth embodiment can also be used to produce a casting in the same way as structure 1 of the first embodiment.

[0062] Structure IB has the outer covering layer 36 of the male joint 13, and can therefore prevent leakage from structure IB during the pouring of molten metal. This point is described in detail below. When IB structures are coupled to each other, a gap is sometimes created between the end face 1e of the male joint 13 of one IB structure and the end face 12e located inside the female joint 12 of the other IB structure. Molten metal entering this gap presents a risk of penetration between the outer circumferential surface 11b of the male joint 13 of one IB structure and the inner circumferential surface 12a of the female joint 12 of the other IB structure. However, the IB structure can prevent molten metal from penetrating between the outer circumferential surface 11b and the inner circumferential surface 12a. This is because the outer circumferential surface 11b of the male joint 13 is also covered by the outer covering layer 36.Furthermore, this is due to the fact that the outer covering layer 36 of the male joint 13 is arranged between the outer circumferential surface 11b of the male joint 13 of one structure IB and the inner circumferential surface 12a of the female joint 12 of the other structure IB. In addition, it is preferable for structure IB to have the outer covering layer 36 of the male joint 13 and the inner covering layer of the body 31, and for both the outer and inner faces of the male joint 13 to be covered. This effectively prevents leakage of molten metal through the male joint 13 during pouring.

[0063] The outer covering layer 36 of the male joint 13 may be discontinuous in the circumferential direction of the structure IB but is preferably continuous over the entire circumference in the circumferential direction of the structure IB from the point of view of effectively preventing leakage of molten metal.

[0064] In the fifth embodiment, the inner body coating layer 31 covers the entire region of the inner face of the body part 11 as described above. This protects the entire region of the inner face of the main body 20, and thus more effectively prevents leakage of molten metal during pouring.

[0065] Also in structure IB of the fifth embodiment, the effect whereby leakage of molten metal during pouring of molten metal can be more effectively prevented is more remarkably achieved when the internal diameter D3 of the body part 11 in structure 1 is large as with structure 1 of the first embodiment. A preferred numerical range of the internal diameter D3 of the male joint 13 according to the fifth embodiment is the same as that of the first embodiment.

[0066] Fig. 16 shows the IB structure of the sixth embodiment. Structure IB preferably comprises the outer covering layer 36 of the male joint 13 and an end face covering portion 37 covering the end face of the male joint 13 (hereinafter also referred to as the "end face covering portion of the male joint"). The end face covering portion 37 may cover only a part of the end face of the male joint 13 or may cover the entire end face region.

[0067] The end face cover portion 37 of the male joint 13 is provided, and consequently, leakage of molten metal during pouring can be more effectively prevented. This point is described in detail below. When IB structures are coupled to each other, a gap is sometimes generated between the end face of the male joint 13 of one IB structure and the end face 12e arranged inside the female joint 12 of the other IB structure. The IB structure presents the end face cover portion 37 of the male joint 13, and can thus reduce the gap to make gap formation difficult. This example is shown in [Fig. 16].

[0068] When structure IB has the outer cover layer 36 of the male joint 13, the outer cover layer 36 and the end face cover portion 37 of the male joint 13 may be discontinuous. However, from the point of view of more effectively preventing leakage of molten metal during pouring, the outer cover layer 36 and the end face cover portion 37 are preferably continuous, and preferably molded as a single unit.

[0069] When the structure IB has the inner body cover layer 31, the end face cover portion 37 of the male joint 13 is preferably continues with layer 31 of inner body cover, and these are preferably molded together. The outer covering layer 36 of the male joint 13 preferably extends to the inner face of the body part 11 through the end face of the male joint 13.

[0070] The external diameter DI of the male joint 13 is preferably equal to or less than the internal diameter D2 of the end part on the other end side opposite one end in the axial direction Z in the body part 11, i.e. the female joint 12. Thus, the male joint 13 of structure IB can be easily inserted into the female joint 12 of the other structure IB, and the two can be easily joined to each other. A preferred numerical range of the ratio D1 / D2 between the external diameter DI and the internal diameter D2 is the same as the preferred numerical range of the ratio D1 / D2 in the first embodiment.

[0071] The inner body covering layer 31 is preferably arranged on the innermost side in the radial direction of each of the structures 1 and IB in the portion where the inner body covering layer 31 is arranged. Thus, the inner body covering layer 31 in each of the structures 1 and IB comes into contact with the molten metal flowing through the interior of each of the structures 1 and IB, and therefore the main body 20 in each of the structures 1 and IB is easily protected. In the example of structure 1 shown in [Fig. 1], the radial direction of structure 1 in the portion where the inner body covering layer 31 is arranged is the radial direction in the cross-section orthogonal to the axial direction Z of structure 1. In the example of structure 1 shown in [Fig. 1], the radial direction of structure 1 in the portion where the inner body covering layer 31 is arranged is the radial direction in the cross-section orthogonal to the axial direction Z of structure 1.l7](d), the radial direction of the structure 1 in the portion where the inner body cover layer 31 is arranged is the radial direction in the cross-section orthogonal to the axial direction Zx of the first part 18 in the case of the inner body cover layer 31 arranged in the first part 18 and is the radial direction in the cross-section orthogonal to an axial direction Zy of the second part 19, i.e. the consecutive connection direction Y of the female joint 12, in the case of the inner body cover layer 31 arranged in the female joint 12. .

[0072] The outer cover layer 32 of the female joint 12 is preferably disposed on the outermost side in the radial direction in the right section orthogonal to the axial direction Z of the structure 1. Thus, both the simplicity of production and the protection of the main body 20 can be achieved.

[0073] The main body 20 may have a stratified structure in which two or more layers are stratified. However, from the point of view of simple production, the main body 20 preferably has a single-layer structure.

[0074] The main body 20 is preferably molded integrally in the circumferential direction. Thus, the main body 20 becomes continuous over the entire circumference in the circumferential direction, and consequently the formation of gaps or holes in the main body 20 can be prevented, and leakage of molten metal during pouring of the molten metal can be effectively prevented. Structures 1 and IB preferably have portions not covered by the coating layers 32, 35, and 36 in parts of the outer face of the main body 20. During the pouring of the molten metal, gas is generated when the organic fibers, binder, and similar materials contained in the main body 20 are thermally decomposed due to the flow of the molten metal into structure 1. Since parts of the outer face of the main body 20 are not covered by the coating layers 32, 35, and 36, the gas can preferably be vented from these parts toward the pouring sand side, i.e., the outside of structures 1 and IB.

[0075] The outer face of any of the body part 11, the male joint 13, and the female joint 12 in the main body 20 may have portions not covered by the coating layers 32, 35, and 36.From the point of view of effectively presenting the effect of preferential evacuation of gas to the outside of structures 1 and IB, a portion not covered by the outer covering layer of body 35 is preferably present on the outer face of the part of body 11 in the main body 20. . An uncovered area ratio which is a ratio between the area of ​​the portion not covered by the outer cover layer of body 35 and a whole area SI of the outer face of the part of body S 11 is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more from the point of view of preferential evacuation of gas to the outside of structures 1 and IB. The ratio of uncovered area is preferably 100% or less, more preferably 95% or less, and even more preferably 90% or less from the point of view of preventing leakage of molten metal outside of structure 1 during pouring of molten metal. From the point of view of accomplishing these two elements, the ratio of uncovered area 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, constituent materials of structures 1 and IB are described. The main body 20 typically contains organic fibers, inorganic fibers, inorganic particles (hereafter also referred to as first inorganic particles), and a binder (hereafter also referred to as first binder). Such a main body 20 is typically produced by the following process. First, a slip composition containing organic fibers, inorganic fibers, first inorganic particles, first binder, and a dispersion medium (hereafter referred to as the slip raw material) is prepared. Next, an intermediate casting of the main body 20, for example, a main body in a water-containing state, is converted into a sheet using a sheet-making mold and dehydration molding. Then, by heating and drying the intermediate casting using the mold, the main body 20 can be formed.

[0077] The organic fibers are intertwined with the inorganic fibers, the inorganic particles before being used for casting in the main body 20 and have the effect of maintaining the shapes of structures 1 and IB. During casting, all or part of the organic fibers burn under the effect of the heat of the molten metal.

[0078] For organic fibers, one or two or more types selected from pulp fibers, synthetic fibers, regenerated fibers (for example, rayon fibers), and the like are usable. Among these, pulp fibers are preferred. The reason is that pulp fibers can be molded into various shapes by sheet production, the molded, dehydrated, and dried product exhibits excellent strength characteristics, and pulp fibers are readily available, stable, and economical. For pulp fibers, one or two or more types selected from wood pulp, cotton pulp, linter pulp, bamboo, straw, and other non-wood pulps may be used. In addition, one or two or more types selected from virgin pulp or waste pulp (recycled product) may be used. With regard to good availability, environmental protection and reduced production costs, waste paper pulp, such as newspaper waste, is preferably contained.

[0079] The inorganic fibers improve the mechanical strength of structures 1 and IB before being used primarily for casting in the main body 20. The inorganic fibers retain their shape without burning, even under the effect of the heat of the molten metal during casting. In particular, when organic binders described later are used, the inorganic fibers can suppress the thermal shrinkage caused by the combustion of the organic fibers by the heat of the molten metal and the thermal decomposition of the organic binder.

[0080] For inorganic fibers, one or two or more types selected from carbon fibers, artificial mineral fibers such as rock wool, ceramic fibers, glass fibers, and natural mineral fibers are usable. Among these, carbon fibers are preferably included, which have high mechanical strength even at high temperatures where the metal melts, from the point of view of suppressing the thermal shrinkage described above. With regard to reducing production costs, one or two or more types selected from rock wool and glass wool fibers are preferably included.

[0081] As first inorganic particles, one or two or more types selected from refractory aggregate particles, such as mullite, graphite, mica, silica, hollow ceramics, and fly ash, are usable.

[0082] From the point of view of improving the air permeability of the main body 20, the average particle size of the first inorganic particles is preferably 10 qm or more and more preferably 15 qm or more. The average particle size of the first inorganic particles is preferably 100 sqm or less from the point of view of improving the moldability of the main body 20. When the average size of the initial inorganic particles is equal to or greater than the lower limits specified above, the permeability of the main body 20 is improved, and the gas pressure in the mold during casting decreases moderately. Furthermore, the improved permeability of the main body 20 increases the spaces between the materials within the main body 20, enhances the permeability of a coating composition described later within the main body 20, and makes peeling the coating layers from the main body 20 difficult. When the average size of the first inorganic particles is equal to or greater than the upper limits above, the inorganic particles fall with difficulty from the surface of the main body 20, and moldability is improved.

[0083] From the point of view of the dispersibility of the raw materials, the apparent density of the first inorganic particles is preferably 0.5 or more and more preferably 2.8 or more. From the point of view of weight reduction, the apparent density of the first inorganic particles is preferably 3 or less, more preferably 2.8 or less, and even more preferably 2.5 or less. Apparent density is the specific density of hollow particles assuming that the volume of the hollow portion inside the hollow particle is part of the volume of the hollow particle, and coincides with the true density in the case of solid particles not having an internal hollow portion. The apparent density of the first inorganic particles falls within the range specified above, thus improving the dispersibility of the raw material in a sheet manufacturing step when water is used as the dispersion medium. Furthermore, the mass of the main body obtained by molding can be reduced, thereby improving workability. The composition of the main body 20 can be determined by considering the overall density as well as the apparent density of the first inorganic particles. The overall density is obtained by measuring the quantity of particles that a container of fixed volume can hold when the particles are placed in the container in a fixed state and determining the mass per unit volume.

[0084] The first inorganic particles can be hollow. The use of hollow particles can reduce the apparent density of the first inorganic particles.

[0085] In the present invention, one or two or more types selected from organic and inorganic binders may be used as the first binder. The organic binder is preferably contained from the point of view of excellent shrinkage capacity after casting. As an organic binder, one or two or more types chosen from thermosetting resins, such as a phenolic resin, an epoxy resin and a furan resin, are usable. Among these, phenolic resin is preferably contained because phenolic resin generates hardly any flammable gas, has a combustion-suppressing effect, and has a high residual charcoal ratio after thermal decomposition (carbonization).

[0086] As a phenol resin, one or two or more types selected from phenol resins, such as a novolac phenol resin and a resol type, and phenol resins modified with urea, melamine, epoxy, and the like, for example, are usable. Among these, phenolic resin of the resol type is preferably contained because the odor during the molding of the main body 20 and the casting defects when the main body 20 is used as a mold can be reduced without the need for curing agents, such as acids and amines.

[0087] When novolac phenolic resin is used, the curing agent is preferably used in combination. The curing agent is readily soluble in water and is therefore preferably applied to the surface of the main body 20 after dehydration. Hexamethylenetetramine and similar compounds are preferably used as curing agents.

[0088] As an inorganic binder, one or two or more types selected from a phosphoric acid binder, soluble glass, such as silicate, gypsum, sulfate, a silica binder and a silicon binder are usable.

[0089] As a dispersion medium used for the raw material slip, one or two or more types selected from solvents such as water, ethanol, methanol, dichloromethane, acetone and xylene are usable. Among these, water is preferably contained from the point of view of ease of handling.

[0090] The main body 20 may contain paper reinforcing materials in addition to organic fibers, inorganic fibers, first inorganic particles, and the first binder. The paper reinforcing materials help maintain the shape of the intermediate molded body. As paper reinforcement materials, one or two or more types selected from latex, acrylic emulsion, polyvinyl alcohol, carboxymethylcellulose, polyacrylamide resin, epichlorohydrin polyamide resin, and the like are usable.

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

[0092] With regard to refractory inorganic particles, the term "refractory" means that the melting point is 1,500 °C or more, preferably 1,600 °C or more, and more preferably 1,700 °C or more. For the second inorganic particles, one or two or more types chosen from the group consisting of metal oxides and metal silicates may be used. Specifically, one or two or more types chosen from mullite, zircon, zirconia, alumina, olivine, spinel, magnesia, chromite, and the like may be used. From the point of view of improving gaseous defects in castings, zircon is preferably contained. Cast steel having a lower carbon content than cast iron preferably contains aggregated particles other than carbonaceous substances and more preferably contains zircon having a high melting point and low wettability with molten metal.

[0093] From the point of view of the sealing properties of the surface of the main body 20 and the adhesion between the main body 20 and the coating layers, the average size of the second inorganic particles is preferably 1 pm or more and more preferably 3 pm or more. The average size of the second inorganic particles is preferably 100 pm or less, more preferably 70 pm or less, and even more preferably 40 pm or less.

[0094] In structures 1 and IB, the ratio between the average size of the first inorganic particles contained in the main body 20 and the average size of the second inorganic particles contained in the cover layers is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.8 or more in terms of [average size of the first inorganic particles] / [average size of the second inorganic particles] from the point of view of the sealing properties of the surface of the main body 20. The ratio between the average size of the first inorganic particles contained in the main body 20 and the average size of the second inorganic particles contained in the cover layers is preferably 35 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 6 or less in terms of [average size of the first inorganic particles] / [average size of the second inorganic particles] from the point of view of the sealing properties of the surface of the main body 20. In structures 1 and IB, the proportion of second inorganic particles in the cover layer is preferably 50% by mass or more and less than 100% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 90% by mass or more.

[0095] The topcoats preferably contain clay minerals to improve heat resistance and provide viscosity during application. By combining clay minerals in a dispersion liquid (coating composition) to obtain the topcoats, a suitable viscosity is imparted to the dispersion liquid, and the prevention of sedimentation of raw materials in the dispersion liquid and the dispersibility of the raw materials are improved. As clay minerals, one, two, or more types selected from stratified silicate minerals, double-chain structure minerals, and the like are usable. These substances may be natural or synthetic. As stratified silicate minerals, one or two or more types selected from clay minerals belonging to the smectite group, the kaolin genus and the illite genus, for example, bentonite, smectite, hectorite, activated clay, kibushi clay, zeolite, and the like, are usable. As double-chain structure minerals, one or two or more types selected from attapulgite, sepiolite, palygorskite and the like are usable. From the point of view of improving heat resistance and ensuring viscosity during application, one or two or more types chosen from attapulgite, sepiolite, bentonite and smectite are preferably used, and one or two or more types chosen from attapulgite and sepiolite are more preferentially used. Clay minerals are distinguished in that clay minerals have a stratified structure or a double-chain structure from refractory inorganic particles containing mainly a hexagonal close-packed structure and generally do not have the stratified structure or double-chain structure, for example. Clay minerals are contained in a proportion preferably of 0.5 parts by mass or more and more preferably of 1 part by mass or more for 100 parts by mass of refractory inorganic particles. Clay minerals are contained in a proportion preferably of 30 parts by mass or less, more preferably of 20 parts by mass or less, and even more preferably of 2 parts by mass or less for 100 parts by mass of refractory inorganic particles. When the proportion of clay minerals is equal to or greater than the lower limits above in the proportions above, an appropriate viscosity can be imparted to the dispersion liquid, and the sedimentation and flotation of raw materials in the dispersion liquid can be prevented.

[0096] The coating layers preferably also contain the second binder from the point of view of improving heat resistance. The use of the second binder in the formation of the coating layers is preferable from the point of view of improving the normal temperature resistance and the heat resistance of the production structure of a casting. As a second binder, one or two or more types chosen from organic and inorganic binders are usable, and inorganic binders are preferably contained. As an organic binder, one or two or more types selected from a phenolic resin, an epoxy resin, a furan resin, a water-soluble alkyd resin, Water-soluble butyral resin, vinyl polyalcohol, water-soluble acrylic resin, water-soluble polysaccharide, vinyl acetate resin or a copolymer thereof, and similar products may be used, for example. As an inorganic binder, one or two or more types chosen from various sols, such as a sol of sulfate, silicate, phosphate, lithium silicate, zirconia, colloidal silica and an alumina sol, and the like, are usable, and one or two or more types chosen from the group consisting of colloidal silica and aluminum phosphate are preferably used, and colloidal silica is preferably contained. The second binder is preferably contained in a proportion of preferably 1 part by mass or more and more preferably 3 parts by mass or more in terms of effective component per 100 parts by mass of the second inorganic particles. The second binder is preferably contained in a proportion of preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 7 parts by mass or less in terms of effective component per 100 parts by mass of the second inorganic particles.

[0097] A preferable aspect of a production method for a production structure of a casting of the present invention is described using a production method for structure 1 shown in [Fig. 18] by way of example. The production process for this aspect typically includes a body part application step consisting of forming the inner body cover layer 31 and a female joint application step consisting of forming the outer female joint cover layer 32. In the application step of female joint according to this aspect, the inner cover layer of female joint 33 and the end face cover part of female joint 34 are also formed in addition to the outer cover layer of female joint 32.

[0098] In the body part application step, the inner body cover layer 31 is preferably formed by applying a coating composition to the inner face of the body part 11 of the main body 20. Specifically, it is preferable to pour a coating composition 70 into the body part 11 and to fill the body part 11 with the coating composition 70 (see Figures 18(a) and 18(b)). In detail, a cover 60 is fitted to one end of the male joint 13. Then, the body part 11 is filled with the coating composition 70. When the upper surface of the coating composition 70 reaches the desired height, the filling process is complete. After a certain time, the cover 60 is opened. Then, the composition coating 70 is evacuated leaving the coating composition 70 on the inner face of the body part 11.

[0099] Next, it is preferable that the body part 11 on which the coating composition 70 remains is left in a state where the axial direction Z of the body part 11 is fixed to be substantially parallel to the vertical direction Zl, and that the coating composition 70 remaining on the inner face of the body part 11 is dried and solidified to form the inner coating layer of body 31 on the inner face of the body part 11 (see La [Fig. 18](c)).

[0100] The female joint application step is preferably carried out after the body part application step. In the female joint application step, the coating composition is preferably applied to the inner face, the outer face, and the end face of the female joint 12 in the main body 20 over the entire circumference of the female joint 12. In detail, the female joint 12 in the main body 20 is preferably immersed in a coating composition 71. Then, the coating composition 71 is spread over the inner face, the outer face, and the end face of the female joint 12 (see Fig. 18(d)). Then, after a certain time has elapsed, the female joint 12 is removed from the coating composition 71. Next, the coating film, i.e., the coating composition 71 remaining on the inner face, the outer face, and the end face of the female joint 12, is dried and solidified to form, respectively, the inner coating layer of the female joint 33, the outer coating layer of the female joint 32, and the end face coating portion of the female joint 34. Thus, structure 1 is produced which has the inner body cover layer 31, the inner cover layer of the female joint 33, the outer cover layer of the female joint 32 and the end face cover part of the female joint 34. According to the production process of this aspect, structure 1 can be produced efficiently.

[0101] In the body part application step, the coating composition 70, which is to fill the body part 11, may reach the upper surface 12e of the tread part 15 (see [Fig. 18](b)) or may not reach the upper surface 12e (see [Fig. 19](a)). The coating composition 70, which is to fill the body part 11, may reach the female joint 12 (see Figures 19(b) and 19(c)). When the coating composition 70 reaches the female joint 12, it may reach the opening end of the female joint 12 (see [Fig. 19](b)) or may not have to reach the opening end of the female joint 12 (see [Fig. 19](c)).

[0102] In the body part application step, the coating composition 70 can be applied to the inner face of the body part 11 by applying the coating composition 70 to the inner face of the body part 11 using a brush or similar, for example, instead of filling the body part 11 with the coating composition 70. From the point of view of enabling easy formation of the inner covering layer of body 31 to produce structure 1 more efficiently, the coating composition 70 is preferably applied by filling the part of body 11 with the coating composition 70.

[0103] In the female joint application step, the female joint 12 can be immersed in the coating composition 71 towards a lower surface 15a of the walking part 15 in the main body 20 (see [Fig.18](d)), only a portion of the side one end la relative to the lower surface 15a of the walking part 15 in the female joint 12 can be immersed in the coating composition 71 (see [Fig.19](d)), or the female joint 12 can be immersed in the coating composition 71 towards a position on the other end side 1b relative to the lower surface 15a of the walking part 15 in the main body 20 (see [Fig.19](e)).

[0104] In the application step of the female joint in this aspect, the inner coating layer of the female joint 33, the outer coating layer of the female joint 32, and the end face coating portion of the female joint 34 are formed. However, in the application step, only the outer coating layer of the female joint 32 can be formed. The coating composition 71 can be applied to the outer face of the female joint 12 by applying the coating composition 71 to the outer face of the female joint 12 using a brush or similar tool, for example.From the point of view of enabling easy formation of the inner cover layer of female joint 33, the outer cover layer of female joint 32, and the end face cover part of female joint 34 to produce structure 1 more efficiently, the coating composition 71 is more preferentially applied by immersing the female joint 12 in the main body 20 in the coating composition 71 (see [Fig.18](d)).

[0105] The order in which the female joint application step and the body part application step are carried out is not particularly limited. For example, the body part application step may be carried out after the female joint application step, or the female joint application step and the body part application step may be carried out simultaneously. The coating composition 70 in the body part application step and the coating composition 71 in the female joint application step may be identical or different from each other.

[0106] The main body 20 can be produced by the following process, for example. <Procédé de production du corps principal 20> The main body 20 can be produced by a molding process comprising a sheet manufacturing step. Such a molding process is described in paragraphs

[0052] to

[0071] of JP 2012-024841 A, for example. Specifically, first, a raw material slip is prepared, containing organic fibers, inorganic fibers, first inorganic particles, and the first binder in a predetermined proportion. The raw material slip is prepared by dispersing the organic fibers, inorganic fibers, first inorganic particles, and the first binder in a predetermined dispersion medium. The first binder can be incorporated into the main body by impregnation instead of being incorporated into the raw material slip.

[0107] As a dispersion medium, one or two or more types of solvents, such as ethanol, methanol, dichloromethane, acetone and xylene, may be used, in addition to water. Among these, water is preferably contained from the point of view of ease of handling. As a ratio of the content of organic fibers, inorganic fibers, first inorganic particles and first binder in the raw material slip, the ratio of each component is adjusted appropriately to obtain the target main body composition 20. The raw material slip may have additives added, such as paper strengthening agents, flocculants, and antiseptics, as required.

[0108] Then, the intermediate molded body of the main body 20 is converted into a sheet using the raw material slip. In the sheet-making step of the intermediate molded body, a sheet-making and dehydration mold is used. Inside this mold, a cavity shaped to match the external shape of the intermediate molded body is formed by joining two wedge molds forming a pair, for example. A predetermined quantity of the raw material slip is then poured under pressure from an opening at the top into the mold cavity. This pressurizes the cavity to a predetermined pressure. Each wedge mold has a plurality of communicating holes connecting the exterior of each wedge mold and the cavity, and the inner face of each wedge mold is covered with a mesh of a predetermined size. A pressure pump is used, for example, for pouring under pressure. pressure of the raw material slip. The pressure of the pressure pouring of the raw material slip 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 interior of the cavity is pressurized, and consequently, the dispersion medium in the raw material slip is expelled from the mold through the communication holes. The solids content of the raw material slip is deposited onto the mesh covering the cavity, and a fiber laminate forms uniformly on the mesh. The fiber laminate thus obtained is one in which the organic and inorganic fibers are intricately intertwined, and the binder is present between the fibers. Therefore, high shape retention properties can be achieved even when the shape is complex or even after drying and molding. Furthermore, the interior of the cavity is pressurized, and consequently, the raw material slip flows into the cavity and is agitated even when a hollow intermediate molded body is being molded.Consequently, the slip concentration in the cavity is made uniform, and the fiber laminate is deposited evenly on the mesh.

[0110] Once the fiber laminate has been formed, the pressurized pouring of the raw material slurry is stopped, and air is injected under pressure into the cavity to pressurize and dehydrate the fiber laminate. Then, the pressurized air injection is stopped, the contents of the cavity are aspirated through the communication holes, and a flexible, expandable, hollow elastic core is inserted into the cavity. The core is preferably made of urethane, fluororubber, silicone rubber, elastomer, or a similar material having excellent tensile strength, impact resilience, elasticity, and similar properties.

[0111] Next, a pressurized fluid is introduced 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 face of the cavity. Thus, the fiber laminate is pressed against the inner face of the cavity, and the shape of the inner face of the cavity is transferred to the outer face of the fiber laminate, and dehydration of the fiber laminate occurs.

[0112] For the pressurized fluid used to expand the elastic core, compressed air (heated air), oil (heated oil), or various other types of liquids are used, for example. The supply pressure of the pressurized fluid is preferably 0.01 MPa or more and 5 MPa or less when considering 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 point of view of efficient production. When the supply pressure is 0.01 MPa or more, the drying efficiency of the fiber laminate is good, and the properties of Surface area and transferability are also sufficient. When the supply pressure is less than or equal to 5 MPa, a good effect can be achieved and the device can be reduced in size.

[0113] As described above, the fiber laminate is pressed against the inner face of the cavity from within the cavity itself, and consequently, the shape of the inner face can be accurately transferred to the outer face of the fiber laminate even when the shape of the inner face of the cavity is complex. Furthermore, even when a molded product to be produced has a complex shape, it is not necessary to perform a bonding step for each portion, and therefore, the final part obtained is free of joints or thick portions caused by bonding. More specifically, the main body 20 to be obtained in the end is a product molded solidly in the circumferential direction of the main body 20.

[0114] When the shape of the inner face of the cavity is sufficiently transferred to the outer face of the fiber laminate, and the fiber laminate can be dehydrated to a predetermined moisture content, the pressurized fluid in the elastic core is withdrawn, and the elastic core is automatically shrunk back to its original size. The shrunk elastic core is then removed from inside the cavity. Furthermore, the mold is opened, and the wet fiber laminate, having a predetermined moisture content, is removed. Alternatively, the fiber laminate can be dehydrated and molded solely by pressurizing and dehydrating it through the injection of air into the cavity under pressure, without the above-described pressing and dehydration of the fiber laminate using the elastic core.

[0115] The dehydrated and molded fibre laminate is then transferred to a heating and drying stage. In the heating and drying stage, a drying and molding mold is used in which a cavity with a shape corresponding to the external shape of the intermediate molded body is formed. The mold is then heated to a predetermined temperature, and the dehydrated, wet-molded fiber laminate is loaded into the mold.

[0116] Next, an elastic core similar to the elastic core used in the sheet manufacturing step is inserted into the fiber laminate. A pressurized fluid is introduced into the elastic core to expand it, and the expanded elastic core presses the fiber laminate against the inner face of the cavity. Preferably, an elastic core surface-modified with a fluororesin, silicone resin, or similar material is used. The pressure of the pressurized fluid is preferably the same as that of the dehydration step. Under these conditions, the fiber laminate is heated and dried, and the intermediate molded body is dried and molded.

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

[0118] When the fiber laminate is sufficiently dry, the pressurized fluid in the elastic core is removed, and the core is shrunk and removed from the fiber laminate. Then, the mold is opened and the intermediate molded body is removed. The intermediate molded body is used as the main body 20 by curing a thermosetting resin through heat treatment.

[0119] The resulting main body 20 is pressed by the elastic core, and therefore both the inner and outer surfaces have a high degree of smoothness. Consequently, the casting accuracy is high, and a high-precision structure can be obtained even when the structure has joints or threaded parts. Therefore, structures coupled with joints or threaded parts allow the molten metal to flow smoothly inside the structures. Furthermore, the thermal shrinkage ratio of the main body 20 during casting is less than 5%, and therefore leakage of molten metal due to cracks, deformations, and similar issues in the structures can be prevented without any problems.

[0120] The resulting intermediate molded body can further be partially or fully impregnated with the first binder. Moreover, when the intermediate molded body is impregnated with the first binder and is not immersed in the raw material slip, the processing of the raw material slip or white water is simplified. When a thermosetting binder is used as the first binder, the thermosetting binder is thermally cured by heating and drying the intermediate molded body at a predetermined temperature, thus completing the production of the main body 20.

[0121] Although the present invention is described above on the basis of embodiments and preferred aspects thereof, the present invention is not limited to the embodiments and aspects described above. The embodiments and their modifications described above may be combined insofar as their content does not contradict each other. For example, the production structure of a casting of the present invention may have both the outer covering layer 32 of the female joint 12 and the outer covering layer 36 of the male joint 13.

[0122] The present invention is described in more detail below on the basis of examples, but the present invention is not limited to the examples below.

[0123] [Example 1] Structure 1 shown in [Fig. 9] was produced by the production process described above and was used as the production structure for a casting of Example 1. The composition of the production structure for a casting of Example 1 is as shown in Table 1 and as described below. Specifically, the top layer contained 1.25 parts by mass of attapulgite and 5 parts by mass of colloidal silica per 100 parts by mass of zirconia. The main body contained 10.2 parts by mass of recycled newspaper, 8.5 parts by mass of carbon fibers, 66 parts by mass of spherical silica, and 15.3 parts by mass of phenolic resin when the total of all components was fixed at 100 parts by mass. Zircon: Zircosil No. 1 manufactured by HAKUSUI TECH. Attapulgite: Attagel 50 manufactured by Hayashi Kasei Co., Ltd. Colloidal silica: Snowtex 50 manufactured by Nissan Chemical Corporation. Carbon fibers: TORAYCA chopped fibers manufactured by Toray Industries, Inc. Spherical silica: S85-P manufactured by Micron Co., Ltd. Phenolic resin: Bell Pearl S890 manufactured by AIR WATER PERFORMANCE CHEMICAL INC. The male joint had an internal diameter of 99.4 mm and an external diameter of 102.4 mm. The thickness T2 of the inner cover layer of the female joint was 0.1 mm, the thickness T3 of the inner cover layer of the body was 0.3 mm, and the thickness Tl of the portion where the inner cover layer of the female joint and the inner cover layer of the body overlapped was 0.4 mm.

[0124] [Example 2] Structure 1 shown in [Fig. 1] was produced by the production process described above and was used as the production structure for a casting of Example 2. In the female joint application step, coating composition 70 was applied to the external face of the female joint 12. 12 using a brush or similar. The composition of the production structure of a casting of Example 2 is the same as that of the production structure of a casting of Example 1.

[0125] [Comparative Example 1] A production structure for a casting was created in the same way as in Example 1, except that the step of applying the female joint was not performed.

[0126] [Table 1] Ex. 1 Ex. 2 Ex. Comp. 1 Presence or absence of internal cover layer of female joint Presence Presence Absence Presence or absence of part of the end face cover of female joint Presence Absence Absence Presence or absence of external cover layer of female joint Presence Presence Absence Female joint Internal diameter (mm) 102.5 102.5 102.7 External diameter (mm) 105.3 105.3 105.1 Presence or absence of leakage Absence - Presence

[0127] [Evaluation of the presence or absence of molten metal leakage during molten metal pouring] For each of the casting production structures in Example 1 and Comparative Example 1, the cylindrical bodies for producing a casting were coupled to create cylindrical bodies. The molten metal was then poured into a sand mold, with each cylindrical body acting as a pouring channel pipe to produce a casting. Five tons of SC450 carbon steel (JIS classification) were used for the molten metal. The surface of each cylindrical body remaining after the molten metal solidified was then visually inspected, and the cut surfaces of the joints were observed. Any instance where the sand mold and the metal inside the cylindrical body could be separated without any leakage of the molten metal from the cylindrical body was rated as "No Leakage."A case where molten metal leaked from the cylindrical body and the casting sand from the sand mold partially caused metal penetration was assessed as "A leak occurred".

[0128] As shown in Table 1, molten metal leakage occurred in Comparative Example 1. In contrast, molten metal leakage did not occur in Example 1. Therefore, it is observed that the production structure of a part The casting of the present invention can eliminate metal penetration caused by leakage from the joints.

[0129] Industrial applicability The production structure of a casting of the present invention can prevent leakage of molten metal during the pouring of the molten metal. The production process for a casting production structure of the present invention can efficiently produce a casting production structure capable of preventing leakage of molten metal during the pouring of molten metal.

Claims

Demands

1. Cylindrical production structure of a casting comprising a cylindrical main body, wherein the cylindrical main body comprises a body part, and a female joint connected consecutively to the body part and having an internal diameter equal to or greater than an external diameter of the body part, and the cylindrical structure comprises an inner body cover layer covering an internal face of the body part, and an outer cover layer covering an external face of the female joint.

2. Production structure of a casting according to claim 1, wherein the outer covering layer covers an entire region of the outer face of the female joint.

3. production structure of a casting according to claim 1 or 2, comprising an inner cover layer of female joint covering an inner face of the female joint.

4. Production structure of a casting according to claim 3, wherein the inner cover layer of the female joint extends to the inner face of the body part, and partially overlaps the inner cover layer of the body, and the portion, where the inner cover layer of the female joint and the inner cover layer of the body overlap, has a thickness greater than the two thicknesses of a portion having a greater thickness in the inner cover layer of the female joint and a portion having a greater thickness in the inner cover layer of the body.

5. Production structure of a casting according to claim 3 or 4, wherein a position of an edge of the inner cover layer of the female joint on a proximal end side in a subsequent connection direction of the female joint coincides with a position of an edge of the outer cover layer on a proximal side in the subsequent connection direction of the female joint.

6. Production structure of a casting according to any one of claims 1 to 5, comprising an end face cover portion covering an end face of the female joint.

7. Production structure of a casting according to claim 6, comprising an outer cover layer of female joint covering the outer face of the female joint, and the outer cover layer of female joint and the end face cover portion being continuous.

8. Production structure of a casting according to any one of claims 1 to 7, comprising: an inner cover layer of female joint covering an inner face of the female joint, in which the end face cover portion and the inner cover layer of female joint are continuous.

9. Production structure of a casting according to any one of claims 1 to 8, wherein the outer covering layer extends to the inner face of the body part through an end face of the female joint.

10. Production structure for a casting according to any one of claims 1 to 9, wherein an internal diameter of an end portion of the production structure for a casting other than the female joint is 100 mm or more.

11. Cylindrical production structure of a casting comprising a cylindrical main body, wherein the cylindrical main body comprises a body part, and a male joint in an end part of the body part, the male joint shall be joined internally to a female joint, the male joint shall have an external diameter equal to or less than an internal diameter of the female joint, and the cylindrical structure comprises an inner body cover layer covering an internal face of the body part, and an outer cover layer covering an external face of the male joint.

12. Production structure of a casting according to claim 11, comprising an end face cover portion covering an end face of the male joint.

13. A method for producing a cylindrical structure for producing a casting, wherein the production structure for a casting comprises a cylindrical main body, the cylindrical main body comprises a body part, and a female joint connected consecutively to the body part in the axial direction, the female joint has an internal diameter equal to or greater than an external diameter of the body part, and the method comprises: a body part application step where a coating composition is applied to an internal face of the body part to form an internal body covering layer covering the internal face of the body part;and a female joint application step in which a coating composition is applied to an external face of the female joint over a circumference of the female joint to form an outer covering layer covering the external face of the female joint.

14. Method of producing a mold for cast steel, comprising coating the production structure of a casting according to any one of claims 1 to 12 in casting sand leaving a portion of the opening of the production structure of a casting.

15. A method for producing a cast steel part, comprising: a mold production step consisting of producing a mold by coating the production structure of a cast part according to any one of claims 1 to 12 in casting sand leaving a portion of the opening of the production structure of a cast part; and a pouring step consisting of pouring molten metal into the mold.

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