Casting evaluation device

Abstract

The present invention provides a casting evaluation apparatus that can be used to perform casting evaluation tests on metallic materials that form a coarse structure. [Solution] The casting evaluation device 1 comprises a mold 20 having a cavity 30 into which molten metal can be injected, and an insulating material 40 provided on the inner wall surface of the mold 20 facing the cavity 30, wherein the cavity 30 integrally comprises two molten metal pools 31 and 32 spaced apart from each other in the axial direction A, and a cylindrical axial core 33 whose cross-sectional area perpendicular to the axial direction A is smaller than that of the two molten metal pools 31 and 32, and which connects the two molten metal pools 31 and 32 along the axial direction A, and the insulating material 40 is provided on the inner wall surface of the mold 20, occupying an area of ​​80% or more of the region constituting the axial core 33.

Description

Technical Field

[0001] The present invention relates to a casting evaluation apparatus, and more particularly to a casting evaluation apparatus that can evaluate casting processes such as defect evaluation for metal materials that form coarse structures, such as Fe alloys and Ni alloys.

Background Art

[0002] When casting a metal material, defects such as fractures may occur in the manufactured casting due to factors such as the physical properties of the metal material, the shape and material of the mold, and the casting conditions. Since these defects affect the characteristics of the product, it is desirable to suppress them as much as possible. However, in order to suppress the generation of defects, it is important to obtain basic knowledge related to the casting process, such as the nature of these defects and the behavior of the metal material during casting. In order to obtain such knowledge, a casting evaluation test may be performed using a casting evaluation apparatus that mimics an actual casting apparatus. For example, casting is performed under conditions where defects are likely to occur intentionally, and detailed analysis of the generated defects and analysis of the casting conditions are performed.

[0003] As a casting evaluation apparatus suitable for artificially forming defects and obtaining knowledge about defects, an I-beam type evaluation apparatus is known. The I-beam type casting evaluation apparatus has a cavity surrounded by a mold, which has two molten metal reservoirs and an axial core part connecting between the molten metal reservoirs, and has a cross-sectional shape like the letter "I". That kind of I-beam type casting evaluation apparatus is disclosed in, for example, Patent Document 1 and Non-Patent Document 1. In those documents, a heat insulating material is adhered to the inner wall surface of the mold in a partial region in the middle of the region corresponding to the axial core part. At the location where this heat insulating material is provided, shrinkage stress is generated in the metal material during solidification, thereby artificially generating defects. In those documents, a casting evaluation test for an Al alloy is performed using such an I-beam type casting evaluation apparatus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] [Non-Patent Document 1] Seiji Saikawa et al., "Casting cracks and solidification structure of Al-Mg-Si alloys cast in I-beam molds," Casting Engineering, Vol. 87, pp. 39-45, 2015. [Overview of the project] [Problems that the invention aims to solve]

[0006] When performing casting evaluation tests on metallic materials with fine structures, such as Al alloys, it is effective to use the I-beam type casting evaluation apparatus disclosed in Patent Document 1 and Non-Patent Document 1. By bonding insulating material to the middle of the core, artificial defects can be suitably formed in metallic materials with such fine structures. However, when performing casting evaluation tests on metallic materials that form coarser structures than Al alloys, such as Fe alloys and Ni alloys, the I-beam type casting evaluation apparatus disclosed in Patent Document 1 and Non-Patent Document 1 is not necessarily suitable. When casting Fe alloys and Ni alloys, a coarse structure is formed due to the slow cooling of the molten metal. However, in the casting evaluation apparatuses described in those documents, the cooling rate is faster in areas other than where the insulating material is placed, making it easier to form a finer structure than in actual industrial casting processes. If a fine structure is formed, it becomes difficult to perform casting evaluations that mimic actual industrial casting processes and appropriately reflect the knowledge gained from those evaluations in actual casting processes, as this is accompanied by the occurrence of defects.

[0007] The problem that this invention aims to solve is to provide a casting evaluation apparatus that can be used to perform casting evaluation tests on metallic materials that form a coarse structure. [Means for solving the problem]

[0008] To solve the above problems, the casting evaluation apparatus according to the present invention has the following configuration.

[0009] [1] The casting evaluation apparatus according to the present invention comprises a mold having a cavity into which molten metal can be injected, and an insulating material provided on the inner wall surface of the mold facing the cavity, wherein the cavity integrally comprises two molten metal reservoirs spaced apart from each other in the axial direction, and a cylindrical axial core having a cross-sectional area perpendicular to the axial direction and smaller than that of the two molten metal reservoirs, and connecting the two molten metal reservoirs along the axial direction, and the insulating material is provided so as to occupy an area of ​​80% or more of the region of the inner wall surface that constitutes the axial core.

[0010] [2] In the embodiment of [1] above, it is preferable that the mold is provided with the axial direction set vertically.

[0011] [3] In the embodiment of [2] above, it is preferable that the mold is provided with a tapered portion at a position corresponding to the upper end of the shaft core, in which the cross-sectional area of ​​the cavity perpendicular to the axial direction decreases as it goes upward.

[0012] [4] In any of the embodiments described in [1] to [3] above, the mold may be divided into multiple parts along the axial direction at the portion constituting the axial core.

[0013] [5] In any of the embodiments described in [1] to [4] above, the thermal insulation material may be composed of an aggregate of fibrous or porous thermal insulation materials. [Effects of the Invention]

[0014] The casting evaluation apparatus according to the present invention, having the configuration described in [1] above, has a dumbbell-shaped structure with an axial core between two molten metal reservoirs. In this dumbbell-shaped structure, the inner wall surface of the mold is provided with insulating material covering an area of ​​80% or more of the region constituting the axial core. In this way, since most of the inner wall surface of the axial core is covered with insulating material, the cooling of the molten metal injected into the cavity proceeds slowly. As a result, the microstructure obtained by casting does not become too fine. Therefore, casting evaluation tests can be suitably conducted for metal materials such as Fe alloys and Ni alloys, which form coarse microstructures by casting. In particular, compared to the molds of Patent Document 1 and Non-Patent Document 1, which are for Al alloys that tend to form fine microstructures, if a larger mold is constructed, casting evaluation tests for metal materials that form coarse microstructures can be conducted even more suitably.

[0015] In the embodiment described in [2] above, the mold is positioned vertically along its axial direction. That is, two molten metal reservoirs are arranged vertically, and the casting evaluation test is performed by injecting molten metal from above according to gravity while the mold is in a vertical position with its axial core upright. In this case, axial symmetry is increased. Also, compared to the case where the mold is positioned horizontally, the free surface area of ​​the molten metal is smaller, so radiant heat loss from the molten metal can be suppressed. This reduces the cooling rate of the molten metal, making it easier to form a coarse structure through casting. It should be noted that in Patent Document 1 and Non-Patent Document 1, judging from the description in the drawings and the configuration of the base material supporting the mold, the mold is positioned horizontally.

[0016] In the embodiment described in [3] above, a tapered portion is provided at the upper end of the shaft core. By providing this tapered portion, the boundary between the shaft core and the molten metal reservoir can be configured in such a way that the area in which the molten metal directly contacts the mold or is positioned in close proximity to the mold is reduced. As a result, heat dissipation from the upper end of the shaft core is suppressed, and the cooling rate of the molten metal is kept low, making it easier to form a coarse metal structure. In addition, by providing the tapered portion, when the molten metal is injected into the cavity, the insulating material placed inside the mold is prevented from floating up relative to the mold.

[0017] In the aspect of [4] above, the mold can be divided into a plurality of parts in the axial direction at the location constituting the axial core part. In this case, by utilizing the division of the mold at that location, the length of the axial core part can be easily changed. By changing the length of the axial core part, the mode of progress of casting can be changed. As a result, the state of the obtained casting material, such as the presence or absence of defects and the nature thereof, can be changed.

[0018] In the aspect of [5] above, the heat insulating material is configured as an aggregate of fibrous or porous heat insulating materials. Examples of that type of heat insulating material include glass wool and ceramic wool, which are liable to achieve both high heat insulating properties and light weight. In particular, when using a dividable mold as in the aspect of [4] above, if a fibrous or porous heat insulating material is used, when changing the length of the axial core part by utilizing the division of the mold, the length of the heat insulating material can also be easily changed accordingly.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view showing the configuration of a casting evaluation apparatus according to an embodiment of the present invention. In the figure, an example of suitable dimensions is entered in parentheses (unit: mm). [Figure 2] (a) It is a photograph of the obtained casting material when a taper is provided at the upper end of the axial core part of the casting evaluation apparatus, and (b) when it is not provided. (a) shows the external appearance and (b) shows the cross section. [Figure 3] It is an optical microscope image observing the structure collected from the fracture part of the casting material in Fig. 2(a) above. (a) is a wide area observation image and (b) is an enlarged observation image.

Modes for Carrying Out the Invention

[0020] Hereinafter, a casting evaluation apparatus according to an embodiment of the present invention will be described. The casting evaluation apparatus according to the present embodiment is an apparatus for conducting a casting evaluation test simulating an actual industrial casting process.

[0021] [Configuration of the Casting Evaluation Device] The schematic of a casting evaluation device 1 according to an embodiment of the present invention is shown in FIG. 1. The casting evaluation device 1 has a basic structure in which a mold 20 is placed on a base 10. Molten metal can be poured into the mold 20.

[0022] The base 10 is a plate-like member made of a refractory material such as graphite. A molten metal receiving ring 11 is erected around the lower part of the mold 20 to receive the molten metal leaking from the placed mold 20.

[0023] The mold 20 is configured as a dumbbell-shaped mold. That is, the mold 20 has a cavity 30 into which molten metal can be poured inside, and the cavity 30 has an upper molten metal reservoir 31, a lower molten metal reservoir 32, and an axial core part 33 continuously. The two molten metal reservoirs 31 and 32 are separated from each other along the axial direction A extending in the vertical direction, and the axial core part 33 is configured as a cylindrical part connecting between the two molten metal reservoirs 31 and 32 along the axial direction A. The cross-sectional area of the cavity 30 perpendicular to the axial direction A is smaller at the axial core part 33 than at the two molten metal reservoirs 31 and 32. Although the specific shapes of the molten metal reservoirs 31 and 32 and the axial core part 33 are not particularly specified, it is preferable that they each have a cylindrical shape.

[0024] The mold 20 may be integrally formed as a whole, but it is preferably composed of a plurality of members. For example, a lower end mold 21 surrounding the lower molten metal reservoir 32, an upper end mold 22 surrounding the upper molten metal reservoir 31, a lower mold 23 surrounding the joint part at the lower end of the lower molten metal reservoir 32 and its vicinity, an upper mold 24 surrounding the joint part at the upper end of the upper molten metal reservoir 31 and its vicinity, and an axial core mold 25 surrounding the outer periphery of the region of the axial core part 33 excluding the upper and lower ends can be combined to form the mold 20. Among these, the upper end mold 22 can be configured as a pressing frame. Also, the lower mold 23 and the upper mold 24 can be configured as chill blocks.

[0025] Furthermore, it is preferable that the core mold 25, which constitutes the outer wall of the core 33, is divisible into multiple parts along the axial direction A. For example, the core mold 25 can be composed of multiple cylindrical divided units 25a, and these divided units 25a can be stacked in the axial direction A. In the illustrated configuration, four divided units 25a are stacked, excluding the unit on which the thermocouple 50 is provided. Gaps may be appropriately provided at the divisions of the mold 20 to form shrinkage gaps 26. The shrinkage gaps 26 absorb the solidification shrinkage of the metal material and suppress the generation of defects caused by solidification shrinkage.

[0026] It is preferable to provide a tapered portion 27 in the upper part of the mold 20, specifically in the upper mold 24, which corresponds to the upper end of the axial core portion 33. The tapered portion 27 is provided as a structure in which the cross-sectional area perpendicular to the axial direction A of the cavity 30 surrounded by the inner wall surface of the mold 20 decreases as it goes upward. For example, the tapered portion 27 can be formed as a frustoconical, tapering shape.

[0027] The constituent material of the mold 20 is not particularly limited, but it is preferable to use a high-strength metal material such as cast iron so as to withstand the thermal stress generated during the solidification of the metal material. In particular, when the mold 20 is made large, as illustrated in the figure with dimensions in parentheses, it is preferable that the mold 20 has high strength. On the inner wall surface of the mold 20, in areas where the heat insulating material 40 described below is not provided, a coating layer 2a made of a refractory ceramic material such as magnesia may be provided as a measure against melting. In the illustrated form, the coating layer 2a is provided on the bottom of the upper molten metal pool 31 and on the surface of the lower mold 23.

[0028] Insulating material 40 is placed on the inner wall surface of the mold 20 facing the cavity 30. Molten metal is poured into the cavity 30 inside the mold 20 into the area surrounded by insulating material 40. In the casting evaluation apparatus 1 according to this embodiment, insulating material 40 is placed over 80% of the area of ​​the inner wall surface of the mold 20 that constitutes the axial core portion 33. In other words, over 80% of the area of ​​the inner wall surface of the combined area of ​​the upper mold 24, axial core mold 25, and lower mold 23 is covered with insulating material 40. Preferably, insulating material 40 is placed over 90% of the area of ​​the inner wall surface of the mold 20 that constitutes the axial core portion 33, and more preferably over 95%. Furthermore, insulating material 40 is placed over the entire inner wall surface of the axial core mold 25, except for areas where insulating material 40 cannot be placed due to unavoidable circumstances.

[0029] The thickness of the insulation material 40 should be uniform across the entire inner wall surface of the axial core mold 25. At the location of the tapered portion 27 provided in the upper mold 24, the insulation material 40 should be made thinner towards the top, in accordance with the tapering shape of the tapered portion 27, so that the entire surface of the tapered portion 27 is covered with the insulation material 40. This is preferable so that the shape and cross-sectional area perpendicular to the axial direction A in the space surrounded by the insulation material 40 and supplied with molten metal are constant across the entire area of ​​the upper mold 24 and the axial core mold 25. It is also preferable to provide the insulation material 40 on the inner wall surface of the upper end mold 22 that constitutes the upper molten metal reservoir 31. The thermal insulation material 40 may be constructed as a single continuous piece or may be divided along the axial direction A. In the illustrated configuration, the thermal insulation material 40 is divided between the upper mold 22 and the upper mold 24, and between the upper mold 24 and the axial core mold 25, as well as in the center of the axial core mold 25.

[0030] The constituent materials of the thermal insulation material 40 are not particularly limited, as long as they have a lower thermal conductivity than the mold 20 and possess heat resistance that prevents them from being easily damaged by contact with molten metal. However, it is preferable to use a material composed of an aggregate of fibrous thermal insulation materials, such as glass wool or ceramic wool, as the thermal insulation material 40. Alternatively, it is also preferable to use a porous material, such as refractory thermal insulation brick or refractory thermal insulation mortar. These materials offer superior thermal insulation while remaining lightweight compared to materials made of compressed solid oxides, such as magnesia.

[0031] It is preferable that the casting evaluation device 1 is equipped with a thermocouple 50 and configured to measure the temperature of the molten metal in the cavity 30. In the illustrated configuration, insertion holes are provided in the center of the axial mold 25 and at the boundary between the axial mold 25 and the upper mold 24, through which the thermocouple 50 can be inserted. The sheathed thermocouple 50 is inserted through these insertion holes and further through the insulation material 40. Penetration of the insulation material 40 can be achieved by inserting the thermocouple 50 into the divided sections of the insulation material 40. Alternatively, through holes may be provided in the insulation material 40.

[0032] [Casting using a casting evaluation device] Next, a casting evaluation test using the casting evaluation apparatus 1 according to this embodiment will be described. To perform the casting evaluation test, molten metal having a predetermined component composition is poured into the cavity 30 from above the upper molten metal reservoir 31 and filled into the cavity 30 by gravity. The molten metal poured into the cavity 30 is cooled and solidifies to become a casting material.

[0033] The knowledge gained from casting evaluation tests can be applied to actual industrial casting processes. In the casting process, defects such as fractures and voids may form in the resulting cast material. Information on the nature of these defects and the progress of the casting process is useful as basic information for suppressing these defects. This information can be obtained through casting evaluation tests using the casting evaluation device 1. For example, defects in the cast material obtained from the casting evaluation test can be analyzed in detail, or the changes in defect generation behavior when the component composition of the metal material, the shape and size of the mold, and the casting conditions are changed can be analyzed. In a dumbbell-shaped casting evaluation device such as the casting evaluation device 1 according to this embodiment, the cavity 30 has an elongated axial core portion 33, making it easy for fractures to occur in the middle of the axial core portion 33, and thus suitable for artificially creating fractures for analysis.

[0034] In the casting evaluation apparatus 1 according to this embodiment, the heat insulating material 40 is provided over a large area of ​​more than 80% of the inner wall surface of the mold 20, in the region constituting the axial core portion 33. Therefore, heat dissipation from the molten metal through the mold 20 is reduced, and the cooling rate of the molten metal slows down. As the cooling rate slows down, the structure formed when the molten metal solidifies tends to be coarse. For this reason, the casting evaluation apparatus 1 according to this embodiment can be suitably used to accurately reproduce the structure obtained in actual industrial casting processes for metal materials that are manufactured into casting materials having a coarse structure, such as Fe alloys and Ni alloys. If the heat insulating material 40 were provided only in a small area in the middle of the axial core portion 33, as in the embodiments disclosed in Patent Document 1 and Non-Patent Document 1, the cooling rate of the molten metal would increase, and the structure would tend to become finer. In that case, unlike when evaluating metal materials that form a fine structure, such as Al alloys, which are the subject of those documents, it would be difficult to accurately reproduce the coarse structure formed in actual industrial casting processes and conduct casting evaluation tests. The casting evaluation apparatus 1 according to this embodiment can be suitably applied to metal materials that provide a casting material containing a coarse crystalline structure exceeding 100 μm, for example.

[0035] In casting evaluation tests, it is also effective to configure the entire casting apparatus to be large in order to facilitate the formation of a coarse structure. Patent Document 1 discloses a range for the size of the cavity, with a length of 30 to 200 mm and a width of 10 to 40 mm in the axial core portion, and Non-Patent Document 1 also falls within this range. In contrast, in the casting evaluation apparatus 1 according to this embodiment, as illustrated in Figure 1, it is preferable to configure the mold 20 to be large, with a length (height) of 200 mm or more and an inner diameter (axial core diameter) of 20 mm or more as the size of the space surrounded by the heat insulating material 40 in the axial core portion 33. From the viewpoint of increasing the strength of the mold 20, it is preferable to increase the wall thickness of the mold 20, for example, it is preferable to make the wall thickness greater than the axial core diameter and 25 mm or more. From the viewpoint of sufficiently improving the heat insulating properties, it is also preferable for the thickness of the heat insulating material 40 to be thick, for example, 20 mm or more at the axial core portion 33.

[0036] The above describes a configuration in which the casting evaluation device 1 is installed vertically, but this does not prevent it from being installed horizontally, that is, with the axial direction A horizontal. However, when installed vertically, radiant heat dissipation from directions other than above is suppressed, so a lower cooling rate for the molten metal and a greater effect in suppressing the refinement of the casting structure can be obtained compared to when it is installed horizontally.

[0037] Furthermore, in the vertically positioned casting evaluation apparatus 1, providing a tapered portion 27 at the upper end of the axial core portion 33 can suppress the rapid cooling of the metal material by the mold 20. If the tapered portion 27 is not provided, and the upper mold 24, which acts as a chill, is constructed as a straight cylinder with the same cross-sectional shape as the lower axial core portion mold 25, then it is easy to adopt a structure in which the molten metal directly contacts the surface of the mold 20 or is positioned close to the surface of the mold 20 at the upper mold 24, or at the boundary between the upper mold 24 and the upper end mold 22. In that case, rapid cooling of the molten metal via the upper mold 24 makes it easier for shrinkage cavities to form on the upper part of the resulting casting material. This is not a problem if shrinkage cavities are the target of analysis, but if defects other than shrinkage cavities, such as fracture, are the target of analysis, the formation of shrinkage cavities may hinder normal analysis and evaluation. Therefore, by providing a tapered portion 27 in the upper mold 24, the molten metal is less likely to come into direct contact with or be placed in close proximity to the surface of the mold 20, thereby suppressing the formation of shrinkage defects due to rapid cooling of the upper end. In addition, the tapered portion 27 provided at the upper end of the axial core portion 33 also serves another purpose. Specifically, the surface of the tapered portion 27 presses down on the inner insulating material 40, preventing the insulating material 40 from floating up when the molten metal is injected into the cavity 30.

[0038] In the configuration described above, the core mold 25 is divided into multiple divided units 25a. By making the mold 20 divisible along the axial direction A at the point where the core 33 is formed, the length of the core 33 can be easily changed by increasing or decreasing the number of stacked divided units 25a, etc., by utilizing the division of the mold 20 at that point. By changing the length of the core 33, it is possible to change the behavior of the metal material in the core 33. For example, it is possible to change the ease with which defects such as fractures are formed, as well as the location and characteristics of the fractures that are formed. In this way, if the length of the core mold 25 can be changed using the divided units 25a, and the thermal insulation material 40 is formed as an aggregate of fibrous or porous thermal insulation materials such as glass wool or ceramic wool, the length of the thermal insulation material 40 can be easily changed in accordance with the change in the length of the core mold 25 by cutting or adding to the thermal insulation material 40. [Examples]

[0039] The present invention will be described in detail below using examples. The present invention is not limited to the following examples. Here, a casting evaluation test was actually performed using a casting evaluation apparatus according to an embodiment of the present invention. Furthermore, the effect of providing a tapered portion at the upper end of the shaft core was confirmed.

[0040] [Test Method] A casting evaluation apparatus according to an embodiment of the present invention, having the structure shown in Figure 1 and described above, was constructed. The dimensions of each part were also as indicated in Figure 1. The mold was made of cast iron, and the heat insulating material was made of ceramic wool. For the tapered portion (27) of the upper mold, both configurations were prepared: one with a tapered portion and one without. In the case where the tapered portion was not provided, the shape and dimensions of the cross-section perpendicular to the axial direction on the inner wall surface of the upper mold were made the same as those of the lower axial core mold, and the entire axial core was configured as a straight cylinder.

[0041] Ni alloy casting was performed using the prepared casting evaluation apparatus. The Ni alloy used had an approximate composition of 52.5Ni-19Cr-3Mo-5.1Nb-0.9Ti-0.5Al-18Fe. The casting temperature was 1600°C.

[0042] Castings obtained using each casting evaluation device were observed to check for defects and their condition. Furthermore, for castings obtained using a casting evaluation device equipped with a tapered section, the tissue sampled from the defective area was observed using an optical microscope.

[0043] [Evaluation Results] Figure 2 shows photographs of cast materials obtained by casting using each casting evaluation device. (a) shows the appearance when a tapered section is provided in the casting evaluation device, and (b) shows the cross-section when a tapered section is not provided in the casting evaluation device.

[0044] Looking at the photographs of the cast materials in Figures 2(a) and 2(b), in both cases, as indicated by the arrows, it can be seen that there are areas where the continuity of the metal material is interrupted in the elongated region cast in the axial core, indicating the presence of defects. In other words, it can be confirmed that defects can be introduced into the cast material by performing casting using the casting evaluation apparatus according to this embodiment, in which a large area of ​​heat insulating material is placed on the inner wall surface of the mold constituting the axial core. The obtained cast material can be used for evaluation such as defect analysis.

[0045] As shown above, defects are formed in the casting material whether or not a tapered section is provided in the casting evaluation device, but the type of defect differs between the two. In the case where a tapered section is provided as shown in Figure 2(a), the casting material is divided in the middle of the elongated region cast at the axial core, and a fracture is formed as a defect. In contrast, in the case where a tapered section is not provided as shown in Figure 2(b), the region cast at the axial core is continuous in shape and not divided, but a void is formed near the upper end that is not occupied by the metal material within the structure. In other words, a shrinkage cavity defect is formed as a defect. When a tapered section is not provided, it is thought that the molten metal comes into direct contact with the mold at the upper end, resulting in greater heat dissipation from above and thus the formation of a shrinkage cavity defect. In contrast, when a tapered section is provided, the molten metal does not come into direct contact with the mold at the upper end, and heat dissipation from above is suppressed, making it less likely for a shrinkage cavity defect to form. It is thought that the solidification shrinkage of the metal material caused the fracture because a shrinkage cavity defect was not formed.

[0046] Figure 3 shows optical microscope images of the casting material shown in Figure 2(a), obtained using a casting evaluation device equipped with a tapered section. The images show the fracture location indicated by the arrow and its vicinity. (a) is a wide-area observation image, and (b) is a magnified observation image of the area indicated by the diamond mark in (a). In Figures 3(a) and (b), a metallic structure with irregularly shaped edges is observed corresponding to the fracture. These edges correspond to the brittle fracture surface. Looking at the magnified observation image in Figure 3(b), it can be seen that numerous crystalline structures with a size of several hundred μm have been formed. The size of these crystalline structures is comparable to the crystalline structures obtained in industrial casting processes. Furthermore, the crystalline structure of the obtained casting material constitutes a dendritic structure, which is branched like a tree and is characteristic of the fracture area of ​​casting material. From these findings, it is confirmed that by using the casting evaluation device according to the embodiment of the present invention, it is possible to produce a casting material with a coarse crystalline structure that closely reproduces the structure obtained in industrial casting processes for Ni alloys.

[0047] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention. [Explanation of symbols]

[0048] 1. Casting evaluation device 10 units 20 molds 21 Lower mold 22 Upper mold 23 Lower mold 24 Upper mold 25. Mold for the shaft core 25a Split Unit 27 Tapered section 30 cavities 31 Upper hot spring pool 32 Lower hot spring pool 33 Axis center 40 Insulation 50 Thermocouples A-axis

Claims

1. A mold having a cavity inside into which molten metal can be poured, The mold has an insulating material provided on the inner wall surface facing the cavity, The cavity integrally comprises two molten metal reservoirs spaced apart from each other in the axial direction, and a cylindrical axial core having a cross-sectional area perpendicular to the axial direction and smaller than that of the two molten metal reservoirs, connecting the two molten metal reservoirs along the axial direction. The aforementioned heat insulating material is provided on the inner wall surface, occupying an area of ​​80% or more of the region constituting the axial core, in a casting evaluation apparatus.

2. The casting evaluation apparatus according to claim 1, wherein the mold is provided with the axial direction set vertically.

3. At the position corresponding to the upper end of the aforementioned shaft core, The casting evaluation apparatus according to claim 2, wherein the mold is provided with a tapered portion in which the cross-sectional area of ​​the cavity perpendicular to the axial direction decreases as it approaches the top.

4. The casting evaluation apparatus according to any one of claims 1 to 3, wherein the mold is divisible into multiple parts along the axial direction at the portion constituting the axial core.

5. The casting evaluation apparatus according to claim 4, wherein the thermal insulation material is composed of an aggregate of fibrous or porous thermal insulation materials.

Images