Cast product manufacturing device and cast product manufacturing method

Abstract

This cast product manufacturing device 10 comprises: a die 20 comprising a fixed mold 30, a movable mold 40 which can move toward or away from the fixed mold 30, and a molding space 60 which is partitioned by at least the fixed mold 30 and the movable mold 40, and in which a hollow pipe 100 that is at least partially hollow and has a thickness of 1-5 mm and a diameter of 5-20 mm e can be disposed; a first pressurizing device 80 for injecting molten metal into the molding space 60 in which the hollow pipe 100 is disposed, and primarily pressurizing the molten metal at 5-30 MPa; and a second pressurizing device 90 for secondarily pressurizing, at a second pressure of 100-300 MPa, the molten metal primarily pressurized at a first pressure.

Description

Casting manufacturing apparatus and casting manufacturing method

[0001] The present invention relates to a casting manufacturing apparatus and a method for manufacturing a casting.

[0002] A method called insert casting has been used in the manufacture of castings. For example, a casting manufactured by insert casting incorporates a pipe (e.g., a hollow pipe having at least a hollow portion) that has been manufactured separately from the casting of the casting itself. More specifically, in insert casting, a hollow pipe is placed in advance in a mold for manufacturing the casting, and then a molten metal of a metal material such as an aluminum alloy is poured into the mold. This produces a casting incorporating the hollow pipe. For example, a driving motor case is an example of a casting incorporating a hollow pipe.

[0003] For example, Patent Document 1 discloses a method for manufacturing a casting in which a smart core, in which a filler material is filled inside a tubular pipe (i.e., a hollow pipe), is inserted into a mold having a cavity, and after molten metal is poured into the cavity, the filler material inside the smart core is removed. In Patent Document 1, the inside of the tubular pipe is filled with a filler material in advance to prevent the tubular pipe from deforming when molten metal is poured into the cavity.

[0004] Japanese Patent Application Laid-Open No. 2020-124743

[0005] While the technique disclosed in Patent Document 1 can suppress deformation of the tubular pipe, it requires a dedicated device for filling the tubular pipe with filler and removing the filled filler, separate from the casting manufacturing device. Furthermore, the need for a filler filling process and a filler removal process may reduce productivity.

[0006] The present invention has been made in consideration of these points, and its object is to provide a casting manufacturing apparatus, a casting manufacturing method, and a casting that can more easily manufacture castings in which deformation of hollow pipes that are at least partially hollow is suppressed.

[0007] The casting manufacturing apparatus according to the present invention comprises a mold including a fixed mold, a movable mold that can move toward or away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold, is at least partially hollow, and can accommodate a hollow pipe that has a wall thickness of 1 mm or more and 5 mm or less and a diameter of 5 mm or more and 20 mm or less; a first pressurizing device that injects molten metal into the molding space in which the hollow pipe is disposed and primarily pressurizes the molten metal at a first pressure of 5 MPa or more and 30 MPa or less; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less.

[0008] In the casting manufacturing apparatus according to the present invention, a first pressurizing device injects molten metal into a molding space containing a hollow pipe and primarily pressurizes the molten metal at a first pressure of 5 MPa to 30 MPa. The hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa, deformation of the hollow pipe can be suppressed while filling the entire molding space with the molten metal and gradually solidifying the molten metal around the hollow pipe. The second pressurizing device then secondary pressurizes the molten metal primarily pressurized at the first pressure at a second pressure of 100 MPa to 300 MPa. This allows the molten metal filled in the molding space to solidify while reducing the occurrence of casting cavities. Because the molten metal around the hollow pipe begins to solidify before secondary pressurization, the second pressure is not directly applied to the hollow pipe, thereby suppressing deformation of the hollow pipe.

[0009] Another casting manufacturing apparatus according to the present invention comprises a mold including a fixed mold, a movable mold that can move toward or away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold, is at least partially hollow, and can accommodate a hollow pipe having a wall thickness of 1 mm or more and 5 mm or less; a first pressurizing device that injects molten metal into the molding space in which the hollow pipe is disposed and primarily pressurizes the molten metal at a first pressure of 5 MPa or more and 30 MPa or less; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less, wherein the first pressurizing device holds the molten metal in a state in which it is primarily pressurized at the first pressure for a first time, and the second pressurizing device holds the molten metal in a state in which it is secondarily pressurized at the second pressure for a second time that is longer than the first time but shorter than five times the first time.

[0010] According to another casting manufacturing apparatus according to the present invention, a first pressurizing device injects molten metal into a molding space in which a hollow pipe is disposed, primarily pressurizes the molten metal at a first pressure of 5 MPa to 30 MPa, and maintains the molten metal under the first pressure for a first period of time. The hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa and maintaining the first pressurized state for the first period of time, deformation of the hollow pipe is suppressed, and the molten metal can be filled throughout the molding space while gradually solidifying around the hollow pipe. The second pressurizing device then secondarily pressurizes the molten metal, which has been primarily pressurized at the first pressure, at a second pressure of 100 MPa to 300 MPa, and maintains the molten metal under the first pressure for a second period of time. This allows the molten metal filled in the molding space to solidify while more reliably reducing the occurrence of blowholes. Note that because the molten metal around the hollow pipe begins to solidify before the secondary pressure is applied, the second pressure is not directly applied to the hollow pipe, thereby suppressing deformation of the hollow pipe.

[0011] Another casting manufacturing apparatus according to the present invention comprises a mold including a fixed mold, a movable mold that can move toward or away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold, is at least partially hollow, and can accommodate a hollow pipe having a wall thickness of 1 mm or more and 5 mm or less; a first pressurizing device that injects molten metal into the molding space in which the hollow pipe is arranged and primarily pressurizes the molten metal at a first pressure of 5 MPa or more and 30 MPa or less; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less, wherein the first pressurizing device maintains the molten metal in a state that is primarily pressurized at the first pressure for a first time, and the second pressurizing device starts secondary pressurization at the second pressure during the first time.

[0012] According to another casting manufacturing apparatus according to the present invention, a first pressurizing device injects molten metal into a molding space containing a hollow pipe, primarily pressurizes the molten metal at a first pressure of 5 MPa to 30 MPa, and maintains the molten metal under the first pressure for a first period of time. The hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa and maintaining the first pressurized state for the first period of time, deformation of the hollow pipe can be suppressed while filling the entire molding space and gradually solidifying the molten metal around the hollow pipe. Then, during the first period of time, a second pressurizing device secondarily pressurizes the molten metal, which has been primarily pressurized at the first pressure, at a second pressure of 100 MPa to 300 MPa. This allows the molten metal filled in the molding space to solidify while more reliably reducing the occurrence of porosity. Since the molten metal around the hollow pipe begins to solidify before the second pressure is applied, the second pressure is not applied directly to the hollow pipe, and deformation of the hollow pipe can be suppressed.

[0013] a mold clamping step of bringing the movable mold closer to the fixed mold and closing the mold; an injection step of injecting molten metal into the molding space; a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa or more and 30 MPa or less; a secondary pressurizing step of secondarily pressurizing the molten metal primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less; and a removal step of separating the movable mold from the fixed mold to open the mold and remove the casting.

[0014] According to the method for manufacturing a casting according to the present invention, in the primary pressurizing step, molten metal is injected into a molding space containing a hollow pipe, and the molten metal is primarily pressurized at a first pressure of 5 MPa to 30 MPa. Here, the hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa, it is possible to fill the entire molding space with the molten metal while gradually solidifying the molten metal around the hollow pipe, while suppressing deformation of the hollow pipe. Then, in the secondary pressurizing step, the molten metal primarily pressurized at the first pressure is secondarily pressurized at a high second pressure of 100 MPa to 300 MPa. This allows the molten metal filled in the molding space to solidify while reducing the occurrence of casting cavities. Because the molten metal around the hollow pipe has already begun to solidify before secondary pressurization, the second pressure is not directly applied to the hollow pipe, thereby suppressing deformation of the hollow pipe.

[0015] Another method for producing a casting according to the present invention is a method for producing a casting comprising a hollow pipe that is at least partially hollow and has a wall thickness of 1 mm to 5 mm, and a metal material that encases the hollow pipe, and includes the following steps: a preparation step of preparing a mold comprising a fixed mold, a movable mold that can approach or move away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold and in which the hollow pipe can be placed; an arrangement step of placing the hollow pipe in the molding space; a mold clamping step of bringing the movable mold close to the fixed mold and closing the mold; an injection step of injecting molten metal into the molding space; and a casting step of casting the molten metal into the molding space. The method includes a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa or more and 30 MPa or less, a secondary pressurizing step of secondarily pressurizing the molten metal primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less, and a removal step of separating the movable mold from the fixed mold to open the mold and remove the casting, wherein in the primary pressurizing step, the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first time, and in the secondary pressurizing step, the state in which the molten metal is secondarily pressurized at the second pressure is maintained for a second time that is longer than the first time but shorter than five times the first time.

[0016] According to another method for manufacturing a casting according to the present invention, in the primary pressurizing step, molten metal is injected into a molding space containing a hollow pipe, and the molten metal is primarily pressurized at a first pressure of 5 MPa to 30 MPa, and the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first period of time. Here, the hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, which makes the pipe relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa and maintaining the primarily pressurized state for the first period of time, deformation of the hollow pipe is suppressed, and the molten metal can be filled throughout the molding space while gradually solidifying around the hollow pipe. Then, in the secondary pressurizing step, the molten metal primarily pressurized at the first pressure is secondarily pressurized at a higher second pressure of 100 MPa to 300 MPa, and the state in which the molten metal is primarily pressurized at the first pressure is maintained for a second period of time. This allows the molten metal filled in the molding space to solidify while more reliably reducing the occurrence of blowholes. Note that because the molten metal around the hollow pipe begins to solidify before the secondary pressure is applied, the second pressure is not directly applied to the hollow pipe, thereby suppressing deformation of the hollow pipe.

[0017] Another method for producing a casting according to the present invention is a method for producing a casting comprising a hollow pipe that is at least partially hollow and has a wall thickness of 1 mm to 5 mm, and a metal material that encases the hollow pipe, the method comprising the steps of: preparing a mold comprising a fixed mold, a movable mold that can approach or move away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold and in which the hollow pipe can be placed; placing the hollow pipe in the molding space; closing the mold by bringing the movable mold close to the fixed mold; The method includes an injection step of injecting molten metal into the molding space, a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa or more and 30 MPa or less, a secondary pressurizing step of secondarily pressurizing the molten metal primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less, and an ejection step of separating the movable mold from the fixed mold to open the mold and eject the casting, wherein in the primary pressurizing step, the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first time, and the secondary pressurizing step is started during the primary pressurizing step.

[0018] According to another method for producing a casting according to the present invention, in the primary pressurizing step, molten metal is injected into a molding space containing a hollow pipe, and the molten metal is primarily pressurized at a first pressure of 5 MPa to 30 MPa, and the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first period of time. Here, the hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa and maintaining the primarily pressurized state for the first period of time, deformation of the hollow pipe can be suppressed while the molten metal fills the entire molding space and gradually solidifies around the hollow pipe. Then, a secondary pressurizing step is initiated during the primary pressurizing step, and the molten metal primarily pressurized at the first pressure is secondarily pressurized at a high second pressure of 100 MPa to 300 MPa, inclusive. This allows the molten metal filled in the molding space to solidify while more reliably reducing the occurrence of blowholes. Since the molten metal around the hollow pipe begins to solidify before the second pressure is applied, the second pressure is not applied directly to the hollow pipe, and deformation of the hollow pipe can be suppressed.

[0019] According to the present invention, it is possible to provide a casting manufacturing apparatus and a casting manufacturing method that can more easily manufacture a casting in which deformation of a hollow pipe that is at least partially hollow is suppressed.

[0020] FIG. 1 is a perspective view of an apparatus for manufacturing a cast product according to one embodiment. FIG. 2 is a front view of the apparatus for manufacturing a cast product according to one embodiment. FIG. 3 is a side view of the apparatus for manufacturing a cast product according to one embodiment. FIG. 4 is a perspective view of a portion of a mold and a portion of a sleeve according to one embodiment. FIG. 5 is an exploded perspective view of a portion of a mold according to one embodiment. FIG. 6 is a perspective view schematically showing a hollow pipe. FIG. 7A is a perspective view schematically showing a cast product according to one embodiment. FIG. 7B is a side view schematically showing a cast product according to one embodiment. FIG. 8 is a perspective view of a portion of a movable mold according to one embodiment. FIG. 9 is a perspective view showing a hollow pipe attached to a portion of the movable mold according to one embodiment. FIG. 10 is a perspective view showing a hollow pipe arranged in a portion of a fixed mold according to one embodiment. FIG. 11 is a perspective view showing a hollow pipe arranged in a core according to one embodiment. FIG. 12 is a perspective view showing a state in which an insertion portion of a slide core is inserted into a midsection of a hollow pipe according to one embodiment. FIG. 13 is a perspective view of a slide core according to one embodiment. Fig. 14 is a side view showing the positional relationship between the protruding member, the protruding portion, and the hollow pipe when the hollow pipe is placed in the molding space. Fig. 15 is a cross-sectional view schematically showing a part of a casting manufacturing apparatus according to one embodiment. Fig. 16 is a flowchart showing a casting manufacturing method. Fig. 17 is a diagram showing the relationship between the injection step, the primary pressurizing step, and the secondary pressurizing step. Fig. 18 is a plan view showing a hollow pipe according to an example. Fig. 19 is a diagram showing test results of the example.

[0021] Hereinafter, an embodiment of a casting manufacturing apparatus according to the present invention will be described with reference to the drawings. It should be noted that the embodiment described here is not intended to limit the present invention. Furthermore, the same reference numerals are used to designate components and parts that perform the same functions, and redundant descriptions will be omitted or simplified as appropriate.

[0022] FIG. 1 is a perspective view of a casting manufacturing apparatus 10 according to the present embodiment. The casting manufacturing apparatus 10 employs a die-casting method, i.e., a high-speed, high-pressure casting method (known as high-pressure casting). Here, high pressure refers to, for example, a pressure of 100 MPa or more and 300 MPa or less. The casting manufacturing apparatus 10 is an apparatus for manufacturing a casting 140 (see FIG. 7A) including a hollow pipe 100 (see FIG. 6) and a metal material 120 (see FIG. 7A) that encases the hollow pipe 100. The casting manufacturing apparatus 10 includes a mold 20, a first pressurizing device 80, and a second pressurizing device 90. Here, the direction in which a movable mold 40 (described later) moves relative to a fixed mold 30 is defined as a first direction D1, a direction perpendicular to the first direction D1 in a plan view is defined as a second direction D2, and a vertical direction is defined as a third direction D3. The second direction D2 is an example of a predetermined direction. However, the above directions are merely defined for the convenience of explanation, and do not limit the manner in which the mold 20 is installed, nor do they limit the present invention in any way.

[0023] The hollow pipe 100 is made of a metal (e.g., an aluminum alloy) with high thermal conductivity. The hollow pipe 100 is at least partially hollow. In this embodiment, the hollow pipe 100 is hollow throughout. The hollow pipe 100 has a circular cross section. Note that the cross section of the hollow pipe 100 is not limited to a circular cross section, and may be, for example, an elliptical cross section. As shown in FIG. 6 , the hollow pipe 100 has a linear first end 102, a linear second end 106 parallel to the first end 102, and a middle portion 110 located between the first end 102 and the second end 106. The first end 102, the second end 106, and the middle portion 110 are integrally formed. The first end 102 has a first opening 103. The second end 106 has a second opening 107. The first end 102 and the second end 106 have the same length from the midpoint 110, but may have different lengths. The first end 102 and the second end 106 are aligned in the second direction D2. The first end 102 and the second end 106 extend in the same direction from the midpoint 110. That is, the first opening 103 and the second opening 107 open in the same direction. Note that the first opening 103 and the second opening 107 may open in different directions. The midpoint 110 is formed in a spiral shape extending in the second direction D2. The midpoint 110 has multiple bent portions 112 that bend in an arc shape. The bent portions 112 bend by 90° or more (e.g., 180° or more). The bent portions 112 are aligned in the second direction D2. When the hollow pipe 100 is cast in the metal material 120, the bent portion 112 is covered by the metal material 120 and is not exposed to the outside. As shown in FIG. 9 , the midway portion 110 has a plurality of interlocking portions 113 arranged in the second direction D2. The interlocking portions 113 are part of the bent portion 112. Note that the shape of the midway portion 110 is not limited to a spiral shape. As shown in FIG. 6 , the wall thickness TH of the hollow pipe 100 is, for example, 1 mm or more and 5 mm or less (e.g., 1 mm or more and 2 mm or less). The diameter RH of the hollow pipe 100 is, for example, 5 mm or more and 20 mm or less (e.g., 5 mm or more and 10 mm or less). The ratio of the diameter RH to the wall thickness TH (diameter RH / wall thickness TH) is, for example, 4 or more and 20 mm or less.As described above, the hollow pipe 100 has a relatively thin wall thickness TH and a relatively short diameter RH, and therefore has the property of being easily deformed.

[0024] As shown in FIG. 7A , the casting 140 includes a hollow pipe 100 and a metal material 120 that surrounds the hollow pipe 100. The hollow pipe 100 and the metal material 120 are integrated together. A portion of the first end 102, a portion of the second end 106, and the entire middle portion 110 (i.e., the entire bent portion 112) of the hollow pipe 100 are covered with the metal material 120. A portion of the first end 102 including the first opening 103 and a portion of the second end 106 including the second opening 107 are exposed to the outside from the metal material 120. The metal material 120 is, for example, the same metal as the hollow pipe 100. The metal material 120 is, for example, an aluminum alloy. Note that the metal material 120 and the hollow pipe 100 may be different metals. As shown in FIGS. 7A and 7B , when viewed from the second direction D2, the metal material 120 has an inner circumferential surface 122 located radially inward of the midway portion 110, an outer circumferential surface 123 located radially outward of the midway portion 110, and a recess 124 recessed radially outward from the inner circumferential surface 122. The recess 124 extends in the second direction D2. The recess 124 opens in the second direction D2 at one end of the inner circumferential surface 122 in the second direction D2. Note that the recess 124 may also open in the second direction D2 at the other end of the inner circumferential surface 122 in the second direction D2. The recesses 124 are provided at equal intervals around the circumferential direction of the inner circumferential surface 122. Here, the metal material 120 has four recesses 124, but the number of recesses 124 is not limited to four. Note that a portion of the midway portion 110 may be exposed to the outside at the recess 124. The metal material 120 includes a chill layer located around the hollow pipe 100. The thickness of the chill layer is thinner than the wall thickness TH (see FIG. 6 ) of the hollow pipe 100. The thickness of the chill layer is, for example, 0.1 mm or more and 0.5 mm or less (e.g., 0.4 mm). The casting 140 can be used, for example, as a case for a drive motor.

[0025] As shown in FIG. 1 , the mold 20 includes a mold body 25. The mold body 25 includes a fixed mold 30, a movable mold 40 that can move toward or away from the fixed mold 30, a core 50 with at least a portion located between the fixed mold 30 and the movable mold 40, and a sliding core 55 with at least a portion located between the fixed mold 30 and the movable mold 40. The fixed mold 30 has a cavity portion 31 (see FIG. 10 ) formed therein and used to form a portion of the casting 140. The movable mold 40 has a core portion 41 (see FIG. 8 ) formed therein and used to form a portion of the casting 140. The core 50 is a member that slides in the third direction D3. The sliding core 55 is a member that slides in the second direction D2. As shown in FIG. 5 , the sliding core 55 includes a main body portion 56 and a cylindrical (including hollow and solid) insert portion 57. The insert portion 57 extends in the second direction D2. As shown in FIG. 12, the insertion portion 57 is inserted into the middle portion 110 of the hollow pipe 100 (inside the spiral portion).

[0026] As shown in FIG. 14 , the mold 20 has a molding space 60 in which a hollow pipe 100 can be placed. The molding space 60 is the space in which the hollow pipe 100 is placed. The molding space 60 is the space into which molten metal material (molten metal) is poured. The molding space 60 is the space in which a casting 140 is molded. When the movable mold 40, the core 50, and the sliding core 55 are brought close to the fixed mold 30 and the mold 20 is closed, the molding space 60 is formed by the movable mold 40, the fixed mold 30, the core 50, and the sliding core 55. The molding space 60 is defined by the fixed mold 30, the movable mold 40, the core 50, and the sliding core 55. Note that if the mold body 25 does not have the core 50 and the sliding core 150, the molding space 60 is defined by the fixed mold 30 and the movable mold 40.

[0027] The mold 20 has holding portions 42 (see FIG. 8 ) that hold both ends of the hollow pipe 100 (i.e., the first end 102 and the second end 106). As shown in FIG. 9 , the movable mold 40 has a first holding portion 42A (see also FIG. 8 ) that holds the first end 102 of the hollow pipe 100 and a second holding portion 42B (see also FIG. 8 ) that holds the second end 106 of the hollow pipe 100. The first holding portion 42A and the second holding portion 42B are through holes formed in the movable mold 40. When the hollow pipe 100 is placed in the molding space 60 (i.e., when the hollow pipe 100 is attached to the movable mold 40), the first end 102 is inserted into the first holding portion 42A, and the second end 106 is inserted into the second holding portion 42B. In this way, the hollow pipe 100 is held by the movable mold 40. 14 , in this embodiment, the first holding portion 42A and the second holding portion 42B are provided on the movable mold 40, but they may also be provided on the fixed mold 30. When the hollow pipe 100 is placed in the molding space 60 (i.e., when the hollow pipe 100 is attached to the movable mold 40), the middle portion 110 of the hollow pipe 100 does not come into contact with the inner surface 40A of the movable mold 40, the inner surface 30A of the fixed mold 30, or the inner surface 50A of the core 50.

[0028] The mold 20 includes a plurality of protruding members 70 that restrict movement of the hollow pipe 100 within the molding space 60 when molten metal is injected into the molding space 60. The protruding members 70 are configured to restrict movement of the midsection 110 of the hollow pipe 100 in the second direction D2. The protruding members 70 are configured to restrict movement (e.g., radial outward movement) of the midsection 110 of the hollow pipe 100 in a direction intersecting the second direction D2 (e.g., a direction perpendicular to the second direction D2, e.g., a radial direction of the midsection 110). The protruding members 70 protrude from the inner surface of the mold body 25 toward the molding space 60. As shown in FIG. 14 , the protruding members 70 include a fixed mold-side protruding member 71 provided on the fixed mold 30, a movable mold-side protruding member 72 provided on the movable mold 40, and a core-side protruding member 73 provided on the core 50.

[0029] As shown in FIG. 8 , the movable mold side protruding member 72 is provided on the movable mold 40. The movable mold side protruding member 72 is formed integrally with the movable mold 40. However, the movable mold side protruding member 72 may also be formed separately from the movable mold 40. That is, the movable mold side protruding member 72 may be detachably provided on the movable mold 40. The movable mold side protruding member 72 protrudes from the inner surface 40A of the movable mold 40 toward the molding space 60. The movable mold side protruding member 72 protrudes from the inner surface 40A of the movable mold 40 toward the fixed mold 30. The movable mold side protruding member 72 extends in the first direction D1. As shown in FIG. 9 , the multiple movable mold side protruding members 72 are provided so as to be respectively positioned between adjacent locked portions 113 when the hollow pipe 100 is placed in the molding space 60 (i.e., when the hollow pipe 100 is attached to the movable mold 40). The movable mold side protruding member 72 is provided so as to be able to come into contact with the hollow pipe 100 (more specifically, the locked portion 113). The multiple movable mold side protruding members 72 have the same amount of protrusion (length in the first direction D1) from the inner surface 40A of the movable mold 40. However, the multiple movable mold side protruding members 72 may have different amounts of protrusion from the inner surface 40A of the movable mold 40.

[0030] As shown in FIG. 10 , the fixed mold side protruding member 71 is provided on the fixed mold 30. The fixed mold side protruding member 71 is formed integrally with the fixed mold 30. However, the fixed mold side protruding member 71 may also be formed separately from the fixed mold 30. That is, the fixed mold side protruding member 71 may be provided detachably on the fixed mold 30. The fixed mold side protruding member 71 protrudes from the inner surface 30A of the fixed mold 30 toward the molding space 60. The inner surface 30A faces the inner surface 40A of the movable mold 40. The fixed mold side protruding member 71 protrudes from the inner surface 30A of the fixed mold 30 toward the movable mold 40. The fixed mold side protruding member 71 extends in the first direction D1. The multiple fixed mold side protruding members 71 are provided so as to be respectively positioned between adjacent locked portions 113 when the hollow pipe 100 is placed in the molding space 60 (i.e., when the mold 20 is closed). The fixed mold side protruding member 71 is provided so as to be able to come into contact with the hollow pipe 100 (more specifically, the locked portion 113). The fixed mold side protruding members 71 have the same protruding amount (length in the first direction D1) from the inner surface 30A of the fixed mold 30. However, the fixed mold side protruding members 71 may have different protruding amounts from the inner surface 30A of the fixed mold 30.

[0031] As shown in FIG. 11 , the core-side protruding member 73 is provided on the core 50. The core-side protruding member 73 is formed integrally with the core 50. However, the core-side protruding member 73 may also be formed separately from the core 50. That is, the core-side protruding member 73 may be detachably attached to the core 50. The core-side protruding member 73 protrudes from the inner surface 50A of the core 50 toward the molding space 60. The inner surface 50A is perpendicular to the inner surface 40A of the movable mold 40 and the inner surface 30A of the fixed mold 30. The core-side protruding member 73 protrudes downward from the inner surface 50A of the core 50. The core-side protruding member 73 extends in the third direction D3. The multiple core-side protruding members 73 are arranged so as to be positioned between adjacent locked portions 113 when the hollow pipe 100 is placed in the molding space 60 (i.e., when the mold 20 is closed). The core side protruding member 73 is arranged so as to be able to come into contact with the hollow pipe 100 (more specifically, the engaged portion 113) when the hollow pipe 100 is placed in the molding space 60 (i.e., when the mold 20 is closed).

[0032] As shown in Fig. 5, the mold 20 has a plurality of protrusions 58 that prevent the hollow pipe 100 from moving within the molding space 60 when molten metal is injected into the molding space 60. The protrusions 58 are provided on the slide core 55. The protrusions 58 are configured to prevent the middle portion 110 of the hollow pipe 100 from moving (e.g., moving radially inward) in a direction intersecting the second direction D2 (e.g., a direction perpendicular to the second direction D2; e.g., a radial direction of the middle portion 110). The protrusions 58 are provided so as to be able to come into contact with the middle portion 110. During the process of inserting the slide core 55 into the middle portion 110 of the hollow pipe 100, a gap large enough to allow insertion of the slide core 55 is formed between the outer diameter ends of the protrusions 58 and the inner circumferential surface of the middle portion 110. When the slide core 55 is completely inserted into the intermediate portion 110, the outer diameter end of the protruding portion 58 is in contact with the inner peripheral surface of the intermediate portion 110. However, when the slide core 55 is completely inserted into the intermediate portion 110, the outer diameter end of the protruding portion 58 does not have to be in contact with the inner peripheral surface of the intermediate portion 110. As shown in FIG. 13 , the protruding portions 58 are formed on the outer peripheral surface 57S of the insertion portion 57 of the slide core 55. The protruding portions 58 extend in the second direction D2. The protruding portions 58 are formed to be spaced apart from each other in the circumferential direction of the outer peripheral surface 57S. The protruding portions 58 are provided at equal intervals in the circumferential direction of the outer peripheral surface 57S. As shown in FIGS. 12 and 14 , the protruding portions 58 protrude toward the intermediate portion 110.

[0033] 14 , when the hollow pipe 100 is placed in the molding space 60, the movable mold-side protruding member 72, the fixed mold-side protruding member 71, and the core-side protruding member 73 are positioned between adjacent locked portions 113 of the hollow pipe 100, thereby suppressing movement of the hollow pipe 100 (particularly, movement of the midway portion 110 radially outward and in the second direction D2). Furthermore, when the hollow pipe 100 is placed in the molding space 60, the protruding portion 58 is positioned radially inward of the midway portion 110, thereby suppressing movement of the midway portion 110 radially inward. When the hollow pipe 100 is placed in the molding space 60, the movable mold-side protruding member 72, the fixed mold-side protruding member 71, the core-side protruding member 73, and the protruding portion 58 can hold the midway portion 110 of the hollow pipe 100 in a predetermined position. When the slide core 55 is inserted into the mid-portion 110, the protrusion 58 and the mid-portion 110 may come into contact with each other, but the outer peripheral surface 57S of the insertion portion 57 of the slide core 55 and the mid-portion 110 do not come into contact with each other.

[0034] The mold 20 is provided with an injection port 65 (see FIGS. 8 and 10 ) through which molten metal can be injected into the molding space 60. The injection port 65 is formed by the movable mold 40 and the fixed mold 30 when the movable mold 40 is brought close to the fixed mold 30 and the mold 20 is closed. That is, the injection port 65 is located at the boundary between the movable mold 40 and the fixed mold 30. The injection port 65 is defined by a movable mold-side injection port 65A (see FIG. 8 ) formed in the movable mold 40 and a fixed mold-side injection port 65B (see FIG. 10 ) formed in the fixed mold 30. The movable mold-side injection port 65A is formed in the contact surface 40C of the movable mold 40 that comes into surface contact with the contact surface 30C of the fixed mold 30. The fixed mold-side injection port 65B is formed in the contact surface 30C of the fixed mold 30 that comes into surface contact with the contact surface 40C of the movable mold 40. The injection port 65 opens downward.

[0035] The mold 20 has a flow path 68 (see FIGS. 8 and 10 ) that communicates the injection port 65 and the molding space 60. The flow path 68 is formed by the movable mold 40 and the fixed mold 30 when the mold 20 is closed by bringing the movable mold 40 close to the fixed mold 30. That is, the flow path 68 is located at the boundary between the movable mold 40 and the fixed mold 30. The flow path 68 is defined by a movable mold-side flow path 68A (see FIG. 8 ) formed in the movable mold 40 and a fixed mold-side flow path 68B (see FIG. 10 ) formed in the fixed mold 30. As shown in FIG. 8 , the flow path 68 includes a first outlet 61, a second outlet 62, and a third outlet 63 that discharge the molten metal toward the molding space 60. The first outlet 61, the second outlet 62, and the third outlet 63 communicate with the injection port 65. The first outlet 61 is defined by a movable-mold-side first outlet 61A (see FIG. 8) formed in the movable mold 40 and a fixed-mold-side first outlet 61B (see FIG. 10) formed in the fixed mold 30. The second outlet 62 is defined by a movable-mold-side second outlet 62A (see FIG. 8) formed in the movable mold 40 and a fixed-mold-side second outlet 62B (see FIG. 10) formed in the fixed mold 30. The third outlet 63 is defined by a movable-mold-side third outlet 63A (see FIG. 8) formed in the movable mold 40 and a fixed-mold-side third outlet 63B (see FIG. 10) formed in the fixed mold 30. The movable-mold-side flow path 68A, the movable-mold-side first outlet 61A, the movable-mold-side second outlet 62A, and the movable-mold-side third outlet 63A are formed in the contact surface 40C of the movable mold 40. The fixed mold side flow path 68B, the fixed mold side first outlet 61B, the fixed mold side second outlet 62B, and the fixed mold side third outlet 63B are formed on the contact surface 30C of the fixed mold 30.

[0036] The first pressurizing device 80 injects molten metal into the molding space 60 in which the hollow pipe 100 is disposed. The first pressurizing device 80 primarily pressurizes the molten metal at a first pressure. The first pressurizing device 80 maintains the state in which the molten metal is primarily pressurized at the first pressure for a first time. As shown in FIG. 15 , the first pressurizing device 80 includes a sleeve 82, a plunger tip 84, and an injection cylinder (not shown).

[0037] As shown in Figures 4 and 15, the sleeve 82 is inserted into the mold 20. The sleeve 82 passes through the fixed mold 30. A portion of the sleeve 82 is provided in the movable mold 40. The sleeve 82 has an internal space 82S through which molten metal flows. The sleeve 82 communicates with the molding space 60. The sleeve 82 has a first opening 82H and a second opening 82M. The first opening 82H is located outside the mold 20. The molten metal is supplied from the first opening 82H to the internal space 82S using a ladle or the like. The second opening 82M is located inside the mold 20. The second opening 82M communicates with the injection port 65 of the mold 20.

[0038] As shown in FIG. 15 , the plunger tip 84 is disposed in the internal space 82S. The plunger tip 84 slides relative to the sleeve 82. The plunger tip 84 slides inside the sleeve 82. The plunger tip 84 moves in a first direction D1. As the plunger tip 84 moves in the first direction D1 from the fixed die 30 toward the movable die 40, the molten metal in the internal space 82S fills the molding space 60. With the molten metal filled in the internal space 82S, the plunger tip 84 is slid to a predetermined position relative to the sleeve 82, thereby primarily pressurizing the molten metal with a first pressure. Then, the plunger tip 84 is held at the predetermined position for a first time, thereby maintaining the molten metal in a state primarily pressurized with the first pressure. The first pressure is a pressure at which the hollow pipe 100 does not deform. The first pressure is, for example, 5 MPa or more and 30 MPa or less (e.g., 5 MPa or more and 10 MPa or less). The first time is equal to or longer than the time required for the molten metal around the hollow pipe 100 to solidify to an extent that deformation of the hollow pipe 100 can be suppressed when the molten metal is secondarily pressurized with a second pressure, as described below. The first time is, for example, 1 second or more and 10 seconds or less (e.g., 3 seconds or more and 5 seconds or less). The first time is an example of a predetermined time.

[0039] The injection cylinder has a rod 85 connected to the plunger tip 84. The injection cylinder moves the plunger tip 84 in the first direction D1 via the rod 85. The injection cylinder is, for example, a hydraulic cylinder.

[0040] The second pressurizing device 90 secondarily pressurizes the molten metal, which has been primarily pressurized at the first pressure, at a second pressure higher than the first pressure. The second pressurizing device 90 maintains the state in which the molten metal is secondarily pressurized at the second pressure for a second time. The second pressurizing device 90 starts the second pressurization at the second pressure while the first pressurizing device 80 is performing the primary pressurization. That is, the second pressurizing device 90 starts the second pressurization at the second pressure during the first time. The second pressurizing device 90 starts the second pressurization at the second pressure before one-half of the first time has elapsed (e.g., before one-third has elapsed, before one-quarter has elapsed, or before one-fifth has elapsed). Note that the second pressurizing device 90 may start the second pressurization at the second pressure when the first time has elapsed or after the first time has elapsed. As shown in FIGS. 2 and 3 , the second pressurizing device 90 is disposed below the mold 20. The second pressure device 90 includes a pressure pin 92 , a pressure cylinder 94 , and a cylinder holder 96 .

[0041] 3, the cylinder holder 96 is provided on the movable die 40. The cylinder holder 96 is located below the movable die 40. The cylinder holder 96 moves integrally with the movable die 40. The cylinder holder 96 may also be provided on the fixed die 30.

[0042] As shown in FIG. 15 , the pressure pin 92 is provided so as to be positionable in the internal space 82S of the sleeve 82 and the injection port 65. The pressure pin 92 moves in a third direction D3 relative to the sleeve 82 and the mold 20. As the pressure pin 92 moves upward, the molten metal in the internal space 82S is filled into the molding space 60. With the internal space 82S filled with the molten metal, the pressure pin 92 is slid to a predetermined position relative to the sleeve 82 and the mold 20, thereby secondarily pressurizing the molten metal with a second pressure. The pressure pin 92 is then held in the predetermined position for a second period of time, thereby maintaining the molten metal in a state in which it is secondarily pressurized with the second pressure. The second pressure is a pressure that may deform the hollow pipe 100 if the molten metal around the hollow pipe 100 has not solidified. The second pressure is, for example, 100 MPa or more and 300 MPa or less (e.g., 120 MPa or more and 200 MPa or less). The second pressure is, for example, 3.3 times or more and 60 times or less than the first pressure. The second time is longer than the first time. The second time is, for example, shorter than 5 times the first time. The second time is, for example, shorter than twice the first time. The second time is, for example, 2 seconds or more and 30 seconds or less (e.g., 5 seconds or more and 10 seconds or less).

[0043] The pressure cylinder 94 is held by a cylinder holder 96. The pressure cylinder 94 moves the pressure pin 92 in the third direction D3. The pressure cylinder 94 is, for example, a hydraulic cylinder.

[0044] Next, a method for manufacturing the casting 140 will be described. FIG. 16 is a flowchart showing the method for manufacturing the casting 140 (hereinafter simply referred to as the manufacturing method). As shown in FIG. 14, the manufacturing method includes a preparation step (step S10), a placement step (step S20), a mold clamping step (step S30), an injection step (step S40), a primary pressurization step (step S50), a secondary pressurization step (step S60), and a removal step (step S70). Here, the casting 140 (see FIG. 7A) is manufactured using a casting manufacturing apparatus 10 including a mold 20, a first pressurization device 80, and a second pressurization device 90, as shown in FIG. 1.

[0045] First, in a preparation step (step S10), a mold 20 is prepared as shown in FIG. 1 . More specifically, the mold 20 includes a fixed mold 30, a movable mold 40 that can move toward or away from the fixed mold 30, a core 50, a sliding core 55, a molding space 60 that is defined by the fixed mold 30, the movable mold 40, the core 50, and the sliding core 55 and that can accommodate a hollow pipe 100, an injection port 65 that can inject molten metal into the molding space 60, and a first holding portion 42A and a second holding portion 42B that hold a first end 102 and a second end 106 of the hollow pipe 100, respectively. Also, in the preparation step (step S10), a first pressurizing device 80 and a second pressurizing device 90 are prepared. That is, in the preparation step (step S10), a casting manufacturing apparatus 10 that includes the mold 20, the first pressurizing device 80, and the second pressurizing device 90 is prepared. The first pressurizing device 80 is configured to inject molten metal into the molding space 60 in which the hollow pipe 100 is disposed, and to primarily pressurize the molten metal at a first pressure. The second pressurizing device 90 is configured to secondarily pressurize the molten metal that has been primarily pressurized at the first pressure at a second pressure higher than the first pressure.

[0046] Next, in the placement step (step S20), the hollow pipe 100 is placed in the molding space 60. More specifically, the first end 102 of the hollow pipe 100 is held by the first holding portion 42A of the movable mold 40 and the second end 106 is held by the second holding portion 42B of the movable mold 40 so that the hollow pipe 100 contacts the protruding member 70 (here, so that the locked portion 113 of the hollow pipe 100 contacts the movable mold-side protruding member 72), and the hollow pipe 100 is attached to the movable mold 40.

[0047] Next, in the mold clamping process (step S30), the movable mold 40, the core 50, and the sliding core 55 are brought close to the fixed mold 30, and the mold 20 is closed. As a result, a molding space 60 in which the casting 140 is molded is defined by the cavity portion 31 of the fixed mold 30 and the core portion 41 of the movable mold 40, the core 50, and the sliding core 55. When the mold 20 is closed, the middle portion 110 of the hollow pipe 100 is in contact with the movable mold-side protruding member 72, the fixed mold-side protruding member 71, and the core-side protruding member 73, and therefore movement of the middle portion 110 is restricted by the movable mold-side protruding member 72, the fixed mold-side protruding member 71, and the core-side protruding member 73. Furthermore, because the sliding core 55 is inserted into the middle portion 110, the protruding portion 58 of the sliding core 55 restricts radial inward movement of the middle portion 110.

[0048] Next, in the injection process (step S40), molten metal is injected through the injection port 65 of the mold 20 into the molding space 60 formed by the movable mold 40, the fixed mold 30, the core 50, and the sliding core 55. The molten metal is injected into the molding space 60 by, for example, the first pressurizing device 80. For example, the molten metal is supplied to the internal space 82S from a first opening 82H provided in the sleeve 82 of the first pressurizing device 80 using a ladle. Then, the plunger tip 84 is slid within the sleeve 82 to inject the molten metal from the internal space 82S into the molding space 60 through the injection port 65. The injection process (step S40) includes a first injection process (step S41) and a second injection process (step S42). As shown in FIG. 17 , in the first injection process (step S41), the molten metal is injected into the molding space 60 at a first speed (e.g., 0.1 m / s or more and 0.5 m / s or less). At time T1, the injection of molten metal begins at a first speed. From time T1 to time T2, the molten metal is injected at the first speed. The time for injecting the molten metal at the first speed is, for example, 0.5 to 2 seconds (e.g., 1.2 seconds). In the second injection step (step S41), the molten metal is injected into the molding space 60 at a second speed (e.g., 1 m / s to 5 m / s) that is faster than the first speed. At time T2, the injection of molten metal begins at the second speed. From time T2 to time T3, the molten metal is injected at the second speed. The time for injecting the molten metal at the second speed is, for example, 0.01 to 0.1 seconds (e.g., 0.03 seconds). The time for injecting the molten metal at the first speed is approximately 5 to 200 times the time for injecting the molten metal at the second speed.

[0049] Next, in a primary pressurizing step (step S50), the molten metal is primarily pressurized at a first pressure of 5 MPa to 30 MPa (e.g., a pressure at which the hollow pipe 100 does not deform). For example, with the molten metal filled in the internal space 82S of the sleeve 82 of the first pressurizing device 80, the plunger tip 84 is slid to a predetermined position relative to the sleeve 82, thereby primarily pressurizing the molten metal at the first pressure. In the primary pressurizing step (step S50), the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first time. For example, after sliding the plunger tip 84 to a predetermined position relative to the sleeve 82, the plunger tip 84 is maintained at the predetermined position for a first time, thereby maintaining the state in which the molten metal is primarily pressurized at the first pressure. Because the first pressure is relatively small, when the molten metal is primarily pressurized, the molten metal around the hollow pipe 100 can be solidified while suppressing deformation of the hollow pipe 100. That is, the primary pressurizing step (step S50) is a step of applying a relatively small pressure to first solidify the molten metal around the hollow pipe 100. The primary pressurizing step (step S50) starts after the injection step (step S40) is completed (including both simultaneously with completion and several seconds after completion). As shown in FIG. 17 , the primary pressurizing step (step S50) starts at time T3. From time T3 to time T5, the molten metal is primarily pressurized at a first pressure. Note that the primary pressurizing step (step S50) may also start during the injection step (step S40). That is, after the injection step (step S40) is started, the injection step (step S40) and the primary pressurizing step (step S50) may be performed simultaneously.

[0050] Next, in a secondary pressurizing step (step S60), the molten metal after the primary pressurization is secondarily pressurized at a second pressure of 100 MPa or more and 300 MPa or less. For example, with the molten metal filled in the internal space 82S of the sleeve 82 of the first pressurizing device 80, the pressurizing pin 92 of the second pressurizing device 90 is slid to a predetermined position relative to the sleeve 82 and the mold 20, thereby secondarily pressurizing the molten metal at the second pressure. In the secondary pressurizing step (step S60), the state in which the molten metal is primarily pressurized at the second pressure is maintained for a second time. For example, after the pressurizing pin 92 is slid to a predetermined position relative to the sleeve 82 and the mold 20, the pressurizing pin 92 is maintained at the predetermined position for a second time, thereby maintaining the state in which the molten metal is secondarily pressurized at the second pressure. The secondary pressurizing step (step S60) starts while the molten metal is being primarily pressurized at the first pressure for a first time in the primary pressurizing step (step S50). The secondary pressurizing step (step S60) is initiated before half of the first time has elapsed (e.g., before one-third of the time has elapsed, before one-quarter of the time has elapsed, or before one-fifth of the time has elapsed). As shown in FIG. 17 , the secondary pressurizing step (step S60) is initiated at time T4. The secondary pressurizing step (step S60) is initiated, for example, 0.5 seconds to 1 second (e.g., 0.6 seconds) after the start of the second pouring step (step S42). Between time T4 and time T6, the molten metal is secondarily pressurized at the second pressure. The secondary pressurizing step (step S60) may be initiated when 30% to 50% of the molten metal around the hollow pipe 100 has solidified. In the secondary pressurizing step (step S60), because the molten metal around the hollow pipe 100 has sufficiently solidified, deformation of the hollow pipe 100 can be suppressed even when a higher pressure is applied. Furthermore, applying a higher pressure more reliably solidifies the entire molten metal, thereby further suppressing the occurrence of blowholes. The secondary pressurizing step (step S60) may be started after the primary pressurizing step (step S50) is completed. In the secondary pressurizing step (step S60), the molten metal in the mold 20 is completely solidified to form the casting 140.

[0051] Next, in the removal process (step S70), the movable die 40, the core 50, and the sliding core 55 are separated from the fixed die 30 to open the mold 20. At this time, the formed casting 140 is fixed to the movable die 40. Then, an ejector pin (not shown) is pressed against the casting 140 fixed to the movable die 40 to remove the casting 140 from the movable die 40. In this manner, the casting 140 is formed, which includes the hollow pipe 100 and the metal material 120 that casts around the hollow pipe 100.

[0052] Examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples.

[0053] <Preparation of hollow pipes> In Examples 1 to 6, hollow pipes 100 made of aluminum alloy were prepared as shown in Figure 18. The hollow pipes 100 had bent portions 112. The hollow pipes 100 in Examples 1 and 2 had a wall thickness of 0.5 mm and a diameter of 10 mm. The hollow pipes 100 in Examples 3 and 4 had a wall thickness of 1 mm and a diameter of 10 mm. The hollow pipes 100 in Examples 5 and 6 had a wall thickness of 5 mm and a diameter of 20 mm.

[0054] (Examples 1, 3, and 5) In Examples 1, 3, and 5, molten metal was poured into a molding space in which a hollow pipe 100 was disposed, and the molten metal was subjected to a primary pressurization at 5 MPa for 3 seconds. After the primary pressurization, the molten metal was subjected to a secondary pressurization at 300 MPa for 5 seconds to form a cast product. Here, the secondary pressurization started when the primary pressurization had lasted 0.57 seconds.

[0055] (Examples 2, 4, and 6) In Examples 2, 4, and 6, molten metal was poured into a molding space in which a hollow pipe 100 was disposed, and the molten metal was subjected to a primary pressurization at 30 MPa for 3 seconds. After the primary pressurization, the molten metal was subjected to a secondary pressurization at 100 MPa for 5 seconds to form a cast product. Here, the secondary pressurization started when the primary pressurization had lasted 0.57 seconds.

[0056] The castings of Examples 1 to 6 were checked for the presence or absence of blowholes and deformation of the hollow pipe 100. The results are shown in Figure 19. As shown in Figure 19, no blowholes were found in any of the castings of Examples 1 to 6. This is thought to be because sufficient pressure was applied to the molten metal during the secondary pressurization. Furthermore, while no deformation of the hollow pipe 100 was confirmed in the castings of Examples 3 to 6, deformation of the hollow pipe 100 was confirmed in the castings of Examples 1 and 2. This is thought to be because the wall thickness of the hollow pipe 100 in Examples 1 and 2 was too thin, even when a relatively low pressure was applied during the primary pressurization.

[0057] As described above, in the casting manufacturing apparatus 10 of this embodiment, the first pressurizing device 80 injects molten metal into the molding space 60 in which the hollow pipe 100 is disposed and primarily pressurizes the molten metal at a first pressure of 5 MPa to 30 MPa. Here, the hollow pipe 100 has a wall thickness TH of 1 mm to 5 mm and a diameter RH of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa, it is possible to fill the entire molding space 60 with the molten metal while suppressing deformation of the hollow pipe 100, and gradually solidify the molten metal around the hollow pipe 100. The second pressurizing device 90 then secondary pressurizes the molten metal, which has been primarily pressurized at the first pressure, at a second pressure of 100 MPa to 300 MPa. This allows the molten metal filled in the molding space 60 to solidify while reducing the occurrence of porosity. Since the molten metal around the hollow pipe 100 has already started to solidify before the second pressure is applied, the second pressure is not directly applied to the hollow pipe 100, and deformation of the hollow pipe 100 can be suppressed.

[0058] In the casting manufacturing apparatus 10 of this embodiment, the second pressure is a pressure that may deform the hollow pipe 100 if the molten metal around the hollow pipe 100 has not yet solidified. According to the above-described aspect, the molten metal filled in the molding space 60 can be solidified more reliably while further reducing the occurrence of blowholes. Note that when secondary pressurization is performed at the second pressure, the molten metal around the hollow pipe 100 has solidified, so the hollow pipe 100 will not deform.

[0059] In the casting manufacturing apparatus 10 of this embodiment, the molten metal is filled in the internal space 82S, and the plunger tip 84 is slid to a predetermined position relative to the sleeve 82 to primarily pressurize the molten metal at a first pressure, and the plunger tip 84 is held at the predetermined position for a first time, thereby maintaining the molten metal in a state primarily pressurized at the first pressure. According to the above-described aspect, the molten metal around the hollow pipe 100 can be solidified more reliably.

[0060] In the casting manufacturing apparatus 10 of this embodiment, the first time period is equal to or longer than the time required for the molten metal around the hollow pipe 100 to solidify to an extent that deformation of the hollow pipe 100 can be suppressed when the molten metal is secondarily pressurized at the second pressure. According to the above aspect, deformation of the hollow pipe 100 can be more reliably suppressed when the molten metal is secondarily pressurized at the second pressure.

[0061] In the casting manufacturing apparatus 10 of this embodiment, the mold 20 is provided with an injection port 65 through which molten metal can be injected into the molding space 60, and a first holding portion 42A and a second holding portion 42B that respectively hold the first end 102 and the second end 106 of the hollow pipe 100. According to the above-described aspect, when molten metal is injected into the molding space 60 through the injection port 65, the hollow pipe 100 can be held in a predetermined position in the molding space 60.

[0062] In the casting manufacturing apparatus 10 of this embodiment, the first pressurizing device 80 maintains the molten metal in a state where it is primarily pressurized at a first pressure for a first time, and the second pressurizing device 90 maintains the molten metal in a state where it is secondarily pressurized at a second pressure for a second time that is longer than the first time but shorter than five times the first time. According to the above-described aspect, it is possible to suppress deformation of the hollow pipe 100 while reducing the occurrence of blowholes.

[0063] In the casting manufacturing apparatus 10 of the present embodiment, the first time period is 1 second or more and 10 seconds or less, and the second time period is 2 seconds or more and 30 seconds or less. According to the above-described aspect, it is possible to suppress deformation of the hollow pipe 100 while reducing the occurrence of blowholes.

[0064] In the casting manufacturing apparatus 10 of this embodiment, the second pressurizing device 90 starts secondary pressurization at the second pressure during the first period. According to the above-described aspect, the occurrence of blowholes can be further reduced.

[0065] In the casting manufacturing apparatus 10 of this embodiment, the second pressurizing device 90 starts the secondary pressurization at the second pressure before half of the first time period has elapsed. According to the above-described aspect, the occurrence of blowholes can be further reduced.

[0066] According to the manufacturing method of the casting 140 of this embodiment, in the primary pressurizing step (step S50), molten metal is poured into the molding space 60 in which the hollow pipe 100 is disposed, and the molten metal is primarily pressurized at a first pressure of 5 MPa to 30 MPa. Here, the hollow pipe has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, making it relatively susceptible to deformation when pressure is applied. However, by primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa, deformation of the hollow pipe can be suppressed while filling the entire molding space 60 with the molten metal and gradually solidifying the molten metal around the hollow pipe 100. Then, in the secondary pressurizing step (step S60), the molten metal primarily pressurized at the first pressure is secondarily pressurized at a high second pressure of 100 MPa to 300 MPa. This allows the molten metal filled in the molding space 60 to solidify while reducing the occurrence of blowholes. Since the molten metal around the hollow pipe 100 has already started to solidify before the second pressure is applied, the second pressure is not directly applied to the hollow pipe 100, and deformation of the hollow pipe 100 can be suppressed.

[0067] In the manufacturing method of this embodiment, the second pressure is a pressure that may deform the hollow pipe 100 if the molten metal around the hollow pipe 100 has not yet solidified. According to the above aspect, the molten metal filled in the molding space 60 can be solidified more reliably while further reducing the occurrence of blowholes. Note that when secondary pressurization is performed at the second pressure, the molten metal around the hollow pipe 100 has solidified, so the hollow pipe 100 will not deform.

[0068] In the manufacturing method of this embodiment, the secondary pressurizing step (step S60) is started after the molten metal is primarily pressurized at a first pressure in the primary pressurizing step (step S50) and the first pressure is maintained for a first time period. According to the above aspect, the molten metal around the hollow pipe 100 can be solidified more reliably.

[0069] In the manufacturing method of this embodiment, in the primary pressurizing step (step S50), the molten metal is held in a state of being primarily pressurized at a first pressure for a first time period before the secondary pressurizing step (step S60) is started, and the secondary pressurizing step (step S60) is started during the primary pressurizing step (step S50). According to the above aspect, the occurrence of blowholes can be further reduced.

[0070] In the manufacturing method of this embodiment, the secondary pressurizing step (step S60) is started before half of the first time period has elapsed. According to the above aspect, the occurrence of blowholes can be further reduced.

[0071] In the manufacturing method of this embodiment, the first time period is equal to or longer than the time required for the molten metal around the hollow pipe 100 to solidify to an extent that deformation of the hollow pipe 100 can be suppressed when the molten metal is secondarily pressurized with the second pressure. According to the above aspect, deformation of the hollow pipe 100 can be more reliably suppressed when the molten metal is secondarily pressurized with the second pressure.

[0072] In the manufacturing method of this embodiment, in the primary pressurizing step (step S50), the molten metal is held in a state where it is primarily pressurized at a first pressure for a first time, and in the secondary pressurizing step (step S60), the molten metal is held in a state where it is secondarily pressurized at a second pressure for a second time that is longer than the first time but shorter than five times the first time. According to the above aspect, it is possible to suppress deformation of the hollow pipe 100 and reduce the occurrence of blowholes.

[0073] In the manufacturing method of this embodiment, the first time period is 1 second or more and 10 seconds or less, and the second time period is 2 seconds or more and 30 seconds or less. According to the above aspect, it is possible to suppress deformation of the hollow pipe 100 and reduce the occurrence of blowholes.

[0074] In the manufacturing method of this embodiment, the primary pressurizing step (step S50) may be started after the injection step (step S40) is completed. According to the above aspect, the injection step (step S40) and the primary pressurizing step (step S50) are independent of each other, which makes control easy.

[0075] In the manufacturing method of this embodiment, the primary pressurizing step (step S50) is started during the pouring step (step S40). According to this aspect, the molten metal can be filled into the molding space 60 more quickly.

[0076] Although the preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples, and the present invention can be embodied in various other forms.

[0077] In the above-described embodiment, the mold 20 includes a plurality of protruding members 70, but this need not be the case. Also, the mold 20 includes the holding portions 42 that hold both ends of the hollow pipe 100, but this need not be the case.

[0078] In the above-described embodiment, the pressure pin 92 of the second pressure device 90 is provided so as to be positionable in the internal space 82S of the sleeve 82 and the injection port 65, but this is not limiting. For example, the pressure pin 92 may be provided so as to be positionable in the molding space 60, and the pressure pin 92 may be configured to apply a second pressure to the molten metal in the molding space 60.

[0079] DESCRIPTION OF SYMBOLS 10 Casting manufacturing apparatus 20 Mold 30 Fixed mold 40 Movable mold 42 Holding portion 42A First holding portion 42B Second holding portion 50 Core 55 Slide core 60 Molding space 65 Inlet 80 First pressure device 82 Sleeve 82S Internal space 84 Plunger tip 90 Second pressure device 92 Pressure pin 94 Pressure cylinder 100 Hollow pipe 102 First end 106 Second end 120 Metal material 140 Casting

Claims

1. A casting manufacturing apparatus comprising: a mold having a fixed mold, a movable mold that can move toward or away from said fixed mold, and a molding space that is partitioned by at least said fixed mold and said movable mold, is at least partially hollow, and can accommodate a hollow pipe that has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm; a first pressurizing device that injects molten metal into said molding space in which said hollow pipe is disposed and primarily pressurizes said molten metal at a first pressure of 5 MPa to 30 MPa; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa to 300 MPa.

2. A casting manufacturing apparatus as described in claim 1, wherein the second pressure is a pressure that can deform the hollow pipe if the molten metal around the hollow pipe has not solidified.

3. The casting manufacturing apparatus according to claim 1, wherein the first pressurizing device comprises: a sleeve having an internal space through which the molten metal flows and communicating with the molding space; and a plunger tip provided in the internal space and sliding relative to the sleeve, and is configured to primarily pressurize the molten metal at the first pressure by sliding the plunger tip to a predetermined position relative to the sleeve when the internal space is filled with the molten metal, and to maintain the molten metal in a state where it is primarily pressurized at the first pressure by holding the plunger tip at the predetermined position for a predetermined time.

4. A casting manufacturing apparatus as described in claim 3, wherein the specified time is equal to or longer than the time required for the molten metal around the hollow pipe to solidify to an extent that deformation of the hollow pipe can be suppressed when the molten metal is secondarily pressurized at the second pressure.

5. The casting manufacturing device according to claim 1, wherein the mold is provided with an injection port through which the molten metal can be injected into the molding space, and holding portions that hold both ends of the hollow pipe.

6. The casting manufacturing apparatus according to claim 1, wherein the hollow pipe has a first end, a second end, and a middle portion located between the first end and the second end, and the middle portion has at least one bent portion that is bent by 90 degrees or more.

7. The casting manufacturing apparatus according to claim 6, wherein the intermediate portion is formed in a spiral shape.

8. The casting manufacturing apparatus according to claim 1, wherein the first pressurizing device maintains the state in which the molten metal is primarily pressurized at the first pressure for a first time, and the second pressurizing device maintains the state in which the molten metal is secondarily pressurized at the second pressure for a second time that is longer than the first time but shorter than five times the first time.

9. The casting manufacturing apparatus according to claim 8, wherein the first time period is 1 second or more and 10 seconds or less, and the second time period is 2 seconds or more and 30 seconds or less.

10. A casting manufacturing apparatus as described in claim 1, wherein the first pressurizing device maintains the molten metal in a state where it is primarily pressurized at the first pressure for a first period of time, and the second pressurizing device starts secondary pressurization at the second pressure during the first period of time.

11. The casting manufacturing apparatus of claim 10, wherein the second pressurizing device initiates secondary pressurization at the second pressure before half of the first time period has elapsed.

12. A casting manufacturing apparatus comprising: a mold having a fixed mold, a movable mold that can approach or move away from said fixed mold, and a molding space that is partitioned by at least said fixed mold and said movable mold, is at least partially hollow, and can accommodate a hollow pipe with a wall thickness of 1 mm or more and 5 mm or less; a first pressurizing device that injects molten metal into said molding space in which said hollow pipe is arranged, and primarily pressurizes said molten metal at a first pressure of 5 MPa or more and 30 MPa or less; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa or more and 300 MPa or less, wherein said first pressurizing device holds said molten metal in a state in which it is primarily pressurized at the first pressure for a first time; and said second pressurizing device holds said molten metal in a state in which it is secondarily pressurized at the second pressure for a second time that is longer than said first time but shorter than 5 times said first time.

13. A casting manufacturing apparatus comprising: a mold having a fixed mold, a movable mold that can move toward or away from said fixed mold, and a molding space that is partitioned by at least said fixed mold and said movable mold, is at least partially hollow, and can accommodate a hollow pipe with a wall thickness of 1 mm or more and 5 mm or less; a first pressurizing device that injects molten metal into said molding space in which said hollow pipe is arranged, and primarily pressurizes said molten metal at a first pressure of 5 MPa or more and 30 MPa or less; and a second pressurizing device that secondarily pressurizes the molten metal that has been primarily pressurized at said first pressure at a second pressure of 100 MPa or more and 300 MPa or less, wherein said first pressurizing device maintains said molten metal in a state in which it is primarily pressurized at said first pressure for a first period of time, and said second pressurizing device commences secondary pressurization at said second pressure during said first period.

14. The casting manufacturing apparatus of claim 13, wherein the second pressurizing device initiates secondary pressurization at the second pressure before one-half of the first time period has elapsed.

15. A method for manufacturing a casting comprising a hollow pipe that is at least partially hollow, has a wall thickness of 1 mm to 5 mm and a diameter of 5 mm to 20 mm, and a metal material that encases the hollow pipe, the method comprising the following steps: a preparation step of preparing a mold comprising a fixed mold, a movable mold that can approach or move away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold and in which the hollow pipe can be placed; an arrangement step of placing the hollow pipe in the molding space; a clamping step of bringing the movable mold close to the fixed mold and closing the mold; an injection step of injecting molten metal into the molding space; a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa; a secondary pressurizing step of secondarily pressurizing the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa to 300 MPa; and a removal step of separating the movable mold from the fixed mold to open the mold and remove the casting.

16. The manufacturing method according to claim 15, wherein the second pressure is a pressure that would cause the hollow pipe to deform if the molten metal around the hollow pipe had not solidified.

17. The manufacturing method according to claim 16, wherein the secondary pressurizing step is initiated after the molten metal has been primarily pressurized at the first pressure in the primary pressurizing step and the first pressure has been maintained for a predetermined period of time.

18. A manufacturing method as set forth in claim 15, wherein, in the primary pressurizing step, the molten metal is maintained in a state of being primarily pressurized at the first pressure for a first time period before the secondary pressurizing step is started, and the secondary pressurizing step is started during the primary pressurizing step.

19. The method of claim 18, wherein the secondary pressurizing step begins before one-half of the first time period has elapsed.

20. A manufacturing method as described in claim 18, wherein the first time period is equal to or longer than the time required for the molten metal around the hollow pipe to solidify to an extent that deformation of the hollow pipe can be suppressed when the molten metal is secondarily pressurized with the second pressure.

21. A manufacturing method as described in claim 15, wherein in the primary pressurizing step, the molten metal is maintained in a state where it is primarily pressurized at the first pressure for a first time, and in the secondary pressurizing step, the molten metal is maintained in a state where it is secondarily pressurized at the second pressure for a second time that is longer than the first time but shorter than five times the first time.

22. The manufacturing method according to claim 21, wherein the first time period is 1 second or more and 10 seconds or less, and the second time period is 2 seconds or more and 30 seconds or less.

23. The manufacturing method according to claim 15, wherein the primary pressurizing step is initiated after the injection step is completed.

24. The manufacturing method according to claim 15, wherein the primary pressurizing step is started during the injection step.

25. The manufacturing method according to claim 15, wherein the hollow pipe has a first end, a second end, and a middle portion located between the first end and the second end, and the middle portion has at least one bent portion that is bent by 90 degrees or more.

26. The manufacturing method according to claim 25, wherein the intermediate portion is formed in a spiral shape.

27. A method for manufacturing a casting comprising a hollow pipe that is at least partially hollow and has a wall thickness of 1 mm to 5 mm, and a metal material that encases the hollow pipe, comprising: a preparation step of preparing a mold comprising a fixed mold, a movable mold that can approach or move away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold and in which the hollow pipe can be placed; an arrangement step of arranging the hollow pipe in the molding space; a mold clamping step of bringing the movable mold close to the fixed mold and closing the mold; an injection step of injecting molten metal into the molding space; a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa; a secondary pressurizing step of secondarily pressurizing the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa to 300 MPa; and a removal step of separating the movable mold from the fixed mold, opening the mold, and removing the casting. the molten metal is held in a state where it is primarily pressurized at the first pressure for a first time in the primary pressurizing step; and the molten metal is held in a state where it is secondarily pressurized at the second pressure for a second time that is longer than the first time but shorter than five times the first time in the secondary pressurizing step.

28. A method for manufacturing a casting comprising a hollow pipe that is at least partially hollow and has a wall thickness of 1 mm to 5 mm, and a metal material that encases the hollow pipe, comprising: a preparation step of preparing a mold comprising a fixed mold, a movable mold that can approach or move away from the fixed mold, and a molding space that is partitioned by at least the fixed mold and the movable mold and in which the hollow pipe can be placed; an arrangement step of arranging the hollow pipe in the molding space; a mold clamping step of bringing the movable mold close to the fixed mold and closing the mold; an injection step of injecting molten metal into the molding space; a primary pressurizing step of primarily pressurizing the molten metal at a first pressure of 5 MPa to 30 MPa; a secondary pressurizing step of secondarily pressurizing the molten metal that has been primarily pressurized at the first pressure at a second pressure of 100 MPa to 300 MPa; and a removal step of separating the movable mold from the fixed mold, opening the mold, and removing the casting. In the primary pressurizing step, the state in which the molten metal is primarily pressurized at the first pressure is maintained for a first time period, and the secondary pressurizing step is started during the primary pressurizing step.

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