JPH0957422A - Reduced pressure casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust filling speed of molten metal while maintaining the good quality of a casting. SOLUTION: A crucible 10 is pressed to a die plate 20 and a metallic mold 30 is laid on the die plate. Suction valves 13, 37 are opened, and a space part of the crucible and a cavity 33 in the metallic mold are simultaneously evacuated to reduce the pressure therein through suction pipes 12, 36 with a vacuum pump. Thereafter, the suction valves 13, 37 are closed and the suction pipes 12, 36 are closed with a cavity independent valve 39. A leak valve 15 is opened and gas is introduced into the space of the crucible 10 through a leak pipe 14 to release the reduced pressure state. A large pressure difference is caused between the space in the crucible 10 and the cavity 33, and molten metal M is supplied into the cavity 33 through a molten metal sleeve 22 and fills up the cavity 33. As a result, the filling speed of the molten metal M into the cavity 33 can be adjusted and also, the quality of the casting is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum casting method using a casting apparatus equipped with a closed holding furnace and a mold connected to the holding furnace with a hot water supply sleeve.

[0002]

2. Description of the Related Art Conventionally, as a casting method of this type, as shown in, for example, Japanese Patent Laid-Open No. 2-127958, the inside of a holding furnace containing the molten metal is decompressed to degas the molten metal.
With the pressure inside the holding furnace kept at a reduced pressure, the pressure inside the mold cavity is reduced to a pressure lower than the pressure inside the holding furnace, and the molten metal is sucked into the cavity to fill it. It was known that the molten metal was solidified while carrying out.

[0003]

However, according to the above casting method, since the pressure difference between the holding furnace and the cavity of the mold cannot be made large, the molten metal pushing force becomes small, the casting speed becomes slow, and the casting speed becomes low. Weight is also limited. In addition, if the degree of pressure reduction in the holding furnace is lowered (the degree of vacuum is lowered) in order to increase the pressure difference between the two, there is a problem that the degassing effect of the molten metal is reduced and the quality of the casting is reduced.
Furthermore, when depressurizing the mold cavity while maintaining the depressurization inside the holding furnace, the molten metal suddenly enters the cavity simultaneously with depressurization, and the air remaining in the cavity is entrained to improve the quality of the casting. There is a problem of lowering it.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a vacuum casting method capable of adjusting the filling rate of the molten metal into the cavity while maintaining the quality of the casting.

[0005]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the structural feature of the invention according to claim 1 is that the holding furnace is sealed and the holding furnace is connected by a hot water supply sleeve. Using a casting apparatus equipped with a mold and a decompression means for decompressing the holding furnace and the cavity of the mold, depressurizing the holding furnace and the cavity to degas the molten metal contained in the holding furnace, and then The purpose is to introduce gas into the holding furnace to increase the pressure, and to fill the molten metal into the cavity by the pressure difference with the inside of the cavity.

According to the invention according to claim 1 as described above, the inside of the holding furnace and the cavity of the mold are sufficiently depressurized, so that the degassing of the molten metal is effectively performed.
The quality of castings can be improved. In addition, by sufficiently depressurizing the holding furnace and the cavity, and then introducing gas into the holding furnace, a large pressure difference between the holding furnace and the cavity can be obtained, and the filling rate of the molten metal into the cavity can be increased. Can be increased and casting time can be shortened. Further, the filling rate of the molten metal can be adjusted by adjusting the degree of introduction of gas into the holding furnace. That is, the speed can be adjusted in the range from low pressure low speed casting to high speed die casting.

Further, when the molten metal is filled, the cavity is sufficiently depressurized and the molten metal can be filled in a laminar flow, so that there is no risk of entrainment of air and the casting quality can be improved. Further, since the pressure difference between the holding furnace and the cavity can be increased, the casting weight is not limited and a large amount of casting can be performed. Further, the structural feature of the invention according to claim 2 is that, in the vacuum casting method according to claim 1, after the molten metal is filled in the cavity, gas is further introduced into the holding furnace to increase the pressure. , To raise the water.

As a result, the effect of the hot water is further enhanced,
It is possible to obtain a dense and high quality casting.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view showing a schematic structure of a vacuum casting apparatus according to one embodiment.
The reduced pressure casting apparatus is provided with a crucible 10 which is a holding container for containing the molten metal. The crucible 10 is made of graphite, ceramics, or the like, is a cylindrical container having an open upper end, and has a flange portion 11 extending outward at the upper end. A suction pipe 12 for pressure reduction is provided at a position near the upper end of the crucible 10 and penetrates the crucible wall surface at one end. A suction valve 13 is interposed in the suction pipe, and the other end of the suction pipe 12 is connected to a vacuum pump (not shown).
The leak pipe 1 is provided near the suction pipe 12.
4 is provided at one end through the wall surface of the crucible.
A leak valve 15 is interposed in the leak pipe 14. The other end of the leak pipe 14 is connected to a high-pressure supply source (not shown) of an inert gas such as nitrogen gas or argon gas. The crucible 10 is pressed against the die plate 20 while containing the molten metal M of metal such as aluminum. An O-ring 11 a is interposed in the brim portion 11 of the crucible 10, and the crucible 10 and the die plate 2
0 is a close contact state, and the inside of the crucible 10 is shielded from the outside air. Actually, the crucible 10 is supported by a furnace body (not shown), and the furnace body is hydraulically operated (not shown).
It is adapted to be pressed against the die plate 20 by being pushed up by.

A through hole 21 is provided in the die plate 20, and an elongated cylindrical molten metal sleeve 22 is attached to the through hole 21 downward. A die 30 is mounted on the die plate 20. The mold 30 is the upper mold 31
And a lower mold 32, and a cavity 33 is provided inside the upper mold 31 and the lower mold 32. Below the cavity 33, a push gate 34, which is a cylindrical space connected to the melt sleeve 22, is provided. An O-ring 35a is provided on the mating surfaces of the upper die 31 and the lower die 32, and an O-ring 35b is provided between the lower die 32 and the die plate 20. Thereby, the cavity 33 and the sprue gate 3
4 is cut off from the outside. The upper mold 31 is provided with a suction pipe 36 for depressurization that penetrates through the mold from above and is connected to the cavity 33, and a suction valve 37 is interposed in the suction pipe 36. Further, the upper mold 31 has a cavity 33 of the suction pipe 36 that penetrates the mold from the side.
A through hole 38 reaching a communication position with the rod-shaped cavity independent valve 39 is inserted into the through hole 38. By moving the cavity independent valve 39, the suction pipe 36 can be opened or closed.

Next, the operation of the embodiment configured as described above will be described. First, the crucible 10 containing the molten metal M is pressed against the die plate 20 by a hydraulic device (not shown). Then, the lower mold 32 of the mold 30 is placed on the die plate 20 with the press gate 34 aligned with the molten metal sleeve 22, and the upper mold 31 and the lower mold 32 are matched. Next, the leak valve 15 is closed, the suction valves 13 and 37 are opened, and then the space portion of the crucible 10 and the mold 3 are passed through the suction pipes 12 and 36 by a vacuum pump.
Simultaneously sucking in the cavity 33 of 0, 1 to 10 Tor
Depressurize to r range. As a result, the degassing of the molten metal M contained in the crucible 10 is effectively promoted, and the molten metal M is brought into a good state containing no bubbles.

Next, the suction valves 13 and 37 are closed to end the depressurizing operation, and as shown in FIG. 2, the cavity independent valve 39 is pushed in to close the suction pipe 36. As a result, the inside of the cavity 33 is blocked from the suction pipe 36, and the molten metal M is prevented from flowing into the suction pipe 36. Further, the leak valve 15 is opened to adjust the gas leak amount, and the gas is introduced into the space of the crucible 10 through the leak pipe 14 to release the low pressure state in the space. As a result, a large pressure difference is generated between the space of the cavity 33 in the low pressure state and the crucible 10 in which the low pressure state is released, and the molten metal containing no bubbles in the crucible 10 is supplied to the cavity 33 through the molten metal sleeve 22 and the sprue port 34. Then, as shown in FIG. 3, the inside of the cavity 33 is filled with the molten metal. At this time, the amount of gas leak is gradually increased, so that the flow of the molten metal M is a smooth laminar flow.

As described above, since a large pressure difference can be secured between the crucible 10 and the cavity 33,
It is possible to increase the filling speed of the molten metal into the cavity and shorten the casting time. In addition, the pouring speed of the molten metal can be adjusted by adjusting the amount of gas leaked into the crucible 10. That is, low pressure low speed casting (0.0
1m / sec) to high speed die casting (5m / se)
The speed can be adjusted within the range of (c). Furthermore, when the molten metal is filled, the inside of the cavity 33 is sufficiently decompressed,
Moreover, since the molten metal M is laminarly filled, there is no risk of air being entrained in the molten metal M, and the casting quality can be improved.
Further, since the pressure difference between the crucible 10 and the cavity 33 can be increased, the casting weight is not limited and a large amount of casting can be performed.

Next, after the cavity 33 is filled with the molten metal M, the amount of gas leaked into the crucible 10 is adjusted,
The pressure in the crucible 10 is made higher than that at the time of filling the molten metal so that the molten metal M
The molten metal M is solidified while increasing the pressure applied to. As a result, the effect of pushing the molten metal in the cavity 33 is increased, and a dense, high-quality casting can be obtained. Further, since the molten metal M is filled after the molten metal M is filled in the cavity 33, it is not necessary to make the pressurizing force excessive, so that the dissolution of hydrogen gas in the molten metal can be suppressed.

After the molten metal is solidified, the inside of the crucible 10 is returned to the atmospheric pressure, the mold 30 is split, and the product is taken out, thereby completing the casting manufacturing process. The shape, material, and the like of each part of the vacuum casting apparatus are not limited to those shown in the above embodiment, and can be changed as appropriate.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a vacuum casting apparatus used in an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which the inside of the crucible space and the inside of the cavity of the vacuum casting apparatus are in a low pressure state, and the suction pipe is closed by a cavity independent valve.

FIG. 3 is a vertical cross-sectional view showing a state where the inside of the cavity of the vacuum casting apparatus is filled with molten metal.

[Explanation of symbols]

10 ... crucible, 11 ... collar part, 11a ... O-ring, 12
... suction pipe, 13 ... suction valve, 14 ... leak pipe, 15 ... leak valve, 20 ... die plate, 22 ...
Molten metal sleeve, 30 ... Mold, 31 ... Upper mold, 32 ... Lower mold,
33 ... Cavity, 34 ... Faucet, 35a, 35b ...
O-ring output terminal, 36 ... suction pipe, 37 ... suction valve, 38 ... through hole, 39 ... cavity independent valve, M ...
Molten metal.

Claims (2)

[Claims] 1. A casting apparatus provided with a closed holding furnace, a mold connected to the holding furnace with a hot water supply sleeve, and a pressure reducing means for reducing the pressure in the holding furnace and the cavity of the mold, Reduced pressure in the holding furnace and the cavity, then introducing gas into the holding furnace to increase the pressure, and filling the molten metal into the cavity by the pressure difference between the holding furnace and the cavity. Law. 2. The reduced pressure casting method according to claim 1, wherein after the molten metal is filled in the cavity, gas is further introduced into the holding furnace to increase the pressure to raise the molten metal.