Structure for producing casting

Abstract

A cast-manufacturing structure (1) is cylindrical and is provided with a cylindrical body part (20) having: a trunk section (11); and a female fitting section (12) that is connected to the trunk secti

Description

Title of the Invention: STRUCTURE FOR PRODUCING CASTING Technical Field

[0001] The present invention relates to a structure for producing a casting. Background Art

[0002] In the production of castings, generally, a mold having a cavity inside is formed using casting sand and a receiving port, a sprue, a runner, and a gate for supplying molten metal to the cavity are formed to communicate with the cavity, and further, a gas vent communicating with the outside, a riser, and a strain relief are formed. Inside the cavity, a core is sometimes arranged. The applicant has previously proposed structures for producing a casting usable as the runner or the strain relief (Patent Literatures 1 and 2). The structure for producing a casting described in each of Patent Literatures 1 and 2 has a cylindrical main body and a cover layer formed on the inner face of the main body. Patent Literature 3 describes a runner obtained by fixing refractories to the inner face or the outer face of a paper pipe. Citation List Patent Literatures

[0003] Patent Literature 1: JP 2021-70052 A Patent Literature 2: JP 2012-24841 A Patent Literature 3: JP 1981-34834 Y Summary of Invention

[0004] The present invention relates to a cylindrical structure for producing a casting. In one embodiment, it is preferable that a cylindrical main body is provided which has a body part and a female joint consecutively connected to the body part and 17 03 25 having an inner diameter equal to or larger than the outer diameter of the body part. In one embodiment, it is preferable that a body inside cover layer covering the inner face of the body part and an outside cover layer covering the outer face of the female joint are provided.

[0005] In one embodiment, it is preferable that a cylindrical main body is provided which has a body part, and a male joint, which is to be internally joined to the female joint, in one end part of the body part. In one embodiment, it is preferable that the male joint has an outer diameter equal to or smaller than the inner diameter of the female joint. In one embodiment, it is preferable that a body inside cover layer covering the inner face of the body part and an outside 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 structure for producing a casting is provided with a cylindrical main body having a body part and a female joint consecutively connected to the body part and having an inner diameter equal to or larger than the outer diameter of the body part. In one aspect, it is preferable that a body part applying step is provided where a coating composition is applied to the inner face of the body part to form a body inside cover layer covering the inner face of the body part. In one aspect, it is preferable that a female joint applying step is provided where a coating composition is applied to the outer face of the female joint over the entire circumference of the female joint to form an outside cover layer covering the outer face of the female joint. Brief Description of Drawings

[0007] [Fig. 1] Fig. I is a perspective view schematically showing a preferable one embodiment 17 03 25 of a structure for producing a casting according to the present invention. [Fig. 2] Fig. 2(a) is a Ila-Ila line cross-sectional view of Fig. 1, Fig. 2(b) is a Ilb-IIb line cross-sectional view of Fig. 1, and Fig. 2(c) is a IIc-IIc line cross-sectional view of Fig. 1. [Fig. 3] Fig. 3 is a perspective view schematically showing a state in which the structures for producing a casting shown in Fig. 1 are coupled to each other. [Fig. 4] Fig. 4 is enlarged cross-sectional view of a principal part of Fig. 3. [Fig. 5] Fig. 5 is a schematic cross-sectional view of a mold housing the structure for producing a casting shown in Fig. 1 inside. [Fig. 6] Fig. 6(a) is a cross-sectional view schematically showing another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). Fig. 6(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 6(a) are coupled to each other, and is a view equivalent to Fig. 4. [Fig. 7] Fig. 7(a) is a cross-sectional view schematically showing a yet another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). Fig. 7(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 7(a) are coupled to each other, and is a view equivalent to Fig. 4. [Fig. 8] Fig. 8(a) is a cross-sectional view schematically showing a yet another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). Fig. 8(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 8(a) are coupled to each other, and is a view equivalent to Fig. 4. [Fig. 9] Fig. 9(a) is a cross-sectional view schematically showing a yet another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). Fig. 9(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 9(a) are coupled to each other, and is a view equivalent to Fig. 4. [Fig. 10] Fig. 10(a) is a cross-sectional view schematically showing a yet another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). Fig. 10(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 9(a) are coupled to each other, and is a view equivalent to Fig. 4. 17 03 25 [Fig. 11] Fig. 11 is an enlarged cross-sectional view of a principal part schematically showing another preferable embodiment of the structure for producing a casting according to the present invention. [Fig. 12] Fig. 12 is a perspective view schematically showing another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 1. [Fig. 13] Fig. 13(a) is a Xllla-XIIIa line cross-sectional view of Fig. 12, and Fig. 13(b) is a Xlllb-XIIIb line cross-sectional view of Fig. 12. [Fig. 14] Fig. 14 is a perspective view schematically showing a state in which the structures for producing a casting shown in Fig. 12 are coupled to each other, and is a view equivalent to Fig. 3. [Fig. 15] Fig. 15 is an enlarged cross-sectional view of a principal part of Fig. 14. [Fig. 16] Fig. 16(a) is a cross-sectional view schematically showing a yet another preferable embodiment of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 13(a). Fig. 16(b) is an enlarged cross-sectional view of a principal part schematically showing a state in which the structures for producing a casting shown in Fig. 16(a) are coupled to each other, and is a view equivalent to Fig. 15. [Fig. 17] Figs. 17(a) to 17(d) are perspective views schematically showing modifications of the structure for producing a casting according to the present invention, and is a view equivalent to Fig. 2(a). [Fig. 18] Figs. 18(a) to 18(e) are schematic cross-sectional views explaining one preferable aspect of a method for producing a structure for producing a casting according to the present invention. [Fig. 19] Figs. 19(a) to 19(e) are schematic cross-sectional views explaining modifications of one preferable aspect of the method for producing a structure for producing a casting according to the present invention. Description of Embodiments

[0008] A structure for producing a casting of Patent Literature 1 includes a cylindrical body part and a joint consecutively connected to the body part. With respect to the structure for producing a casting in the same literature, two or more of the structures for producing a casting can be coupled to each other by inserting one end part on the side far 17 03 25 from a joint in the body part of one of the adjacent structures for producing a casting into a joint of the other structure for producing a casting for joining. The structure for producing a casting in the same literature is configured to be able to suppress peeling of the cover layers in the pouring of the molten metal in a portion where the adjacent structures are joined to each other by setting the inner diameter of the one end part of the body part to be smaller by 1.0 mm or more than the inner diameter of the other end part. However, the structure for producing a casting has room for improvement in a possibility that the molten metal leaks to the outside of the structure for producing a casting when the pressure of the molten metal inside the structure for producing a casting is high in the pouring of the molten metal. The leakage of the molten metal is particularly likely to occur in a portion where the adjacent structures for producing a casting are joined to each other. The structure for producing a casting in Patent Literature 2 also has similar room for improvement. Patent Literature 3 does not describe anything about using a plurality of cylindrical structures for producing a casting joined to each other as a runner, and does not consider anything about preventing the leakage of the molten metal in a portion where the adjacent structures for producing a casting are joined to each other. The present invention relates to a structure for producing a casting capable of preventing the leakage of the molten metal in the pouring of the molten metal.

[0009] Hereinafter, the present invention is described based on preferable embodiments thereof. Fig. 1 shows a structure for producing a casting (hereinafter also simply referred to as a "structure") 1 according to a preferable first embodiment of the structure for producing a casting of the present invention. The structure 1 is typically cylindrical. The "cylindrical" used herein includes a straight one as shown in Fig. 1, one having a bent part 17 in a part in the axial direction as shown in Fig. 17(a), one in which the entirety in the axial direction is curved in an arc shape as shown in Fig. 17(b), one having a cylindrical second part 19 branched from a cylindrical first part 18 as shown in Figs. 17(c) and 17(d), and the like. Further, whilst the following description describes the structure as "cylindrical", the present invention includes not only tubes that are a cylindrical shape having a circular cross section but also tubes having a non-circular or polygonal cross section. The cross-sectional shape 17 03 25 orthogonal to the axial direction of a non-circular tube structure may be an oval shape. The cross-sectional shape orthogonal to the axial direction of a polygonal tube structure may be a square shape, or may be a triangular shape, a rectangular shape, a pentagonal shape or the like, and may also be a shape in which the corners of the polygon are rounded. Such structures are collectively described as being a “tube” or having a “tubular” shape

[0010] The structure 1 has a cylindrical main body 20. The main body 20 typically contains organic fibers, inorganic fibers, inorganic particles, and a binder. Each component contained in the main body 20 is described later. The main body 20 is a portion constituting a main part of the structure 1. The main body 20 preferably has a body part 11 and a female joint 12 consecutively connected to the body part 11 and having an inner diameter equal to or larger than the outer diameter of the body part 11. The female joint 12 may be formed at one end la in the axial direction of the body part 11. This example is shown in Fig. 2. In one example of the structure 1 shown in Fig. 2, the main body 20 preferably has the inner diameter larger on the one end la side in an axial direction Z than on the other end lb side.

[0011] The female joint 12 may be formed to be branched from the body part 11. This example is shown in Fig. 17(d). In one example of the structure 1 shown in Fig. 17(d), the inner diameters of end parts 1c and Id other than the female joint 12 in the structure 1 are preferably equal to or smaller than the inner diameter of the female joint 12. In one example of the structure 1 shown in Fig. 17(d), the inner diameter of the end part 1c of the structure 1 and the inner diameter of the end part Id of the structure 1 may be the same or different from each other. Only the inner diameter of any of the end part 1c and the end part Id of the structure 1 may be equal to or smaller than the inner diameter of the female joint 12.

[0012] The female joint 12 preferably has both the inner diameter and the outer diameter 17 03 25 larger than those of the body part 11. In one example of the structure 1 shown in Fig. 2, an end part on the one end la side in the axial direction Z in the body part 11 is formed with a step part 15 projecting outward in the radial direction of the body part 11, and the female joint 12 is consecutively connected to the body part 11 via the step part 15.

[0013] As the structure 1, it is preferable that more than one structure of the same or a similar type can be coupled to each other. In one example of the structure 1 shown in Fig. 1, both the ends in the axial direction Z in the main body 20 are opened. An outer diameter DI of an end part of the structure 1 other than the female joint 12 is preferably equal to or smaller than an inner diameter D2 of the female joint 12. In one example of the structure 1 shown in Figs. 1 and 2, the end part of the structure 1 other than the female joint 12 refers to an end part on the other end lb side opposite to the one end la in the axial direction Z in the body part 11. In one example of the structure 1 shown in Fig. 17(d), the end part of the structure 1 other than the female joint 12 refers to the end parts 1c and Id of a first part 18. When an outer diameter Dll of the end part 1c of the first part 18 is different from an outer diameter D12 of the end part Id of the first part 18, the outer diameter DI is the smaller diameter of the outer diameter Dll and the outer diameter DI 2. Only one of the outer diameter Dll of the end part 1c of the first part 18 and the outer diameter D12 of the end part Id of the first part 18 may be equal to or smaller than the inner diameter D2 of the female joint 12. Both the outer diameter Dll and the outer diameter D12 are more preferably equal to or smaller than the inner diameter D2 of the female joint 12. In the specification of the present application, the inner diameter and the outer diameter mean the inner diameter and the outer diameter in the entire structure 1 including both the main body and cover layers covering the surfaces of the main body, unless otherwise particularly specified.

[0014] The structure 1 is preferably configured such that the structures 1 can be coupled to each other by inserting and joining the end part 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 17 03 25 Fig. 3). The end part of the structure 1 other than the female joint 12 preferably serves as a male joint 13 internally joined to the female joint having an inner diameter equal to or larger than the outer diameter of the body part 11. In one example of the structure 1 shown in Fig. 17(d), only one of the outer diameter Dll of the end part 1c of the first part 18 and the end part Id of the first part 18 may serve as the male joint 13. Both the end part 1c and the end part Id more preferably serve as the male joints 13.

[0015] The male joint 13 means a portion inserted into the female joint 12 when the end part of the structure 1 other than the female joint 12 is internally joined to the female joint 12 of the structure 1 of the same type or a similar type. In detail, a length LI of the male joint 13 is the same as a depth L2 of the female joint 12. Herein, the "same" means not only a case where the length LI of the male joint 13 and the depth L2 of the female joint 12 are the same, but a case where the length LI and the depth L2 are approximated to such an extent that the length LI and the depth L2 are assumed to be substantially equal to each other. Specifically, when a ratio of the length LI of the male joint 13 to the depth L2 of the female joint 12 is preferably 80% or more and 120% or less, more preferably 90% or more and 110% or less, and even more preferably 95% or more and 105% or less, the depth L2 and the length LI are assumed to be the same. Examples of the length LI and the depth L2 are shown in Figs. 2(a) and 17(d). In one example of the structure 1 shown in Fig. 2, the length LI of the male joint 13 is the length of the male joint 13 along the axial direction Z of the body part 11. In one example of the structure 1 shown in Fig. 17(d), the length LI 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 one 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 one 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 substantially serves as the male joint 13. 17 03 25

[0017] The structure 1 preferably has a body inside cover layer 31 covering the inner face of the body part 11 and an outside cover layer 32 covering the outer face of the female joint 12 (hereinafter also referred to as the "outside cover layer of the female joint"). This example is shown in Fig. 2(a). The body inside cover layer 31 and the outside cover 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 both the cover layers 31 and 32 is described later.

[0018] The body inside cover layer 31 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. This example is shown in Fig. 2(b). Further, the body inside cover layer 31 is preferably continuous over the entire region of the body part 11 in the axial direction Z. More specifically, the body inside cover layer 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 into the structure 1, gas is generated from casting sand when the organic fibers, the binder, and the like contained in the main body 20 are thermally decomposed. The structure 1 has the body inside cover layer 31, and therefore can prevent the entry of the gas into the structure 1. This makes it hard for the gas to get mixed into the molten metal flowing in the structure 1. From the viewpoint of more remarkably exhibiting this effect, the body inside cover layer 31 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 body part 11.

[0020] The outside cover layer 32 of the female joint 12 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. This example 17 03 25 is shown in Fig. 2(c). The outside cover 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 outside cover 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] The structure 1 can be used to produce a casting as follows, for example. First, the structures 1 are coupled to each other to form the cylindrical body 10. Then, as shown in Fig. 5, the cylindrical body 10 is embedded in a predetermined position in 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 a part of opening parts. Specifically, the structure 1 positioned on the most upstream side among the plurality of structures 1 coupled to each other to form the cylindrical body 10 is preferably embedded in a state where the opening part on the upstream side is exposed to the outside of the casting sand. There are no particular limitations on a method for embedding the cylindrical body 10; for example, the casting sand may be arranged after the cylindrical body 10 is arranged at a predetermined position or the cylindrical body 10 may be arranged after casting sand is arranged at a predetermined position. For the casting sand of the sand mold 40, common casting sand that has been conventionally used to produce the casting of this type is usable without limitations.

[0022] Then, 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 supplied into a cavity 42 for casting. At this time, the warm strength is maintained and the heat shrinkage due to the thermal decomposition is small in the structure 1. Therefore, cracks in each structure 1 and damage to the structure 1 itself are suppressed, and the insertion of the molten metal into the structure 1 or the adhesion of the casting sand or the like to the structure 1 is also hard to occur. After the casting, the temperature is reduced to a predetermined temperature, the casting sand is removed by disassembling a flask, and the structure for producing a casting is removed through blasting treatment, exposing a casting. Thereafter, the 17 03 25 casting is subjected to post-treatment, such as trimming, as required, to complete the production of the casting. The structure 1 is suitably used as a runner or a strain relief runner used for casting, for example. Further, the structure 1 is particularly suitably used as a runner or a strain relief runner in the production of cast steel This is because the cast steel has a melting point higher than that of cast iron, and therefore the temperature of the molten metal in the pouring of the molten metal is high and the kinematic viscosity is likely to be lower.

[0023] The structure 1 has the outside cover layer 32 of the female joint 12, and thus can prevent the leakage in the pouring of the molten metal. Hereinafter, this point is described in detail. When the structures 1 are coupled to each other, it is hard to bring an end face lie of the end part other than the female joint 12 in one structure 1, i.e., the end face He 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 with each other without any gaps. Therefore, a gap is sometimes generated between the end face lie 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 step part 15. In the pouring of the molten metal, the molten metal entering the gap comes into contact with a comer part formed by an inner circumferential surface 12a of the female joint 12 and the upper surface 12e of the step part 15 (hereinafter also referred to as the "corner part of the female joint"). This sometimes damages the corner part, resulting in the generation of a pore passing through the female joint 12. The molten metal flowing in the structure 1 has a risk of leaking to the outside of the structure 1 through such a pore. However, by covering the outer face of the female joint 12 with the outside cover layer 32, the molten metal can be prevented from passing through the female joint 12 to leak out to the outside of the structure 1. The outside cover layer 32 covers the outer face of the female joint 12 as described above, and therefore poses no risk of peeling when the male joint 13 is joined to the female joint 12. Therefore, the effect of preventing the leakage of the molten metal can be surely exhibited. From the viewpoint of more effectively preventing the leakage of the molten metal, a female joint inside cover 17 03 25 layer 33 covering the inner face of the female joint 12 is preferably provided in addition to the outside cover layer 32. The female joint inside cover layer 33 is described later.

[0024] When the molten metal leaks to the outside of the structure 1, the molten metal comes into contact with the casting sand, resulting in metal penetration in which the casting sand is mixed into the molten metal. In general, when the casting is produced, a product portion formed by the solidification of the molten metal in the cavity of the sand mold and a portion other than the product formed by the solidification of the molten metal inside a runner pipe are obtained. By suppressing the mixing of the casting sand into the molten metal, the portion other than product can be easily re-used. Further, a step for removing the casting sand from the molten metal obtained by remelting the portion other than the product can be omitted, and therefore the cost can be reduced, and the quality of the molten metal obtained by remelting the portion other than product can be stabilized.

[0025] The effect of preventing the leakage of the molten metal from the structure 1 in the pouring of the molten metal is more remarkably exhibited when an inner diameter D3 of the body part 11 in the structure 1 is large. In general, the leakage of the molten metal in the pouring of the molten metal is likely to occur when the molten metal of the structure 1 has a high pressure. When the cavity 42 of the mold 40 used for the casting is large, the amount of the molten metal to be poured becomes large. To prevent a decrease in the temperature of a large amount of the molten metal during the pouring of the molten metal, one, in which the inner diameter D3 of the body part 11 is large, capable of increasing the flow rate of the molten metal to be poured is preferably used as the structure 1 constituting the cylindrical body 10 embedded in the mold 40. When the cavity 42 is large, the mold 40 also becomes large in connection therewith, and therefore the vertical height of the cylindrical body 10 is likely to be large. Therefore, when the inner diameter D3 of the body part 11 in the structure 1 is large, the structure 1 is used under a condition where the pressure of the molten metal is high in many cases. Specifically, when the inner diameter D3 of the other end part on the side opposite to the one end la side in the axial direction Z in the body part 11, i.e., the male joint 13, is 45 mm or more, it is supposed that the structure 1 is used under a condition where the molten metal has a high pressure. 17 03 25 The structure 1 of the present invention can prevent the leakage of the molten metal in the pouring of the molten metal, even when the inner diameter D3 of the body part 11 in the structure 1 is large and the pressure of the molten metal in the body part 11 is high. From the viewpoint of more remarkably exhibiting the effect of being able to prevent the leakage of the molten metal in the pouring of the molten metal, the inner diameter D3 of the male joint 13 is preferably 65 mm or more and more preferably 90 mm or more. Further, from the viewpoint of handling properties, the inner 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 outside cover layer 32 of the female joint 12 may be discontinuous in the circumferential direction of the structure 1. However, from the viewpoint of effectively preventing the leakage of the molten metal, the outside cover layer 32 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. Further, the outside cover layer 32 of the female joint 12 may cover only a part of the outer face of the female joint 12 in the axial direction Z. However, from the viewpoint of effectively preventing the leakage of the molten metal, the outside cover 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 outside cover layer 32 is continuous over the entire circumference in the circumferential direction of the structure 1 and covers the entire region of the outer face of the female joint 12 in the axial direction Z. In other words, the outside cover layer 32 more preferably covers the entire region of the outer face of the female joint 12.

[0027] In the structure 1, the outer diameter DI of the end part of the structure 1 other than the female joint 12 is preferably equal to or smaller than the inner diameter D2 of the female joint 12 as described above. This makes it easier to insert the end part of the structure 1 other than the female joint 12 into the female joint 12 of the other structure 1, and thus both the structures can be easily joined to each other. 17 03 25 From the viewpoint of making it much easier to insert 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 of the outer diameter DI to the inner diameter D2 is preferably 1 or less, more preferably 0.999 9 or less, and even more preferably 0.999 5 or less. Further, from the viewpoint of preventing the gap between the outer face of the male joint 13 and the inner face of the female joint 12 from becoming excessively large and further stabilizing the joined state therebetween when the male joint 13 of the structure 1 and the female joint 12 of the other structure 1 are joined to each other, the ratio D1 / D2 is preferably 0.9 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. From the viewpoint of achieving both of these, the ratio D2 / D1 is preferably 0.9 or more and less than 1, more preferably 0.95 or more and 0.999 9 or less, and even more preferably 0.99 or more and 0.999 5 or less.

[0028] In the structure 1, an outer diameter D4 of the female joint 12 is preferably the largest among the outer diameters of the structure 1. Thus, when the molten metal is poured in the state where the plurality of structures 1 is coupled to each other, the flow of the molten metal can be made smooth. Further, in the structure 1, the inner diameter D2 of the female joint 12 is preferably the largest among the inner diameters of the structure 1. Thus, when the molten metal is poured in the state where the plurality of structures 1 is coupled to each other, the flow of the molten metal can be made smooth.

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

[0030] Fig. 6 shows the structure I of the second embodiment. 17 03 25 The structure 1 preferably has the female joint inside cover layer 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 step part 15. The female joint inside cover layer 33 preferably covers both the inner circumferential surface 12a and the upper surface 12e. Tn other words, the female joint inside cover layer 33 covers the entire region of the inner face of the female joint 12. This example is shown in Fig. 6.

[0031] The structure 1 has the female joint inside cover layer 33, and therefore can more effectively prevent the leakage of the molten metal in the pouring of the molten metal. Hereinafter, this point is described in detail. When the structures 1 are coupled to each other, the gap is sometimes generated between the end face lie of one structure 1 and the end face 12e arranged inside the other structure 1 as described above. Since the female joint inside cover layer 33 is provided, the gap can be made smaller and can be made hard to generate. Further, even when the gap is generated 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, particularly the inner face of the corner part of the female joint, is covered with the female joint inside cover layer 33. This example is shown in Fig. 6.

[0032] The molten metal entering the gap has a risk of entering 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 with the female joint inside cover layer 33, and therefore this entry can also be prevented. This is because the female joint inside cover layer 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 the molten metal enters between both the surfaces, the female joint 12 can be protected. This is because the inner circumferential surface 12a of the female joint 12 is covered with the female joint inside cover layer 33. This example is shown in 17 03 25 Fig. 6.

[0033] The structure 1 preferably has not only the female joint inside cover layer 33 but the outside cover layer 32 of the female joint 12. More specifically, both the inner face and the outer face of the female joint 12 are preferably covered. This also contributes to more effectively preventing the leakage of the molten metal to the outside of the structure 1 in the pouring of the molten metal.

[0034] From the viewpoint of more remarkably exhibiting the effect of protecting the female joint 12, the female joint inside cover layer 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 female joint inside cover layer 33 and the body inside cover layer 31 are preferably continuous. This makes it possible to protect the inner faces of the female joint 12 and the body part 11 without any gap. The female joint inside cover layer 33 and the body inside cover layer 31 may be discontinuous. For example, the female joint inside cover layer 33 and the body inside cover layer 31 may be separate bodies.

[0036] The entire region of the inner face of the main body 20 is more preferably covered with the female joint inside cover layer 33 and the body inside cover layer 31. This makes it possible to protect the entire region of the inner face of the main body 20, and therefore the leakage of the molten metal in the pouring of the molten metal can be more effectively prevented.

[0037] Fig. 7 shows the structure 1 of the third embodiment. The structure 1 preferably has an end face cover part 34 covering the outermost 17 03 25 end face of the structure 1 in the female joint 12 (hereinafter also referred to as the "end face cover part of the female joint"). The end face cover part 34 may cover only a part of the end face of the female joint 12 or may cover the entire region of the end face.

[0038] The end face cover part 34 of the female joint 12 is provided, and therefore the leakage of the molten metal from the structure 1 in the pouring of the molten metal can be more effectively prevented. Hereinafter, this point is described in detail. When the structures 1 are coupled to each other, the molten metal sometimes enters the gap generated between the end face lie of one structure 1 and the end face 12e of the other structure 1 as described above. Thereafter, the 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 has a risk of leaking to the outside of the structure 1 from the one end la side of one structure 1, i.e., the end face side of the female joint 12 of one structure 1. However, the leakage of the molten metal from the end face side of the female joint 12 of the structure 1 to the outside of the structure 1 can be prevented by covering the end face of the female joint 12 by the end face cover part 34. From the viewpoint of more remarkably exhibiting this effect, the end face cover part 34 is preferably continuous over the entire circumference in the circumferential direction of the structure 1, and more preferably covers the entire region of the end face of the female joint 12.

[0039] In the structure 1 having the outside cover layer 32 of the female joint 12, the outside cover layer 32 and the end face cover part 34 of the female joint 12 may be discontinuous. However, from the viewpoint of more effectively preventing the leakage of the molten metal in the pouring of the molten metal, the outside cover layer 32 and the end face cover part 34 are preferably continuous, and preferably integrally molded.

[0040] Fig. 8 shows the structure I of the fourth embodiment. 17 03 25 The structure 1 preferably has a body outside cover layer 35 covering the outside of the body part 11. Further, the structure 1 preferably has the body inside cover layer 31. In the structure 1, both the inner face and the outer face of the body part 11 are more preferably covered. This example is shown in Fig. 8.

[0041] Since the structure 1 has the body inside cover layer 31 and the body outside cover layer 35, the leakage of the molten metal in the pouring of the molten metal, particularly the leakage of the molten metal through the body part 11, can be effectively prevented. For example, even when the molten metal in the structure 1 has a high pressure, the leakage of the molten metal can be prevented. From the viewpoint of more remarkably exhibiting this effect, the body outside cover layer 35 is preferably continuous over the entire circumference in the circumferential direction of the structure 1.

[0042] In the structure 1 having the female joint inside cover layer 33, the female joint inside cover layer 33 and the body inside cover layer 31 are preferably continuous, and both are more preferably integrally molded from the viewpoint of protecting the female joint 12 and the inner face of the body part 11 without any gap.

[0043] The outside cover 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 outside cover layer 32 of the female joint 12, the end face cover part 34 of the female joint 12, the female joint inside cover layer 33, and the body inside cover layer 31 are preferably continuous. The body outside cover layer 35 also preferably extends to 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 body outside cover layer 35, the outside cover layer 32 of the female joint 12, the end face cover part 34 of the female joint 12, the female joint inside cover layer 33, and the body inside cover layer 31, and that these are continuous. 17 03 25

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

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

[0046] When the female joint inside cover layer 33 partially overlaps with the body inside cover layer 31, a thickness T1 of a portion where both overlap with each other is preferably larger than both the thickness of a portion having the largest thickness in the female joint inside cover layer 33 (hereinafter also referred to as a "maximum thickness of the female joint inside cover layer") T2 and the thickness of a portion having the largest thickness in the body inside cover layer 31 (hereinafter also referred to as a "maximum thickness of the body inside cover layer") T3. Fig. 9 shows examples of T1 to T3. The body inside cover layer 31 and the female joint inside cover layer 33 preferably have a fixed thickness. Herein, the "fixed thickness" includes a case where 17 03 25 unintended slight changes in thickness occur, such as changes in thickness that are inevitable during production.

[0047] The advantage that the thickness T1 is larger than the thickness T2 is as follows. When the plurality of structures 1 is coupled to each other and the molten metal is poured, the flow of the molten metal is likely to be disturbed in connection parts between the structures 1. However, the thickness T1 is larger than the thickness T2, and therefore the flow of the molten metal can be prevented from being disturbed and the molten metal can be suppressed from colliding with the comer part of the female joint 12, and therefore the corner part of the female joint 12 can be protected. The advantage that the thickness T1 is larger than the thickness T3 is as follows. In general, when the molten metal is poured, the molten metal is made to flow from the one end la side of the structure 1 where the female joint 12 is arranged toward the other end lb side. The thickness T1 is larger than the thickness T3, and therefore the molten metal flowing in the structure 1 can be prevented from colliding with the end part on the one end la side in the body inside cover layer 31. This can protect the body inside cover layer 31 in the pouring of the molten metal.

[0048] A ratio T1 / T2 of the thickness T1 to the thickness T2 is preferably more than 1, more preferably 1.5 or more, and even more preferably 2 or more from the viewpoint of protecting the comer 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 viewpoint of protecting the female joint inside cover layer 33 from friction when the structures 1 are connected to each other. From the viewpoint of achieving both of these, the ratio T1 / T2 is preferably more 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 of the thickness T1 to the thickness T3 is preferably more than 1, more preferably 1.1 or more, and even more preferably 1.2 or more from the viewpoint of 17 03 25 protecting the body inside cover layer 31 in the pouring of the molten metal. The ratio T1 / T3 is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less from the viewpoint of smoothing the flow of the molten metal in the connection parts between the structures 1 in the pouring of the molten metal. From the viewpoint of achieving both of these, the ratio T1 / T3 is preferably more 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 female joint inside cover layer 33 is preferably smaller than the maximum thickness T3 of the body inside cover layer 31. Thus, the end part on the other end lb side of the other structure 1 can be easily inserted and joined to the female joint 12 of the structure 1. From the viewpoint of making it easy to join the end part on the other end lb side of the other structure 1 to the female joint 12 of the structure 1, a ratio T2 / T3 of the thickness T2 to the thickness T3 is preferably less than 1, more preferably 0.8 or less, and even more preferably 0.5 or less. Further, from the viewpoint of protecting the main body 20 in the female joint 12, the ratio T2 / T3 is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. From the viewpoint of achieving both of these, the ratio T2 / T3 is preferably 0.01 or more 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 body inside cover layer 31 and the female joint inside cover layer 33 do not have to be fixed. Fig. 10 shows an example of the structure 1 in which the thickness of the body inside cover layer 31 is not fixed.

[0052] When the thickness of the body inside cover layer 31 is not fixed, the body inside cover layer 31 preferably has a portion having a thickness larger than that of a portion 31a arranged in the end part on the one end la side in the axial direction Z of the body part 11 17 03 25 in the body inside cover layer 31. Thus, when the molten metal flowing inside the cylindrical body 10 obtained by coupling the structures 1 passes through the inside of the body part 11 of the structure 1 on the upstream side in a direction Z1 in which the molten metal flows to enter the body part 11 of the structure 1 on the downstream side in the direction Zl, the flow of the molten metal is hard to directly collide with the surface of the body inside cover layer 31 covering the inner face of the end part on the one end la side of the body part 11 in the structure 1 on the downstream side. This prevents the application of impact to the end part on the one end la side of the body part 11 of the structure 1 on the downstream side, and thus the body inside cover layer 31 can be protected. From the viewpoint of more remarkably exhibiting this effect, the portion 31a preferably has the smallest thickness in the body inside cover layer 31. The thickness of the body inside cover layer 31 preferably gradually increases from the one end la side toward the other end lb side in the axial direction Z. This example is shown in Fig. 10.

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

[0054] Herein, the description "the position of the edge 33b of the female joint inside cover layer 33 and the position of the edge 32b of the outside cover layer 32 coincide with each other" includes not only a case where both the positions in the consecutively connecting direction Y of the female joint 12 completely coincide with each other but a case where both the positions are approximated to such an extent that the positions are assumed to substantially coincide with each other. Specifically, when a ratio of a 17 03 25 distance L5 in the consecutively connecting direction Y between the edge 33b of the female joint inside cover layer 33 and the edge 32b of the outside cover layer 32 to a length L4 in the consecutively connecting direction Y 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 female joint inside cover layer 33 and the position of the edge 32b of the outside cover layer 32 are assumed to coincide with each other. Examples of the length L4 and the distance L5 are shown in Fig. 11.

[0055] In the structure 1, the thickness of the female joint inside cover layer 33 is preferably the smallest among the cover layers covering the surfaces of the main body 20. In other words, the thickness of the female joint inside cover layer 33 is preferably smaller than the thicknesses of the cover layers other than the female joint inside cover layer 33. Thus, the end part of the structure 1 other than the female joint 12 can be easily inserted into the female joint 12, and both can be easily joined to each other. Even in a case where the cover layers are peeled when the male joint 13 is joined to the female joint 12, the peeling amount can be reduced and influence on the product quality can be reduced.

[0056] Fig. 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 one end part of the body part 11. The male joint 13 is preferably internally joined to the female joint. The male joint 13 preferably has an outer diameter equal to or smaller than the inner diameter of the female joint. In the structure IB, the female joint 12 having the inner diameter equal to or larger than the outer 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 the inner diameter and the outer diameter 17 03 25 larger than those of the body part 11. Typically, the end part on the female joint 12 side in the body part 11 is formed with the step part 15 projecting outward in the radial direction of the body part 11, and the female joint 12 is consecutively connected to the body part 11 via the step part 15.

[0058] As the structure IB, it is preferable that more than one structure of the same or a similar type can be coupled to each other. In the structure IB of the example shown in Fig. 12, both the ends in the axial direction Z in the main body 20 are opened. The inner diameter of the female joint 12 is preferably equal to or larger than the outer diameter on the male joint 13 side of the body part 11. The structure IB is preferably configured such that the structures IB can be coupled to each other by inserting and joining the male joint 13 of the structure IB to the female joint 12 of the other structure IB. By coupling a desired number of the structures IB, a long cylindrical body 10 having a desired length can be formed. This example is shown in Fig. 14.

[0059] The structure IB preferably has the body inside cover layer 31 and an outside cover layer 36 covering the outer face of the male joint 13 (hereinafter also referred to as the "outside cover layer of the male joint"). The outside cover 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 outside cover layer 36 is described later.

[0060] The body inside cover layer 31 is preferably continuous over the entire circumference in the circumferential direction of the structure IB. This example is shown in Fig. 13(b). The body inside cover layer 31 is preferably continuous over the entire region of the body part 11 in the axial direction Z. More specifically, the body inside cover layer 17 03 25 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). The structure IB has the body inside cover layer 31, and therefore gas is hard to get mixed into the molten metal flowing in the structure IB. From the viewpoint of more remarkably exhibiting this effect, the body inside cover layer 31 is preferably continuous over the entire circumference in the circumferential direction of the structure IB and more preferably covers the entire region of the inner face of the body part 11.

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

[0062] The structure IB has the outside cover layer 36 of the male joint 13, and therefore can prevent the leakage from the structure IB in the pouring of the molten metal. Hereinafter, this point is described in detail. When the structures IB are coupled to each other, a gap is sometimes generated between end face lie of the male joint 13 of one structure IB and the end face 12e arranged inside the female joint 12 of the other structure IB. The molten metal entering the gap has a risk of entering 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. However, the structure IB can prevent the molten metal from entering 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 with the outside cover layer 36. Further, this is because the outside cover layer 36 of the male joint 13 is arranged between the outer circumferential surface lib 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. Further, it is preferable that the structure IB has the outside cover layer 36 of the male joint 13 and the body inside cover layer 31, and the outer face and the inner face of the male joint 13 are covered. This makes it possible to effectively prevent the leakage of the molten metal through the male joint 13 in the pouring of the molten metal. 17 03 25

[0063] The outside cover 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 viewpoint of effectively preventing the leakage of the molten metal.

[0064] In the fifth embodiment, the body inside cover layer 31 covers the entire region of the inner face of the body part 11 as described above. This makes it possible to protect the entire region of the inner face of the main body 20, and therefore the leakage of the molten metal in the pouring of the molten metal can be more effectively prevented.

[0065] Also in the structure IB of the fifth embodiment, the effect that the leakage of the molten metal in the pouring of the molten metal can be more effectively prevented is more remarkably exhibited when the inner diameter D3 of the body part 11 in the structure 1 is large as with the structure 1 of the first embodiment. A preferable numerical range of the inner 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 structure IB of the sixth embodiment. The structure IB preferably has the outside cover layer 36 of the male joint 13 and an end face cover part 37 covering the end face lie of the male joint 13 (hereinafter also referred to as the “end face cover part of the male joint"). The end face cover part 37 may cover only a part of the end face of the male joint 13 or may cover the entire region of the end face.

[0067] The end face cover part 37 of the male joint 13 is provided, and therefore the leakage of the molten metal from in the pouring of the molten metal more can be effectively prevented. Hereinafter, this point is described in detail. When the structures IB are coupled to each other, a gap is sometimes generated between the end face lie of the male joint 13 of one structure IB and the end face 12e arranged inside the female joint 12 of the other structure IB. The structure IB has the end face cover part 37 of the male joint 13, and thus can reduce the gap to make it hard to form the gap. This example is shown in Fig. 16.

[0068] When the structure IB has the outside cover layer 36 of the male joint 13, the outside cover layer 36 and the end face cover part 37 of the male joint 13 may be discontinuous. However, from the viewpoint of more effectively preventing the leakage of the molten metal in the pouring of the molten metal, the outside cover layer 36 and the end face cover part 37 are preferably continuous, and preferably integrally molded.

[0069] 17 03 25 When the structure IB has the body inside cover layer 31, the end face cover part 37 of the male joint 13 is preferably continuous with the body inside cover layer 31, and these are preferably integrally molded. The outside cover 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 outer diameter DI of the male joint 13 is preferably equal to or smaller than the inner diameter D2 of the end part on the other end side opposite to one end in the axial direction Z in the body part 11, i.e., the female joint 12. Thus, the male joint 13 of the structure IB can be easily inserted into the female joint 12 of the other structure IB, and both can be easily joined to each other. A preferable numerical range of the ratio D1 / D2 of the outer diameter DI to the inner diameter D2 is the same as the preferable numerical range of the ratio D1 / D2 in the first embodiment.

[0071] The body inside cover 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 body inside cover layer 31 is arranged. Thus, the body inside cover layer 31 in each of the structures 17 03 25 1 and IB conies into contact with the molten metal passing through the inside 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 the structure 1 shown in Fig. 1, the radial direction of the structure 1 in the portion where the body inside cover layer 31 is arranged is the radial direction in the transverse cross section orthogonal to the axial direction Z of the structure 1. In the example of the structure 1 shown in Fig. 17(d), the radial direction of the structure 1 in the portion where the body inside cover layer 31 is arranged is the radial direction in the transverse cross section orthogonal to the axial direction Zx of the first part 18 in the case of the body inside cover layer 31 arranged in the first part 18 and is the radial direction in the transverse cross section orthogonal to an axial direction Zy of the second part 19, i.e., the consecutively connecting direction Y of the female joint 12, in the case of the body inside cover layer 31 arranged in the female joint 12.

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

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

[0074] The main body 20 is preferably integrally molded in the circumferential direction. Thus, the main body 20 becomes continuous over the entire circumference in the circumferential direction, and therefore the formation of gaps or holes in the main body 20 can be prevented, and the leakage of the molten metal in the pouring of the molten metal can be effectively prevented. The structures 1 and IB preferably have portions not covered with the cover layers 32, 35 and 36 in parts of the outer face of the main body 20. In the pouring of the 17 03 25 molten metal, gas is generated when the organic fibers, the binder, and the like contained in the main body 20 are thermally decomposed due to the flow of the molten metal into the structure 1. Since parts of the outer face of the main body 20 are not covered with the cover layers 32, 35, and 36, the gas can be preferentially discharged from the parts to the casting sand side, i.e., the outside of the 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 with the cover layers 32, 35 and 36. From the viewpoint of effectively exhibiting the effect of preferentially discharging the gas to the outside of the structures 1 and IB, a portion not covered with the body outside cover layer 35 is preferably present in the outer face of the body part 11 in the main body 20. An uncovered area ratio that is a ratio of the area of the portion not covered with the body outside cover layer 35 to an entire area SI of the outer face of the body part 11 is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more from the viewpoint of preferentially discharging the gas to the outside of the structures 1 and IB. The uncovered area ratio is preferably 100% or less, more preferably 95% or less, and even more preferably 90% or less from the viewpoint of preventing the leakage of the molten metal to the outside of the structure 1 in the pouring of the molten metal. From the viewpoint of achieving both of these, the uncovered area ratio is preferably 30% or more and 100% or less, more preferably 50% or more and 95% or less, and even more preferably 70% or more and 90% or less.

[0076] Next, constituent materials of the structures 1 and IB are described. The main body 20 typically contains organic fibers, inorganic fibers, inorganic particles (hereinafter also referred to as first inorganic particles), and a binder (hereinafter also referred to as a first binder). Such a main body 20 is typically produced by the following method. First, a slurry composition containing organic fibers, inorganic fibers, the first inorganic particles, the first binder, and a dispersion medium (hereinafter referred to as a raw material slurry) is prepared. Subsequently, an intermediate molded body of the main body 20, e.g., a 17 03 25 main body in a water-containing state, is made into a sheet using a mold for sheet-making and dehydration molding. Next, by heating and drying the intermediate molded body using the mold, the main body 20 can be formed.

[0077] The organic fibers are entangled with the inorganic fibers, the inorganic particles before being used for casting in the main body 20 and exhibit the effect of maintaining the shapes of the structures 1 and IB. In casting, some or all of the organic fibers bum by the heat of the molten metal.

[0078] For the organic fibers, one type or two or more types selected from pulp fibers, synthetic fibers, regenerated fibers (for example, rayon fibers), and the like are usable. Among the above, pulp fibers are preferably contained. The reason therefor is that the pulp fibers can be molded into various shapes by sheet-making, the dehydrated and dried molded product has excellent strength characteristics, and the pulp fibers are easily available, stable, and economical. For the pulp fibers, one type or two or more types selected from wood pulp, cotton pulp, linter pulp, bamboo, straw, and other non-wood pulp are usable. Further, one type or two or more types selected from virgin pulp or waste paper pulp (recycled product) are usable. In the respects of easy availability, environmental protection, and reduction in production cost, waste paper pulp, such as waste newspaper, is preferably contained.

[0079] The inorganic fibers improve the strength of the structures 1 and IB before being used mainly for casting in the main body 20. The inorganic fibers maintain the shape without burning even by the heat of the molten metal in casting. In particular, when organic binders described later are used, the inorganic fibers can suppress the heat shrinkage caused by the burning of the organic fibers by the heat of the molten metal and the thermal decomposition of the organic binder. 17 03 25 For the inorganic fibers, one type 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 the above, carbon fibers are preferably contained, which have high strength even at high temperatures where metal melts, from the viewpoint of suppressing the above-described heat shrinkage. In the respect of reducing the production cost, one type or two or more types selected from rock wool and glass fibers are preferably contained.

[0081] As the first inorganic particles, one type 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 viewpoint of improving the air permeability of the main body 20, the average particle size of the first inorganic particles is preferably 10 pm or more and more preferably 15 pm or more. The average particle size of the first inorganic particles is preferably 100 pm or less from the viewpoint of improving the moldability of the main body 20. When the average particle size of the first inorganic particles is equal to or larger than the lower limits above, the permeability of the main body 20 is improved, and the gas pressure in the mold in casting moderately decreases. Further, the improvement of the permeability of the main body 20 increases gaps between the materials of the main body 20, improves the permeability of a coating composition described later into the main body 20, and makes it hard for the cover layers to peel from the main body 20. When the average particle size of the first inorganic particles is equal to or larger than the upper limits above, the inorganic particles are hard to fall off from the surface of the main body 20, and the moldability is improved.

[0083] From the viewpoint of raw material dispersibility, the apparent specific gravity of the first inorganic particles is preferably 0.5 or more and more preferably 2.8 or more. 17 03 25 From the viewpoint of weight reduction, the apparent specific gravity of the first inorganic particles is preferably 3 or less, more preferably 2.8 or less, and even more preferably 2.5 or less. The apparent specific gravity is the specific gravity of hollow particles supposing that the volume of the hollow portion inside the hollow particle is a part of the volume of the hollow particle, and coincides with the true specific gravity in the case of solid particles having no internal hollow portion. The apparent specific gravity of the first inorganic particles is in the range above, and therefore the raw material dispersibility in a sheet-making step when water is used as a dispersion medium is improved. Further, the mass of the main body 20 obtained by molding can be reduced, and therefore the handleability is improved. The composition of the main body 20 can be determined considering the bulk specific gravity together with the apparent specific gravity of the first inorganic particles. The bulk specific gravity is obtained by measuring the amount of particles that a container with a 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 may be hollow. The use of the hollow particles can reduce the apparent specific gravity of the first inorganic particles.

[0085] In the present invention, one type or two or more types selected from organic binders and inorganic binders are usable as the first binder. The organic binder is preferably contained from the viewpoint of excellent removability after casting. As the organic binder, one type or two or more types selected from thermosetting resins, such as a phenol resin, an epoxy resin, and a furan resin, are usable. Among the above, the phenol resin is preferably contained because the phenol resin hardly generates flammable gas, has a combustion suppressing effect, and has a high residual coal ratio after thermal decomposition (carbonization). 17 03 25 As the phenol resin, one type or two or more types selected from phenol resins, such as a novolak phenol resin and a resol type, and modified phenol resins modified with urea, melamine, epoxy, and the like, for example, are usable. Among the above, the resol-type phenol resin is preferably contained because the odor in molding of the main body 20 and casting defects when the main body 20 is used as a mold can be reduced without requiring curing agents, such as acids and amines

[0087] When the novolac phenol resin is used, the curing agent is preferably used in combination. The curing agent is easily soluble in water, and therefore is preferably applied to the surface of the main body 20 after dehydration. For the curing agent, hexamethylenetetramine and the like are preferably used.

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

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

[0090] The main body 20 may contain paper strengthening materials in addition to the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder. The paper strengthening materials act on maintaining the shape of the intermediate molded body. As the paper strengthening materials, one type or two or more types selected from latex, an acrylic emulsion, polyvinyl alcohol, carboxymethyl cellulose, a polyacrylamide resin, a polyamide epichlorohydrin resin, and the like are usable. 17 03 25

[0091] The body inside cover layer 31, the outside cover layer 32 of the female joint 12, the female joint inside cover layer 33, the end face cover part 34 of the female joint 12, the body outside cover layer 35, the outside cover layer 36 of the male joint 13, and the end face cover part 37 of the male joint 13 (hereinafter, these are sometimes collectively referred to as "cover layers") can be typically 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 a second binder), and clay minerals.

[0092] With respect to the refractory inorganic particles, the "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 type or two or more types selected from the group consisting of metal oxides and metal silicates are usable. Specifically, one type or two or more types selected from mullite, zircon, zirconia, alumina, olivine, spinel, magnesia, chromite, and the like are usable. From the viewpoint of improving gas defects of castings, zircon is preferably contained. Cast steel having a carbon content smaller than that of cast iron preferably contains aggregate particles other than carbonaceous substances and more preferably contains zircon having a high melting point and low wettability with molten metal.

[0093] From the viewpoint of the sealing properties of the surface of the main body 20 and the adhesion between the main body 20 and the cover layers, the average particle size of the second inorganic particles is preferably 1 pm or more and more preferably 3 pm or more. The average particle 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. 17 03 25

[0094] In the structures 1 and IB, the ratio between the average particle size of the first inorganic particles contained in the main body 20 and the average particle 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 particle size of first inorganic particles ] / [Average particle size of second inorganic particles] from the viewpoint of the sealing properties of the surface of the main body 20. The ratio between the average particle size of the first inorganic particles contained in the main body 20 and the average particle 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 yet even more preferably 6 or less in terms of [Average particle size of first inorganic particles ] / [Average particle size of second inorganic particles] from the viewpoint of the sealing properties of the surface of the main body 20. In the structures 1 and IB, the proportion of the 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 yet even more preferably 90% by mass or more.

[0095] The cover layers preferably contain clay minerals from the viewpoint of improving the hot strength and imparting viscosity in application. By compounding clay minerals in a dispersion liquid (coating composition) for obtaining the cover layers, appropriate viscosity is imparted to the dispersion liquid, and the prevention of sedimentation of the raw materials in the dispersion liquid and the raw material dispersibility are improved. As the clay minerals, one type or two or more types selected from layered silicate minerals, double chain structure minerals, and the like are usable. These substances may be natural or synthetic. As the layered silicate minerals, one type or two or more types selected from clay minerals belonging to the smectite group, the genus kaolin, and the genus illite, e.g., bentonite, smectite, hectorite, activated clay, kibushi clay, zeolite, and the like, are usable. As the double chain structure minerals, one type or two or more types selected from attapulgite, sepiolite, palygorskite, and the like are usable. 17 03 25 From the viewpoint of improving the hot strength and ensuring viscosity in application, one type or two or more types selected from attapulgite, sepiolite, bentonite, and smectite are preferably used, and one type or two or more types selected from attapulgite and sepiolite are more preferably used. The clay minerals are distinguished in that the clay minerals have a layered structure or a double chain structure from the refractory inorganic particles mainly containing a hexagonal close-packed structure and generally does not have the layered structure or the double chain structure, for example. The clay minerals are contained in a proportion of preferably 0.5 parts by mass or more and more preferably 1 part by mass or more based on 100 parts by mass of the refractory inorganic particles. The clay minerals are contained in a proportion of preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 2 parts by mass or less based on 100 parts by mass of the refractory inorganic particles. When the proportion of the clay minerals is equal to or larger than the lower limits above in the proportions above, appropriate viscosity can be imparted to the dispersion liquid, and sedimentation and floating of the raw materials in the dispersion liquid can be prevented.

[0096] The cover layers preferably further contain the second binder from the viewpoint of improving the hot strength. The use of the second binder in the formation of the cover layers is preferable from the viewpoint of improving the normal temperature strength and the heat resistance of the structure for producing a casting. As the second binder, one type or two or more types selected from the organic binders and the inorganic binders are usable, and the inorganic binders are preferably contained. As the organic binder, one type or two or more types selected from a phenol resin, an epoxy resin, a furan resin, a water-soluble alkyd resin, a water-soluble butyral resin, polyvinyl alcohol, a water-soluble acrylic resin, water-soluble polysaccharide, a vinyl acetate resin or a copolymer thereof, and the like are usable, for example. As the inorganic binder, one type or two or more types selected from various sols, such as sulfate, silicate, phosphate, lithium silicate, zirconia sol, colloidal silica, and alumina sol, and the like are usable, and one type or two or more types selected from the 17 03 25 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 the effective component based on 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 the effective component based on 100 parts by mass of the second inorganic particles.

[0097] One preferable aspect of a method for producing a structure for producing a casting of the present invention is described using a method for producing the structure 1 shown in Fig. 18 as an example. The production method of this aspect typically includes a body part applying step of forming the body inside cover layer 31 and a female joint applying step of forming the female joint outside cover layer 32. In the female joint applying step according to this aspect, the female joint inside cover layer 33 and the female joint end face cover part 34 are also formed in addition to the female joint outside cover layer 32.

[0098] In the body part applying step, the body inside 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 fill the coating composition 70 into the body part 11 (see Figs. 18(a) and 18(b)). In detail, a lid 60 is arranged at an opening end of the male joint 13. Then, the coating composition 70 is filled into the body part 11. When the upper surface of the coating composition 70 reaches the desired height, the filling with the coating composition 70 is finished. Then, after a certain period of time has elapsed, the lid 60 is opened. Then, the coating composition 70 is discharged leaving the coating composition 70 remaining on the inner face of the body part 11. 17 03 25

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

[0100] The female joint applying step is preferably performed after the body part applying step. In the female joint applying 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 dipped in a coating composition 71. Then, the coating composition 71 is spread to the inner face, the outer face, and the end face of the female joint 12 (see Fig. 18(d)). Thereafter, after a certain period of time has elapsed, the female joint 12 is taken out from the coating composition 71. Then, 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 the female joint inside cover layer 33, the female joint outside cover layer 32, and the female joint end face cover part 34, respectively. Thus, the structure 1 is produced which has the body inside cover layer 31, the female joint inside cover layer 33, the female joint outside cover layer 32, and the female joint end face cover part 34. According to the production method of this aspect, the structure 1 can be efficiently produced.

[0101] In the body part applying step, the coating composition 70 to be filled into the body part 11 may reach the upper surface 12e of the step part 15 (see Fig. 18(b)) or do not have to reach the upper surface 12e (see Fig. 19(a)). The coating composition 70 to be filled into the body part 11 may reach up to the female joint 12 (see Figs. 19(b) and 19(c)). When the coating composition 70 reaches the female joint 12, the coating composition 70 may reach the opening end of the female joint 12 (see Fig. 19(b)) or do not have to reach the opening end of the female joint 12 (see Fig. 19(c)). 17 03 25

[0102] In the body part applying step, the coating composition 70 may 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 with a brush or the like, for example, in place of filling the coating composition 70 into the body part 11. From the viewpoint of making it possible to easily form the body inside cover layer 31 to more efficiently produce the structure 1, the coating composition 70 is preferably applied by filling the coating composition 70 into the body part 11.

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

[0104] In the female joint applying step of this aspect, the female joint inside cover layer 33, the female joint outside cover layer 32, and the female joint end face cover part 34 are formed. However, in the female joint applying step, only the female joint outside cover layer 32 may be formed. The coating composition 71 may 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 with a brush or the like, for example. From the viewpoint of making it possible to easily form the female joint inside cover layer 33, the female joint outside cover layer 32, and the female joint end face cover part 34 to more efficiently produce the structure 1, the coating composition 71 is more preferably applied by dipping the female joint 12 in the main body 20 in the coating composition 71 (see Fig. 18(d)).

[0105] The order of performing the female joint applying step and the body part 17 03 25 applying step is not particularly limited. For example, the body part applying step may be performed after the female joint applying step or the female joint applying step and the body part applying step may be simultaneously performed. The coating composition 70 in the body part applying step and the coating composition 71 in the female joint applying step may be the same or different from each other.

[0106] The main body 20 can be produced by the following method, for example. <Method for producing main body 20> The main body 20 can be produced by a molding method having a sheet-making step. Such a molding method is described in paragraphs

[0052] to

[0071] of JP 2012-024841 A, for example. Specifically, first, a raw material slurry is prepared, which contains the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder in a predetermined proportion. The raw material slurry is prepared by dispersing the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder in a predetermined dispersion medium. The first binder may be compounded in the main body 20 by impregnation instead of being compounded in the raw material slurry.

[0107] As the dispersion medium, one type or two or more types selected from solvents, such as ethanol, methanol, dichloromethane, acetone, and xylene, are usable, in addition to water. Among the above, water is preferably contained from the viewpoint of ease of handling. As the content ratio of the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder in the raw material slurry, the ratio of each component is appropriately adjusted to achieve the composition of the target main body 20. The raw material slurry can be added with additives, such as paper strengthening agents, flocculants, and antiseptics, as necessary.

[0108] Next, the intermediate molded body of the main body 20 is made into a sheet 17 03 25 using the raw material slurry. In the sheet-making step of the intermediate molded body, a sheet-making and dehydration molding mold is used inside which a cavity having a shape corresponding to the outer shape of the intermediate molded body is formed by butting two split molds forming one pair to each other, for example. Then, a predetermined amount of the raw material slurry is poured under pressure from an upper opening part into the cavity of the mold. This pressurizes the inside of the cavity to a predetermined pressure. Each split mold is provided with a plurality of communication holes bringing the outside of each split mold and the cavity into communication with each other, and the inner face of each split mold is covered with a net having meshes of a predetermined size. For the pouring under pressure of the raw material slurry, a pressure pump is used, for example. The pressure of the pouring under pressure of the raw material slurry is preferably 0.01 MPa or more and 5 MPa or less, more preferably 0.01 MPa or more and 3 MPa or less, and even more preferably 0.1 MPa or more and 0.5 MPa or less.

[0109] As described above, the inside of the cavity is pressurized, and therefore the dispersion medium in the raw material slurry is discharged to the outside of the mold from the communication holes. The solid content in the raw material slurry is deposited on the net covering the cavity, and a fiber laminate is uniformly formed on the net. The fiber laminate thus obtained is a laminate in which the organic fibers and the inorganic fibers are complicatedly entangled and the binder is present between the fibers. Therefore, high shape retention properties can be obtained even when the shape is complicated or even after drying and molding. Further, the inside of the cavity is pressurized, and therefore, the raw material slurry flows inside the cavity and the raw material slurry is stirred even when a hollow intermediate molded body is molded. Therefore, the slurry concentration in the cavity is made uniform, and the fiber laminate is uniformly deposited on the net.

[0110] After the fiber laminate is formed, the pouring under pressure of the raw material slurry is stopped, and air is press-injected into the cavity to pressurize and dehydrate the fiber laminate. Thereafter, the press-injection of the air is stopped, the inside of the cavity is sucked through the communication holes, and an elastic, expandable, and hollow 17 03 25 core (elastic core) is inserted into the cavity. The core is preferably formed of urethane, fluororubber, silicone rubber, elastomer, or the like having excellent tensile strength, impact resilience, elasticity, and the like. [OHl] Next, a pressurized fluid is supplied into the elastic core inserted into the cavity to expand the elastic core, and the expanded elastic core presses the fiber laminate against the inner face of the cavity. Thus, the fiber laminate is pressed against the inner face of the cavity, and the inner face shape of the cavity is transferred to the outer face of the fiber laminate and the dehydration of the fiber laminate proceeds.

[0112] For the pressurized fluid used to expand the elastic core, compressed air (heated air), oil (heated oil), or the other various 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 considering the production efficiency of the molded body, and is more preferably 0.1 MPa or more and 3 MPa or less and even more preferably 0.1 MPa or more and 0.5 MPa or less from the viewpoint of efficient production. When the supply pressure is 0.01 MPa or more, the drying efficiency of the fiber laminate is good, and the surface properties and the transferability are also sufficient. When the supply pressure is 5 MPa or less, a good effect can be obtained and the device can be downsized.

[0113] As described above, the fiber laminate is pressed against the inner face of the cavity from the inside thereof, and therefore, the inner face shape can be accurately transferred to the outer face of the fiber laminate even when the inner face shape of the cavity is complicated. Further, even when a molded product to be produced has a complicated shape, there is no need for a sticking step of each portion, and therefore the finally obtained part is free from joints or thick portions caused by sticking. More specifically, the main body 20 to be finally obtained is a product integrally molded in the circumferential direction of the main body 20. 17 03 25 When the inner face shape of the cavity is sufficiently transferred to the outer face of the fiber laminate and the fiber laminate can be dehydrated to have a predetermined moisture content, the pressurized fluid in the elastic core is removed and the elastic core is automatically shrunk to its original size. Then, the shrunk elastic core is taken out from the inside of the cavity. Further, the mold is opened and the fiber laminate in a wet state having a predetermined moisture content is taken out. The fiber laminate can also be dehydrated and molded only by the pressurization and dehydration by the press-injection of the air into the cavity without the above-described pressing and dehydration of the fiber laminate using the elastic core.

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

[0116] Next, an elastic core similar to the elastic core used in the sheet-making step is inserted into the fiber laminate, a pressurized fluid is supplied into the elastic core to expand the elastic core, and the expanded elastic core presses the fiber laminate against the inner face of the cavity. An elastic core surface-modified with a fluororesin, a silicone resin, or the like is preferably used. The supply pressure of the pressurized fluid is preferably the same as that of the dehydration step. Under this condition, 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 viewpoint of improving the surface properties or the viewpoint of shortening drying time. The heat treatment time cannot be generalized because the heat treatment time varies 17 03 25 depending on the heating temperature. From the viewpoint of improving the quality and the 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 300°C or less, the surface properties of the intermediate molded body are good. When the heating temperature is 100°C or more, the drying time of the intermediate molded body can also be shortened.

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

[0119] The main body 20 thus obtained is pressed by the elastic core, and therefore the inner face and the outer face have high smoothness. Therefore, the molding accuracy is high, and thus a structure having high accuracy can be obtained even when the structure has joints or threaded parts. Accordingly, the structures coupled with the joints or the threaded parts enable the molten metal to smoothly flow through the inside of the structures. Further, the heat shrinkage ratio of the main body 20 in casting is less than 5%, and therefore the leakage of the molten metal due to cracks, deformation, and the like of the structures can be prevented without any problem.

[0120] The obtained intermediate molded body can be further partially or entirely impregnated with the first binder. On the other hand, when the intermediate molded body is impregnated with the first binder and is not dipped in the raw material slurry, the treatment of the raw material slurry 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, completing the production of the main body 20. 17 03 25

[0121] Although the present invention is described above based on the preferable embodiments and aspects thereof, the present invention is not limited to the above-described embodiments and aspects. The above-described embodiments and modifications thereof can be combined insofar as their contents do not contradict each other. For example, the structure for producing a casting of the present invention may have both the outside cover layer 32 of the female joint 12 and the outside cover layer 36 of the male joint 13.

[0122] Hereinafter, the present invention is detailed in more detail based on Examples, but the present invention is not limited to Examples below.

[0123] [Example 1] The structure 1 shown in Fig. 9 was produced by the above-described production method, and was used as a structure for producing a casting of Example 1. The composition of the structure for producing a casting of Example 1 is as shown in Table 1 and is as described below. Specifically, the cover layer contained 1.25 parts by mass of attapulgite and 5 parts by mass of colloidal silica based on 100 parts by mass of zircon. The main body contained 10.2 parts by mass of waste newspaper, 8.5 parts by mass of carbon fibers, 66 parts by mass of spherical silica, and 15.3 parts by mass of phenol resin when the total of all the components was set to 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. Phenol resin: Bell Pearl S890 manufactured by AIR WATER PERFORMANCE CHEMICAL INC. The male joint had an inner diameter of 99.4 mm and an outer diameter of 102.4 mm. The thickness T2 of the female joint inside cover layer was 0.1 mm, the thickness T3 of the body inside cover layer was 0.3 mm, and the thickness T1 of the portion where the female joint inside cover layer and the body inside cover layer overlapped with each 17 03 25 other was 0.4 mm.

[0124] [Example 2] The structure 1 shown in Fig. 1 was produced by the above-described production method, and was used as a structure for producing a casting of Example 2. In the female joint applying step, the coating composition 70 was applied to the outer face of the female joint 12 by applying the coating composition 70 to the outer face of the female joint 12 with a brush or the like. The composition of the structure for producing a casting of Example 2 is the same as that of the structure for producing a casting of Example 1.

[0125] [Comparative Example 1] A structure for producing a casting was produced in the same manner as Example 1, except that the female joint applying step was not performed.

[0126] [Table 1] __________ _______ Ex. 1 Ex. 2 Comp. Ex. 1 Presence or absence of female joint inside cover layer Presence Presence Absence Presence or absence of female joint end face cover part Presence Absence Absence Presence or absence of female joint outside cover layer Presence Presence Absence Female joint Inner diameter (mm) 102.5 102.5 102.7 Outer diameter (mm) 105.3 105.3 105.1 Presence or absence of leakage Absence - Presence

[0127] [Evaluation of presence or absence of leakage of molten metal in the pouring of molten metal] With respect to each of the structures for producing a casting of Example 1 and Comparative Example 1, the cylindrical bodies for producing a casting were coupled to produce cylindrical bodies. Then, molten metal was poured into a sand mold having each cylindrical body as a runner pipe to produce a casting. For the molten metal, 5 tons 17 03 25 of carbon steel casting SC450 (JIS classification) was used. Then, the surface of each cylindrical body remaining after the solidification of the molten metal was visually observed, and the cut surfaces of the joints were observed. A case where the sand mold and the metal inside the cylindrical body were able to be separated without the leakage of the molten metal from the cylindrical body was evaluated as "No leakage". A case where the molten metal leaked out from the cylindrical body and the casting sand of the sand mold partially causes metal penetration was evaluated as "Leakage occurred".

[0128] As shown in Table 1, the leakage of the molten metal occurred in Comparative Example 1. In contrast thereto, the leakage of the molten metal did not occur in Example 1. Therefore, it is found that the structure for producing a casting of the present invention can suppress the metal penetration caused by the leakage from the joints. Industrial Applicability

[0129] The structure for producing a casting of the present invention can prevent the leakage of molten metal in the pouring of the molten metal. The method for producing a structure for producing a casting of the present invention can efficiently produce a structure for producing a casting capable of preventing the leakage of molten metal in the pouring of the molten metal. 17 03 25

Claims

1. A tube structure for supplying molten metal in the production of a casting, the tube structure comprising a tubular main body, whereinthe tubular main body comprisesa body part, anda female joint consecutively connected to the body part and having an inner diameter equal to or larger than an outer diameter of the body part, andthe tube structure further comprisesa body inside cover layer covering an inner surface of the body part around its entire circumference, andan outside cover layer covering an outer surface of the female joint around its entire circumference.

2. The tube structure for supplying molten metal in the production of a casting according to claim 1, wherein the outside cover layer covers an entire region of the outer face of the female joint.

3. The tube structure for supplying molten metal in the production of a casting according to claim 1 or 2, comprising:a female joint inside cover layer covering an inner surface of the female joint around its entire circumference.

4. The tube structure for supplying molten metal in the production of a casting according to claim 3, wherein the female joint inside cover layer extends to the inner surface of the body part, and partially overlaps with the body inside cover layer.

5. The tube structure for supplying molten metal in the production of a casting according to claim 4, wherein the female joint inside cover layer is arranged on an inner side relative to the body inside cover layer, in a radial direction of the structure for producing a casting, in a portion where the female joint inside cover layer and the body inside cover layer overlap with each other.17 03 256. The tube structure for supplying molten metal in the production of a casting according to claim 4 or 5, wherein the portion, where the female joint inside cover layer and the body inside cover layer overlap with each other, has a thickness larger than both thicknesses of a portion having a largest thickness in the female joint inside cover layer and a portion having a largest thickness in the body inside cover layer.

7. The tube structure for supplying molten metal in the production of a casting according to any one of claims 3 to 6, wherein, in a consecutively connecting direction of the female joint, a position of an edge of the female joint inside cover layer on a proximal end side coincides with a position of an edge of the outside cover layer on the proximal end side.

8. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 7, comprising: an end face cover part covering an end face of the female joint.

9. The tube structure for supplying molten metal in the production of a casting according to claim 8, comprising a female joint outside cover layer covering the outer surface of the female joint around its entire circumference, andthe female joint outside cover layer and the end face cover part being continuous.

10. The tube structure for supplying molten metal in the production of a casting according to any one of claim 1 to 9, comprising:a female joint inside cover layer covering an inner surface of the female joint around its entire circumference, wherein the end face cover part and the female joint inside cover layer are continuous.

11. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 10, wherein the outside cover layer extends to the inner surface of the body part through an end face of the female joint.

12. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 11, comprising a female joint inside cover layer17 03 25covering an inner surface of the female joint around its entire circumference, wherein the female joint inside cover layer has a thickness smaller than thicknesses of the cover layers other than the female joint inside cover layer.

13. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 12, wherein an end part of the tube structure for supplying molten metal in the production of a casting other than the female joint has an outer diameter equal to or smaller than the inner diameter of the female joint.

14. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 13, wherein an inner diameter of an end part of the structure for supplying molten metal in the production of a casting other than the female joint is 100 mm or more.

15. A tube structure for supplying molten metal in the production of a casting, the tube structure comprising a tubular main body, whereinthe tubular main body comprisesa body part,a male joint in one end part of the body part, anda female joint consecutively connected to the other end of the body part and having an inner diameter equal to or larger than an outer diameter of the body part,the male joint has an outer diameter equal to or smaller than an inner diameter of the female joint,the male joint is arranged to be internally joined to the female joint of a like tube structure, andthe tube structure further comprisesa body inside cover layer covering an inner surface of the body part around its entire circumference, andan outside cover layer covering an outer surface of the male joint around its entire circumference.

16. The tube structure for supplying molten metal in the production of a casting17 03 25according to claim 15, comprising an end face cover part covering an end face of the male joint.

17. The tube structure for supplying molten metal in the production of a casting according to any one of claim 15 or 16, wherein the male joint has an inner diameter of 45 mm or more and 700 mm or less.

18. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 17, wherein the body inside cover layer is arranged on an innermost side in the radial direction of the tube structure for supplying molten metal in the production of a casting in a portion where the body inside cover layer is arranged.

19. The tube structure for supplying molten metal in the production of a casting according to any one of claims 1 to 18, wherein the outside cover layer is arranged on an outermost side in the radial direction of the tube structure for supplying molten metal in the production of a casting.

20. The tube structure for supplying molten metal in the production of a castingaccording to any one of claims 1 to 19, wherein the main body has a single layerstructure.

21. The tube structure for supplying molten metal in the production of a castingaccording to any one of claims 1 to 20, wherein the main body is integrally molded in acircumferential direction of the main body.

22. A method for producing a tube structure for supplying molten metal in the production of a casting, whereinthe tube structure comprises a tubular main body,the tubular main body comprisesa body part, anda female joint consecutively connected to the body part in axial direction, the female joint has an inner diameter equal to or larger than an outer diameter of the body part, and17 03 25the method comprises:a body part applying step where a coating composition is applied to an inner face of the body part to form a body inside cover layer covering the inner surface of the body part around its entire circumference; anda female joint applying step where a coating composition is applied to an outer surface of the female joint over an entire circumference of the female joint to form an outside cover layer covering the outer surface of the female joint around its entire circumference.

23. A method for producing a mold for cast steel, comprising embedding the structure for supplying molten metal in the production of a casting according to any one of claims 1 to 22 in casting sand leaving a part of opening parts of the structure for producing a casting.

24. A method for producing a cast steel casting, comprising:a mold production step of producing a mold by embedding the structure for supplying molten metal in the production of a casting according to any one of claims 1 to 22 in casting sand leaving a part of opening parts of the structure for producing a casting; anda casting step of pouring molten metal into the mold.

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