Core member and method for manufacturing the core member

Abstract

To provide a core member having satisfactory collapsibility and capable of suppressing gas defects in a mold to be produced, and a core member production method.SOLUTION: A casting core member 30 having a hollow structure is formed of molding sand used for molding a cast 1 and a binder cured by combining the particles of the molding sand with each other, and comprises a gas vent hole 35 connecting a hollow side and a mold formation side of a wall part 32 forming the hollow structure. Further, the gas vent hole 35 is formed such that the hollow side is located above and the mold formation side is located below during casting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a core member and a method for manufacturing a core member. [Background technology]

[0002] A core member is a type of mold used to produce hollow castings, and is typically a sand core made from sand and a binder that hardens to bind the sand particles together. A casting method using a core member involves placing the core member in a main mold, pouring molten metal into the inlet, cooling the molten metal, and then demolding the mold to obtain the resulting casting.

[0003] While core members enable the production of complex-shaped castings, they are often placed in locations that make it difficult to dismantle the mold from the outside. Therefore, core members are required to have excellent collapsibility. For example, in the invention described in Patent Document 1, the surface layer of the core member is impregnated with salt that has a higher melting point than the metal being cast, thereby achieving both pressure resistance and collapsibility. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-307596 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the use of core materials increases the risk of gas defects due to poor gas evacuation. Specifically, gas defects can occur in castings due to the release of nitrogen or hydrogen gas dissolved in the molten metal, moisture contained in the sand mold, thermal decomposition of the binder, or bubbles generated when air is not properly evacuated from the mold when the molten metal is poured into the mold. Solid core materials are particularly prone to such gas defects. Therefore, there is a demand for core materials that not only have good collapsibility but also can suppress gas defects.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a core member that has good disintegration properties and is capable of suppressing gas defects in the resulting casting, and a method for manufacturing a core member. [Means for solving the problem]

[0007] (1) In order to achieve the above object, the core member of the present invention is a core member for casting having a hollow structure, which is formed of molding sand used to form a mold and a binder that binds the particles of the molding sand together and hardens, and has a gas vent hole that connects the hollow side of the wall portion that forms the hollow structure with the casting forming side. The gas vent holes are formed so that the hollow side is on top and the casting forming side is on the bottom during casting. It is characterized by the following.

[0008] In this way, the hollow structure provides excellent collapsibility, and the presence of gas vent holes that connect the hollow side with the casting forming side makes it possible to suppress gas defects in the resulting casting.

[0009] Also, The gas vent hole is formed so that the hollow side faces up and the casting forming side faces down during casting. By This prevents the molten metal from leaking, making it easier for only the gas to escape.

[0010] ( 2 ) Core member of the present invention is a core member for casting having a hollow structure, which is formed from molding sand used to form a mold and a binder that binds the particles of the molding sand together and hardens, and has gas vent holes that connect the hollow side of a wall portion that forms the hollow structure with the casting forming side, The gas vent holes are characterized in that they are formed so that their cross-sectional area decreases from the hollow side toward the casting forming side. In this way, the hollow structure makes it easy to disintegrate, and the presence of gas vent holes that connect the hollow side to the casting side makes it possible to suppress gas defects in the resulting casting. This further prevents the molten metal from leaking, making it easier for only the gas to escape.

[0011] ( 3) The core member of the present invention is characterized in that the number of vent holes per unit area is greater in those adjacent to thicker regions of the casting than in those adjacent to thinner regions of the casting. The larger the volume of the casting formed, the more gas that is the cause of gas defects is generated. Therefore, by forming more vent holes in thicker regions of the casting, gas defects in the resulting casting can be further suppressed.

[0012] ( 4 ) In the core member of the present invention, the number of vent holes per unit area is greater in the area adjacent to the region farther from the weir, which is the opening through which molten metal can be poured into the mold, than in the area closer to the weir. This allows gas generated in a position difficult to discharge from the weir to be discharged from the hollow side through the vent holes, thereby further suppressing gas defects in the resulting casting.

[0013] ( 5 In the core member of the present invention, the diameter of the gas vent hole on the casting forming side is φ2 mm or less, which prevents leakage of molten metal and allows only gas to escape easily.

[0014] ( 6 ) In the core member of the present invention, the thickness of the wall portion is set to 3 mm or more and 12 mm or less, which makes it possible to obtain a core member with excellent collapsibility.

[0015] ( 7 ) The method for manufacturing a core member of the present invention is the above (1) to ( 6 ) is a method for manufacturing a core member described in any one of the above, characterized in that the shaped body is formed using an additive manufacturing device by repeating a series of steps including a step of spreading the shaping sand evenly to a certain thickness and a step of spraying the binder onto a predetermined part that will become the shaped body and hardening it.

[0016] This makes it possible to easily manufacture even a core member having a hollow structure and having a gas vent hole that connects the hollow side with the casting forming side. [Effects of the Invention]

[0017] According to the present invention, the core member has good disintegration properties, and gas defects in the resulting casting can be suppressed. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a partial cross-sectional view showing the schematic configuration of a core member and a casting according to the first embodiment. [Figure 2] FIG. 2 is a perspective view showing a state in which a core member according to the first embodiment is installed in a main mold. [Figure 3] FIG. 2 is a partial cross-sectional view showing a state in which a core member according to the first embodiment is installed in a main mold. [Figure 4] FIG. 3 is an enlarged cross-sectional view of a portion of a wall portion of a core member provided with a gas vent hole according to the first embodiment. [Figure 5] FIG. 1 is a perspective view showing a casting according to a first embodiment. [Figure 6] FIG. 10 is a partial cross-sectional view showing a state in which a core member according to a second embodiment is installed in a main mold. [Figure 7] FIG. 10 is a perspective view showing a state in which a core member according to a second embodiment is installed in a main mold. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a portion of a wall portion of a core member provided with a gas vent hole according to a second embodiment. [Figure 9] FIG. 10 is a partial cross-sectional view showing a state in which a core member according to a third embodiment is installed in a main mold. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a portion of a wall portion of a core member provided with a gas vent hole according to a third embodiment. [Figure 11] FIG. 10 is a partial cross-sectional view showing a state in which a core member of a comparative example is installed in a main mold. DETAILED DESCRIPTION OF THE INVENTION

[0019] [First embodiment] Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. In each embodiment, differences from the basic embodiment will be mainly described, and descriptions of similar configurations will be omitted.

[0020] [Core material] FIG. 1 is a partial cross-sectional view showing a core member 30 and a casting 100 according to a first embodiment of the present invention. The core member 30 is formed from shaping sand and a binder. The shaping sand is sand used to create a mold using a 3D printer (additive manufacturing device). The binder binds the shaping sand particles together and hardens them. Note that if the shaping sand is sintered with a laser, the binder may not be necessary.

[0021] Core member 30 has a hollow portion 31 surrounded by wall portions 32 that form a hollow structure, and gas vent holes 35 formed in wall portions 32. Details of gas vent holes 35 will be described later. The hollow structure refers to a structure made up of wall portions 32 and hollow portion 31, and hollow portion 31 refers to the space itself surrounded by wall portions 32 (excluding the walls). As shown in FIG. 1, wall portions 32 need only be formed in a portion that contacts casting forming portion 12 (casting 100 in FIG. 1), which will be described later, and do not need to surround the entire hollow portion 31.

[0022] The wall 32 of the core member 30 is preferably thin. Gases generated during casting can occur in both the molten metal and the core, depending on the type of metal being poured and the type of mold. Additive 3D printer molds and core members are produced by hardening only the necessary portions of a uniformly thick layer of sand and then layering them one by one. Additive 3D printers cannot use any molding sand; the layer thickness must be consistent and the surface must be flat. Therefore, materials for additive 3D printers are specially formulated. Molds made with such materials tend to have higher bulk density and poorer breathability than general molds with the same average particle size. Furthermore, since most additive 3D printers require a layer thickness of 300 μm or less, the average particle size of the molding sand is generally 150 μm or less, as described below. The smaller the sand particle size, the smaller the pores in the sand, resulting in poorer breathability. Furthermore, when a test specimen based on JIS Z 2601 was created using an additive 3D printer using the material used for the core and the air permeability of the test specimen was measured, it was found to be less than 50. In this way, cores created using an additive 3D printer have low air permeability.

[0023] From the above viewpoints, the thickness of the wall 32 of the core member 30 is preferably 12 mm or less. A thickness of 12 mm or less of the wall 32 ensures sufficient breathability. The thickness of the wall 32 forming the hollow structure is preferably 5 mm or more. A thickness of 5 mm or more of the wall 32 reduces the risk of breakage as a mold and maintains sufficient strength. It is more preferable that the thickness of the wall 32 is 2 mm or more. If the thickness is less than 2 mm, the risk of breakage increases when handling the core member 30, so the practical lower limit is 2 mm.

[0024] Furthermore, core member 30 is placed in main mold 20, which forms the outer shape of casting 100, to form mold 1 capable of casting casting 100 together with main mold 20. Figures 2 and 3 show the state in which core member 30 is placed in the main mold. Core member 30 shown in Figures 2 and 3 is placed between main mold 20, which is made up of upper mold 24 and lower mold 25, to form mold 1. Mold 1 has a molten metal weir 11 and a casting forming portion 12.

[0025] Weir 11 is an opening in mold 1 into which molten metal can be poured, and is used as a flow path through which molten metal from the runner flows into casting formation section 12. Note that a sprue is an opening through which molten metal is poured into the mold during casting, and a runner is a hole that guides molten metal from the sprue to the mold during casting.

[0026] The weir 11 may be formed in a position that allows easy pouring of molten metal, and is preferably designed to be formed in a position that will be the upper end during casting. In the mold 1 shown in Figures 2 and 3, the weir 11 is provided in the upper mold 24. In the mold 1 shown in Figures 2 and 3, two weirs 11 are provided, but the molten metal may be poured into either weir 11. The size of the weir 11 is not particularly limited and is set appropriately depending on the shape of the mold 1 to be produced. The casting forming section 12 has a hollow structure realized by the main mold wall 22 formed of molding sand and binder and the core member wall 32, and a casting 100 is formed in the casting forming section 12 by pouring molten metal through the weir 11.

[0027] Next, the vent holes 35 of the core member 30 will be described in detail. FIG. 4 is an enlarged schematic diagram showing the periphery of the wall portion 32 in which the vent holes 35 are provided. In FIG. 4, hatching has been omitted from the cross section of the wall portion 32 to make the vent holes more visible. The vent holes 35 are formed to communicate between the hollow side and the casting side. That is, the vent holes 35 communicate between the hollow portion 31 and the casting forming portion 12 during casting. This allows gas generated during casting to be discharged from the hollow portion through the vent holes, thereby preventing gas defects from occurring in the casting formed in the casting forming portion. Core members 30 formed by additive 3D printers are particularly suitable for castings with complex shapes, but ensuring breathability presents a challenge. Therefore, providing the vent holes 35 is effective.

[0028] Furthermore, the vent holes 35 are preferably formed so that the hollow side faces upward and the casting side faces downward during casting. This allows gas generated during casting to be easily discharged from the casting side toward the hollow side. In FIG. 4, the vent holes 35 are formed in the wall 32, which is parallel to the mounting surface. The center line L of the vent holes 35 formed in the wall 32 is perpendicular to the mounting surface. The mounting surface refers to the surface that the underside of the mold 1 contacts during casting. For example, in the mold 1 shown in FIG. 3, the outer surface of the lower mold 25 of the main mold 20 is the underside of the mold 1 during casting, and it is placed so that it contacts the mounting surface of a mounting table (not shown). In this case, the core member 30 is positioned so that the opening of the vent holes on the hollow side is located vertically upward and the opening on the casting side is located vertically downward. According to such a core member 30, the surface (front surface) of the wall portion 32 facing the casting and the surface (back surface) facing the hollow portion are parallel to the mounting surface, so that it is easy to form a gas vent hole 35 having a center line L perpendicular to the mounting surface, and such a gas vent hole 35 makes it even easier for gas to escape.

[0029] Furthermore, it is preferable that the vent hole 35 be formed so that its cross-sectional area decreases from the hollow side toward the casting formation side. This makes it difficult for the molten metal to leak from the vent hole 35, and makes it easier for only the gas to escape. The vent hole 35 may have a cross-sectional area that decreases from the hollow side toward the casting formation side, and may have a step, for example. It is preferable that the cross-sectional area decreases monotonically toward the casting formation side. In particular, it is preferable that the vent hole 35 be frustum-shaped. The cross-sectional shape of the vent hole 35 may be polygonal, but a circle is particularly preferable. For the above reasons, it is particularly preferable that the vent hole be frustum-shaped.

[0030] The diameter of the gas vent hole on the casting forming side is preferably φ2 mm or less, which makes it more difficult for the molten metal to leak from the gas vent hole 35 and makes it easier for only the gas to escape.

[0031] Furthermore, it is preferable that the number of gas vent holes 35 per unit area be greater in those that are in contact with thicker regions of the casting 100 than in those that are in contact with thinner regions of the casting 100. The amount of gas generated during casting depends on the volume of the casting 100. Therefore, by providing more gas vent holes in thicker regions of the casting, gas defects in the resulting casting can be suppressed.

[0032] It is preferable that the number of gas venting holes 35 per unit area be greater in those adjacent to the region far from the weir 11 than in those adjacent to the region close to the weir 11. Gas generated within the casting forming section 12 is usually discharged through the weir 11. However, gas generated in the region far from the weir 11 cannot reach the weir 11 and remains within the casting forming section 12, which may cause gas defects. Therefore, by providing more gas venting holes in the region far from the weir, gas defects in the resulting casting can be suppressed.

[0033] For example, in the mold 1 shown in FIG. 3, if molten metal is poured through weir 11a and weir 11b is closed during casting, the opening of weir 11b is blocked and the weir 11b does not function as a weir. In this case, the radially inner side of the wall 32a is farther from weir 11a than the radially outer side of the mold 1 relative to the central axis C1. Therefore, it is preferable that the number of holes per unit area on the surface (back surface) of the mold 1 facing the hollow portion be greater in the radially outer region than in the radially inner region. Furthermore, on the surfaces (back surfaces) of the walls 32a and 32b that form different hollow portions, the number of holes per unit area of ​​the wall 32a closest to weir 11a may be greater than the number of holes per unit area of ​​the wall 32b.

[0034] As mentioned above, core members produced using an additive 3D printer have low permeability. In contrast, the core member 30 of the present invention is provided with vent holes 35 to facilitate the escape of gas generated during casting. The number of vent holes 35 per unit area is greater in those adjacent to thicker regions of the casting than in those adjacent to thinner regions, and the number of vent holes per unit area is greater in those adjacent to regions farther from the weir 11 than in those adjacent to regions closer to the weir. The diameter of the vent holes 35 on the casting forming side is φ2 mm or less. This hole configuration is particularly effective for core members produced using an additive 3D printer that have low permeability.

[0035] [Method of manufacturing core parts] (Entire process) A method for manufacturing the core member 30 configured as above will be described. The core member 30 is manufactured using a layered 3D printer (additive manufacturing device). A commercially available binder jet type 3D printer can be used as the 3D printer.

[0036] The data for the core member 30 input into the 3D printer does not leave the shape of the hollow portion of the casting as is, but rather creates a hollow structure while maintaining the outer shape. In addition, by forming gas vent holes 35, the structure is designed to allow gas to easily escape from the casting forming portion 12 during casting. Gas generated during casting can be released through these holes 35. Note that the hollow structure refers to a structure made up of wall portions and a hollow portion, and the hollow portion refers to the space itself surrounded by the wall portions (excluding the wall portions).

[0037] In this way, a 3D printer is used to spread sand to a uniform thickness, then spray binder onto the designated areas of the object, allowing it to harden. This process repeats a series of steps to create a molded object. This allows for high dimensional accuracy to be maintained even for cores with complex shapes, without the need for multiple divisions. Details of molding materials will be provided later.

[0038] Once molding is complete, the hardened molded body (e.g., core member 30) is buried in unhardened sand within the formed laminate. The molded body is extracted by removing the unhardened sand from the laminate. If the molded body is hollow, unhardened sand remains in the hollow portion even after the surrounding unhardened sand is removed. For this reason, it is preferable that the core member 30 has a partially open hollow structure.

[0039] (Modeling materials) Sand dedicated to layered 3D printers is used as the molding sand. Any commercially available specialized sand can be selected and used. Examples of commercially available specialized sand include the original material of the 3D printer and TCaST (registered trademark, manufactured by Taiheiyo Cement Corporation). The specialized sand can be selected, for example, taking into account the heat resistance depending on the molten metal temperature to be cast. Furthermore, commercially available specialized sand may be modified and used as the molding sand. The average particle size of the molding sand is preferably 60 μm or more and 150 μm or less, and more preferably about 100 μm.

[0040] The binder can be an organic material such as a phenolic resin or a furan resin that hardens through condensation or polymerization. However, depending on the type of organic material, its use at high temperatures may be limited. Therefore, when using the binder at high temperatures, or to prevent environmental impacts such as odors caused by the evaporation of organic materials during casting, or defects in the casting due to generated gases, it is preferable for the binder to be primarily composed of inorganic hydraulic substances such as calcium aluminate, cement, gypsum, or lime. For example, when using a calcium aluminate compound as the binder, gas generation is suppressed because it does not contain components that cause sulfur-based gases generated when using cement or gypsum. Furthermore, the provision of gas vent holes can more effectively suppress the occurrence of gas defects such as pinholes and blowholes.

[0041] [Casting method] (Entire process) A casting method using the above-mentioned core member 30 will now be described. Upper and lower dies 24 and 25 constitute main die 20, which is formed so as to have a shape that follows the outer diameter of casting 100 shown in Fig. 5 when mated, and is designed so that by providing core member 30 between upper and lower dies 24 and 25, casting forming portion 12 is formed by wall portion 22 of the main die and wall portion 32 of the core member.

[0042] During casting, first, core member 30 is placed in lower mold 25. Then, upper mold 24 is mated with lower mold 25 and core member 30, and upper mold 24 and lower mold 25 are closed to assemble mold 1. Once mold 1 is ready, molten metal is poured into mold 1. At this time, mold 1 may be placed in a molding flask, and molding sand may be filled into the flask so as to cover the outer surface of mold 1 except for weir 11.

[0043] Furthermore, when molten metal is poured into mold 1, gas is generated from the molten metal and core member 30. However, because core member 30 has gas vent holes 35 that connect hollow portion 31 and casting forming portion 12, gas can escape from casting forming portion 12 through gas vent holes 35, thereby suppressing gas defects in casting 100 produced using mold 1.

[0044] The molten metal is then cooled, and the casting 100 produced in the mold 1 is removed. At this time, the mold 1 is disassembled. FIG. 5 is a perspective view showing the produced casting 100. The casting 100 has a shaft portion arranged along the central axis of the casting, six blade portions extending in a direction different from the central axis, and side plates arranged on both sides of the blade portions. The casting 100 is a so-called closed impeller.

[0045] [Second embodiment] Next, a second embodiment of the present invention will be described. The core member of the second embodiment differs from the first embodiment in that a gas vent hole is provided in a wall portion that is not parallel to the mounting surface, but otherwise has the same configuration.

[0046] Fig. 6 is a partial cross-sectional view showing the state in which core member 60 is placed in main mold 50, and Fig. 7 is a perspective view of mold 2. As shown in Fig. 6, main mold 50 consists only of lower mold 55, and mold 2 is formed by placing core member 60 in lower mold 55. In mold 2 shown in Fig. 6, weir 41 is formed by placing core member 60 in main mold 50. By pouring molten metal through weir 41, a screw-shaped casting is formed in casting forming section 42. The shaft is arranged along the central axis of the casting and has a diameter that decreases downward, and blades that continue in a spiral shape.

[0047] FIG. 8 is an enlarged schematic diagram showing the periphery of a wall 62 provided with a vent hole 65. In the core member 60, the vent hole 65 is formed in the wall 62, which extends in a direction not parallel to the mounting surface. The vent hole 65 is preferably formed so that the hollow side is on top and the casting side is on the bottom during casting. If the wall 62 of the core member is not parallel to the mounting surface, for example, when the hole diameters on the hollow side and the casting side are significantly different, it may be difficult to confirm that the hollow side is on top during casting. In this case, it is sufficient that the vent hole is formed so that the hollow side is on top and the casting side is on the bottom along the center line L of the vent hole.

[0048] [Third embodiment] Next, a third embodiment of the present invention will be described. The core member of the third embodiment differs from the first embodiment in that a gas vent hole is provided in a wall portion perpendicular to the mounting surface, but otherwise has the same configuration.

[0049] Figure 9 is a partial cross-sectional view showing a state in which core member 90 is placed in main mold 80. As shown in Figure 9, core member 90 is cylindrical and is placed inside the axis forming portion of main mold 80, which forms the axis of the casting, to form mold 3. In mold 3 shown in Figure 9, weir 71 is formed between the inner surface of main mold 80 and the outer surface of core member 90. By pouring molten metal through weir 71, a screw-shaped casting is formed in casting forming portion 72, which has an axis portion that is arranged along the central axis of the casting and spirally continuing blade portions.

[0050] 10 is an enlarged schematic diagram showing the periphery of a wall portion 92 provided with a vent hole 95. In the core member 90, the vent hole 95 is formed in the wall portion 92 extending perpendicularly to the mounting surface. The vent hole 95 is preferably formed so that the hollow side of the center line L during casting is at the top and the casting formation side is at the bottom. This makes it easier for gas generated during casting to be discharged from the casting formation portion toward the hollow portion.

[0051] [Summary of each embodiment] As described above, the core member according to the present invention suppresses gas defects in the resulting casting by allowing gas generated during casting to be discharged from the casting forming portion through the gas vent holes. Furthermore, because the core member according to the present invention has a hollow structure, it also has excellent collapsibility. Therefore, by casting using the core member according to the present invention, a good casting can be obtained.

[0052] [Example] A mold was created according to the above method, and casting was performed. The 3D printer used was the CJP660 (manufactured by 3D Systems). The molding sand used was TCaST (manufactured by Taiheiyo Cement Corporation, average particle size 100 μm).

[0053] As an example, a mold having the shape shown in Figures 2 and 3 was produced. The molding conditions are as shown in Table 1. The produced mold had a wall thickness (thickness of the wall and lid) of 5 mm. Furthermore, as Comparative Example 1, a mold having the shape shown in Figure 11 was produced. The mold of Comparative Example 1 shown in Figure 11 was produced in the same manner as the example, except that no vent holes were provided and the core member was solid rather than hollow. As Comparative Example 2, a mold similar to the example was produced, except that no vent holes were provided. [Table 1]

[0054] Casting and mold disassembly were performed, and if the core material could be removed without any problems, it was evaluated as ○, and if it could not be easily removed, it was evaluated as × for collapsibility. Then, the castings produced from the molds of the examples and comparative examples were evaluated for the presence or absence of gas defects. The evaluation results are shown in Table 2. [Table 2]

[0055] The core member of Comparative Example 1 was not hollow, so it had poor collapsibility and was difficult to remove. In addition, because it did not have a gas vent hole, gas defects occurred in the castings produced using the mold.

[0056] The core member of Comparative Example 2 had excellent collapsibility, but gas defects occurred in the center of the produced casting. However, the generation of gas defects was suppressed compared to Comparative Example 1. This is thought to be because, unlike the solid core member of Comparative Example 1, the core member of Comparative Example 2 has a hollow structure, which suppresses the amount of gas generated from the core member and therefore suppresses the generation of gas defects.

[0057] In contrast, the core member of the Example not only exhibited excellent disintegration properties, but also did not produce gas defects in the castings produced using the mold. This indicates that the precision of the castings was improved compared to the Comparative Examples. From the above, it was confirmed that the core member having a hollow structure exhibited excellent disintegration properties. Furthermore, it was confirmed that providing gas vent holes in the wall of the core member prevented gas generated during casting from remaining in the casting formation area, thereby preventing the occurrence of gas defects in the casting. [Explanation of symbols]

[0058] 1, 2, 3 Mold 11, 11a, 11b, 41, 71 Weir 12, 42, 72 Casting forming section 20, 50, 80 main type 22, 52, 82 (Main mold) wall 24 Upper mold 25, 55 lower mold 30, 60, 90 core material 31, 61, 91 Hollow part 32, 32a, 32b, 62, 92 (core member) wall 35, 65, 95 Gas vent holes 100 Castings C1 center axis L center line

Claims

1. A casting core member having a hollow structure, Molding sand used to form molds; and a binder that binds the particles of the shaping sand together and hardens, a gas vent hole that connects the hollow side of the wall portion that forms the hollow structure with the casting forming side, A core member characterized in that the gas vent holes are formed so that the hollow side faces up and the casting forming side faces down during casting.

2. A casting core member having a hollow structure, Molding sand used to form molds; and a binder that binds the particles of the shaping sand together and hardens, a gas vent hole that connects the hollow side of the wall portion that forms the hollow structure with the casting forming side, The core member is characterized in that the gas vent holes are formed so that their cross-sectional area decreases from the hollow side toward the casting forming side.

3. 3. The core member according to claim 1, wherein the number of gas vent holes per unit area is greater in those adjacent to regions where the casting is thicker than in those adjacent to regions where the casting is thinner.

4. 4. The core member according to claim 1, wherein the number of vent holes per unit area is greater in a region adjacent to a weir, which is an opening through which molten metal can be poured into the mold, than in a region adjacent to the weir.

5. 5. The core member according to claim 1, wherein the diameter of the gas vent hole on the casting forming side is φ2 mm or less.

6. 6. The core member according to claim 1, wherein the wall portion has a thickness of 3 mm or more and 12 mm or less.

7. A method for manufacturing a core member according to any one of claims 1 to 6, a step of spreading the shaping sand to a uniform thickness; and a step of injecting the binder into a predetermined portion of the shaped body and hardening it, thereby forming the shaped body using an additive manufacturing device.

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