JP3104293B2 - Metal casting method and casting apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for casting a metal used for obtaining a casting such as a refractory metal or an active metal.

[0002]

2. Description of the Related Art A refractory metal or an active metal composed of a simple substance or an alloy such as Ti, W, Mo, Zr, and Li includes:
Since it has a high melting point and is active, it easily forms an oxide film on the surface of the molten metal, and when the molten metal is disturbed at the time of casting, gas is easily entrained.

In order to prevent such disturbance of the molten metal, it is necessary to put the molten metal in a rectifying state and to inject it into the casting space of the mold.

The present inventors have developed a method of sucking the inside of a mold in order to inject the molten metal into the mold in a rectified state, and have greatly improved the effect (see, for example, Japanese Patent Application No. 2-2).
12104, Japanese Patent Application No. 2-146743, Japanese Patent Application No. 2-
124383).

[0005]

However, in the above-described casting method in which the inside of the mold is sucked, there is a risk that the inert gas in the melting chamber may be entrained, so that a large difference in gas pressure cannot be obtained. Therefore, there is a problem that it is not possible to say that there is no possibility of causing a run-out failure, and it has been a problem to solve such a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and does not involve an inert gas in a melting chamber in a crucible at the time of casting, thereby preventing the occurrence of gas defects and imperfect runoff. It is an object of the present invention to provide a metal casting method and a casting apparatus capable of obtaining a high quality casting.

[0007]

According to the present invention, there is provided a method for casting a metal, wherein a metal base material in a water-cooled copper crucible in which the inside is hermetically sealed and the atmosphere at the time of melting is evacuated is vacuum-melted by induction heating. Then, into a casting space of a mold in which a runner is communicated with the molten metal, the molten metal is pushed up through the runner by gas pressurization to the molten metal, and is cast in the casting space. In the embodiment, the atmosphere during melting is vacuum in both the water-cooled copper crucible and the casting space, and an inert gas is introduced into the water-cooled copper crucible during casting to melt by differential pressure. It is characterized in that metal is pushed up and cast in a casting space.

[0008] The metal casting apparatus according to the present invention comprises:
A water-cooled copper crucible in which the atmosphere during melting can be vacuum-sealed by sealing the inside, an induction heating means for vacuum melting the metal base material in the water-cooled copper crucible, a mold having a runner and a casting space, Means for raising and lowering a mold and / or a water-cooled copper crucible for communicating the runner into the molten metal; and melting the molten metal via the runner by gas-pressing the molten metal while the runner is communicated with the molten metal. It is characterized by having a configuration provided with a gas pressure supply means for pushing up the metal into the casting space, and in the embodiment, the mold is made of a permeable ceramic, or the mold is made of a permeable metal. Or the runner is made of a ceramic having no air permeability, and is related to the metal casting method and casting apparatus described above. And a means for solving the conventional problems described above with a light structure.

[0009]

In the method and apparatus for casting metal according to the present invention, the molten metal melted under vacuum in the water-cooled copper crucible is subjected to the gas pressurization of the molten metal so that the molten metal is run. The gas is pushed up into the casting space of the mold in a rectified state through the, and there is no possibility that the inert gas in the melting chamber is entrained, so that gas defects do not occur and a large differential pressure of the gas can be obtained. As a result, no run-off failure occurs, and the cast product is excellent in both internal quality and shape accuracy.

[0010]

1 to 3 show an embodiment of the present invention.

As shown in FIGS. 1 and 2, a metal casting apparatus 1 according to one embodiment of the present invention has a seal pipe 2 on a lower side thereof, and a heat insulating material 3 on a bottom side of the seal pipe 2. A water-cooled copper crucible 4 is provided above the heat insulating material 3 and inside and at the upper end of the seal pipe 2.

As shown in FIG. 2, the water-cooled copper crucible 4 is composed of a plurality of water-cooled copper segments 4 arranged in an annular shape while being insulated from each other by insulators 5a,.
, 4h, each segment 4a,.
, 4h are provided with water cooling pipes 6a,..., 6h so that water can be cooled by flowing cooling water in the directions of arrows A ₁ and A _{2 in} FIG.
It has a structure as follows.

On the bottom side of the water-cooled copper crucible 4,
A conductive refractory material (graphite) 8 and a non-magnetic refractory material (BN) 9 that generate heat during induction heating are provided, and the inside of the melting chamber 10 is airtightly sealed and shut off from the outside. ing.

Further, on the outer peripheral side of the seal pipe 2, an induction heating coil 11 as an induction heating means is provided.

On the other hand, a casting chamber casing 12 is provided on the upper side of the magnetic shield portion 7 and has a glass window 13 for observation, and an annular flange 14 is provided on the outer peripheral side of the upper end. An upper plate 16 is provided on the annular flange 14 via a seal ring 15, and an elevating rod 18 is provided on the upper plate 16 via a seal ring 17 so as to be able to move up and down.

The elevating rod 18 has a large diameter portion 18a in the casting chamber casing 12 and a large diameter portion 18a.
a ventilation hole 18b on the lower side of
8 has an opening 18c connected to the decompression means 19 on the upper side.

A casting chamber 21 is fixed to the large diameter portion 18a of the elevating rod 18, and a casting mold 24 having a runner 23 formed by a graphite pipe 22 is installed inside the casting chamber 21. I have.

The mold 24 is made up of a heat-permeable fiber 24b and a lower refractory 24c, which are the same as the gas-permeable inner refractory 24a forming the casting space 25, and has a tapered hole formed in the casting chamber 21. 21a.

Further, a gas pressure supply pipe 28 connected to gas pressure supply means 27 is provided on the wall of the casting chamber casing 12.

When a hot wheel for a turbocharger is manufactured by using such a metal casting apparatus 1, a Ti-Al-based alloy is used as a melting base material 31.

Then, after 400 g of the melting base material 31 is charged into the melting chamber 10, the interior of the casting space 25 and the interior of the melting chamber 10 are evacuated (10 Torr or less) by the pressure reducing means 19, and By applying a current, the melting base material 31 was induction-melted under vacuum.

At this time, at the time of melting, so-called cold crucible levitating melting using a water-cooled copper crucible 4 in which water-cooled copper segments 4a,..., 4h are divided by insulators 5a,. As a result, an eddy current is formed inside the water-cooled copper crucible 4 by the high-frequency induction heating by the induction heating coil 11, and the eddy current induces and melts a skin eddy current in the melting base material 31, thereby melting the molten metal 32. (See FIG. 3).

The molten metal 32 is slightly separated from the inner surface of the water-cooled copper crucible 4 by a repulsive force of currents having phases opposite to each other on the surfaces of the water-cooled copper crucible 4 and the molten metal 32 to form a gap. .

Therefore, the heat transfer from the molten metal 32 to the water-cooled copper crucible 4 is suppressed by the formation of the gap, so that the molten metal 32 has a high temperature and a good running property.

After dissolving the base material 31 shown in FIG.
As shown in FIG. 3, the lifting rod 18 is lowered, and the graphite pipe 22 is immersed in the molten metal 32 to allow the runner 23 to communicate with the molten metal 32.

Next, Ar gas, which is an inert gas, is supplied from the gas pressure supply means 27 through the gas pressure supply pipe 28,
By applying a gas pressure to the surface of the molten metal 32, the molten metal 32 was pushed up in the runner 23 by the differential pressure, and the molten metal 32 was pushed into the casting space 25 of the mold 24.
The differential pressure at this time was adjusted to 500 Torr.

After removing the mold 24, the mold was separated and the cast product was taken out. The occurrence of gas defects and poor run-off was examined. As a result, a turbocharger hot wheel belonging to the most complicated cast product was used. The non-defective rate of the cast product was improved to 90% or more.

[0028]

According to the method and apparatus for casting metal according to the present invention, since it has the above-described structure,
The molten metal vacuum-melted in the water-cooled copper crucible is pushed up into the casting space of the mold in a rectified state through the runner by gas pressurization of the molten metal, and the inert gas in the melting chamber is melted. Since it does not get caught in the inside, it is difficult for gas defects to occur, and since it is possible to take a large differential pressure, there is no run-off failure, and the internal quality and shape accuracy are excellent. This has the significant advantage of being able to produce castings.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view of a metal casting apparatus according to an embodiment of the present invention when a metal base material is melted.

FIG. 2 is an explanatory horizontal sectional view of the water-cooled copper crucible of FIG.

FIG. 3 is an explanatory vertical sectional view of the metal casting apparatus shown in FIG. 1 during casting of molten metal.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal casting apparatus 4 water-cooled copper crucible 10 melting chamber 11 induction heating coil (induction heating means) 18 elevating rod (elevating means) 19 decompression means 23 runner 24 mold 25 casting space 27 gas pressure supply means 31 metal base material 32 melting metal

Claims (7)

(57) [Claims] 1. A casting space for a mold in which a metal base material in a water-cooled copper crucible in which the inside is airtightly sealed and the atmosphere during melting is vacuum is melted by induction heating under vacuum, and then a molten metal is connected to a runner. A casting method for casting the molten metal in the casting space by pushing up the molten metal through the runner by pressurizing the molten metal with gas. 2. The metal casting method according to claim 1, wherein the atmosphere during melting is vacuum in both the water-cooled copper crucible and the casting space. 3. The metal casting method according to claim 1, wherein an inert gas is introduced into the water-cooled copper crucible during casting, and the molten metal is pushed up by a differential pressure to perform casting in the casting space. 4. A water-cooled copper crucible whose interior is airtightly sealed so that the atmosphere during melting can be evacuated, an induction heating means for vacuum-melting a metal base material in the water-cooled copper crucible, a runner and a casting space. Mold, and a mold and / or a water-cooled copper crucible elevating means for allowing the runner to communicate with the molten metal,
A gas pressure supplying means for pressurizing the molten metal into the casting space through the runner by gas-pressing the molten metal in a state where the runner is communicated with the molten metal. Casting equipment. 5. The metal casting apparatus according to claim 4, wherein the mold is made of a ceramic having air permeability. 6. The metal casting apparatus according to claim 4, wherein the mold is made of a metal having air permeability. 7. The metal casting apparatus according to claim 4, wherein the runner is made of a ceramic having no air permeability.