JPH0512058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for casting castings used in the foundry industry. More specifically, the present invention relates to a casting method using a fugitive model.

BACKGROUND ART Conventionally, methods for casting castings using fugitive models are known.

The above-mentioned model is generally made of foamed polystyrene, etc., and a breathable and fire-resistant coating is provided on the outside, and in that state, sand or the like is filled in a container-shaped cast flask made of iron. It is buried inside an object, and a vanishing runner is connected to it.

Since these are already well known, illustration thereof will be omitted. Then, the model is gasified and disappeared by molten metal (hereinafter referred to as hot water) supplied from the runner, and the hot water enters the space created in the coating mold to perform casting. The gas generated from the model passes through the gap between the layer of the coating mold and the filler such as sand, and is discharged to the outside of the flask. In this case, the gas is naturally discharged to the outside or is forcibly discharged by a pump. Alternatively, like the invention disclosed earlier by the inventor of this invention (Utility Application No. 62-61800),
It is forcibly ignited at the top of the flask and burned. This is a casting method using a fugitive model.

Problems to be Solved by the Invention The fugitive models used in the above-mentioned conventional methods or in the methods disclosed by the present inventor are usually made of expanded polystyrene. This is generally formed into a foam using microscopic polystyrene particles using evaporation, and at this time, it is formed into the shape of the desired model.

However, in this case, on the surface of the model to be formed,
A large number of tortoiseshell patterns as shown in FIGS. 9 and 10 are produced.

In the figure, 1 is a disappearing model, 2 is a hexagonal pattern, and 3 is a groove, the depth of which is approximately 0.1 to 0.3 mm. However, the above pattern is faithfully reproduced on the surface of the product (not shown) when casting is performed. Such a product is not desirable in terms of appearance, and the grooves formed therein, although shallow, cause a decrease in fatigue strength, which is not desirable in terms of the strength of the product.

Another problem is that the coating mold is preformed in liquid form, and is generally a slurry made by mixing fine powder of silica, alumina, clay, diatomaceous earth, etc. However, the above-mentioned coating liquid is usually imported, is expensive, requires time for painting, and takes a long time to dry. This drying time is an example
It lasts up to 20 hours.

This invention was made in order to solve the various problems mentioned above, and its purpose is to provide a casting method using a fugitive model that can produce a cast product without a hexagonal pattern on the surface. Another purpose is that the coating mold can be omitted, the cost of raw material liquid for the coating mold can be reduced to zero, the trouble of painting can be eliminated, and the drying time of the coating mold can be long. An object of the present invention is to provide a method for casting a casting using a fugitive model that can be omitted.

Still another object is to provide a method for casting a casting, which can further enhance the effectiveness of the casting apparatus previously disclosed by the inventor of the present invention.

Means for Solving the Problems The present invention, which achieves the above object, is to form a fugitive model by forming a layer of wax on the outer surface of a fugitive model made of foamed polystyrene provided with a runner. Then, the fugitive model is buried in a nonflammable filling housed in a container-shaped casting flask, and molten metal is injected into the fugitive model through the runner, and the molten metal melts the fugitive model and The wax layer on the outer surface of the model is gasified and disappeared, and casting is performed by entering the disappeared space, and the gas of the disappeared expanded polystyrene and wax is passed through the filling and brought into contact with the filling in advance. The gas is introduced through the small hole into a burner having a small hole, and is ignited and combusted by an ignition device at the upper end of the burner, and the pressure inside the burner is reduced by the rise due to combustion of both gases. , a method for casting a casting characterized in that both gases in the filling are sucked.

Function A layer of wax is formed on the outer surface of a fugitive model made of expanded polystyrene, and this wax fills in the irregularities of the tortoiseshell pattern on the outer surface of the model to form a smooth surface. The model is buried in a non-combustible filling in the flask,
A runner is connected to the fugitive model in advance, and hot water is poured through the runner. Then, this hot water reaches the vanishing model from the runner, gasifies and vanishes the model, and enters the space created by this vanishing.
In this state, it is solidified and cast. in this case,
The fugitive model, including the wax layer formed on its outer layer, disappears by gasification. The hot water then reaches the outer surface of the wax and solidifies there.

In this case, the filling maintains its shape without collapsing and penetrating into the hot water.
Thereafter, the solidified product is removed from the filling.

As a result, a cast product with a smooth outer surface and without the tortoiseshell pattern can be obtained. As described above, the wax and expanded polystyrene gas passes through the filling and is previously provided in contact with the filling. It goes into a burner with small holes. Then, at the upper end of the burner, it is ignited by a pre-installed ignition device and combusts.
This combustion causes both gases to rise, thereby reducing the pressure within the burner. This reduction causes suction of the gas present in the filling. In this case, the wax generates a large amount of gas due to the molten metal, and since it burns well at the upper end of the burner, the combustion on the burner can further enhance this rise, thereby increasing the pressure inside the burner. Since the drop can be strengthened, the suction of gas in the filling can thereby be effectively increased.

Example In FIG. 1, 1 is a fugitive model made of expanded polystyrene, 4 is a layer of wax formed on its outer surface, and 5 is the fugitive model thus formed. Further, 6 is a container-shaped casting flask, 7 is a non-flammable filler such as sand housed in the casting flask 6, 8 is a runner made of expanded polystyrene, 9 is a sprue, and 10 is a furnace. 11 is hot water, 12 is a burner, 13 is a small hole formed in the burner 12, 14 is a gas chamber, 15
is an outer wall that partially doubles as a burner member. 16 is a roof, 17 is a hole formed in the roof 16, 18 is an ignition device, 19 is a flame, and 20 is a roller. Note that the small hole 13 may be a slit, and the present invention also includes that. Hot water 11 is injected from the furnace 10 into the sprue 9, passes through the runner 8 and disappears through gasification, reaches the fugitive model 5, where it gasifies and disappears, enters the space created here and solidifies, and the casting is completed. It will be done. The generated gas passes through the gap in the filling 7 and passes through the small holes 13 of the burner 12.
The gas enters the gas chamber 14 through the gas chamber 14, rises through the gas chamber 14, exits through the hole 17, and is ignited by the ignition device 18.

When the hot water 11 is replaced with the fugitive model 5 and cast, as shown in FIGS. 4 and 5,
The outer surface of the layer of wax 4 is filled with hot water 11 and cast.

In this case, the filling 7 does not collapse into the hot water 11. That is, as is clear from this, the coating mold can be made unnecessary according to this method.

The filling material 7 is densely packed around the model 5 due to vibration when the model 5 is set in the filling material 7, as in the case of casting using a normal fugitive model. be.

Next, the production of the evanescent model 5 will be explained.

First, use polstyrene to foam as usual to form the desired disappearing model, then immerse it in wax 4 that has been melted at about 80°C in advance as shown in Figure 6, and take it out immediately. . (Illustration omitted)
In the figure, 22 indicates a container, and 23 indicates a heating device.
In this case, the thickness of the layer of wax 4 formed is about 0.1 mm to 0.3 mm, filling the grooves of the hexagonal pattern, and solidifies immediately.

Note that the wax 4 is paraffin wax, for example.

In addition to dipping, the wax 4 may be formed into an emulsion, sprayed, and dried. In this case, drying takes about 5 minutes at room temperature. Next, the fugitive model 5 (see FIG. 1) thus formed has a layer of wax 4 that covers the irregularities of the hexagonal pattern 2 and has a smooth surface.

Effects of the Invention The present invention is configured as described above, and forms a fugitive model by forming a layer of wax on the outer surface of a fugitive model made of expanded polystyrene.
The outer surface of the casting thus formed is embedded in a nonflammable filling housed in a container-shaped casting flask, and cast by injecting molten metal into the fugitive model and dissipating it by gasification. In this case, the hexagonal pattern described in the conventional example can be eliminated. Therefore, the appearance can be improved, and continuous cracks caused by the hexagonal pattern grooves can be eliminated, so that the strength can be increased accordingly. Furthermore, since the coating mold as described in the conventional example can be omitted, the cost of the raw material liquid for the coating mold can be reduced to zero, and the labor and skill of forming the coating mold can be reduced. Long drying times can be omitted. In addition, since the wax applied to the outer surface of the fugitive model emits a large amount of gas due to the molten metal used for casting, by burning this gas together with the gas from the expanded polystyrene at the upper end of the burner 12, a large amount of combustion can be achieved. The gas rises and this rise causes
Since the gas reduces the pressure in the burner more strongly than if the foamed polystyrene were used alone, the suction of the gas contained between the packings can be increased even more.

That is, in this way, the wax can be used to increase the suction efficiency of the burner.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, and FIG. 1 is a cross-sectional view of a casting apparatus for explaining the method of casting a casting.
2 is a plan view of the device shown in FIG. 1, FIG. 3 is a sectional view of a portion of the device shown in FIG. 1, FIG. 4 is an enlarged detailed view of the portion shown in FIG. A diagram showing the positional relationship of each part when the state changes due to injection of molten metal, Figure 6 is a diagram showing the process of creating a fugitive model used in this invention, and Figure 7 was created by the process shown in Figure 6. A partially exaggerated cross-sectional view of the vanishing model;
FIG. 8 is an enlarged detailed view of the portion shown in FIG.
FIG. 0 is an enlarged sectional view of a portion of the model shown in FIG. 9. 1... Disappearing model, 4... Wax, 5... Disappearing model, 6... Casting flask, 7... Filling, 8... Runway, 11... Molten metal.

Claims (1)

[Claims] 1 A fugitive model is formed by forming a layer of wax on the outer surface of a fugitive model made of foamed polystyrene provided with a runner, and the fugitive model is housed in a container-shaped mold with non-flammable filling. burying the fugitive model in a material, injecting molten metal into the fugitive model through the runner, gasifying and disappearing the fugitive model and the wax layer on the outer surface of the model with the molten metal, and entering the disappeared space. Casting is then carried out, and the gas from the lost expanded polystyrene and wax is passed through the filling,
The filler is introduced into a burner having a small hole provided in advance in contact with the filler, and is ignited and combusted by an ignition device at the upper end of the burner. A method for casting a casting, characterized in that the pressure inside the burner is reduced, thereby sucking out both gases in the filling.