JPH0367787B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The disclosed technology belongs to the field of casting technology in which molten metal is sucked by reducing the pressure in the cavity of a mold. Therefore, the invention of this application, when reducing the pressure inside the cavity formed in the mold using a vacuum suction device,
This invention relates to a vacuum suction casting method in which a downward sprue connected to an upper cavity is sealed with a sealing member of the same quality as the molten metal to increase negative pressure inside the cavity, and an apparatus directly used in the method. In particular, the sealing member comprises a first sealing material having sufficient rigidity not to be deformed against the negative pressure and a second sealing foil member covering the sprue,
This invention relates to a vacuum suction casting method in which the sealing member is prevented from being concavely deformed into the cavity when the pressure is reduced, and an apparatus directly used in the method. <Prior art> As is well known, vacuum suction casting has recently been adopted in a variety of industrial products due to its advantages in that the molten metal flows well and can be easily produced even in products with relatively thin wall parts. . Accordingly, in this embodiment, a cavity formed in the mold is depressurized by a vacuum suction device, and the molten metal is caused to flow into the cavity from the sprue using the negative pressure to produce a predetermined product. <Problems to be Solved by the Invention> By the way, since the above negative pressure is generated when the sprue is immersed in the molten metal, not only is it not possible to arbitrarily set the degree of pressure reduction, but the initial degree of pressure reduction is low. Therefore, the hot water cannot be turned quickly, and as a result, the only solution is to raise the temperature of the mold or increase the temperature of the hot water, resulting in technical constraints. Furthermore, since the negative pressure is generated and the molten metal flows in at the same time, the existing gas in the cavity cannot be smoothly replaced, resulting in casting defects such as cavities. To deal with this, for example,
As shown in Figure 1 as in the publication, the opening 1' of the sprue 1 is sealed with a foil member 2 as a sealing member, and a concave deformation is actively applied due to the difference between the internal negative pressure and the external pressure. For example, if the molten metal is aluminum,
An embodiment in which the foil member 2 is made of aluminum foil, and after the negative pressure inside the cavity is maintained at a set pressure, it is immersed in molten metal, and the foil member 2 is melted with the high-temperature molten metal to achieve predetermined casting. has been adopted. However, although such a foil member 2 can be easily deformed and has the advantage of being easy to attach to the sprue, the part corresponding to the sprue is deformed into a concave shape as described above due to the negative pressure inside the cavity. As a result, during casting, the gas contained in the recesses is mixed into the cavity together with the molten metal, making it impossible to achieve a desired degree of vacuum, and as a result, casting defects such as so-called blowholes are caused. The purpose of the invention of this application is to solve the problems associated with negative pressure in the vacuum suction casting technology based on the above-mentioned prior art, to obtain an initial negative pressure as set,
It is an object of the present invention to provide an excellent vacuum suction casting method that has a short casting time and prevents casting defects such as cavities and blowholes from occurring, thereby benefiting the application of casting technology in the machine manufacturing industry, and an apparatus that can be directly used in the method. It is something to do. <Means for Solving the Problems> In order to solve the above-mentioned problems, the structure of the invention of this application, which is based on the above-mentioned claims, is to seal the sprue with a sealing material of the same quality as the molten metal, thereby sealing the cavity. A vacuum suction casting method in which the sealing material is melted by immersing the sprue in molten metal while a negative pressure is generated inside the cavity, and the molten metal is sucked into the cavity. A vacuum suction casting method using a highly rigid first sealing material that does not cause concave deformation and a second sealing foil member that covers a sprue, and a sprue that communicates with a cavity in a mold connected to a vacuum suction device. A vacuum suction casting device in which an opening of the molten metal is sealed with a sealing member of the same quality as the molten metal, wherein the sealing member is a first sealing material having sufficient rigidity and a second sealing foil member that covers the sprue. The vacuum suction casting device is comprised of the following: and the sealing material is sealed facing the opening. <Function> Then, the opening of the downward sprue that communicates with the upper cavity formed in the mold is sealed with a first sealing material having sufficient rigidity, which is the same as the molten metal, and the surrounding area is similarly sealed. When the sealing foil member of the backup member of the second sealing member is encapsulated and attached to the sprue, and then the vacuum suction device is operated to reduce the pressure inside the cavity, the sealing material will have its rigidity and the sealing foil member of the backup member. A predetermined negative pressure is generated without concave deformation due to the support of It was designed to be sucked in. <Example> Next, an example of the invention of this application will be described below with reference to FIGS. 2 to 4. 3 is a vacuum suction casting device which constitutes one of the gist of the invention of this application, in which a mold 4 is hung on hooks 7', 7' at the lower part of a clamp arm 7 connected to a hydraulic cylinder 6 vertically disposed on an upper frame 5. The interior of the decompression hood 8, which is stopped and tightly attached to its upper surface, is connected to a vacuum suction device 9. On the other hand, below the mold 4, a furnace 11 for charging and storing molten aluminum (AC4C) 10 is installed in a lower frame 12. Also, the mold 4 is attached to the hook 7' of the clamp arm 7,
A sprue 1 integrally protrudes downward from the center of a surface plate 13 whose both sides are hooked to the surface plate 7' has an opening 1' and is directed toward the furnace 11. In the disposed casting flask 14, a mold 15 is integrally formed on the lower side with a cavity 16 made of air-permeable organic binder sand and a runner 17 communicating with the cavity 16 and facing the sprue 1 facing downward. As shown in FIG.
8 is attached, and the aluminum seal member 18
is an aluminum plate 19 as a sealing material that is brought into contact with and sealed in the opening 1', and the aluminum plate 19 and the sprue 1.
and an aluminum seal foil member 20 which is a backup member and encloses both from below. The thickness t of the aluminum plate 19 is the same as the thickness t of the aluminum plate 19.
In addition, the plate thickness t' of the sealing foil member 20 is such that it can hold the aluminum plate 19 and be sufficiently deformed to the shape of the sprue 1 to be brought into close contact with the aluminum plate 19. There is. Therefore, if the negative pressure is, for example, -750 mmHg, a commercially available product with t=1.0 mm and t'=0.02 mm may be used. On the other hand, in the vacuum suction device 9, the vacuum hood 8
A flexible hose 21 is connected to a suction blower 24 via a variable throttle 22 and a valve 23. In the above-mentioned configuration, the illustrated embodiment shows the mold 4 being preliminarily latched and fixed to the clamp arm 7, but in order to assemble the mold 4, first, the cavity 16 and the runner 17 are formed in a predetermined manner outside the system. mold 4
The surface plate 13 is attached to the hook 7' of the clamp arm 7,
7', and then a vacuum hood 8 connected to a vacuum suction device 9 is brought into close contact with the upper surface of the mold 4. An aluminum seal member 18 is attached to the downward sprue 1 of the mold 4 assembled in this manner. In this manner, an aluminum plate 19 previously processed into a predetermined shape is brought into contact with and sealed in the opening 1' of the sprue 1, and then an aluminum seal foil member 20 is applied to seal the aluminum plate 19 from below. It is encapsulated to maintain it and brought into close contact with the sprue 1. Therefore, when the valve 23 of the vacuum suction device 9 is opened, the air in the cavity 16 is discharged to the outside of the system via the decompression hood 8 by the suction blower 24 which has been activated in advance. Then, the sealing member 18 is caused by the negative pressure drawn from the suction blower 24 to cause the aluminum plate 19 to close to the sprue 1.
The sealing foil member 20 is adhered to the periphery of the sprue 1 by suction to the opening 1' of the gate 1, and by negative pressure caused by air leaking between the opening 1' and the aluminum plate 19. During this time, since the aluminum plate 19 has sufficient rigidity, it will not be deformed into a concave shape inside the runner 17 as in the conventional embodiment shown in FIG. Therefore, the pressure inside the cavity 16 is reduced and a negative pressure is generated. Therefore, the hydraulic cylinder 6 is activated to lower the mold 4, and the sprue 1 is inserted into the molten aluminum 1 in the furnace 11 from above.
When it is immersed in the water to a predetermined depth, its descent is stopped. Then, first the sealing foil member 20 and then the aluminum plate 19 are gradually melted into the molten metal 10 of the same quality, and the runner 17 is brought into communication with the molten metal 10. The molten metal 10 is quickly sucked into the cavity 16 by sufficient negative pressure generated in the cavity 16 in advance. After a predetermined amount of the molten metal 10 is sucked into the cavity 16 and solidified over time, the hydraulic cylinder 6
One casting process is completed by raising the mold 4 and returning it to the initial position. According to the experiment, the comparison between Example (A), the conventional casting mode with the sprue exposed (B), and the casting mode with only the foil member attached to the sprue (C) is as follows. As shown in the table.

[Table] Also, as shown in the graph shown in Fig. 4, a comparison between the defective rate P on the vertical axis and the degree of pressure reduction d on the horizontal axis is shown in Example (A). −740
At mmHg, the residual gas in the cavity 16 is drawn into the molten metal and a blowhole is generated. However, it can be seen that this does not occur at a reduced pressure lower than -750 mmHg. It should be noted that the embodiments of the invention of this application are of course not limited to the above-mentioned embodiments. For example, the sealing member may be shaped like a cone to the outside of the system, or the sealing foil member and the sealing material may be integrally formed. Various embodiments may be adopted, such as the mold may be formed into a vent, and the mold may be a non-ventilated mold having a vent. <Effects of the Invention> As described above, according to the invention of this application, in the vacuum suction casting method and the apparatus directly used in the method,
Basically, the seal of the lower upward sprue that is immersed in the molten metal during casting does not deform concavely against the negative pressure inside the cavity, so the negative pressure inside the cavity remains until the seal is melted in the molten metal. There is no fluctuation in the pressure, negative pressure adjustment is simple, and process control is easy. In addition, since the sealing member that seals the opening of the sprue is sealed with a sealing material having sufficient rigidity that will not be deformed by negative pressure, the vacuum suction device will not remove the inside of the cavity. The sealing material does not deform against reduced pressure, and therefore has the excellent effect of completely preventing casting defects such as blow holes caused by trapping of air through concave deformation of the sealing material as in the past. It is played. Furthermore, since the sealing member is composed of a sealing material and a sealing foil member, the sealing foil member completely covers the sprue due to the negative pressure caused by the leaking air between the opening and the sealing material. As a result, it is easy to sufficiently reduce the pressure inside the cavity while maintaining the strength of the sealing member, and as a result, high-speed casting is possible, and the service life of the mold is improved without raising the mold temperature more than necessary. The excellent effect of forming thin-walled portions with good water circulation is achieved. Therefore, there is an advantage that high melting point alloys can be cast without quality deterioration. In addition, the sealing material has a secondary merit that it can be recycled by processing waste materials.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the main parts based on the conventional technology, Figure 2
The following figures are explanatory diagrams of embodiments of the invention of this application, FIG. 2 is an overall schematic diagram, and FIG. 3 is FIG. 2A.
The enlarged cross-sectional view of FIG. 4 is a graph showing the relationship between the degree of pressure reduction and the defective rate. 1... Sprue, 16... Cavity, 10... Molten metal, 9... Vacuum suction device, 4... Mold, 1'...
Opening portion, 18... Seal member, 3... Vacuum suction casting device, 20... Seal foil member, 19... Seal member.

Claims (1)

[Scope of Claims] 1. The sprue is sealed with a sealing material of the same quality as the molten metal, and the sprue is immersed in the molten metal with negative pressure generated in the cavity, so that the sealing material melts and the molten metal flows into the cavity. In the vacuum suction casting method using suction and inflow, the above-mentioned sealing is performed by a highly rigid first sealing material that does not undergo concave deformation against negative pressure, and a second sealing foil member that covers the sprue. Characteristic vacuum suction casting method. 2. In a vacuum suction casting device in which a sealing member of the same quality as the molten metal is sealed at the opening of a sprue that communicates with a cavity in the mold connected to a vacuum suction device,
The sealing member comprises a first sealing material having sufficient rigidity and a second sealing foil member covering the sprue, and the sealing material is sealed facing the opening. Vacuum suction casting equipment featuring: