Casting production structure

Abstract

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

Description

Title of the invention: Casting production structure

[0001] Technical field The present invention relates to a structure for producing a casting.

[0002] State of the art In the production of castings, generally, a mold having a cavity inside is formed using casting sand and a receiving orifice, a casting jet, a runner and a grid 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 an expander are formed. Inside the cavity, a core is sometimes arranged. The applicant has previously proposed structures for producing a casting usable as a runner or expander (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 casting channel obtained by fixing refractories to the inner face or outer face of a paper pipe.

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

[0004] Summary of the invention 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 portion and a female joint consecutively connected to the body portion and having an inner diameter equal to or greater than the outer diameter of the body portion. In one embodiment, it is preferable that an inner body cover layer covering the inner face of the body portion and an outer 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 portion, and a male joint, which is to be internally joined to the female joint, in an end portion of the body portion. 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 an inner body cover layer covering the inner face of the body portion and an outer cover layer covering the outer face of the male joint are provided.

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

[0007] Brief description of the drawings [Fig.l] [Fig.l] is a perspective view schematically showing a preferable embodiment of a production structure of a casting according to the present invention. [Fig.2] [Fig.2](a) is a sectional view along line IIa-IIa of [Fig.l], [Fig.2](b) is a sectional view along line IIb-IIb of [Fig.l], and [Fig.2](c) is a sectional view along line IIc-IIc of [Fig.l]. [Fig. 3] [Fig. 3] is a perspective view schematically showing a state in which the production structures of a casting shown in [Fig.l] are coupled together. [Fig.4] [Fig.4] is an enlarged sectional view of a main part of [Fig. 3]. [Fig.5] [Fig.5] is a schematic sectional view of a mold housing the production structure of a casting shown in [Fig.l] therein. [Fig.6] [Fig.6](a) is a schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is a view equivalent to [Fig.2](a), [Fig.6](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures 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 schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is an equivalent view to [Fig.2](a), [Fig.7](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures shown in [Fig.7](a) are coupled to each other, and is an equivalent view to [Fig.4]. [Fig.8] [Fig.8](a) is a schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is a view equivalent to [Fig.2](a), [Fig.8](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures 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 schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is an equivalent view to [Fig.2](a), [Fig.9](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures shown in [Fig.9](a) are coupled to each other, and is an equivalent view to [Fig.4]. [Fig. 10] [Fig. 10](a) is a schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is a view equivalent to [Fig. 2](a), [Fig. 10](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures shown in [Fig. 9](a) are coupled to each other, and is a view equivalent to [Fig. 4]. [Fig.l 1] [Fig.l 1] is an enlarged sectional view of a main part schematically showing another preferable embodiment of the production structure of a casting according to the present invention. [Fig. 12] [Fig. 12] is a perspective view schematically showing another preferable embodiment of the production structure of a casting according to the present invention, and is an equivalent view to [Fig.l]. [Fig. 13] [Fig.l3](a) is a sectional view along line XlIIa-XIIIa of [Fig. 12], and [Fig.l3](b) is a sectional view along line XlIIb-XIIIb of [Fig.12]. [Fig. 14] [Fig. 14] is a perspective view schematically showing a state in which the production structures of 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 sectional view of a main part of [Fig.14], [Fig. 16] [Fig.l6](a) is a schematic sectional view showing another preferable embodiment of the casting production structure according to the present invention, and is a view equivalent to [Fig.l3](a), [Fig.l6](b) is an enlarged sectional view of a main part schematically showing a state in which the casting production structures shown in [Fig.l6](a) are coupled to each other, and is a view equivalent to [Fig. 15]. [Fig. 17] Figures 17(a) to 17(d) are perspective views schematically showing modifications of the production structure of a casting according to the present invention, and is a view equivalent to [Fig.2](a). [Fig. 18] Figures 18(a) to 18(e) are schematic sectional views explaining a preferable aspect of a method for producing a production structure of a casting according to the present invention. [Fig. 19] Figures 19(a) to 19(e) are schematic sectional views explaining modifications of a preferable aspect of the production method of a production structure of a casting according to the present invention.

[0008] Description of the embodiments A casting production structure of patent literature 1 includes a cylindrical body portion and a joint consecutively connected to the body portion. With respect to the casting production structure in the same literature, two or more of the casting production structures may be coupled together by inserting an end portion on the side remote from a joint in the body portion of one of the adjacent casting production structures into a joint of the other casting production structure for joining.The casting production structure 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 adjacent structures are joined together by setting the inner diameter of one end portion of the body portion to be 1.0 mm or more smaller than the inner diameter of the other end portion. However, the casting production structure has room for improvement in a possibility that the molten metal leaks to the outside of the casting production structure when the pressure of the molten metal inside the casting production structure is high in the . pouring of molten metal. Molten metal leakage is particularly likely to occur in a portion where adjacent production structures of a casting are joined together. The production structure of a casting in the patent literature 2 also has similar room for improvement. Patent literature 3 does not disclose anything about using a plurality of cylindrical casting-producing structures joined together as a casting channel, and does not consider anything about preventing leakage of molten metal in a portion where adjacent casting-producing structures are joined together. The present invention relates to a structure for producing a casting capable of preventing leakage of molten metal when pouring molten metal.

[0009] The present invention is described below on the basis of preferred embodiments thereof. [Fig.l] shows a casting production structure (hereinafter also simply referred to as "structure") 1 according to a first preferred embodiment of the casting production structure of the present invention. The structure 1 is typically cylindrical. The word "cylindrical" used herein includes one straight as shown in [Fig.l], one having a curved portion 17 in a portion in the axial direction as shown in [Fig.l7](a), one in which the entire axial direction is curved in an arc shape as shown in [Fig.l7](b), one having a second cylindrical portion 19 branching off from a first cylindrical portion 18 as shown in Figs. 17(c) and 17(d), and the like. Furthermore, the term "cylindrical" includes not only a cylindrical shape having a circular cross-section, i.e., a circular cylindrical shape, but a cylindrical shape having a polygonal cross-section, i.e., a square cylindrical shape. The cross-sectional shape orthogonal to the axial direction of a circular cylindrical structure is typically a circular shape, and may also be an oval shape.The cross-sectional shape orthogonal to the axial direction of a square cylindrical structure is typically a square shape, and may also be a triangular shape, a rectangular shape, or a polygonal shape of a pentagonal shape or larger or may be a shape in which the corners of the polygon are rounded.

[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 below. The main body 20 is a constituent portion of 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 greater than the outer diameter of the body part 11. The female joint 12 may be formed at one end 1a in the axial direction of the body part 11. This example is shown in [Fig. 2]. In an example of the structure 1 shown in [Fig. 2], the main body 20 preferably has the larger inner diameter on the one end 1a side in an axial direction Z than on the other end 1b side.

[0011] The female joint 12 may be formed to branch off from the body portion 11. This example is shown in [Fig.l7](d). In one example of the structure 1 shown in [Fig.l7](d), the inner diameters of the end portions 1c and 1d 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.l7](d), the inner diameter of the end portion 1c of the structure 1 and the inner diameter of the end portion 1d of the structure 1 may be the same as or different from each other. Only the inner diameter of any one of the end portion 1c and the end portion 1d 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 larger than those of the body part 11. In an example of the structure 1 shown in [Fig.2], an end portion of the side 1a an end 1a in the axial direction Z in the body part 11 is formed with a step portion 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 portion 15.

[0013] As structure 1, it is preferable that several structures of the same or similar type can be coupled to each other. In an example of the structure 1 shown in [Fig.l], both ends in the axial direction Z in the main body 20 are open. An external diameter DI of an end portion of the structure 1 other than the female joint 12 is preferably equal to or less than an internal diameter D2 of the female joint 12. In an example of the structure 1 shown in Figures 1 and 2, the end portion of the structure 1 other than the female joint 12 means an end portion of the other end side 1b opposite to the one end 1a in the axial direction Z in the body portion 11. In an example of the structure 1 shown in [Fig.l7](d), the end portion of the structure 1 other than the female joint 12 denotes the end portions le and Id of a first part 18. When an external diameter DI 1 of the end part le of the first part 18 is different from an external diameter D12 of the end part Id of the first part 18, the external diameter DI is the smaller diameter between the external diameter DI 1 and the external diameter D12. Only one of the external diameter DI 1 of the end part le of the first part 18 and the external diameter D12 of the end part Id of the first part 18 may be equal to or less than the internal diameter D2 of the female joint 12. Both the external diameter DI 1 and the external diameter D12 are more preferably equal to or less than the internal diameter D2 of the female joint 12. In the patent specification of the present application, the inner diameter and the outer diameter refer to the inner diameter and the outer diameter in the entire structure 1 including both the main body and the cover layers covering the surfaces of the main body, unless otherwise specifically specified.

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

[0015] The male joint 13 refers to a portion inserted into the female joint 12 when the end portion 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 or similar type.In detail, a length L1 of the male joint 13 is the same as a depth L2 of the female joint 12. Here, the term "same" means not only a case where the length L1 of the male joint 13 and the depth L2 of the female joint 12 are the same, but a case where the length L1 and the depth L2 are approximated to such an extent that the length L1 and the depth L2 are assumed to be substantially equal to each other. Specifically, when a ratio of the length L1 of the male joint 13 to the depth L2 of the female joint 12 is preferably 80% or more and 120% or less, more preferably 90% or more and 110% or less, and even more preferably 95% or more and 105% or less, the depth L2 and the . length L1 are assumed to be the same. Examples of length L1 and depth L2 are shown in Figures 2(a) and 17(d). In an example of the structure 1 shown in [Fig.2], the length L1 of the male joint 13 is the length of the male joint 13 along the axial direction Z of the body part 11. In an example of the structure 1 shown in [Fig.17](d), the length L1 of the male joint 13 is the length of the male joint 13 along an axial direction Zx of a first part 18.

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

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

[0018] The inner body covering layer 31 is preferably continuous around the entire circumference in the circumferential direction of the structure 1. This example is shown in [Fig.2](b). Furthermore, the body inner covering layer 31 is preferably continuous over the entire region of the body part 11 in the axial direction Z. More specifically, the body inner covering 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 in the structure 1, gas is generated from the casting sand when the organic fibers, binder and the like contained in the main body 20 are thermally decomposed. The structure 1 has the body inner covering layer 31, and thus can prevent the gas from entering the structure 1. Thus, it is difficult for the gas to mix with the molten metal flowing in the structure 1. From the viewpoint of more remarkably presenting this effect, the body inner covering 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 outer covering layer 32 of the female joint 12 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. This example is shown in [Fig.2](c). The outer covering layer 32 is preferably continuous over the entire region of the outer face of the female joint 12 in the axial direction Z. More specifically, the outer covering layer 32 preferably covers the entire region of the outer face of the female joint 12. This example is shown in [Fig.2](a).

[0021] Structure 1 may 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 by leaving a portion of opening parts. Specifically, the structure 1 positioned on the most upstream side among the plurality of structures 1 coupled together to form the cylindrical body 10 is preferably embedded in a state where the opening part on the upstream side is exposed outside the casting sand. There are no particular limitations on a method of embedding the cylindrical body 10; for example, 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, the common casting sand which has been conventionally used to produce the casting of this type is usable without limitations.

[0022] Next, molten metal is poured into the mold 40 for casting. Specifically, the molten metal is poured from a pouring hole 41 provided at one end of the cylindrical body 10, and the molten metal is supplied into a cavity 42 for casting. At this time, the hot strength is maintained and the thermal shrinkage due to 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 casting sand or the like to the structure 1 also occurs with difficulty. After casting, the temperature is lowered to a predetermined temperature, the casting sand is removed by disassembling a frame, and the production structure of a casting is removed by sandblasting treatment, exposing a casting. Then, the casting is subjected to post-processing, such as deburring, as required, to finalize the production of the casting. Structure 1 is suitably used as a casting channel or expander casting channel used for casting, for example. Furthermore, structure 1 is particularly suitable for use as a pouring channel or expander pouring channel in the production of cast steel. This is because cast steel has a higher melting point than cast iron and, therefore, the temperature of the molten metal in the molten metal pouring is high and the kinematic viscosity is likely to be lower.

[0023] The structure 1 has the outer covering layer 32 of the female joint 12, and can thus prevent leakage in the pouring of the molten metal. This point is described in detail below. When the structures 1 are coupled together, it is difficult to bring an end face 11e of the end portion other than the female joint 12 in one structure 1, i.e., the end face 11e 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 gap. Therefore, a gap is sometimes generated between the end face 11e 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 portion 15. When pouring the molten metal, the molten metal entering the gap comes into contact with a corner portion formed by an inner circumferential surface 12a of the female joint 12 and the upper surface 12e of the step portion 15 (hereinafter also referred to as the “corner portion of the female joint”). This sometimes damages the corner portion, leading to the generation of a pore passing through the female joint 12. The molten metal flowing into 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 outer covering layer 32, molten metal can be prevented from passing through the female joint 12 to leak to the outside of the structure 1. The outer covering layer 32 covers the outer face of the female joint 12 as described above, and thus has no risk of peeling when the male joint 13 is joined to the female joint 12. Therefore, the effect of preventing leakage of molten metal can be safely ensured. From the viewpoint of more effectively preventing the leakage of the molten metal, a female joint inner cover layer 33 covering the inner face of the female joint 12 is preferably provided in addition to the outer cover layer 32. The female joint inner 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, leading to metal penetration in which the casting sand is mixed with the molten metal. Generally speaking, in the production of the casting, a product portion formed by solidifying the molten metal in the sand mold cavity and a non-product portion formed by solidifying the molten metal inside a sprue pipe are obtained. By eliminating the mixing of the casting sand into the molten metal, the non-product portion can be easily reused. Furthermore, a step of removing the casting sand from the molten metal obtained by remelting the non-product portion can be omitted, and therefore the cost can be reduced, and the quality of the molten metal obtained by remelting the non-product portion can be stabilized.

[0025] The effect of preventing leakage of molten metal from the structure 1 when pouring the molten metal is more remarkably accomplished when an inner diameter D3 of the body portion 11 in the structure 1 is large. In general, leakage of molten metal when pouring 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 molten metal to be poured becomes large. To prevent a decrease in the temperature of a large amount of the molten metal when pouring the molten metal, a structure in which the inner diameter D3 of the body portion 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 thus the vertical height of the cylindrical body 10 is likely to be large. Therefore, when the inner diameter D3 of the body portion 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 portion on the opposite side to the one end 1a in the axial direction Z in the body portion 11, i.e., the male joint 13, is 45 mm or more, it is assumed that the structure 1 is used under a condition where the molten metal has a high pressure. The structure 1 of the present invention can prevent the leakage of molten metal when pouring 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 presenting the effect consisting of being able to prevent the leakage of the molten metal when pouring the molten metal, the internal diameter D3 of the male joint 13 is preferably 65 mm or more and more preferably 90 mm or more. Furthermore, from the point of view of handling properties, the 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 outer covering 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 leakage of the molten metal, the outer covering layer 32 is preferably continuous over the entire circumference in the circumferential direction of the structure 1. Furthermore, the outer covering layer 32 of the female joint 12 may cover only a portion of the outer face of the female joint 12 in the axial direction Z. However, from the viewpoint of effectively preventing leakage of molten metal, the outer covering layer 32 preferably covers the entire region of the outer face of the female joint 12 in the axial direction Z. It is more preferable that the outer covering layer 32 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 outer covering layer 32 more preferentially 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 portion 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 facilitates the insertion of the end portion of the structure 1 other than the female joint 12 into the female joint 12 of the other structure 1, and thus the two structures can be easily joined together. From the point of view of considerably facilitating the insertion of the end portion 13 of the structure 1 other than the female joint 12, i.e. the male joint 13 of the structure 1, into the female joint 12 of the other structure 1, a ratio D1 / D2 between the outer diameter DI and the inner diameter D2 is preferably 1 or less, more preferably 0.9999 or less, and even more preferably 0.9995 or less. Furthermore, 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 joining state between them when the male joint 13 of the structure 1 and the female joint 12 of the other structure 1 are joined together, the D1 / D2 ratio is preferably 0.9 or more, more preferably 0.95 or more, and even more preferably 0.99 or more. From the point of view of obtaining both, the ratio D2 / D1 is preferably 0.9 or more and less than 1, more preferably 0.95 or more and 0.9999 or less, and even more preferably 0.99 or more and 0.9995 or less.

[0028] 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 are coupled to each other, the flow of the molten metal can be smoothed. Furthermore, 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 are coupled to each other, the flow of the molten metal can be smoothed.

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

[0030] [Fig.6] shows the structure 1 of the second embodiment. The structure 1 preferably has the female joint inner 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 portion 15. The female joint inner covering layer 33 preferably covers both the inner circumferential surface 12a and the upper surface 12e. In other words, the female joint inner covering 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 inner covering layer 33, and thus can more effectively prevent the leakage of the molten metal when pouring the molten metal. This point is described in detail below. When the structures 1 are coupled to each other, the gap is sometimes generated between the end face 11e of one structure 1 and the end face 12e arranged inside the other structure 1 as described above. Since the female joint inner cover layer 33 is provided, the gap can be made smaller and can be made difficult to generate. In addition, even when the gap is generated and the molten metal enters the gap, the female joint 12 can be protected. Indeed, the inner face of the joint female 12, in particular the inner face of the corner portion of the female joint, is covered by the female joint inner covering layer 33. This example is shown in [Fig.6].

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

[0033] The structure 1 preferably has not only the inner cover layer of the female joint 33 but also the outer cover layer 32 of the female joint 12. More specifically, 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 molten metal to the outside of the structure 1 when pouring the molten metal.

[0034] From the viewpoint of more remarkably presenting the protective effect of the female joint 12, the female joint inner covering 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 inner cover layer 33 and the body inner 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 gaps. The female joint inner cover layer 33 and the body inner cover layer 31 may be discontinuous. For example, the female joint inner cover layer 33 and the body inner cover layer 31 may be separate bodies.

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

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

[0038] The end face covering portion 34 of the female joint 12 is provided, and thus the leakage of the molten metal from the structure 1 when pouring the molten metal can be more effectively prevented. This point is described in detail below. When the structures 1 are coupled together, the molten metal sometimes penetrates into the gap generated between the end face 11e of one structure 1 and the end face 12e of the other structure 1 as described above. Then, the molten metal sometimes penetrates 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 1a side of a structure 1, that is, the end face side of the female joint 12 of a structure 1.However, leakage of 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 with the end face covering portion 34. From the viewpoint of more remarkably presenting this effect, the end face covering portion 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 outer covering layer 32 of the female joint 12, the outer covering layer 32 and the end face covering portion 34 of the female joint 12 may be discontinuous. However, from the viewpoint of more effectively preventing leakage of the molten metal when pouring the molten metal, the outer covering layer 32 and the end face covering portion 34 are preferably continuous, and preferably integrally molded.

[0040] [Fig.8] shows the structure 1 of the fourth embodiment. The structure 1 preferably has an outer body cover layer 35 covering the exterior of the body portion 11. Furthermore, the structure 1 preferably has the inner body cover layer 31. In 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] The structure 1 having the body inner covering layer 31 and the body outer covering layer 35, the leakage of the molten metal when pouring the molten metal, especially the leakage of the molten metal through the body portion 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 presenting this effect more remarkably, the outer body covering 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 inner cover layer 33, the female joint inner cover layer 33 and the body inner 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 outer cover layer 32 preferably extends to the inner face of the body portion 11 through the end face of the female joint 12. In other words, the outer cover layer 32 of the female joint 12, the end face cover portion 34 of the female joint 12, the female joint inner cover layer 33 and the body inner cover layer 31 are preferably continuous. The body outer 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 outer cover layer 35, the outer cover layer 32 of the female joint 12, the end face cover part 34 of the female joint 12, the inner cover layer of the female joint 33, and the body inner cover layer 31, and that these are continuous.

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

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

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

[0047] The advantage that the thickness T1 is greater than the thickness T2 is as follows. When the plurality of structures 1 are coupled together and the molten metal is poured, the flow of the molten metal is likely to be disturbed in its connecting portions between the structures 1. However, the thickness T1 is greater than the thickness T2, and therefore, the flow of the molten metal can be prevented from being disturbed and the collision of the molten metal with the corner portion of the female joint 12 can be suppressed, and therefore the corner portion of the female joint 12 can be protected. The advantage that the thickness T1 is greater than the thickness T3 is as follows. Generally, when the molten metal is poured, the molten metal is caused to flow from the one end side 1a of the structure 1 where the female joint 12 is arranged to the other end side 1b. The thickness T1 is greater than the thickness T3, and therefore, the molten metal flowing into the structure 1 can be prevented from colliding with the end portion of the one end side 1a in the body inner covering layer 31. This can protect the body inner covering layer 31 when pouring the molten metal.

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

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

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

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

[0052] When the thickness of the body inner cover layer 31 is not fixed, the body inner cover layer 31 preferably has a portion having a thickness greater than that of a portion 31a arranged in the end portion of the one end side 1a in the axial direction Z of the body portion 11 in the body inner 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 Z1, the flow of the molten metal hardly directly collides with the surface of the body inner cover layer 31 covering the inner face of the one-end side end part 1a of the body part 11 in the structure 1 on the downstream side. This prevents the application of an impact to the one-end side end part 1a of the body part 11 of the structure 1 on the downstream side, and thus the body inner cover layer 31 can be protected.From the viewpoint of more remarkably presenting this effect, the portion 31a preferably has the smallest thickness in the body inner covering layer 31. . The thickness of the inner body covering layer 31 preferably increases gradually from the one end side 1a toward the other end side 1b in the axial direction Z. This example is shown in [Fig. 10].

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

[0054] Here, the description "the position of the edge 33b of the female joint inner cover layer 33 and the position of the edge 32b of the outer cover layer 32 coincide with each other" includes not only a case where the two positions in the consecutive connection direction Y of the female joint 12 completely coincide with each other, but a case where the two positions are approximated to such an extent that the positions are assumed to substantially coincide with each other.Specifically, when a ratio between a distance L5 in the consecutive connection direction Y between the edge 33b of the female joint inner cover layer 33 and the edge 32b of the outer cover layer 32 and a length L4 in the consecutive connection 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 inner cover layer 33 and the position of the edge 32b of the outer 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 inner covering layer 33 is preferably the smallest among the covering layers covering the surfaces of the main body 20. In other words, the thickness of the female joint inner covering layer 33 is preferably less than the thicknesses of the covering layers other than the female joint inner covering layer 33. Thus, the end portion of the structure 1 other than the female joint 12 can be easily inserted into the female joint 12, and the two can be easily joined to each other. Even in a case where the covering layers are peeled when the male joint 13 is joined to the female joint 12, the amount of peeling can be reduced and the influence on the product quality can be reduced.

[0056] [Fig. 12] shows a structure 1B of the fifth embodiment. The structure 1B is preferably provided with the cylindrical main body 20. The main body 20 preferably has the male joint 13 in an end portion of the body portion 11. The male joint 13 is preferably internally joined to the female joint. The male joint 13 preferably has an external diameter equal to or less than the internal diameter of the female joint. In structure IB, the female joint 12 having an inner diameter equal to or greater than the outer diameter of the body portion 11 is coupled to the other end portion of the body portion 11.

[0057] The female joint 12 preferably has an inner diameter and an outer diameter larger than those of the body part 11. Typically, the end portion of the female joint 12 side in the body part 11 is formed with the step portion 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 portion 15.

[0058] As structure IB, it is preferable that several structures of the same or similar type can be coupled to each other. In the structure IB of the example shown in [Fig.12], both ends in the axial direction Z in the main body 20 are open. The inner diameter of the female joint 12 is preferably equal to or greater than the outer diameter of the male joint 13 side of the body portion 11. The structure IB is preferably configured such that the structures IB can be coupled together 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 structures IB, a long cylindrical body 10 having a desired length can be formed. This example is shown in [Fig. 14].

[0059] The structure 1B preferably has the inner body cover layer 31 and an outer cover layer 36 covering the outer face of the male joint 13 (hereinafter also referred to as the "male joint outer cover layer"). The outer 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 outer cover layer 36 is described later.

[0060] The inner body cover layer 31 is preferably continuous around the entire circumference in the circumferential direction of the structure 1B. This example is shown in [Fig. 13](b). The inner body covering layer 31 is preferably continuous over the entire region of the body portion 11 in the axial direction Z. More specifically, the inner body covering layer 31 covers the entire region of the inner face of body part 11 also in structure IB. This example is shown in [Fig.l3](a). The structure 1B has the body inner covering layer 31, and therefore, the gas hardly mixes with the molten metal flowing in the structure 1B. From the viewpoint of more remarkably presenting this effect, the body inner covering layer 31 is preferably continuous over the entire circumference in the circumferential direction of the structure 1B and more preferably covers the entire region of the inner face of the body part 11.

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

[0062] The structure IB has the outer covering layer 36 of the male joint 13, and thus can prevent the leakage of the structure IB when pouring the molten metal. This point is described in detail below. When the IB structures are coupled to each other, a gap is sometimes generated between the end face 11e of the male joint 13 of one IB structure and the end face 12e disposed inside the female joint 12 of the other IB structure. Molten metal entering the gap presents a risk of penetration between the outer circumferential surface 11b of the male joint 13 of one IB structure and the inner circumferential surface 12a of the female joint 12 of the other IB structure. However, the IB structure can prevent molten metal from penetrating between the outer circumferential surface 11b and the inner circumferential surface 12a. This is because the outer circumferential surface 11b of the male joint 13 is also covered by the outer covering layer 36.Furthermore, this is because the outer covering layer 36 of the male joint 13 is arranged between the outer circumferential surface 11b of the male joint 13 of one structure IB and the inner circumferential surface 12a of the female joint 12 of the other structure IB. Furthermore, it is preferable that the structure IB has the outer covering layer 36 of the male joint 13 and the inner body covering layer 31, and that the outer face and the inner face of the male joint 13 are covered. This can effectively prevent leakage of the molten metal through the male joint 13 when pouring the molten metal.

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

[0064] In the fifth embodiment, the inner body covering 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 thus to more effectively prevent leakage of the molten metal when pouring the molten metal.

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

[0066] [Fig. 16] shows the structure IB of the sixth embodiment. The structure 1B preferably has the outer covering layer 36 of the male joint 13 and an end face covering portion 37 covering the end face 11e of the male joint 13 (hereinafter also referred to as the "end face covering portion of the male joint"). The end face covering portion 37 may cover only a portion of the end face of the male joint 13 or may cover the entire end face region.

[0067] The end face covering portion 37 of the male joint 13 is provided, and therefore, the leakage of the molten metal when pouring the molten metal can be more effectively prevented. This point is described in detail below. When the IB structures are coupled to each other, a gap is sometimes generated between the end face 11e of the male joint 13 of one IB structure and the end face 12e arranged inside the female joint 12 of the other IB structure. The IB structure has the end face covering portion 37 of the male joint 13, and thus can reduce the gap to make it difficult to form the gap. This example is shown in [Fig. 16].

[0068] When the structure 1B has the outer covering layer 36 of the male joint 13, the outer covering layer 36 and the end face covering portion 37 of the male joint 13 may be discontinuous. However, from the viewpoint of more effectively preventing leakage of the molten metal when pouring the molten metal, the outer covering layer 36 and the end face covering portion 37 are preferably continuous, and preferably integrally molded.

[0069] When the structure 1B has the inner body covering layer 31, the end face covering portion 37 of the male joint 13 is preferably continuous with the inner body cover layer 31, and these are preferably integrally molded. The outer covering layer 36 of the male joint 13 preferably extends to the inner face of the body portion 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 portion of the other end side opposite one end in the axial direction Z in the body portion 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 the two can be easily joined to each other. A preferred numerical range of the ratio D1 / D2 between the outer diameter DI and the inner diameter D2 is the same as the preferred numerical range of the ratio D1 / D2 in the first embodiment.

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

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

[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 when pouring the molten metal can be effectively prevented. The structures 1 and 1B preferably have portions not covered by the cover layers 32, 35, and 36 in parts of the outer face of the main body 20. When pouring molten metal, gas is generated when the organic fibers, binder, and the like contained in the main body 20 are thermally decomposed due to the flow of molten metal in the structure 1. Since parts of the outer face of the main body 20 are not covered by the cover layers 32, 35, and 36, the gas can preferentially be discharged from the parts to the casting sand side, i.e., the outside of the structures 1 and 1B.

[0075] The outer face of any of the body part 11, the male joint 13, and the female joint 12 in the main body 20 may have portions not covered by the cover layers 32, 35, and 36.From the viewpoint of effectively presenting the effect of preferentially discharging gas to the outside of the structures 1 and 1B, a portion not covered by the outer body covering layer 35 is preferably present on the outer face of the body part 11 in the main body 20. An uncovered area ratio which is a ratio between the area of ​​the portion not covered by the body outer covering layer 35 and an entire area S1 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 preferential discharge of gas to the outside of the structures 1 and 1B. 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 leakage of the molten metal to the outside of the structure 1 when pouring the molten metal. From the perspective of accomplishing these two elements, 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 structures 1 and 1B 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 first binder). Such a main body 20 is typically produced by the following method. First, a slip composition containing organic fibers, inorganic fibers, the first inorganic particles, the first binder, and a dispersion medium (hereinafter referred to as a raw material slip) is prepared. Then, an intermediate molded body of the main body 20, for example, a main body in a water-containing state, is converted into a sheet using a mold for sheet manufacturing and dehydration molding. Then, 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 have the effect of maintaining the shapes of the structures 1 and 1B. During casting, all or part of the organic fibers burn under the effect of the heat of the molten metal.

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

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

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

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

[0082] From the viewpoint of improving the air permeability of the main body 20, the average particle size of the first inorganic particles is preferably 10 qm or more and more preferably 15 qm or more. The average particle size of the first inorganic particles is preferably 100 qm or less from the viewpoint of improving the moldability of the main body 20. When the average size of the first inorganic particles is equal to or greater than the above lower limits, the permeability of the main body 20 is improved, and the gas pressure in the mold during casting decreases moderately. Furthermore, the improvement in the permeability of the main body 20 increases the gaps between the materials of the main body 20, improves the permeability of a coating composition described later in the main body 20, and makes it difficult to peel off the coating layers of the main body 20. When the average size of the first inorganic particles is equal to or greater than the above upper limits, the inorganic particles are difficult to fall from the surface of the main body 20, and the moldability is improved.

[0083] From the viewpoint of the dispersibility of the raw materials, the apparent density of the first inorganic particles is preferably 0.5 or more and more preferably 2.8 or more. From the point of view of weight reduction, the apparent density of the first inorganic particles is preferably 3 or less, more preferably 2.8 or less, and even more preferably 2.5 or less. Bulk density is the specific density of hollow particles assuming that the volume of the hollow portion inside the hollow particle is part of the volume of the hollow particle, and coincides with the true density in the case of solid particles having no internal hollow portion. The bulk density of the first inorganic particles is within the above range, and thus the dispersibility of the raw material in a sheet manufacturing step when water is used as a dispersion medium is improved. Furthermore, the mass of the main body 20 obtained by molding can be reduced, and thus the workability is improved. The composition of the main body 20 can be determined by considering the overall density as well as the bulk density of the first inorganic particles. The overall density is obtained by measuring the amount of particles that a fixed volume container 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 hollow particles may reduce the apparent density of the first inorganic particles.

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

[0086] As the phenol resin, one type or two or more types selected from phenol resins, such as a phenol novolak resin and a resol type, and phenol resins modified with urea, melamine, epoxy, and the like, for example, are usable. Among these, the resol type phenolic resin is preferably contained because the odor when molding the main body 20 and the 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 novolak phenolic resin is used, the curing agent is preferably used in combination. The curing agent is readily 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 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 a dispersion medium used for the raw material slip, one or two or more kinds selected from solvents, such as water, ethanol, methanol, dichloromethane, acetone and xylene, are usable. Among these, water is preferably contained from the point of view of ease of handling.

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

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

[0092] With respect to refractory inorganic particles, the term "refractory" means that the melting point is 1500°C or higher, preferably 1600°C or higher, and more preferably 1700°C or higher. For the second inorganic particles, one or two or more types selected from the group consisting of metal oxides and metal silicates are usable. Specifically, one or two or more types selected from mullite, zircon, zirconia, alumina, olivine, spinel, magnesia, chromite and the like are usable. From the point of view of improving gas defects in castings, zircon is preferably contained. Cast steel having a lower carbon content than cast iron preferably contains aggregated particles other than carbonaceous substances and more preferably contains zircon having a high melting point and low wettability with molten metal.

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

[0094] In structures 1 and 1B, the ratio of the average size of the first inorganic particles contained in the main body 20 to the average size of the second inorganic particles contained in the covering layers is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.8 or more in terms of [average size of the first inorganic particles] / [average size of the second inorganic particles] from the viewpoint of the sealing properties of the surface of the main body 20. The ratio of the average size of the first inorganic particles contained in the main body 20 to the average size of the second inorganic particles contained in the cover layers is preferably 35 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 6 or less in terms of [average size of the first inorganic particles] / [average size of the second inorganic particles] from the viewpoint of the sealing properties of the surface of the main body 20. In structures 1 and 1B, 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 even more preferably 90% by mass or more.

[0095] The cover layers preferably contain clay minerals from the viewpoints of improving hot strength and imparting viscosity during application. By combining clay minerals in a dispersion liquid (coating composition) to obtain the cover layers, an appropriate viscosity is imparted to the dispersion liquid and the prevention of sedimentation of raw materials in the dispersion liquid and the dispersibility of the raw materials are improved. As clay minerals, one type or two or more types selected from layered silicate minerals, double-chain structure minerals, and the like are usable. These substances can be natural or synthetic. As layered silicate minerals, one type or two or more types selected from clay minerals belonging to the smectite group, kaolin genus and illite genus, for example, bentonite, smectite, hectorite, activated clay, kibushi clay, zeolite, and the like, are usable. As minerals of double-chain structure, one type or two or more types selected from attapulgite, sepiolite, palygorskite and the like are usable. From the viewpoint of improving the hot strength and ensuring the viscosity during application, one or two or more types selected from attapulgite, sepiolite, bentonite and smectite are preferably used, and one or two or more types selected from attapulgite and sepiolite are more preferably used. Clay minerals are distinguished in that clay minerals have a layered structure or a double-chain structure from refractory inorganic particles containing mainly a hexagonal close-packed structure and generally do 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 per 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 per 100 parts by mass of the refractory inorganic particles. When the proportion of clay minerals is equal to or greater than the above lower limits in the above proportions, suitable viscosity can be imparted to the dispersion liquid, and sedimentation and flotation of 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 hot strength of the production structure of a casting. As the second binder, one or two or more types selected from organic binders and inorganic binders are usable, and inorganic binders are preferably contained. As an organic binder, one or two or more kinds selected from phenolic resin, epoxy resin, furan resin, water-soluble alkyd resin, a water-soluble butyral resin, polyvinyl alcohol, a water-soluble acrylic resin, a water-soluble polysaccharide, a vinyl acetate resin or a copolymer thereof, and the like are usable, for example. As the inorganic binder, one or two or more types selected from various sols, such as sulfate sol, silicate sol, phosphate sol, lithium silicate sol, zirconia sol, colloidal silica sol and alumina sol, and the like are usable, and one or two or more types selected from the group consisting of colloidal silica and aluminum phosphate are preferably used, and colloidal silica is preferably contained. The second binder is preferably contained in a proportion of preferably 1 part by mass or more and more preferably 3 parts by mass or more in terms of effective component per 100 parts by mass of the second inorganic particles. The second binder is preferably contained in a proportion of preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 7 parts by mass or less in terms of effective component per 100 parts by mass of the second inorganic particles.

[0097] A preferable aspect of a method for producing a production structure of 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 application step of forming the body inner cover layer 31 and a female joint application step of forming the female joint outer cover layer 32. In the female joint application step according to this aspect, the female joint inner cover layer 33 and the female joint end face cover portion 34 are also formed in addition to the female joint outer cover layer 32.

[0098] In the body part application step, the body inner 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 body part 11 with the coating composition 70 (see FIGS. 18(a) and 18(b)). In detail, a cover 60 is arranged at an opening end of the male joint 13. Then, the body part 11 is filled with the coating composition 70. When the upper surface of the coating composition 70 reaches the desired height, the filling with the coating composition 70 is completed. Then, after a certain time, the cover 60 is opened. Then, the composition of coating 70 is discharged leaving the coating composition 70 on the inner face of the body portion 11.

[0099] Next, it is preferable that the body portion 11 on which the coating composition 70 remains is left in a state where the axial direction Z of the body portion 11 is set to be substantially parallel to the vertical direction Z1, and the coating composition 70 remaining on the inner face of the body portion 11 is dried and solidified to form the body inner covering layer 31 on the inner face of the body portion 11 (see [Fig. 18](c)).

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

[0101] In the body part application step, the coating composition 70 to be filled in the body part 11 may reach the upper surface 12e of the step part 15 (see [Fig.l8](b)) or may not reach the upper surface 12e (see [Fig.l9](a)). The coating composition 70 to be filled in the body part 11 may reach 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.l9](b)) or may not have to reach the opening end of the female joint 12 (see [Fig.l9](c)).

[0102] In the body part application 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 using a brush or the like, for example, instead of filling the body part 11 with the coating composition 70. From the viewpoint of enabling the body inner covering layer 31 to be easily formed to more efficiently produce the structure 1, the coating composition 70 is preferably applied by filling the body portion 11 with the coating composition 70.

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

[0104] In the female joint application step of this aspect, the female joint inner cover layer 33, the female joint outer cover layer 32, and the female joint end face cover portion 34 are formed. However, in the female joint application step, only the female joint outer 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 using a brush or the like, for example.From the viewpoint of enabling the female joint inner cover layer 33, the female joint outer cover layer 32, and the female joint end face cover portion 34 to be easily formed to more efficiently produce the structure 1, the coating composition 71 is more preferably applied by immersing the female joint 12 in the main body 20 in the coating composition 71 (see [Fig.l8](d)).

[0105] The order of performing the female joint applying step and the body part 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 performed simultaneously. The coating composition 70 in the body part application step and the coating composition 71 in the female joint application step may be the same as or different from each other.

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

[0052] to

[0071] of JP 2012-024841 A, for example. Specifically, first, a first raw material slip 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 slip 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 combined into the main body 20 by impregnation instead of being combined into the raw material slip.

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

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

[0109] As described above, the interior of the cavity is pressurized, and therefore the dispersion medium in the raw material slip is discharged to the outside of the mold from the communication holes. The solid content in the raw material slip 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 entangled in a complicated manner 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. Furthermore, the interior of the cavity is pressurized, and therefore the raw material slip flows into the interior of the cavity and the raw material slip is stirred even when a hollow intermediate molded body is molded.Therefore, the slip concentration in the cavity is made uniform, and the fiber laminate is evenly deposited on the net.

[0110] After the fiber laminate is formed, the pressure pouring of the raw material slurry is stopped, and air is injected under pressure into the cavity to pressurize and dehydrate the fiber laminate. Then, the pressure injection of the air is stopped, the interior of the cavity is sucked out through the communication holes, and an elastic, expandable, and hollow 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.

[0111] Then, 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 dehydration of the fiber laminate occurs.

[0112] For the pressurized fluid used for expanding the elastic core, for example, compressed air (heated air), oil (heated oil) or various other types of liquids are used. The supply pressure of the pressurized fluid is preferably 0.01 MPa or more and 5 MPa or less in consideration of 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 properties of surface area and transferability are also sufficient. When the supply pressure is less than or equal to 5 MPa, a good effect can be achieved and the device can be reduced in size.

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

[0114] 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 removed from inside the cavity. Further, the mold is opened and the fiber laminate in a wet state having a predetermined moisture content is removed. The fiber laminate can also be dehydrated and molded only by pressurizing and dehydrating by press-injecting air into the cavity without the above-described pressing and dehydrating 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 drying and molding mold 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 wet-molded fiber laminate is loaded into the mold.

[0116] Next, an elastic core similar to the elastic core used in the sheet manufacturing step is inserted into the fiber laminate, a pressurized fluid is 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 higher and 300°C or lower, more preferably 150°C or higher and 250°C or lower, and even more preferably 190°C or higher and 240°C or lower from the viewpoint of improving the surface properties or from the viewpoint of shortening the drying time. The heat treatment time cannot be generalized because the heat treatment time varies depending on the heating temperature. From the viewpoint of improving the quality and productivity, the heat treatment time is preferably 0.5 minutes or higher and 30 minutes or lower, and more preferably 1 minute or higher and 10 minutes or lower. When the heating temperature is 300°C or lower, the surface properties of the intermediate molded body are good.When the heating temperature is 100°C or higher, the drying time of the intermediate molded body can also be shortened.

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

[0119] The main body 20 thus obtained is pressed by the elastic core, and thus the inner face and the outer face have a high smoothness. Therefore, the molding precision is high, and thus a structure having high precision can be obtained even when the structure has joints or threaded portions. Therefore, the structures coupled to the joints or the threaded portions allow the molten metal to flow smoothly inside the structures. Furthermore, the thermal shrinkage ratio of the main body 20 during casting is less than 5%, and thus the leakage of the molten metal due to cracks, deformations, and the like of the structures can be prevented without any problem.

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

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

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

[0123] [Example 1] Structure 1 shown in [Fig. 9] was produced by the production method described above, and was used as the production structure of a casting of Example 1. The composition of the production structure of 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 per 100 parts by mass of zirconia. 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 phenolic resin when the total of all components was set at 100 parts by mass. Zircon: Zircosil No. 1 manufactured by HAKUSUI TECH. Attapulgite: Attagel 50 manufactured by Hayashi Kasei Co., Ltd. Colloidal Silica: Snowtex 50 manufactured by Nissan Chemical Corporation Carbon Fibers: TORAYCA Chopped Fibers manufactured by Toray Industries, Inc. Spherical Silica: S85-P manufactured by Micron Co., Ltd. Phenolic Resin: Bell Pearl S890 manufactured by AIR WATER PERFORMANCE CHEMICAL INC. The male joint had an inner diameter of 99.4 mm and an outer diameter of 102.4 mm. The thickness T2 of the female joint inner cover layer was 0.1 mm, the thickness T3 of the body inner cover layer was 0.3 mm, and the thickness T1 of the portion where the female joint inner cover layer and the body inner cover layer overlapped was 0.4 mm.

[0124] [Example 2] The structure 1 shown in [Fig.l] was produced by the production method described above, and was used as a production structure of a casting of Example 2. In the female joint application 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 using a brush or the like. The composition of the production structure of a casting of Example 2 is the same as that of the production structure of a casting of Example 1.

[0125] [Comparative Example 1] A production structure of a casting was made in the same manner as Example 1, except that the female joint application step was not performed.

[0126] [Tables 1] Ex. 1 Ex. 2 Ex. Comp. 1 Presence or absence of inner covering layer of female joint Presence Presence Absence Presence or absence of end face covering part of female joint Presence Absence Absence Presence or absence of outer covering layer of female joint Presence Presence Absence Female joint Internal diameter (mm) 102.5 102.5 102.7 External diameter (mm) 105.3 105.3 105.1 Presence or absence of leakage Absence - Presence

[0127] [Evaluation of the presence or absence of molten metal leakage when pouring molten metal] For each of the casting production structures in Example 1 and Comparative Example 1, the casting production cylindrical bodies 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 of SC450 carbon steel casting (JIS classification) were used. Then, the surface of each cylindrical body remaining after the molten metal solidified 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 could be separated without leakage of the molten metal from the cylindrical body was evaluated as "No Leakage."A case where molten metal leaked from the cylindrical body and the casting sand from the sand mold partially caused metal penetration was assessed as "Leakage occurred."

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

[0129] Industrial applicability The production structure of a casting of the present invention can prevent leakage of molten metal when pouring the molten metal. The method for producing a casting production structure of the present invention can effectively produce a casting production structure capable of preventing leakage of molten metal when pouring the molten metal.

Claims

Claims

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

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

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

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

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

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

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

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

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

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

11. A cylindrical structure for producing a casting comprising a cylindrical main body, wherein the cylindrical main body comprises a body part, and a male joint in an end part of the body part, the male joint is to be internally joined to a female joint, the male joint has an outer diameter equal to or smaller than an inner diameter of the female joint, and the cylindrical structure comprises a body inner cover layer covering an inner face of the body part, and an outer cover layer covering an outer face of the male joint.

12. A casting production structure according to claim 11, comprising an end face covering portion covering an end face of the male joint.

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

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

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

Images