JPS58125360A - Method and device for vacuum casting - Google Patents

Abstract

PURPOSE:To cast a thin-walled casting having thick walled parts stably without a defect, by forming the thick walled part of a cavity of a casting mold which is enclosed with hermetically closing members and has heat retaining property and air permeability, and a chiller and charging molten metal into the cavity while evacuating the inside of the mold. CONSTITUTION:A casting mold 10 which has a casting port 22, is enclosed by hermetic members such as a flask body 32, metallic foil 36 and the like, consists of gypsum materials or the like and has heat retaining property and air permeability, forms a cavity 16 consisting of thin walled parts 18 and a thick walled part 20, and forms a part of the thick walled part 20 of a chiller 12. The inside of said mold 10 is connected to an evacuating device (not shown) through evacuating holes 26 formed in the chiller 12, an evacuating vessel 14 and a nozzle 30. With such constitution, molten metal is charged through the port 22 while the air is evacuated from the vessel 14. When the port 22 is closed, the inside of the cavity is evacuated quickly and the molten metal is filled instantaneously and surely into the parts 18. In the part 20, the molten metal is solidified directionally by the chiller 12, and the generation of shrinkage defects is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum casting method and apparatus, and more particularly to a vacuum casting method and apparatus suitable for casting a thin-walled casting having a thick wall S in a part of the product.

Conventionally, when casting a product by the vacuum casting method, an apparatus as shown in FIG. 1 has been used. In this device, a cavity 3 is formed by an upper mold 1 and a lower mold 2 having air permeability and heat retention properties, and a pair of presser plates 4 are provided so as to sandwich the Okazaki mold 1.2. A large number of pressure reducing grooves 5 are formed on the inner surface of the holding plate 4, and a pressure reducing line 6 communicating with the pressure reducing grooves 5 is attached to the outer surface of the holding plate 4.

In addition, a casting lower for pouring metal into the cavity 3 is opened to the atmosphere through a presser plate 4 attached to the upper die 1. With such a device, molten metal is injected from the casting lower without reducing the pressure inside the mold (upper mold 1 and lower mold 2), improving the flow of the molten metal in the cavity 3 and achieving a degassing effect. It is.

However, the vacuum casting method using the above-mentioned conventional apparatus has five problems such as poor sealing between the mold and the vacuum mechanism (the holding plate 4 and the vacuum line 6). That is, in the conventional apparatus, in order to simplify the snowmaking structure, no means for sealing the area around the joint between the upper mold 1 and the mold 2 is not provided. Because of this, the depressurization function is impaired, and casting of thin-walled castings with a wall thickness of 1 inch or less is difficult because hot water circulation is poor. Furthermore, in the case of casting thin-walled castings that have some thick-walled parts, a chiller is used for directional solidification to prevent shrinkage defects and improve mechanical strength. There are some problems when hiring subsidies. That is, a cooling metal is embedded corresponding to the thick wall part of the mold cavity 3, but embedding this cooling metal is very inefficient (it is not possible to manufacture the mold efficiently, and the mold is damaged). This causes deterioration of air permeability.Furthermore, a mold in which a cold metal is embedded has the disadvantage that cracks occur in the mold due to the difference in coefficient of thermal expansion during casting.

Therefore, with the vacuum casting method using conventional equipment, it is difficult to cast a casting that has a wall thickness of 1 W or less and requires finger solidification (5 problems).

Furthermore, there is a method called the V process as a similar vacuum casting method. This method uses vinyl as a sealing jig on the inner wall of the mold cavity, and performs casting by reducing the pressure inside the mold except for the cavity, but with this method, the pressure inside the cavity is not reduced, so the wall thickness is 1. It is difficult to cast the following thin-walled, complex-shaped castings, and has the same problems as the above example.

The present invention provides a vacuum casting method and a vacuum casting method that can stably produce complex-shaped thin-walled castings (thickness of 1 mm or less) that have thick parts in some parts of the product, which were difficult to cast using conventional methods. The purpose is to provide equipment.

In order to achieve the above object, the present invention connects a pressure reducing mechanism to a mold having heat retention and air permeability through a chiller having holes for reducing pressure, and uses the chiller to reduce the thickness of the cavity of the mold. A part of the flesh part is formed, and the outer circumferential surface of the mold excluding the pouring port is surrounded by sealing gI! material, and the molten metal is injected from the pouring hole while reducing the pressure inside the cavity through the pressure reducing hole. It's like a friend.

The following is the implementation 11H of the vacuum casting method and installation according to the present invention.
I will be explained in detail with reference to the drawings.

FIG. 2 shows a sectional view of the vacuum casting apparatus according to this embodiment. As shown in this figure, the vacuum casting apparatus includes a mold 10,
It is composed of a chiller 12 and a decompression tank 14.

The mold 10 is made of foamable or non-foamable gypsum material and has heat retention and air permeability. A mold 10 having a cavity 16 corresponding to the shape of the product is manufactured from this material. This cavity 16 is formed at a position close to the lower end surface side in the figure, and has a thin wall portion 18 corresponding to the blade where the product wall thickness is 1w11 or less, and a thick wall portion [B] corresponding to the boss portion.
It consists of 20. In such a mold 10, a part of the thick wall portion 20 is opened at the lower end surface, and this opening portion is closed by the chiller 12, and the chiller 12 is connected to the thick wall portion 20.
-s'fr. This is to achieve directional solidification of the thick wall portion 20 during casting to prevent shrinkage defects in the product. Further, the mold 10 is provided with a pouring port 22 that opens to the outside, and a runner portion 24 is formed that fully communicates with the pouring port 22 and the cavity 16 . The pouring port 22 is formed on the opposite end surface (the upper end surface in the figure) of the thick walled portion 20.

In such a mold 10, a cold metal 12, which closes the opening of the thick-walled part 1120 to form a part of the thick-walled part 20, is bonded and arranged so as to cover the entire lower end surface of the mold 10. ing. This cooling metal 12 includes mold 1 other than the cavity 16 forming part.
A depressurizing hole 26 that opens at the joint surface with 0 is bored. This depressurization hole 26 is opened into the inside of the decompression tank 14 which is connected to the mold 10 with the cooling metal 12 sandwiched therebetween, and provides communication between the mold 10 and the decompression tank 14 .

The decompression tank 14 connected to the chiller 12 has a box shape with one plane open, and the opening is closed by the chiller 12 to be sealed. This decompression tank 14 and chiller 12
A sealing jig 28 made of heat-resistant rubber or the like is provided at the joint between the two and seals the joint to ensure the decompression function. Further, the pressure reduction 1114 is connected to a pressure reduction device such as a compressor, and a ninth nozzle 30 for extracting air from the side 14 is provided.

The mold 10 in which the chiller 12 and the decompression tank 14 are connected in this way is fitted with a frame 32 that surrounds the outer periphery of the side thereof. This frame 32 is formed from a metal material and is joined to the chiller 12 at its lower edge. Frame body 3
A sealing jig 34 made of heat-resistant rubber or the like is also interposed at the joint between 2 and the cold metal 12 to provide a seal between the two. Further, the upper edge of the frame 32 is raised up to the same plane as the upper end surface of the mold 10, and the entire outer side of the mold 10 is sealed. The upper end surface of such a mold 10 is open to the atmosphere, except for the casting port 22 (the upper end surface is sealed with a metal foil 36 made of aluminum or the like).

A vacuum casting method using such a vacuum casting apparatus is performed as follows. In advance, a pressure reducing device connected to the reduced pressure tank 14 is activated to bleed air from the reduced pressure tank 14. Due to this air bleed action, the entire mold 10 is brought into a slightly reduced pressure state via the pressure reduction holes 26.

At this time, the mold 10 is connected to a sealing jig 34 between the mold 10 and the cooling metal 12.
, and the metal foil 36 to seal the part except the casting opening 22, and the space between the decompression tank 14 and the cooling metal 12 is also sealed by a sealing jig 28. However, since the pouring port 22 is open, the pressure inside the cavity 16 is not reduced. Thereafter, molten metal made of aluminum material, which is a raw material for casting, is poured from the pouring port 22. Casting port 2
When the cavity 2 is closed by the molten metal, the upper end surface of the mold 10 is completely sealed, so that the inside of the cavity 16 is rapidly depleted. As a result, the molten metal is instantaneously and reliably filled even into thin-walled parts having a wall thickness of 1 inch or less. Therefore, when pouring, no air is drawn in (although some gas is sucked in due to the reduced pressure inside the cavity 16, this can be removed from inside the cavity, improving the quality of the product. The thick part 20
There is no fear that shrinkage defects will occur due to directional solidification performed by the chiller 12.

FIG. 3 shows a second embodiment of the vacuum casting apparatus.

This device connects the runner part 24A to the side part of the cavity 16, and connects the thick part 2 of the cavity 16 with the chiller 12.
0, but also a part of the runner 24.

Further, FIG. 4 shows a third embodiment of the same device.

In this device, the mold 10 and the decompression tank 14 are inverted, and a runner 24B has a pouring port 22B passing through the cooling metal 12.
It is provided at the upper end of the pressure reducing tank 14, and is configured to be disposed on the side of the decompression tank 14.

The apparatus according to the second and third embodiments also enables the casting of thin-walled products with a wall thickness of 11 or less, and also allows the casting of thin-walled products with a thickness of 11 or less.
It is also extremely easy to put on.

In the first and second embodiments of the present invention, the mold 10
Although an example has been shown in which the metal foil 36 is attached to the upper end surface of the metal foil 36, this portion does not particularly need to be melted with molten metal, so it may be a metal plate or other four-heat plate material. When using a metal plate or a heat-resistant plate-like body, it is desirable to interpose a member such as heat-resistant rubber between it and the frame 32 and at the outer peripheral edge of the casting port 22.

Specific examples of such a method are shown below.

Example 1 A thin-walled casting (
The wall thickness is 11m1 or less, depending on the thickness, the wall thickness is only 0.5mm), and was cast from aluminum material (AC4C).

In this case, both the present example and the gravity casting method were compared and studied.

In the gravity casting method, the mold temperature is 500℃, and the casting temperature is 1w850.
℃, chilled metal temperature of 400℃, and riser height of 200℃, but it was impossible to cast a product without defects such as poor hot water circulation and surface pinholes.

On the other hand, in the vacuum casting method, the mold conductivity is 250°C5
Casting 1 degree 700℃, cooling degree 250'C, % hot water height 3
Although casting was carried out under conditions of 0*z% reduced pressure/L-aoo Hg or higher, a defect-free product was cast.

In this example, the upper surface of the mold 1°, excluding the casting port 22, was sealed with an aluminum film having a thickness of 20 to 100 μm. Film thickness is 20. This is because if the temperature is less than 100 μm, the aluminum film will be broken due to mold temperature, etc., and if it is more than 100 μm, the sealing function for the mold will be impaired.

Example 2 A mold 10 made of foamable gypsum material was used, and the mold temperature was 2.
00℃, casting temperature of 700℃, chilled metal temperature of 250℃, degree of vacuum less than -100℃Hg, 1: iiJ, as a result of vacuum casting in the same manner as in Example 1, no defects were found. The product could be cast.

As described above, according to the vacuum casting method and apparatus according to the present invention, the injection port can be removed (the mold can be sealed tightly, the VC can improve the vacuum state in the cavity during pouring, and the cooling Since the placement of the gold is easy and the assembly workability is 90%, it is possible to stably manufacture thin-walled castings with complex shapes having thick walls S in some parts without defects.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional vacuum casting device, Fig. 2 is a sectional view of a vacuum casting device according to this embodiment, and Fig. 3 is a sectional view of a conventional vacuum casting device.
FIG. 4 is a sectional view showing the third embodiment. DESCRIPTION OF SYMBOLS 10... Mold, 12... Cold metal, 14... Decompression tank, 16... Cavity, 18... Thin wall part, 20...
・Thick wall part, 22... Casting port, 26... Hole for pressure reduction, 3
2...Frame body, 36...Metal foil. Agent Tatsuyuki Unuma (2 people) Figure 1 Figure 3 Figure 2 Figure 4

Claims (2)

[Claims] (1) A mold having heat retention and air permeability is connected to a decompression mechanism via a chiller having depressurizing holes, and the chiller is used to form a part of the thick walled part of the cavity of the mold. , and a vacuum casting method characterized in that the outer periphery r1n of the mold excluding the casting spout is surrounded by a sealing member, and bath water is injected from the casting spout while reducing the pressure inside the cavity through the vacuum hole. (2) A mold with heat retention and air permeability is equipped with a depressurization mechanism connected via a chiller having depressurizing holes, and the chiller is small (and forms part of the thick walled part of the mold cavity). A vacuum casting apparatus characterized in that the outer circumferential surface of the mold, excluding the casting opening, is surrounded by a sealing member.