Mold and method of manufacturing the same

Abstract

To provide a mold allowing for forming a chill portion along a casting shape, obtaining effective cooling effects and simplifying a post-process by avoiding the generation of unwonted padding or shapes resulting from a chill, and a method of manufacturing the same.SOLUTION: A method of manufacturing a mold, in which a space portion 5 extending along a casting shape is formed within foundry sand so as to form a casting W by pouring melt into the space portion 5, includes: a pattern receiving step S1 that receives a pattern having an outer contour conforming to a casting shape within a flask, a chill-portion forming step S2 that covers at at least a predetermined portion of the pattern received in the flask with a kneaded member of metal particles and a binder and thereafter compacting it to form a chill portion 3, a foundry-sand charging step S3 that fills foundry sand into the flask including the pattern with the chill portion 3 formed, and a space-portion forming step S4 that removes the pattern and the flask and obtains a mold in which a space portion 5 is formed along the casting shape.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mold in which a space that follows the shape of a casting is formed in molding sand and which enables a casting to be formed by pouring molten metal into the space, and to a method for manufacturing the mold. [Background technology]

[0002] To manufacture ferrous castings such as cast iron and steel, and non-ferrous alloy castings such as copper alloys and aluminum alloys, molds (sand molds) are used in which spaces along the shape of the casting are formed in the molding sand. Such molds obtain castings of the desired shape by pouring molten metal into the spaces in the molding sand and cooling and solidifying them. For example, some molds use block-shaped iron chills to promote directional solidification toward the feeder and prevent shrinkage cavities in thick parts (see, for example, Patent Document 1).

[0003] Conventional chills are installed in a state where they are placed against a predetermined portion of a pattern contained in a formwork, and a casting mold (sand mold) is obtained by filling the formwork with molding sand while maintaining the chills in a state where they are placed against the predetermined portion of the pattern, and then removing the pattern from the formwork. In the casting mold obtained in this way, a space portion is formed in the molding sand that corresponds to the pattern, and a casting is formed by pouring molten metal into this space and cooling and solidifying it, and the occurrence of shrinkage cavities can be suppressed by improving the cooling rate of the portion where the chills are installed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 57-165338 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the chills used in the above conventional casting molds are made of iron members formed in a block shape, so when used in a curved portion of the casting shape, they cannot be arranged along the curved shape, and there is a problem in that an effective cooling effect cannot be obtained. Also, gaps are generated between the curved portion of the casting shape and the chills, and molten metal flows into the gaps to form excess metal, requiring a post-process to cut out the excess metal. Furthermore, the surface of the conventional chills is formed with multiple grooves for releasing gases generated during casting, and the shape of the grooves for releasing gases is rolled into the surface of the casting, so that it is also necessary to cut out the grooves in a post-process.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a mold and a manufacturing method thereof, which can form chillers in accordance with the shape of the casting, thereby obtaining an effective cooling effect, and which can avoid the generation of unnecessary excess material and shapes due to the chillers, thereby simplifying subsequent processes. [Means for solving the problem]

[0007] The invention described in claim 1 is a mold in which a space that follows the shape of a casting is formed in molding sand, and molten metal can be poured into the space to form a casting, and is characterized in that a chiller section made of a mixed material of metal particles and binder is formed along the outer contour of at least a predetermined portion of the space.

[0008] The invention as set forth in claim 2 is the mold as set forth in claim 1, wherein the metal particles of the chillers have substantially the same grain size as the molding sand.

[0009] The invention as set forth in claim 3 is characterized in that, in the mold as set forth in claim 2, the grain size of the metal particles and molding sand in the chillers is 590 μm or less.

[0010] The invention according to claim 4 is the mold according to claim 1, wherein the chiller portion has the metal particles made of iron and the binder made of water glass or alkaline phenol.

[0011] The invention described in claim 5 is a manufacturing method for a casting mold in which a space that conforms to the shape of a casting is formed in molding sand and molten metal can be poured into the space to form a casting, the method comprising the steps of: a model containing step of containing a model having an outer contour that conforms to the shape of the casting in a formwork; a chill forming step of covering at least predetermined portions of the model contained in the formwork with a kneaded material of metal particles and binder and then compacting the mixture to form chills; a molding sand filling step of filling the formwork containing the model in which the chills have been formed with molding sand; and a space forming step of removing the model and the formwork to obtain a casting mold in which a space that conforms to the shape of the casting is formed.

[0012] The invention as set forth in claim 6 is the method for manufacturing a mold as set forth in claim 5, characterized in that the metal particles of the chillers have substantially the same grain size as the molding sand.

[0013] The invention as set forth in claim 7 is the method for manufacturing a mold as set forth in claim 6, characterized in that the grain size of the metal particles and molding sand in the chillers is 590 μm or less.

[0014] The invention of claim 8 is the method for manufacturing a mold of claim 5, wherein the chiller portion has the metal particles made of iron and the binder made of water glass or alkaline phenol. Effect of the Invention

[0015] According to the present invention, the chillers are formed from a kneaded material of metal particles and binder, so that the chillers can be formed along the shape of the casting, and an effective cooling effect can be obtained. In addition, the generation of unnecessary excess material and shapes due to the chillers can be avoided, simplifying the subsequent processes. [Brief description of the drawings]

[0016] [Figure 1] A flowchart showing a method for manufacturing a mold according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a plan view showing a mold and a pattern used to manufacture the mold. [Diagram 3] Cross-sectional view of line III-III in Figure 2 [Figure 4] Cross-sectional view of line IV-IV in Figure 2 [Diagram 5] FIG. 11 is a plan view showing a state in which a chiller portion is formed on a model in a mold used to manufacture the same mold. [Figure 6] Cross section of line VI-VI in Figure 5 [Figure 7] Cross-sectional view of line VII-VII in Figure 5 [Figure 8] A cross-sectional view showing the state in which the mold (upper mold) used to manufacture the same mold is filled with molding sand. [Figure 9] A cross-sectional view showing the state in which the mold (lower mold) used to manufacture the same mold is filled with molding sand. [Figure 10] A plan view showing the upper and lower molds obtained after removing the upper and lower mold frames and the model. [Figure 11] FIG. 1 is a plan view and a front view showing a mold formed by mating an upper mold and a lower mold. [Figure 12] Sectional view of line XII-XII in Figure 11 [Figure 13] Cross-sectional view of line XIII-XIII in FIG. [Figure 14] FIG. 1 is a front view and a side view showing a casting obtained using the same mold. [Figure 15] Micrograph showing the structure of a casting obtained using a comparative mold (a mold without chills) [Figure 16] Micrograph showing the composition obtained with the mold of the present invention (composition of the part generated in the chiller section) [Figure 17] Table showing mechanical properties of Comparative Examples 1 and 2 and Examples 1 and 2 obtained by experiment [Figure 18] Table showing the mechanical properties (average) of Comparative Examples 1 and 2 and Examples 1 and 2 obtained by the experiment [Figure 19] Graph showing mechanical properties (tensile strength) of Comparative Examples 1 and 2 and Examples 1 and 2 obtained by experiment [Figure 20] Graph showing mechanical properties (elongation) of Comparative Examples 1 and 2 and Examples 1 and 2 obtained by experiment [Figure 21] Table showing details of molding sand as Comparative Examples 1 and 2 used in the experiment [Figure 22] Table showing details of metal particles (iron particles) used in the experiments as Examples 1 and 2 [Figure 23] Graph showing particle size distribution of Comparative Examples 1 and 2 and Examples 1 and 2 used in the experiment [Figure 24] Graph showing cooling times for Comparative Example 1 and Examples 2 and 3 used in the experiment [Diagram 25] Photographs showing the casting surfaces of castings obtained using the molds of Comparative Example 1 and Example 3 used in the experiment. [Figure 26] Graph showing cooling times for Comparative Example 1 and Examples 2 and 3 used in the experiment [Figure 27] Table showing mechanical properties of Comparative Example 1 and Examples 2 and 3 used in the experiment [Figure 28] Graph showing mechanical properties (tensile strength) of Comparative Example 1 and Examples 2 and 3 obtained by experiment [Figure 29] Graph showing mechanical properties (elongation) of Comparative Example 1 and Examples 2 and 3 obtained by experiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The casting mold of this embodiment is composed of a sand mold in which a space that follows the shape of the casting is formed in the casting sand, and molten metal can be poured into this space to form the casting. As shown in Figures 11 to 13, the mold is composed of an upper mold 1 and a lower mold 2, a chill portion 3 and a casting sand portion 4 formed in the upper mold 1 and the lower mold 2, respectively, a space portion 5 formed by matching the upper mold 1 and the lower mold 2, a sprue 6 and runners 7 and 8.

[0018] The casting W is a product or part formed by a mold, and in this embodiment, it is a workpiece (a workpiece that can be set in a tensile testing device) for testing tensile strength and elongation, as shown in Fig. 14. The space 5 is a space having an outer contour shape that follows the casting shape (the outer peripheral shape of the casting W), and is formed inside the casting sand part 4 and the chiller part 3 by matching the upper mold 1 and the lower mold 2, as shown in Fig. 11.

[0019] Specifically, the space 5 is formed by compacting molding sand and metal particles against the outer peripheral surfaces of the patterns (Ma-Md), and after molten metal of the desired molten metal is poured in, it is cooled and solidified to obtain the casting W. The molding sand portion 4 is formed by filling the mold (upper mold frame K1 and lower mold frame K2) with molding sand, and in this embodiment, in addition to the space 5, a sprue 6 and runners 7 and 8 are formed.

[0020] Here, the chills 3 are made of a kneading material of metal particles and binder, and in this embodiment, minute iron particles (iron spherical members) are used as the metal particles. The chills 3 are formed along the outer contour of predetermined portions (curved portions and portions with complex shapes) of the space 5, and function as chills that prevent the occurrence of porosity due to uneven cooling speed in predetermined portions of the casting W (cast product) during casting.

[0021] Moreover, the metal particles of the chillers 3 according to this embodiment have approximately the same particle size as the molding sand of the molding sand section 4, and for example, the particle sizes of the metal particles of the chillers 3 and the molding sand of the molding sand section 4 are 590 μm or less. Furthermore, the chillers 3 are formed by tamping, at predetermined positions on the models (M1, M2), a mixed material in which a binder made of water glass or alkaline phenol is mixed with metal particles made of iron.

[0022] Next, a method for manufacturing a mold according to this embodiment will be described with reference to the flow chart of FIG. First, a pattern containing step S1 is performed in which a pattern having an outer contour following the shape of the casting is contained in a mold. In this pattern containing step S1, as shown in Figs. 2 to 4, a pattern M1 having half patterns Ma and Mb formed following the outer peripheral shape of the upper half of the casting W is contained in an upper mold frame K1, and a pattern M2 having half patterns Mc and Md formed following the outer peripheral shape of the lower half of the casting W is contained in a lower mold frame K2. In addition to the patterns M1 and M2, a gate shape member Na and runner shape members Nc and Nd are contained in the upper mold frame K1, and in addition to the patterns Mc and Md, a runner shape member Nb is contained in the lower mold frame K2.

[0023] Thereafter, a chiller portion forming step S2 is performed to form the chiller portions 3. In this chiller portion forming step S2, as shown in Figs. 5 to 7, at least predetermined portions (in this embodiment, central portions including curved portions of the half models Ma to Md) of the model M housed in the upper mold frame K1 and the lower mold frame K2 are covered with a kneading material of metal particles and a binder, and then the kneading material is tamped to form the chiller portions 3. As described above, the metal particles constituting the chiller portions 3 are made of minute iron particles (iron granular members) and have a grain size substantially equal to that of the molding sand of the molding sand portion 4 (590 µm or less), and the binder is made of water glass or alkaline phenol.

[0024] Subsequently, a molding sand filling step S3 is performed to form the molding sand portion 4. The molding sand filling step S3 is a step of filling molding sand into the molds (upper mold frame K1 and lower mold frame K2) including the models (M1, M2) on which the chillers 3 are formed, as shown in Figures 8 and 9. After the molding sand filling step S3, the upper mold frame K1 and the model M1, and the lower mold frame K2 and the model M2 are removed, respectively, in a space forming step S4, whereby a space 5 that conforms to the shape of the casting can be formed.

[0025] In the space forming process S4, the gate 6 is formed by removing the gate-shaped member Na, and the runners 7 and 8 are formed by removing the runner-shaped members Nb-Nd. In this manner, by going through the pattern accommodating process S1, the chiller forming process S2, the molding sand filling process S3, and the space forming process S4, the upper mold 1 and the lower mold 2 can be obtained, and by mating these upper mold 1 and lower mold 2 as shown in Fig. 11, a casting mold having a space 5 therein can be obtained.

[0026] The space 5 in the mold thus obtained is formed in communication with the gate 6 and the runners 7 and 8, and when molten metal is supplied from the gate 6, the supplied molten metal reaches the space 5 via the runner 7 and is then poured into the runner 7. After the molten metal poured into the space 5 is cooled and solidified, the upper mold 1 and the lower mold 2 are broken to obtain the casting W (see FIG. 14). The molten metal that flows into the runner 7 during the casting process functions as a feeder when the molten metal in the space 5 is cooled and solidified.

[0027] According to the mold of this embodiment, the chills 3 are formed from a kneaded material of metal particles and binder, so that the chills 3 can be formed along the shape of the casting, and an effective cooling effect can be obtained, while the generation of unnecessary excess material and shapes caused by conventional chills can be avoided, simplifying the post-processing. In addition, since the metal particles of the chills 3 have approximately the same grain size as the molding sand, the mold can function in the same way as a mold (sand mold) made only from conventional molding sand, and gas generated during casting can be smoothly discharged.

[0028] Furthermore, by setting the grain size of the metal particles and molding sand of the chills 3 to 590 μm or less, the chills 3 can be formed to better conform to the shape of the casting. Furthermore, since the metal particles of the chills 3 are made of iron and the binder is made of water glass or alkali phenol, the surface of the resulting casting can be made smoother. However, the grain size of the metal particles and molding sand of the chills 3 may be 590 μm or more, and the binder may be made of another material.

[0029] Next, the results of an experiment to verify the technical superiority of the mold according to this embodiment will be described. In the experiment, the same molten metal was poured to mold castings W of the same shape (see FIG. 14). As comparative examples, a mold made by molding foundry sand containing alkaline phenol as a binder into alumina-based artificial sand (new sand) was prepared as Comparative Example 1, and a mold made by molding foundry sand containing alkaline phenol as a binder into alumina-based artificial sand (regenerated sand) was prepared as Comparative Example 2. More specifically, the foundry sand in Comparative Examples 1 and 2 has a grain size index (AFS: American Foundry Society) as shown in Fig. 21 and a grain size distribution as shown in Fig. 23.

[0030] As examples, a mold made by molding metal particles containing water glass as a binder in iron particles (AFS: 73) was prepared as Example 1, and a mold made by molding metal particles containing water glass as a binder in iron particles (AFS: 132) was prepared as Example 2. More specifically, Examples 1 and 2 are metal particles having a particle size index (AFS: American Foundry Society) as shown in Fig. 22 and a particle size distribution as shown in Fig. 23.

[0031] In the present invention, a chiller section 3 made of a mixing material for metal particles and binder is formed along the outer contour of at least a specified portion of the space section 5. In order to clarify the effect of the chiller section 3 of the present invention, all of the molds in the examples used in the experiments are made of a mixing material for metal particles and binder (not filled with molding sand).

[0032] However, as shown in Fig. 23, the particle size distributions of Examples 1 and 2 have peaks like those of Comparative Examples 1 and 2, and the graphs are similar overall. Therefore, it is found that the metal particles (iron particles) of Examples 1 and 2 have similar moldability to the molding sand of Comparative Examples 1 and 2, and are practical. In addition, since the metal particles (iron particles) of Examples 1 and 2 have the same particle size distribution as the molding sand of Comparative Examples 1 and 2, the casting surface during casting is as good as when molding sand is used, and a separate shaping process in a later step is not required.

[0033] 15 shows a micrograph of the aluminum casting W formed in the mold of Comparative Example 1, and FIG 16 shows a micrograph of the aluminum casting W formed in the mold of Example 2. Comparing their structures (microstructures), it is found that the casting W of Example 2 has a smaller white portion (primary crystal α-Al) (i.e., an index called DAS (dendrite spacing) is smaller) than the casting W of Comparative Example 1. As a result, it is found that the casting W of Example 2 has better mechanical properties (tensile strength and elongation) than the casting W of Comparative Example 1.

[0034] Moreover, the black portions observed in the micrograph of Comparative Example 1 (see FIG. 15) are defects called microshrinkage, which are hardly observed in the micrograph of Example 2. As a result, it is found that the casting W obtained with the mold of Example 2 is less likely to have shrinkage cavities than the casting W obtained with the mold of Comparative Example 1, and the chill effect is exerted.

[0035] Next, the aluminum castings W formed using the molds of Comparative Examples 1 and 2 and the aluminum castings W formed using the molds of Examples 1 and 2 were set in a tensile testing device and compared in terms of mechanical properties (tensile strength and elongation).As shown in the tables of Figures 17 and 18 and the graphs of Figures 19 and 20, it can be seen that the castings W of Examples 1 and 2 are superior to the castings W of Comparative Examples 1 and 2 in terms of both tensile strength and elongation.

[0036] Furthermore, as an example, a mold made by molding metal particles containing alkaline phenol as a binder in iron particles (AFS: 132) was prepared as Example 3. More specifically, Example 3, like Example 2, uses metal particles with a particle size index (AFS: American Foundry Society) as shown in Fig. 22 and a particle size distribution as shown in Fig. 23, but changes the binder from water glass to alkaline phenol (i.e., changes only to the binder compared to Example 2).

[0037] Thermocouples were installed in the spaces of each of the molds of Comparative Example 1 (two samples, α1 and α2, were prepared; the same applies below), the molds of Example 2 (β1, β2), and the molds of Example 3 (γ1, γ2), and JIS aluminum alloy AC2B at 690°C was poured into each space to measure the temperature change during the molding process of the casting W.As a result, it was found that the cooling rate of the mold of Example 3 (γ1, γ2) was the highest, followed by the cooling rate of the mold of Example 2 (β1, β2), as shown in Figure 24.

[0038] Furthermore, the cooling rates (585-565°C) and cooling times (maximum temperature reached-550°C) of the molds (α1, α2) of Comparative Example 1, the molds (β1, β2) of Example 2, and the molds (γ1, γ2) of Example 3 were measured and compared, and it was found that the molds (β1, β2) of Example 2 and the molds (γ1, γ2) of Example 3 had higher cooling rates and shorter cooling times than the molds (α1, α2) of Comparative Example 1, as shown in Fig. 26. Therefore, it is found that the molds (γ1, γ2) of Example 3 and the molds (β1, β2) of Example 2 have higher cooling rates and shorter cooling times than the molds (α1, α2) of Comparative Example 1, and can exert a chill effect.

[0039] In addition, when the surface of the casting W obtained using the molds (α1, α2) of Comparative Example 1 is compared with the surface of the casting W obtained using the molds (γ1, γ2) of Example 3, as shown in Fig. 25, it is found that the surface of the casting W obtained using the molds (γ1, γ2) of Example 3 is smoother than the surface of the casting W obtained using the molds (α1, α2) of Comparative Example 1. Therefore, it is found that the casting W obtained using the molds (γ1, γ2) of Example 3 has a fine casting surface and does not require polishing or requires little polishing in a later process.

[0040] Next, the aluminum casting W formed using the mold of Comparative Example 1 and the aluminum casting W formed using the molds of Examples 2 and 3 were set in a tensile testing device and compared in terms of mechanical properties (tensile strength and elongation).As shown in the table of FIG. 27 and the graphs of FIGS. 28 and 29, it is found that the castings W of Examples 2 and 3 are superior to the casting W of Comparative Example 1 in terms of both tensile strength and elongation.

[0041] Although the present embodiment has been described above, the present invention is not limited to this, and other metals may be used instead of iron as the metal particles constituting the chillers 3, and other binders may be used. That is, in this embodiment, a self-hardening mold using water glass, which is an inorganic binder, or alkali phenol, which is an organic binder, is used, but other inorganic binders or other organic binders may be used. In addition, the inorganic CO 2 In addition to the gas-hardening mold, the present invention may be applied to other types of sand molds, such as clay-based molds and thermosetting molds.

[0042] In this embodiment, the grain size of the metal particles in the chills 3 is approximately equal to the grain size of the molding sand in the molding sand section 4, but the grain size of the metal particles in the chills 3 may be larger or smaller than the grain size of the molding sand in the molding sand section 4. Furthermore, in this embodiment, the grain size of the metal particles and molding sand in the chills 3 is 590 μm or less, but metal particles and molding sand of other grain sizes may be used. [Industrial Applicability]

[0043] The present invention can also be applied to devices with different external shapes or devices with added functions, etc., so long as they have the same gist as the present invention. [Explanation of symbols]

[0044] 1 Upper mold (mold) 2 Lower mold (mold) 3 Chiller section 4. Casting Sand Department 5 Space part 6 Spout 7, 8 Yudo M1, M2 model Ma~Md Half-split model (casting shape) Na Gate Shape Component Nb~Nd Runner shape material K1 Upper formwork K2 Lower formwork W Casting

Claims

1. A mold in which a space portion conforming to a shape of a casting is formed in molding sand, and a casting can be formed by pouring molten metal into the space portion, A mold comprising a chiller section made of a kneading material of metal particles and binder formed along the outer contour of at least a predetermined portion of the space section.

2. 2. The mold according to claim 1, wherein the metal particles of said chills have a grain size substantially equal to that of said molding sand.

3. 3. The mold according to claim 2, wherein the grain size of the metal particles and molding sand in the chillers is 590 μm or less.

4. 2. The mold according to claim 1, wherein the metal particles in the chiller are made of iron, and the binder is made of water glass or an alkaline phenol.

5. A method for manufacturing a mold in which a space portion conforming to a shape of a casting is formed in molding sand, and a casting can be formed by pouring molten metal into the space portion, comprising the steps of: a pattern containing step of containing a pattern having an outer contour following a shape of a casting in a mold; a chiller portion forming step of covering at least a predetermined portion of the model accommodated in the form with a kneading material of metal particles and a binder, and then tamping the material to form a chiller portion; a molding sand filling step of filling a mold including the model on which the chill portions are formed with molding sand; a space forming step of removing the pattern and the form to obtain a mold having a space formed according to the shape of the casting; A method for producing a mold, comprising the steps of:

6. 6. The method for manufacturing a mold according to claim 5, wherein the metal particles of said chills have a grain size substantially equal to that of said molding sand.

7. 7. The method for manufacturing a mold according to claim 6, wherein the grain size of the metal particles in the chillers and the grain size of the molding sand are 590 [mu]m or less.

8. 6. The method for manufacturing a mold according to claim 5, wherein in said chiller portion, said metal particles are made of iron, and said binder is made of water glass or alkaline phenol.

Images