JPH0343934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vacuum casting method using a permeable precision casting mold such as a ceramic mold or a gypsum mold.

(Prior Art) Conventional vacuum casting methods include those shown in FIGS. 1 and 2, for example.

That is, the mold 1 is made of an air permeable mold such as a ceramic mold or a gypsum mold, and is a mold for precision casting, especially for producing a cast product having a thin wall part or a complicated shape. A casting space 7 is formed between an upper mold 2 whose sides are surrounded and has a casting spout 5, and a lower mold 3 which is also surrounded by a flask 6 and faces the upper mold 2.

Further, suction plates 8 and 9 constituting a pressure reducing device are attached to the upper and lower surfaces of the mold 1.

The suction plates 8 and 9 are formed with a large number of grooves 8a and 9a that communicate with the opposing surface of the mold 1, as shown in the lower suction plate 9 in FIG.
Pipes 10, 10 from a vacuum pump (not shown) are connected to the grooves 8a, 9a.

When casting, negative pressure is applied to the grooves 8a and 9a through the pipes 10 and 10 by operating a vacuum pump, and the ceramic or gypsum material is made of ceramic or plaster that has an air permeability that prevents the molten metal from penetrating. While reducing the pressure inside the mold 1 consisting of etc.,
The method used was to perform casting while maintaining a reduced pressure state.

However, in such a vacuum casting method, the suction plates 8 and 9 constituting the pressure reducing device are brought into direct contact with the mold 1 to apply a vacuum effect to the mold 1. If a crack or the like occurs, the molten metal that has been cast may penetrate into the clutch and even reach the suction plates 8, 9, damaging the pressure reducing device such as a vacuum pump that includes the suction plates 8, 9. There is,
In addition, there is a risk of leakage between the upper mold 2 and the lower mold 3, which is very dangerous, so sealing must be applied every time casting is performed to prevent this leakage.

Furthermore, if this sealing is not applied evenly to the mating surfaces of the upper and lower molds, gaps caused by the sealing material will occur, which not only risks leaking, but also prevents the molten metal from being poured into the casting opening 5. Previously, there were problems such as outside air flowing in through gaps in the sealing, causing bubbles to form in the molten metal the moment it was poured.

Further, as shown in FIG. 3 (Japanese Unexamined Patent Publication No. 58-167052), a model 30 made of foamed resin or the like is installed in a formwork 31 equipped with a depressurizing mechanism, and a fireproof wall is placed around the model 30. The inside of the formwork 31 is filled with a filler 32 such as particles, and the inside of the formwork 31 is sealed with a sealing material 33.
There is also a vacuum casting method using a full mold method in which a cast product is obtained at the same time as the model 30 is combusted by injecting molten metal into the model 30 while applying a vacuum effect to the interior of the model 30. In this case, since the filler 32 itself is used as a mold, applying a strong depressurizing action to the filler 32 may deform the model 30, and may also cause residue of the model 30 to burn. Due to the inherent shortcomings of the full mold method, it cannot be used for casting thin-walled objects or precision casting.

(Purpose of the Invention) This invention has been made by focusing on the above-mentioned problems of the conventional technology. By doing this, there is no need to damage mechanisms such as pressure reduction equipment due to molten metal penetrating cracks in the mold, and sealing is applied to eliminate the danger of molten metal leaking from between the upper and lower molds. It is an object of the present invention to provide a vacuum casting method that can eliminate labor and prevent bubbles inside the hot water caused by gaps in the sealing.

(Structure of the Invention) In the vacuum casting method according to the present invention, a permeable mold consisting of an upper mold and a lower mold is installed in a frame provided with a pressure reducing means, and refractory particles etc. are placed around the mold in the frame. After filling with a filler and applying a sealing material to at least the exposed portion of the filler, the pressure inside the frame is reduced, and the casting space in the air-permeable mold is closed to the gap between the air-permeable mold and the filler. It is characterized by having a structure in which casting is performed under reduced pressure through the .

(Example) The present invention will be explained below based on the drawings.

FIGS. 4 to 6 are diagrams illustrating an embodiment of the present invention.

The mold 11 in this embodiment is almost the same as the mold 1 described in the conventional example (see FIG. 1), and as shown in FIG. A casting space 17 is formed between an upper mold 12 having a casting spout 15 projecting upwardly and a lower mold 13 which is also surrounded by a flask 16 and faces the upper mold 12.

The mold 11 is installed in a frame body 18 with an upward opening and equipped with a pressure reduction mechanism, and the particles filled in the frame body 18 are placed in a state where only the casting spout 15 protruding upward is left. A heat-melting resin film 20 serving as a sealing material is embedded in the filler 19 having a shape of
is covered.

As shown in FIG. 5, the frame 18 has a rectangular shape with an upward opening and a bottom plate 21 provided on the lower side, and a hollow decompression chamber 18 is provided in the wall as a decompression means.
Furthermore, an opening 18b through which the decompression chamber 18a opens is provided inside the frame of each wall portion, and a wire mesh filter 22 with a mesh finer than the particles of the filler 19 is installed in the opening 18b. It is stretched.

Further, a mold 11 is provided on the inner bottom side of the frame 18.
Two receiving rods 23, 23 are installed substantially horizontally and parallelly to support the decompression chamber 18a at a distance from the bottom plate 21.
A connection port 24 that communicates with a vacuum pump (not shown)
is provided.

Next, the steps of the vacuum casting method will be sequentially explained based on the above configuration.

First, as shown in FIG. 6a, inside the frame 18,
After filling the filler 19 made of refractory particles to almost the same height as the upper surface of the receiving rod 23, the mold 11 consisting of an upper mold 12 and a lower mold 13 is placed on the receiving rod as shown in FIG. 23 and is installed in the frame 18.

At this time, the casting opening 15 projects higher than the upper surface of the frame 18.

Next, as shown in FIG. 6c, the casting opening 15
The casting opening 15 is closed with a cover 25 that prevents the filler 19 from entering the frame 18.
When the filler 19 is filled up to the upper surface of the mold 1,
1 is in a state where it is embedded in the filler 19 with only the casting opening 15 remaining.

After smoothing the upper surface of the filler 19 and removing the cover 25 of the casting spout 15, the upper surface of the frame 18, the upper surface of the filler 19, and the casting spout are removed, as shown in FIG. 6d. When the inside of the frame 18 is sealed by applying a heat-meltable resin film 20 to the entire surface of the section 15, and then operating a vacuum pump (not shown), the air pressure inside the decompression chamber 18a is reduced. As the pressure decreases, the pressure inside the frame 18 becomes reduced through the wire mesh filter 22, and at the same time, the pressure in the casting space 17 within the mold 11 is reduced through the gap between the filler 19 and the air-permeable mold 11. .

Furthermore, as shown in FIG. 6e, the frame 1
When the molten metal 26 is injected from the casting spout 15 while maintaining the reduced pressure inside the casting spout 15, the molten metal 26 instantly burns a part of the hot melt resin film 20 that was blocking the casting spout 15. and flows into the casting space 17.

In the case of this embodiment, when the pressure inside the frame body 18 is being reduced (the state shown in FIG. Since the frame body 1 is closed,
8 can be completely shut off from the atmosphere, and a more sufficient depressurizing effect can be applied to the mold 11 and the filler 19.

In addition, cracks may occur in the mold 11, and the molten metal 26 may penetrate into the clutch, or the upper mold 12 and lower mold 1
Even if the molten metal 26 leaks from between the mold 11 and the mold 11, the leaked molten metal 26 will be cooled and solidified within the filler 19, and will not leak out from the frame 18 or the bottom plate 21. will never reach.

In the above embodiment, the thermofusible resin film 20 is applied to the upper surface of the frame 18, the upper surface of the filler 19, and the entire surface of the casting spout 15. The resin film 20 may be applied to the resin film 20, and furthermore, in addition to the resin film 20, a paint such as a coating mold may be applied as a sealing material.

(Effects of the Invention) As explained above, according to the vacuum casting method of the present invention, an air permeable mold consisting of an upper mold and a lower mold is installed in a frame provided with a pressure reducing means, and A filler such as refractory particles is filled around the mold, and a sealing material is applied to at least the exposed portion of the filler, and then the pressure inside the frame is reduced and the casting space in the breathable mold is ventilated. Since the casting is performed by reducing the pressure through the gap between the mold and the filler, even if a crack occurs in the mold, the decompression device such as a vacuum pump will not be damaged, and it is also easier to use than the conventional method shown in Fig. 1. Precision molds with upper and lower molds, as shown in Figure 1, require the troublesome work of applying sealing evenly between the upper and lower molds, and the gaps between the sealings can cause air bubbles to form in the molten metal inside the mold. This allows us to prevent damage to the decompression device while performing precision casting, and to perform safe precision casting without worrying about bubbles forming in the molten metal inside the mold.
In addition, since the pressure reducing means is not connected to the breathable mold itself, there is no need to perform troublesome work such as removing and installing the pressure reducing means each time the mold is replaced, and there is no need to perform troublesome work such as removing and installing the pressure reducing means each time the mold is replaced. This has an excellent effect in that all you have to do is take the mold in and take it out.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a mold explaining the conventional vacuum casting method, Figure 2 is a plan view of a suction plate provided under the mold in Figure 1, and Figure 3 is a vacuum casting method using the full mold method. FIG. 4 is a sectional view illustrating a mold installed in the frame according to an embodiment of the present invention, FIG. 5 is a partially cutaway perspective view illustrating the structure of the frame, and FIG. 6 a 6 is a cross-sectional view showing the state in which the filler is filled up to the upper surface of the receiving rod, FIG. 6b is a cross-sectional view showing the state in which the mold is installed in the frame, and FIG. FIG. 6(d) is a sectional view showing a state in which a film is attached to the upper surface of the frame, and FIG. 6(e) is a sectional view showing a state in which molten metal is being poured. DESCRIPTION OF SYMBOLS 11... Mold, 15... Casting opening part, 17... Casting space, 18... Frame body, 19... Filling material, 20...
...Thermofusible resin film (sealing material).

Claims (1)

[Claims] 1. In vacuum casting using a permeable mold consisting of an upper mold and a lower mold such as a ceramic mold or a plaster mold,
After installing the mold in a frame equipped with a pressure reduction means, filling a filler such as refractory particles around the mold in the frame, and applying a sealing material to at least the exposed portion of the filler. . A vacuum casting method, characterized in that casting is performed by reducing the pressure inside the frame and reducing the pressure in the casting space in the air-permeable mold through a gap between the air-permeable mold and the filler.