JPS5850170A - Method and device for reduced pressure casting - Google Patents

Abstract

PURPOSE:To produce thin walled casting products having thick walled parts in part of the products easily without flash by forming part of the thick walled parts of cavities in a chiller, and reducing the pressure in the molds then charging molten metal onto a metallic foil thereby melting the metallic foil. CONSTITUTION:The inside of a pressure reducing chamber 10 is evacuated to reduce the pressure over the entire part of a mold 8 through holes 17 for evacuation. In this time, a chiller 9 energized by an elastic member 18 is brought into abutment airtightly on the opening part in the thick wall part 13 of a vacity 11 to reduce the pressure in the cavity 11 surely. Molten Al is charged from a metallic foil 22 facing a charging port 7 to melt the foil 22 by the heat of the molten metal. Since the inside of the cavity 11 is under reduced pressure, the molten metal is admitted and packed instantaneously therein, but the chiller 9 abuts tightly on the opening part of the part 13; therefore the production of flash by the leakage of the molten metal is prevented surely. Since the molten metal is charged onto the foil 22, the inclusion of gases is prevented as well.

Description

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

Conventionally, when casting products using the pressure casting method,
As shown in 11! A scissor holder is used. In this device, a cavity 3 is formed by an upper W1 and a lower @2 which have air permeability and heat retention properties.

A pair of presser plates 4 are provided to hold 2.

A large number of pressure reducing grooves 6 are formed on the inner surface of the holding plate 4.
l, the pressure reduction line 6 connected to this pressure reduction groove 5 is presser [
It is attached to the outer surface of 4.

In addition, the presser foot [4KFi] attached to the upper lid IKIII, and the casting lower for pouring metal into the cavity 3, are open to the atmosphere.

With such a device, the pressure inside the casting chamber (upper mold 1 and lower lid 2) is reduced and molten metal is injected from the pouring port 1 from the east to improve the environment around the hot water inside the casting chamber 3 and to achieve a degassing effect. It is something that

However, the vacuum casting method using the conventional apparatus described above has a problem in that the mold and the vacuum mechanism (the holding plate 4 and the vacuum line 6) are not tightly sealed. That is, in the conventional device, no sealing means was taken for the casting lower, and in order to simplify the conventional device, upper@1 and lower m! Junction circumference 1
! There is also no means for sealing the IK. For this reason, the depressurization function is impaired, and casting of thin-walled castings with a wall thickness of 1 or less is difficult because the molten metal pipe is bad. In the case of casting castings, a chiller is added for directional solidification in order to prevent shrinkage defects and improve mechanical strength, but there are problems when using this chiller. That is, a cold metal is placed in a mold corresponding to the inside of the casting cavity 30, but placing this cold metal in is very difficult to work with, making it impossible to manufacture molds efficiently, and This causes poor air permeability of the mold. However, a mold into which cold metal is inserted has the disadvantage that cracks occur in the mold due to the difference in thermal expansion coefficient during casting. Therefore, in the vacuum casting method using conventional equipment, there is a problem in that it is WII to cast a casting having a wall thickness of s 1 m 111 or less and requiring directional solidification.

There is a similar vacuum casting method called the V7' process. This method uses vinyl as a sealing jig for the wall inside the mold cavity and performs casting by reducing the pressure inside the mold except for the cavity. It is difficult to cast the following thin-walled and complex-shaped castings, and there are problems similar to those in the above example.

This Oli beak can be used to manufacture complex-shaped thin castings (wall thickness 1 or less) that have thick interiors in some parts of the product without causing cracks, which can be done by conventional casting methods. The object of the present invention is to provide a vacuum casting method and an apparatus therefor.

The present invention will be explained below by way of an embodiment based on the drawings.

Figure #1E2 shows a sectional view of the vacuum casting apparatus according to this embodiment. This vacuum casting apparatus is made up of four castings 11g, a chiller 9, and a vacuum tank IO.

Cast! 18 is made of foamable or non-foamable gypsum material and has heat retention and breathability. This material can be used to create product shapes, such as:
1 is produced in a cast l18. This cavity 1
1 is formed at a position close to the lower end surface side as shown in FIG. It consists of

In such a casting 3110, a part of the thick interior 13 is opened at the lower end surface, and this opening is hermetically sealed by the pre-cooling metal 9, and one side of the intercooling metal 9 is closed. However, the thickness inside 1
30. This cold metal 9 is
This rounding aims at directional solidification of the thick inner part 13 during casting to prevent shrinkage defects in the product.

Further, the casting m8 is provided with a casting spout 1 that opens to the outside, and a runner 14 that communicates the casting lower and the cavity 11.
is formed. This pouring port γ is formed on the end surface opposite to the thickness inside s20, and in FIG. 2, it is provided on the upper end surface.

The casting 1mm and the decompression tank 10 are separated by a communication plate 1i, and the chiller 9 is bored on the upper surface of this communication plate tS, and the running part 1
There are 6 K11 people. A depressurizing hole 17 is bored in the communication 115 so as to connect the upper and lower parts, and the casting gs and the depressurizing tank 10 are communicated through the depressurizing hole 17. Said chiller 9
A heat-resistant elastic member 18 having a substantially flat plate shape is disposed on the surface 11 of the recess 160 into which the chiller 9 is fitted, and the chiller 9 is always urged toward the −118 side. This rounded cooling metal member is strongly pressed around the 1 m thick inner opening of the cast Ill and closely fits a part of the 1wi thick part 13 in an airtight manner. At this time, the tension of the elastic member 18 is as follows.
In a normal state, the chiller 9 should be made to protrude from the upper surface of the communication plate 15 at a predetermined height, and the chiller 9 should be appropriately adjusted so as to be biased with sufficient pressure in the connected state of the communication [15].

As the front cooling plate 9, one that has graphite properties and excellent cooling properties should be used.

The decompression tank 10 is a box with an open top end that is used for pre-delivery [15
is sealed by. This decompression tank 10 and communication plate 1s
A hermetic seal A11 made of heat-resistant rubber or the like is provided at the joint with the main body to maintain the airtightness of the joint and ensure the decompression function. In addition, the pressure reduction tank 10 is connected to a pressure reduction device such as a compressor, and is provided with a nozzle 20 for extracting air from one tank 10P3C).

The casting 111 to which the communication plate 15 and the decompression tank 10 are connected has a frame surrounding the outer periphery of its side. l is attached. This frame 21 is formed from a metal material,
It is connected at its lower edge for communication [11sK].

A sealing jig 19 made of heat-resistant rubber is also interposed at the joint between the frame 81 and the communication [15] to keep the joint airtight. worn.

The upper edge of this frame body 21 rises up to the same plane as the upper end surface of the casting 118, and the entire outside line of -gs is sealed. The upper end surface of such a cast Ill is open to the atmosphere, but this upper end surface is covered with a metal foil 22 made of aluminum material.
It is completely sealed by 1/C. This metal foil 22
is a thin film made of aluminum material, and the film thickness is said to be 20 to 100 mm. This is a rounding process in which the metal foil 22 is melted by the heat of the molten metal and opened when filling the cavity 11 with molten metal. That is, the film thickness is 20
If the pressure is less than μ, it will be destroyed by normal decompression.
This is because if the thickness exceeds 100μ, the sealing function of the casting wire will be lost. The sealing by the metal foil 22 that was assembled is performed by sealing the casting hole and making sure that the frame body 1 covers all the other upper end surfaces of the mold except for the pouring opening 1. For example, if two pieces of metal foil are placed only at the pouring hole γ, it can be pulled out.

The vacuum casting method using such a pressure casting device is carried out as follows: First, the pressure reducing device connected to the vacuum tank - is operated to bleed air from the bulb pressure tank toe.

Due to this bolting action, the entire mold 8 is brought into a depressurized state via the depressurizing hole 17.

At this time, the writing and closing A1G between the casting @S and the communication plate 15,
and a completely sealed state with metal foil z2,
However, 4, there is also a self-closing jig 19 between the decompression tank IO and the communication plate Is.
The rounding is sealed by the efficient yts produced. Further, the cold metal 9 urged by the bullet member 18 is brought into airtight contact with the opening of the thick wall portion 13 of the cavity 11, thereby ensuring that the inside of the cavity 11 is also in a reduced pressure state. After a predetermined degree of pressure reduction is reached by this air extraction, molten metal of aluminum, which is a raw material for casting, is poured from above metal foil 22, not corresponding to pouring port γ. As a result, the molten metal melts and breaks the metal foil 22 due to its heat, and instantaneously flows into and fills the cavity in the reduced pressure state. At this time, since the cavity 11 is in a reduced pressure state, even the thin wall portion 12 forming the wing phase portion having a wall thickness of 1 m or less is filled reliably and rapidly. In addition, since the cooling chamber 9 is still in airtight contact with the opening of the thick interior 13, leakage of the molten metal O into the vicinity of the second opening is reliably prevented, and the generation of paris is prevented. A firmer lower end surface of the thick granite portion 13 can be obtained. Furthermore, since the molten metal is poured onto the metal foil 22 in advance, the mixing of sand and gas, which is different from the case where the molten metal is poured directly into the casting lower, is prevented, and the quality of the product can be improved.

The thickness of the hot water filled in the cavity 11P1 is -@1
In the MPC, directional solidification is performed by cooling IK, so there is no risk of shrinkage defects occurring.

A variant embodiment of such a method is shown below.

Example 1 Thin-walled casting (
Inner thickness less than l■, depending on the position, wall thickness 0. @There are only proverbs)
can be cast from aluminum material (TX11 standard, MuC4C). In this case, both the method according to this example and the gravity casting method were compared and studied.

In the gravity casting method, the mold temperature is 500℃ and the pouring temperature is 850℃.
Although casting was carried out under the conditions of a total cooling temperature of 21SO℃ and a riser height of 200cm, many defects such as poor hot water circulation were observed, making it impossible to cast a product without defects.

On the other hand, in the vacuum casting method, the mold temperature is 850℃, the pouring temperature is TOO℃, the total cooling temperature (water-cooled temperature is 2s℃, the riser height is 30℃, and the vacuum pressure is 93001g or more. The product was cast without any defects.No cracks were observed at the contact area between the mold and the cold metal.

Example 2 A mold 8 made of foamable gypsum material was used, and the mold temperature was 200.
℃, casting temperature 700℃, total cooling temperature (water cooling state) 25℃
It was possible to cast a casting similar to that of Example 1 using the reduced pressure method under conditions where the degree of reduced pressure was 110OH or more.

In this way, l! According to the vacuum casting method and its installation, since casting is performed in a completely sealed state, the cavity 11
Even if the thin wall portion 12 of the cast iron is less than 1-, the hot water area is extremely tight, and even products with thin walls and complicated structures can be cast satisfactorily. t★, the cold metal 9 is not a structure that is collapsed into the mold 8,
Communication [Cast I in the recess 1 of 18 with the elastic member 18! Since it is biased toward the 8 side and brought into close contact with the opening of the thick part 13, there is no occurrence of cracks during cracking during pouring.

Ota. 41, since the casting lower is sealed in advance with a metal foil 22 made of aluonium, the reduced pressure inside the casting aS is maintained until the moment when the metal foil 2'2 melts during pouring, and the lower pressure is maintained during pouring. It becomes possible to cast Al-Z castings without air entrapment and with no defects. The metal foil 22 is completely Kll! during pouring. Although it is IFFed and mixed into the Alonium casting material, there is no problem with rounding of similar metals. Also, temporarily cast materials and metal foil! Even if the metal foils 2 and 2 are two different metals, the metal foil 22 itself is thin and can be ignored as an allowable impurity, so it can be sufficiently cast.

Figure @S shows a second embodiment of vacuum casting loading.

This device communicates the runner 14' with the side of the cavity 110, forms a part of the thick interior 13 with the cooling metal 9, and connects the end of the cooling metal 9 with the communication plate 115 and K. 16. Figure 4 shows a third embodiment of the same device.

In this device, the casting w8 and the depressurizing tank 1G are inverted with respect to the first and second embodiments, and the pouring port γ' penetrates the communication plate 15 in a runner section 14'. It is provided at the upper end of the decompression tank 10, and is configured to be disposed on the side of the decompression tank 10.

Even in the electrical manufacturing according to the second to sII examples, a thin-walled product having an inner thickness of less than 100 mm can be cast without any occurrence of flash at the contact portion with the chiller 9.

According to the vacuum casting method and device of the present invention as described above, the hermeticity of the mold can be ensured.

It has the effect of easily and reliably casting a thin-walled product with a complex structure that has a thick internal part, without molding, by allowing 4 volumes of cold metal placement.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional vacuum casting method, FIG. 2 is a sectional view of a pressure casting apparatus according to this embodiment, and No. 31El is
A sectional view showing the zlI theory example of the same device, FIG.
It is a sectional view showing an example. 1.7′...Cast opening, 8...Mold, 9...
Cold metal, 11... Cavity, 12... Thin wall part,
13...Thick inside. 1 Te...hole for depressurization, 21...frame, 2!・
...Metal foil 1 person Tatsuyuki Unuma (#1 or 2) Figure 1 Figure 2 Figure 3 Figure 4 0

Claims (1)

[Claims] (1) A depressurizing tank is connected to a mold that is surrounded by a frame and has at least the casting opening, which is open to the atmosphere and is covered with metal foil and sealed and has air permeability, through a communication plate that has a chiller. Then, the cooling metal is brought into airtight contact with the mold so as to form a part of the inside of the cavity, and the inside of the mold is depressurized through the depressurization hole drilled in communication 1 [K]. A vacuum casting method characterized in that molten metal is injected from above the metal foil, and the metal foil is scaled by the heat of the molten metal, and the molten metal is filled into the inside of the container. 5) A mold having air permeability is connected to the mold through a communication plate, and is equipped with a vacuum tank, and the above-mentioned communication plate is provided with a hole in the face of the mold, and a brush is inserted into the round part through a heat-resistant insulation member. A cooling metal that forms part of the thick interior and O
A depressurizing hole is formed on the joint surface with the casting lid and communicates the mold with the depressurizing tank, the cooling metal is brought into airtight contact with the mold by an elastic member, and the mold is surrounded by a frame body. 1. A vacuum casting method characterized in that at least the casting opening is covered with metal foil and closed once.