Casting method and cast product

Abstract

[Problem] The present invention addresses the problem of providing: a casting method with which a pull-out hole having a large aspect ratio and a bent pull-out hole can be easily produced, and which is a simple, short-time, and low-cost method that does not require a large pull-out force, and enables size reduction of a device therefor; and a cast product. [Solution] A mold or core 3 having shape retainability is formed in advance by impregnating a ceramic fiber with a binder and solidifying the ceramic fiber into a predetermined shape, a molten material that is composed of a molten metal, semiconductor, or high molecular weight polymer is supplied into the mold or a mold in which the core 3 is placed so as to form a solidified body 6 that is formed from the molten material, and subsequently, the mold or core 3 is softened by having a binder dissolving liquid 7 permeate through the mold or core 3, and a cast product 8 that is formed of the solidified body is obtained by separating the softened mold or core 3 from the solidified body 6.

Description

Casting method and cast product

[0001] The present invention relates to a casting method and a casting such as a porous casting of a metal, a polymer, or a semiconductor material that can be effectively used as a new material in various fields such as heat sinks, heat pipes, heat exchangers, aircraft engines, medical instruments, machine tools, thermoelectric conversion materials, vibration-damping materials, sound-absorbing materials, and shock-absorbing materials.

[0002] Conventional techniques for drilling holes in metals include (1) forming linear pores by solidifying molten metal, (2) removing dissimilar metal wires embedded in metals by chemical polishing, (3) mechanical drilling with a drill, and (4) drilling by local melting with a laser or electron beam. However, all of these methods have the drawbacks of being complicated, requiring a long time for drilling, and being expensive to manufacture.

[0003] Therefore, porous castings have been produced by using a heat-resistant metal wire as a core and drawing it from solidified metal (see Patent Document 1). However, drawing a heat-resistant metal wire requires a dedicated tensile testing machine, and drawing using a jig such as a pinholder with a large number of heat-resistant metal wires arranged on it requires a large pulling force, which requires a large testing machine. Furthermore, there is a problem that the metal wire breaks midway when attempting to form thin holes with a large aspect ratio (the ratio of the length to the diameter of the hole) or holes with complex shapes. Furthermore, there is a risk of damage to the holes due to resistance during drawing.

[0004] WO2020 / 246588

[0005] In view of the above-mentioned circumstances, the present invention aims to solve the problems by providing a casting method and a cast product that can easily produce drawn holes with a large aspect ratio, curved drawn holes, and holes of complex shapes, and that is simple, can be done in a short time, and at low cost, does not require a large drawing force, does not damage the holes, and allows for the equipment to be made smaller.

[0006] In view of the current situation, the inventors conducted extensive research and discovered that by solidifying ceramic fibers with a binder to form a mold or core, and then dissolving the binder after solidifying the material, the mold or core made of ceramic fibers softens, and even when forming holes with large aspect ratios or complex shapes, the holes or cores can be easily and reliably removed without damaging the holes or cores, thereby completing the present invention.

[0007] That is, the present invention includes the following inventions.

[0008] (1) A casting method characterized by: forming a shape-retaining mold or core in advance by impregnating ceramic fibers with a binder and solidifying them into a predetermined shape; supplying a molten material of a molten metal, semiconductor, or polymer into a mold in which the mold or core is placed to form a solidified body of the molten material; softening the mold or core by infiltrating a binder solution that dissolves the binder into the mold or core; and removing the softened mold or core from the solidified body to obtain a casting made of the solidified body.

[0009] (2) The casting method according to (1), wherein the ceramic fiber is a ceramic fiber sheet, a ceramic fiber bulk (cotton-like) material, a ceramic fiber sewing thread (twisted yarn), a ceramic fiber rope, a ceramic fiber cord (solid wire), or a ceramic fiber sleeve (cylindrical hollow body). Suitable ceramic fiber sheets include ceramic fiber cloth, ceramic fiber tape, ceramic fiber nonwoven fabric (felt), ceramic fiber paper, and ceramic fiber knit. Suitable ceramic fiber bulk (cotton-like) materials include chopped ceramic fiber (short fiber body).

[0010] (3) The casting method according to (1), wherein the mold or core is provided with a convex portion formed by solidifying the ceramic fiber into a convex shape, thereby forming a concave hole or groove transferred from the convex portion in the solidified body. For example, the convex portion may be a rod-shaped or plate-shaped portion formed by solidifying the ceramic fiber into a rod-shaped or plate-shaped shape, and the concave hole or groove may be a rod-shaped or plate-shaped hole transferred from the rod-shaped or plate-shaped portion.

[0011] (4) The casting method according to (3), wherein the ceramic fiber is a ceramic fiber sheet, and the ceramic fiber sheet is solidified into the rod-like or plate-like shape by rolling, folding, or stacking multiple sheets of the ceramic fiber sheet using the binder. (5) The casting method according to (3), wherein the ceramic fiber is a ceramic fiber bulk material, and the ceramic fiber solution containing the binder as a solvent is applied to a rod-like or plate-like core material made of a heat-resistant hard material, and the core material is solidified into the rod-like or plate-like shape. (6) The casting method according to (5), wherein the fiber length of the ceramic fiber constituting the ceramic fiber bulk material is 100 μm or less, more preferably 50 μm or less, and even more preferably 35 μm or less.

[0012] (7) The casting method according to (1), wherein the ceramic fiber is solidified and then processed to form a single or multiple concave holes or grooves in the mold or core, thereby forming a single or multiple convex portions in the solidified body to which the holes or grooves are transferred. For example, the concave holes or grooves may be holes or wide grooves, and the convex portions may be single or multiple rod-shaped or plate-shaped bodies to which the holes or wide grooves are transferred.

[0013] (8) The casting method according to (1), wherein the binder is a water-soluble binder and the binder dissolving solution is water.

[0014] (9) The casting method according to (7), wherein the binder is polyvinyl alcohol, an alumina dispersion, a silica dispersion, a heat-resistant adhesive, or a combination thereof.

[0015] (10) The casting method according to (1), wherein a pressurized fluid consisting of the binder solution or air is further pressed against the mold or core permeated with the binder solution, thereby separating the mold or core from the solidified body.

[0016] (11) A casting obtained by the casting method according to any one of (1) to (10).

[0017] According to the present invention as described above, holes with large aspect ratios, curved holes, and holes with complex shapes including surface undulations can be easily produced, and the process is simple, quick, and low cost, does not require a large pulling force, does not damage the holes, and allows for the device to be made smaller.

[0018] 1 is an explanatory diagram showing the steps of a casting method according to a representative embodiment of the present invention. FIG. 1 is an explanatory diagram showing the steps following FIG. 2. (a) and (b) are explanatory diagrams showing a modified example of the casting method. (a) and (b) are explanatory diagrams showing the steps of another modified example of the casting method. (a) and (b) are explanatory diagrams showing the steps of yet another modified example of the casting method. (b) and (b) are explanatory diagrams showing the steps of yet another modified example of the casting method. (b) and (b) are explanatory diagrams showing the steps of yet another modified example of the casting method. (c) and (c) are explanatory diagrams showing the steps of a prototype casting. (a) and (b) are explanatory diagrams showing the steps of a prototype casting, the top one being before the mold or core was removed, and the bottom one being after the mold or core was removed. (c) and (c) are explanatory diagrams showing the steps of a prototype casting. (c) and (b) are explanatory diagrams showing the steps of a prototype casting. (c) and (c) are explanatory diagrams showing the steps of a prototype casting. (c) and (c) are explanatory diagrams showing the steps of a prototype casting, the top one being before the mold or core was removed, and the bottom one after. (c) and (c) are explanatory diagrams showing the steps of a prototype casting ... 1 is an explanatory diagram showing a procedure for forming a rod-shaped body using a ceramic fiber cord. (a) to (d) are explanatory diagrams showing ceramic fiber cords (solid wires) with different cross-sectional shapes. (b) is an explanatory diagram showing a procedure for forming a cylindrical body using a ceramic fiber cord. (cylinder) is an explanatory diagram showing a procedure for forming a rod-shaped body by attaching a ceramic fiber sleeve (cylindrical hollow body) to a core material. (c) is a photograph showing a silica fiber sheet and an alumina fiber sheet, respectively, impregnated with polyvinyl alcohol (PVA) only and solidified, and impregnated with a mixture of PVA and alumina powder, and solidified.

[0019] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0020] 1(a) and 1(b), the casting method according to the present invention involves preforming a shape-retaining mold or core 3 by impregnating ceramic fiber 1 with a binder 110 and solidifying it into a predetermined shape (a rod shape in this example). The ceramic fiber 1 is a fire-resistant, heat-insulating fiber that has excellent high-temperature resistance among artificial mineral fibers whose main components are alumina or silica, and typical examples include amorphous ceramic fiber and crystalline alumina fiber.

[0021] The use of a ceramic fiber sheet as the ceramic fiber 1 is preferable because it provides good workability in forming the mold or core 3 and because it maintains its sheet shape even after being softened with a binder solution (described later), making it easy to remove the mold or core 3 from the solidified body, and also facilitating cleaning of the cast product 8 after removal. It is also preferable that the ceramic fiber 1 is a ceramic fiber bulk material, and that a ceramic fiber solution in which the bulk material is dispersed in a binder is applied to a core (reinforcing structure) made of a heat-resistant hard material, followed by drying and solidification, to form the mold or core 3. This allows the core (reinforcing structure) constituting the mold or core 3 to be easily removed from the solidified body.

[0022] Furthermore, ceramic fiber 1, particularly in the case of crystalline alumina fiber, is provided in various forms such as ceramic fiber cloth, ceramic fiber tape, ceramic fiber sewing thread (twisted yarn), ceramic fiber rope, ceramic fiber cord (solid wire), ceramic fiber sleeve (cylindrical hollow body), ceramic fiber chopped fiber (short fiber body), ceramic fiber nonwoven fabric (felt), ceramic fiber paper, and ceramic fiber knit. These various forms of ceramic fiber 1 can be deformed or impregnated with a binder in the same manner as above, thereby efficiently solidifying them into a predetermined shape and forming a mold or core 3.

[0023] It is preferable to use polyvinyl alcohol, an alumina dispersion, a silica dispersion, a heat-resistant adhesive, or a combination of these as the binder 110. The binder 110 can be impregnated into the ceramic fibers 1 by spraying, dipping, or various other methods.

[0024] The mold or core 3 in this example is provided with a plurality of rod-shaped portions 31 as convex portions 310, which are formed by solidifying ceramic fibers 1 into a rod shape, and the target casting 8, which will be described later, has a plurality of rod-shaped holes 80 (concave holes) formed by transferring the rod-shaped portions 31 (convex portions 310). As shown in FIG. 1( a), each rod-shaped portion 31 can be easily formed by using a ceramic fiber sheet as the ceramic fiber 1 and forming a rod-shaped body 11 by rolling or folding a ceramic fiber sheet impregnated with a binder 110, or by stacking multiple sheets and adhering and solidifying them into a rod shape.

[0025] 1(a), a ceramic fiber sheet is used as the ceramic fiber 1, and the ceramic fiber 1 is impregnated with a binder 110, wound into a rod shape, and solidified to form a rod-shaped body 11. However, as shown in FIG. 20, by using a ceramic fiber cord (solid wire) as the ceramic fiber 1, for example, the rod-shaped body 11 can be more easily formed by simply impregnating the ceramic fiber 1 with a binder 110 and solidifying it. A plurality of ceramic fiber cords (solid wires) can also be twisted together to form a single cord.

[0026] When solidifying, dimensional accuracy can be maintained by placing the rod-shaped bodies 11 in a predetermined mold. Furthermore, during solidification, it is preferable to apply pressure simultaneously with drying of the binder 110, thereby forming a strong mold or core 3 according to the designed dimensions. In this example, a plurality of such rod-shaped bodies 11 are formed, and then a base 32 is formed from a heat-resistant thermoplastic resin 320, cast iron, heat-resistant alloy steel, graphite, refractory ceramics, or the like, as shown in FIG. 1( b), thereby forming a mold or core 3 having a plurality of rod-shaped bodies 31 as a convex portion 310 integrated with each other by the base 32 at the base end, as shown in FIG. 1( c).

[0027] 2(a) and 2(b), a molten material 600 such as a molten metal (e.g., an aluminum alloy), semiconductor, or polymer is supplied (poured) into a mold 4 (crucible) in which the mold or core 3 is placed as a template, and solidified to form a solidified body 6 made of the molten material integrated with the mold or core 3. The illustrated mold 4 is made of a heat-resistant thermoplastic resin, cast iron, heat-resistant alloy steel, graphite, refractory ceramics, or the like, and is composed of a combination of a plate-like mold 40 that forms the bottom surface of the casting and supports the mold or core 3 on its upper surface, and a container-like outer mold 41 that houses the mold or core 3 and forms the outer peripheral surface of the casting.

[0028] The "metal" or "semiconductor material" of the molten material 600 can be various, including aluminum, copper, magnesium, iron, cobalt, nickel, manganese, beryllium, chromium, zinc, titanium, zirconium, vanadium, niobium, molybdenum, palladium, silver, gold, cadmium, indium, tin, platinum, hafnium, tungsten, tantalum, lead, bismuth, alloys thereof, silicon, germanium, compounds thereof, and various other metals or semiconductor materials. Furthermore, the "polymer" can be various thermoplastic synthetic resins or thermosetting synthetic resins. The molten material 600 is preferably degassed before being supplied to prevent the generation of excess gas bubbles. For example, in the case of an aluminum alloy, degassing can be performed by generating argon bubbles in the molten aluminum alloy through a nozzle.

[0029] 3(a) and 3(b), the mold or core 3 is softened by being impregnated with a binder dissolving liquid 7 that dissolves the binder 110. When the binder 110 is a water-soluble binder, such as polyvinyl alcohol, water can be used as the binder dissolving liquid 7. The binder dissolving liquid 7 can be impregnated into the mold or core 3 by immersion, spraying, or other methods.

[0030] The ceramic fibers constituting the mold or core 3 integrated with the solidified body 6 are preferably exposed on the surface, so that the integrated solidified body 6 and mold or core 3 can be immersed in the binder solution 7, and the binder solution can penetrate through the ceramic fiber portions exposed on the surface to soften them. If the ceramic fibers are not exposed, the solidified body can be cut to form grooves or holes until the ceramic fibers are exposed, and then the binder solution 7 can be supplied. In this example, the tips of the rod-shaped portions are exposed on the surface, and the binder solution 7 penetrates from these points.

[0031] 3(c) and 3(d), the mold or core 3 softened by the penetration of the binder solution 7 is removed from the solidified body 6 to obtain a casting 8 made of the solidified body. Rod-shaped holes 80 (concave holes) are formed in the solidified body (casting 8) by transferring the rod-shaped portions 31 of the mold or core 3.

[0032] The softened mold or core 3 can be removed from the solidified body 6 by pulling it out as shown in FIG. 3( c), or by supplying a pressurized fluid (e.g., liquid or air) from the tip end opposite the base 32 to push the mold or core 3 out through holes 80 in the solidified body 6 toward the base end, as shown in FIG. 4( a). If the fluid supplied is the binder dissolving solution 7, it is preferable to omit the pre-impregnation step and soften and push out the mold or core 3 simultaneously by supplying the binder dissolving solution 7 under pressure. In this case, if the base 32 is removed first, or if the base 32 is also composed of ceramic fiber and binder, the mold or core 3 will be pushed out while fiber pieces fly off, as shown in FIG. 4( b), and will lose its original shape after removal.

[0033] In this example, the rod-shaped portions 31 of the mold or core 3 have a structure in which their distal ends protrude as free ends like pins from the base 32 on the proximal end side, but as shown in Fig. 8(a), it is also preferable that the distal ends are provided with a plate-like connecting plate 34 that connects the ends of the rod-shaped portions 31 to each other, similar to the base 32. This allows each rod-shaped portion 31 to be held in a stable state of being supported at both ends, bridged between the base 32 and the connecting plate 34, within the mold 4, as shown in Fig. 8, and prevents bending deformation due to the pressure of the flowing molten material 600 when the molten material 600 is poured, which would cause holes formed in the casting to deviate from the designed shape, thereby enabling the production of a casting with high precision.

[0034] In this case, the mold or core 3 can be easily removed by first removing the connecting plate portion 34 that has been permeated with the binder solution, and then, as in the above example, by pulling out the remaining portion that has been permeated with the binder solution from the base 32 side.

[0035] As another method, as shown in Figures 9(b) and 10(b), it is also preferable to provide a core material 35 with relatively high bending strength at the core of the rod-shaped portion 31 serving as the convex portion 310. Specifically, as shown in Figure 9(a), the base 30 of the mold or core, in which the core material 35 protrudes from the base 32, can be made of a heat-resistant hard material such as a heat-resistant thermoplastic resin, cast iron, heat-resistant alloy steel, graphite, or refractory ceramics, and a ceramic fiber sheet 110 can be wrapped around the base and solidified with a binder 110. Alternatively, as shown in Figures 10(a) and 10(b), a ceramic fiber solution 111 in which ceramic fiber bulk material is dispersed in a binder can be applied to the core material 35 and then dried and solidified. In the example of Figure 9, it is preferable to apply the binder 110 to the core material 35 before wrapping the sheet around it. As another example, as shown in Figure 23, a ceramic fiber sleeve (cylindrical hollow body) having an inner diameter corresponding to the outer diameter of the core material 35 can be used as the ceramic fiber 1, and by attaching it to the core material 35 and solidifying it with a binder 110, it can be realized with greater workability.

[0036] In this case, the sheath layer 12 made of ceramic fibers surrounding the core material 35 is similarly softened by the binder solution, allowing the rod-shaped portion 31 to be easily removed by, for example, pulling it out from the solidified body. Furthermore, even in a cantilevered form, the core material 35 reinforces the rod-shaped portion 31, so that it remains stable without bending even when subjected to the pressure of the flowing molten material 600, thereby enabling a casting having a hole shape as designed to be obtained. Furthermore, when forming a casting having a bent hole, for example, as a bent rod-shaped portion 31, wrapping a sheet of ceramic fibers 1 around the bent core material 35, applying a ceramic fiber solution in which a ceramic fiber bulk material is dispersed in a binder to the bent core material 35, or attaching a ceramic fiber sleeve (cylindrical hollow body) to the bent core material 35 is a preferred method in that it allows the bent rod-shaped portion 31 to be easily formed.

[0037] 10 and other figures, when a ceramic fiber solution in which ceramic fiber bulk material is dispersed in a binder is applied to a core material 35 to form a thin rod-like portion 31 having a diameter of 10 mm or less and a corresponding thin hole is to be formed, it is preferable to use chopped ceramic fiber fibers (short fibers) as the ceramic fiber bulk material, and in this case, the fiber length is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 35 μm or less. If the fiber is longer than 100 μm, it becomes difficult to apply the ceramic fiber solution to the surface of the thin core material 35 with a uniform thickness, which tends to result in unevenness on the outer peripheral surface of the rod-like portion 31 and to result in the formed hole having an uneven inner surface.

[0038] 13(a) is a photograph of a rod-shaped portion 31 obtained by applying and solidifying a ceramic fiber solution made of ceramic fiber bulk material (chopped ceramic fiber fibers (short fiber body)) having an average fiber length of approximately 20 mm to the surface of a metal wire having a diameter of 1.0 mm, and FIG. 13(b) is a photograph of a hole in a casting formed using this. FIG. 14(a) is a photograph of a rod-shaped portion 31 obtained by applying and solidifying a ceramic fiber solution made of bulk material obtained by further crushing the bulk material using a mortar and pestle so that the fiber length is 30 μm or less to the surface of a metal wire having a diameter of 1.0 mm, and FIG. 14(b) is a photograph of a hole in a casting formed using this. It was confirmed that by shortening the fiber length, the surface of the rod-shaped portion 31 was smooth and a neat circular hole was formed.

[0039] Alternatively, instead of or in addition to the reinforcement by the core material 35, it is also preferable to improve strength by adding ceramic powder to a binder, mixing it, and then coating and solidifying the ceramic fiber. Figure 24 shows photographs of a silica fiber sheet (manufactured by Sakaguchi Heat Transfer Co., Ltd.) (top) and an alumina fiber sheet (manufactured by Nichibi Alf Co., Ltd.) (bottom) prepared as ceramic fibers. The photographs show the impregnation and solidification of a binder (polyvinyl alcohol (PVA)) alone (left side of the photograph) and the impregnation and solidification of a binder mixed with alumina powder (right side of the photograph). The hardness of these four sheets was measured using a durometer (rubber hardness tester) (Type A conforming to JIS K 6253). The results are shown in Table 1 below.

[0040]

[0041] Alumina fiber showed only a slight change of 1.6% in hardness, but the addition of ceramic powder to silica fiber increased hardness by 64.1%, demonstrating a significant effect. Alumina fiber is inherently superior in both tensile and bending strength compared to silica fiber, so it was found that adding ceramic powder was particularly effective in increasing the strength of silica fiber. The principle behind this increase in strength is thought to be that the ceramic powder penetrates into the voids in the fiber, strengthening it.

[0042] Furthermore, in the above embodiment, an example was described in which a rod-shaped portion 31 was provided in the mold or core 3 and a rod-shaped hole 80 was formed in the solidified body 6 (cast product 8). However, the present invention is not limited to providing such a rod-shaped hole 80. For example, as shown in Figures 5(a) to 5(c), a plate-shaped portion 31A formed by solidifying ceramic fibers into a plate shape can be provided in the mold or core 3, thereby forming a solidified body 6 (cast product 8) having a plate-shaped hole 80A to which the outer shape of the plate-shaped portion 31A is transferred, as shown in Figure 5(e). The photograph in Figure 15 is a photograph of an actual prototype of the casting of Figure 5(e). The thickness of the plate-shaped portion 31A of the mold or core 3 was set to 1.0 mm, and the thickness of the hole 80A in the produced casting was 1.0 mm.

[0043] Here, the plate-like portion 31A of the mold or core 3 can be constructed by stacking multiple ceramic fiber sheets and solidifying them with a binder to form a plate-like body 11A, as shown in Figure 5(a), forming multiple such plates 11A, and then molding the base 32 with a heat-resistant thermoplastic resin 320 or the like, as shown in Figure 5(b). In this example, as in the example of Figure 9, it is also preferable to provide a core material with relatively high bending strength, such as a thin stainless steel foil (e.g., 0.1 mm thick), at the core of the plate-like portion 31A to improve bending strength for reinforcement. Another preferable example is one in which multiple metal wires 5 are sandwiched between sheets of ceramic fiber 1 and solidified with a binder 110, as shown in Figure 11. The photograph in Figure 16 is a photograph of a prototype casting made using the mold or core in Figure 11. The casting was made by sandwiching a 0.8 mm diameter stainless steel wire between two 1 mm thick ceramic fiber sheets and solidifying the result with a polyvinyl alcohol binder to create a mold or core.

[0044] Also, here, by using, for example, a plate-shaped ceramic fiber cord (solid wire) as the ceramic fiber 1 as shown in Figure 21 (a), it is possible to more easily form a plate-shaped body 11A simply by impregnating it with a binder 110 and solidifying it.

[0045] In the above embodiment, an example was given in which the casting 8 had a rod- or plate-shaped hole 80 (80A). However, the convex portion 310 may have a shape other than a rod or plate, such as a box, partial sphere, cylinder, or other shape, with a concave hole or groove formed by transferring the convex portion. The cross-sectional shape of the convex portion can also be various depending on the desired shape of the concave hole or groove. For example, to obtain a square, triangular, or irregular cross-sectional shape, it is difficult to form the ceramic fiber 1 by winding a ceramic fiber sheet. However, as shown in Figures 21(b) to 21(d), by using a ceramic fiber cord (solid wire) having the desired cross-sectional shape as the ceramic fiber 1, it is possible to more easily form a rod-shaped body 11 having the desired cross-sectional shape. As shown in Figure 22, by using a cylindrical ceramic fiber sleeve (cylindrical hollow body) as the ceramic fiber 1, a hole with a convex portion in the center can also be formed.

[0046] Furthermore, as shown in FIG. 7, by processing the ceramic fibers after solidification into the mold or core 3, one or more concave holes 33 or grooves can be formed, thereby forming a casting 8B having rod-shaped or plate-shaped protrusions 81 protruding therefrom as one or more convex portions 810 transferred with the holes 33 or grooves, as shown in FIG. 7(e).

[0047] 6(a) and 6(b), such a casting is made by first stacking a plurality of ceramic fiber sheets 1, bonding and solidifying them with a binder 110, to form a base 11C that serves as the base of a three-dimensional mold or core 3, and then forming holes 33 and wide grooves in this by machining or the like. The holes 33 and wide grooves may be through-holes or may not be through-holes (with a bottom).

[0048] 7(a) and 7(b), a molten material 600 such as a molten metal (e.g., aluminum alloy), semiconductor, or polymer is supplied (injected) into a mold 4 (crucible) with a mold or core 3 set therein as a template, and solidified to form a solidified body (6B) of the molten material integrated with the mold or core 3. The mold 4 in this example is comprised of a container-shaped first outer mold 42 that houses the mold or core 3 and forms the outer periphery of the casting, and a similar container-shaped second outer mold 43 that forms the main body 82 of the casting. Here, if the inner diameter of the hole 33 is small, the molten material will not penetrate the pores due to the surface tension and viscosity of the molten material. Therefore, as shown in FIG. 12, it is preferable to employ a vacuum suction method in which a vacuum is drawn while supplying the molten material 600, thereby drawing the molten material into the pores. In the figure, reference numeral 50 denotes a heat-resistant porous material such as ceramic fiber that can be suctioned under reduced pressure, and 51 denotes an exhaust pipe. At the end of the exhaust pipe 51 is provided a suction pump (not shown), which is a device that suctions downwards by vacuum.

[0049] Next, as shown in Figure 7(c), binder dissolving liquid 7 is allowed to penetrate into the mold or core 3, thereby softening the mold or core 3. Then, as shown in Figures 7(d) and 7(e), the mold or core 3 softened by the penetration of binder dissolving liquid 7 is separated from the solidified body 6B, thereby obtaining a casting 8B made of the solidified body. A plurality of rod-shaped protrusions 81, to which the holes 33 of the mold or core 3 are transferred, are formed on the casting 8B.

[0050] Figures 17 to 19 are photographs of actual prototype samples of the casting 8B shown in Figure 7(e). The upper photograph in Figure 17 is a photograph of the mold or core 3 and solidified body 6 solidified together, viewed from the hole opening, revealing the tip end of the aluminum alloy solidified within the hole. The lower photograph in Figure 17 is a photograph of the casting after the mold or core was removed. The projections (pins) had a height of 22 mm and several different thicknesses (outer diameters). Figure 18 shows a similar sample, with projections having a height of 20 mm, a thickness (outer diameter) of 1.7 mm, and a staggered arrangement. Figure 19 is a photograph of a sample in which thin projections (pins) were formed using the vacuum decompression suction method, with a thickness (outer diameter) of 0.6 mm and a grid-like arrangement. Such thin projections (thickness (outer diameter) of 1.5 mm or less) can be easily achieved using the vacuum decompression suction method.

[0051] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0052] For example, while the holes 80, 80A and protrusions 81 in the casting shown in the example above are straight, the present invention also makes it possible to form curved holes and protrusions by forming a curved shape on the convex portion 310 (rod-shaped portion 31) and hole 33 of the mold or core 3. Similarly, by forming the convex portion 310 (rod-shaped portion 31) and hole 33 into corresponding shapes, the cross-sectional shape of the formed holes and protrusions can be polygonal, such as a triangle, a square, a pentagon, or a hexagon, in addition to a circle, or various other shapes such as an ellipse, a flat plate (rectangular in cross section), an L-shape, a V-shape, a Y-shape, or a U-shape (katakana).

[0053] It is also possible to form holes or protrusions whose cross-sectional area is not constant in the axial direction but is non-uniform, such as tapered holes or protrusions whose cross-sectional area gradually decreases (increases). Furthermore, it is also possible to form shapes or protrusions whose thickness varies periodically. Furthermore, instead of holes or protrusions extending in one direction, a casting having multiple holes or protrusions extending in different directions can be formed by forming the above-mentioned convex portions 310 (rod-shaped portions 31) or holes 33 as multiple convex portions 310 (rod-shaped portions 31) or holes 33 extending in different directions. Furthermore, a hole that branches midway through the interior can be easily realized by forming a similarly branched rod-shaped portion 31. The present invention is not limited to the formation of "holes" or "protrusions," and various shapes can be formed.

[0054] DESCRIPTION OF SYMBOLS 1 Ceramic fiber 3 Core 4 Mold 5 Wire 6, 6B Solidified body 7 Binder solution 8, 8B Casting 11 Rod-shaped body 11A Plate-shaped body 11C Base 12 Sheath layer 30 Base 31 Rod-shaped portion 31A Plate-shaped portion 310 Convex portion 32 Base 33 Hole 34 Connecting plate portion 35 Core material 40 Plate mold 41 Outer mold 42, 43 Second outer mold 80, 80A Hole 81 Protrusion 810 Convex portion 82 Main body portion 110 Binder 320 Thermoplastic resin 600 Molten material

Claims

1. A casting method comprising the steps of: forming a shape-retaining mold or core in advance by impregnating ceramic fibers with a binder and solidifying the mold or core into a predetermined shape; supplying a molten material of a molten metal, semiconductor or polymer into a mold in which the mold or core is placed to form a solidified body of the molten material; softening the mold or core by infiltrating a binder dissolving liquid that dissolves the binder into the mold or core; and removing the softened mold or core from the solidified body to obtain a casting made of the solidified body.

2. The casting method according to claim 1, wherein a convex portion is provided in the mold or core by solidifying the ceramic fiber into a convex shape, thereby forming a concave hole or groove in the solidified body by transferring the convex portion.

3. The casting method according to claim 1, wherein the ceramic fiber is solidified and then processed in the mold or core to provide a single or multiple concave holes or grooves, thereby forming a single or multiple convex portions in which the holes or grooves are transferred in the solidified body.

4. The casting method according to claim 1, wherein said binder is a water-soluble binder and said binder dissolving liquid is water.

5. The casting method of claim 4, wherein the binder is polyvinyl alcohol, an alumina dispersion, a silica dispersion, or a heat resistant adhesive, or a combination thereof.

6. A casting method according to claim 1, further comprising the step of pressing a pressurized fluid consisting of the binder dissolving liquid or air against the mold or core permeated with the binder dissolving liquid, thereby separating the mold or core from the solidified body.

7. A casting obtained by the casting method according to any one of claims 1 to 6.

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