JPH07121445B2 - Casting method and apparatus using reduced pressure chamber - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a casting method and apparatus having characteristics of both low pressure casting and gravity casting.

[Conventional technology]

Large parts made of aluminum, for example, are generally made by low pressure casting or gravity casting.

In addition, as a general problem in casting technology, the molten metal is gently poured into the mold to prevent foreign matter from being caught in the molten metal to prevent defective products, and to be poured into the feeder and runner. It is possible to increase the yield of castings by reducing the amount of molten metal to be melted and to improve productivity.

First, in the conventional low-pressure casting method, a holding furnace (a furnace that holds the molten metal under a constant molten metal condition) is closed, pressure is applied to the molten metal surface, and the molten metal is pushed up into a mold provided above the lid of the holding furnace to perform casting. To do.

The features of this casting method are that the molten metal is gently cast and there is no entrainment of foreign matter, and that pressure is applied until the casting solidifies, so that no feeder is required, and that after the casting solidifies. If the applied pressure is set to zero, the hot water in the pipe will be efficiently recovered, and the yield of the casting will be good.

Next, the gravity casting method utilizes the self-gravity of the molten metal. In addition to these casting methods, there is a die casting method in which the field of casting technology is different from that of the present invention (Shokai Sho 58-43858).
Issue).

[Problems to be solved by the invention]

In the conventional casting method described above, in the case of the low-pressure casting method, the holding furnace is closed and the mold is mounted above the furnace, so that there are the following problems.

That is, when the molten metal carried in the molten metal ladle is put into the holding furnace, when the lid of the holding furnace is opened and the lid is closed, care must be taken to maintain airtightness. Is required, it is difficult to extrude the product from the lower mold, a mold is attached for each casting, it is difficult to cool the lower mold with water, and the solidification of the casting is slow due to the radiant heat of the holding furnace, and this solidification Since it is necessary to wait while pressurizing until the end, there are drawbacks that it takes a lot of time for casting and the productivity is extremely low.

Also, the level of the molten metal drops during casting, which makes it difficult to balance the head pressure and the pressing force of the molten metal, making the pressurized state unstable and causing problems. There is a problem in that the structure is complicated because a single die corresponds to a large installation space in a foundry and a sealability against pressure is required. In addition, since the lid is closed, there is a problem that it is difficult to degas the molten metal during the casting and to improve the property of the molten metal (molten metal treatment).

On the other hand, in the case of gravity casting, the so-called casting method that determines the placement of the riser and the shape of the runner is difficult, and the escape path of air in the mold is only the gap of the mold dividing surface or the riser part,
If the casting method is not successful, air entrapment occurs and casting defects occur.

Further, since a riser and a sprue are required, there is a problem that the casting yield is low.

[Means for solving problems]

In order to solve the above-mentioned problem, the method according to the present invention is to open a partition plate, suck the hot water of the molten metal pool into the chamber, then close the partition plate, and then open the weir insert provided in the runner. The invention is characterized by pouring the molten metal from below the cavity while lowering the vacuum pressure in the chamber, and opening the partition plate after the pouring is completed to return the molten metal in the runner and the chamber to the holding furnace. In the apparatus for carrying out the method, a molten metal reservoir which communicates with the inside of the holding furnace via a weir is provided outside the holding furnace, and the lower end is immersed in the molten metal of the molten metal reservoir to vertically install the chamber. A vacuum pump and a mold runner are connected to the chamber, a vacuum pressure adjusting valve for adjusting the vacuum pressure in the chamber is provided in the vacuum system of the vacuum pump, and the runner is opened and closed. A weir insert is provided for this purpose. The weir is provided with a partition plate that opens and closes between the molten metal reservoir and the holding furnace.

[Work]

With the above configuration, the molten metal sucked up into the chamber is controlled so that the flow of the molten metal in the spout becomes smooth by both the head pressure (self-weight) of the molten metal and the pressure in the chamber. And by opening the partition plate when the casting solidifies, the molten metal in the chamber and the sprue part,
It is returned to the holding furnace.

On the other hand, the mold can be provided outside the molten metal pool provided outside the holding furnace, and there is no effect of the radiant heat of the holding furnace and a cooling part can be provided inside the lower mold. The coagulation time is shortened. Further, the holding furnace may be an open type.

〔Example〕

One embodiment of the present invention will be described in detail below. First, the apparatus will be described. In FIG. 1, reference numeral 1 is a holding furnace, and a molten metal reservoir 2 is formed outside the holding furnace 1 via a weir 3. Reference numeral 4 denotes a partition plate provided between the holding furnace 1 and the molten metal reservoir 2 so as to be vertically movable, and both of them are shut off or communicated with each other. In the case of this embodiment, the partition plate 4 is provided at the top of the weir 3. Reference numeral 6 denotes a chamber in which the lower end of the ceramic tube 6'is immersed in the molten metal in the molten metal reservoir 2. Reference numeral 10 is a vacuum pump connected to the ceiling of the chamber 6, and 9 is a vacuum pressure adjusting valve connected from a vacuum system via a branch portion 11. This vacuum pressure adjusting valve 9
It is controlled by a microcomputer 8 operated by a vacuum pressure sensor 7.

12 is a lower mold, 13 is an upper mold, and the runner 18 of the cavity 14
Are connected to the chamber 6. These molds are located and attached to the outside of the molten metal reservoir 2. Reference numeral 16 is a water cooling system provided in the lower mold 12, and 19 is a weir nest provided in the runner 18. Reference numeral 17 is an extruder for removing the product of the lower mold 12, and 20 is an extrusion cylinder thereof. 21 is a mold clamping cylinder. 22 is a molten metal processing apparatus. 15 is cavity 14
This is a decompression system for decompressing the inside so that the flow of molten metal becomes smooth.

2 and 3, the mold is connected to the chamber 6 by providing a coil heater 24 on a runner sleeve 28 provided on a sprue part 25 of the chamber 6, and a holder 26 between the runner 18 and the runner 18. Are connected via a weir nest 19 supported by. 26 'is a heater. 23 is an in-mold heater provided around the runner 18. In FIG. 4, 27 is a cartridge heater, b is the seal of the weir insert 19, b is an opening, and c is a cleaning position.

The casting method using this device is as follows. First, the weir insert 19 is sealed in the state shown in FIG. 4A and the partition plate 4 is opened and closed.
Aspirate up to. After that, the partition plate 4 is closed to disconnect the holding furnace 1. Then, the weir insert 19 is opened from the position shown in FIG. It is adjusted in relation to the head pressure of the molten metal, and the molten metal is injected into the cavity 14. After the solidification of the casting is completed, the partition plate 4 is opened to collect the molten metal in the camber 6 and the runner 18.

The operation of the present embodiment configured as above will be described below. First, since the lower end of the chamber 6 is immersed in the molten metal reservoir of the molten metal reservoir 2, the interior of the chamber 6 is completely sealed, and the molten metal is sucked and the vacuum pressure is adjusted reliably.
The sealing portion is only the connecting portion between the mold and the chamber 6, and the sealing is performed by the weir insert 19, so that the sealing reliability is high and the molten metal is once sucked into the chamber 6. In this case, the seal portion is completely sealed by the molten metal itself.

Next, when pouring into the cavity 14, the gravity (head pressure) of the sucked molten metal is adjusted by adjusting the vacuum pressure in the chamber 6 (for example, if the vacuum pressure is made equal to the head pressure of the molten metal, the molten metal is melted). Even if the liquid level of the sucked molten metal changes, the flow of the molten metal flowing through the runner is controlled by adjusting the vacuum pressure regardless of the liquid level. This prevents foreign matter from being caught in the molten metal.

Regarding the yield of castings, by opening the partition plate 4 and setting the pressure in the chamber 6 to atmospheric pressure, the molten metal in the chamber 6 and the molten metal in the runner 18 are recovered, and
At the time of casting, the pressure inside the chamber 6 is adjusted to pour the molten metal, so that there is no need for a presser, and an extra molten metal is not consumed. The recovered molten metal is mixed with the molten metal stored in the holding furnace 1 by opening the partition plate 4, and the molten metal conditions are maintained.

Further, the mold is attached to the outside of the holding furnace 1 (outside of the molten metal reservoir 2), and the in-mold cooling system 16 can be installed.
Moreover, the casting can be cooled and solidified in a short time without being affected by the radiant heat of the holding furnace. Further, the extruder 17 can be installed in the lower die 12, and the demolding is easy.

A plurality of molds can be installed for one holding furnace 1.

〔The invention's effect〕

As described above in detail, according to the present invention, the chamber having the lower end immersed in the molten metal of the molten metal reservoir is provided, and the vacuum pressure in the chamber is adjusted for pouring, so that the molten metal is irrelevant regardless of the liquid level of the molten metal. It was possible to control the flow of the molten metal flowing along the path, to prevent the inclusion of foreign matter in the molten metal, and to obtain a good casting product. As a result, the product yield could be further improved.

Further, since the molten metal in the runner and the chamber is recovered by opening the partition plate, it is possible to greatly improve the yield of castings, because the vacuum pressure in the chamber is adjusted and the molten metal is poured. It was

Furthermore, since the mold can be provided outside the holding furnace, an in-mold cooling system is possible, and since it is not affected by the radiant heat of the holding furnace, the solidification time of the casting can be greatly shortened. The productivity could be greatly improved. Further, by providing the mold outside the holding furnace, it is possible to install a plurality of molds for one holding furnace, which enables an efficient layout of the foundry and further enhances productivity.
Since the temperature of the mold is low, it has an excellent effect that the life of the mold can be extended.

Further, since the sealing portion is completely sealed by the molten metal itself at one place, there is no entrainment of air or the like, the quality is further improved, the structure is simple, and the practical effect is great.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention,
FIG. 1 is a vertical cross-sectional view of the entire casting apparatus using a decompression chamber, FIG. 2 is a vertical cross-sectional view showing a connecting portion between a mold and a chamber, and FIG. 3 is a cross-sectional view taken along the line BB of FIG. 4 and 5 are longitudinal sectional views taken along the line AA in FIG. 1 ... Holding furnace, 2 ... Molten pool, 3 ... Weir, 4 ... Partition plate, 6 ... Chamber, 9 ... Vacuum pressure adjusting valve, 10 ... Vacuum pump, 19 ... Weir nest.

Claims (2)

[Claims] 1. A cavity plate is opened while the partition plate is opened to suck the molten metal in the molten metal pool into the chamber, the partition plate is closed, and then the weir insert provided in the runner is opened to reduce the vacuum pressure in the chamber. A casting method using a decompression chamber, characterized in that the molten metal is poured from below, and the partition plate is opened after the pouring is completed to return the hot water in the runner and the chamber to the holding furnace. 2. A molten metal reservoir is provided outside the holding furnace so as to communicate with the inside of the holding furnace via a weir, and a lower end is immersed in the molten metal of the molten metal reservoir to vertically suspend a chamber, and a vacuum pump is provided in the chamber. And a mold runner are connected, a vacuum pressure adjusting valve for adjusting the vacuum pressure in the chamber is provided in the vacuum system of the vacuum pump, and the weir nest for opening and closing the runner is provided in the runner And a partition plate that opens and closes between the molten metal reservoir and the inside of the holding furnace in the weir, the casting apparatus using a decompression chamber.