JPH0523823A - Stoke for differential pressure casting - Google Patents

Abstract

PURPOSE:To provide a stoke for differential pressure casting, which is suitable to separating method of a product and molten metal by supplying inert gas and is easily restored at the time of developing accident. CONSTITUTION:In the stoke 10 for differential pressure casting, having an inner cylinder 11 connecting the upper end with a sprue in a metallic mold and holding the lower end higher than the surface 8 of the molten metal 7 in a holding furnace and an outer cylinder 12 closing the upper end at between this cylinder and outer face of the inner cylinder 11 and submerging the lower end into the molten metal 7 and arranging a hole 14 for communicating annular range formed between the inner and outer cylinders 11, 12 with the outer part, the inner cylinder 11 is made as possible to be inserted into/removed from upper part and outer diameter 11a of the inner cylinder 11 is gradually reduced downward. As the other way, the inner cylinder 11 is made as possible to be inserted into/removed from upper part and formed with material having coefficient of thermal expansion larger than that of the outer cylinder 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure casting stalk, and more particularly to a stalk suitable for a method for separating a molten metal from a product by supplying an inert gas, and which can be easily restored in the event of an accident.

[0002]

2. Description of the Related Art When casting a product from a material such as aluminum which is easily oxidized by a low pressure casting method,
It is necessary to prevent the oxidation of the molten aluminum in the stalk or to remove the aluminum oxide in the stalk. Conventionally, low pressure casting of aluminum has generally been performed by placing a filter on the lower sprue to remove oxides of aluminum. In this method, the filter is replaced after each casting. The need arises,
Further, since the filter is attached to the scrap material cut off from the sprue part of the product, there is a problem that the scrap material cannot be effectively used.

Therefore, in place of the method of removing the oxide of aluminum, the development of a method of preventing the oxidation of the molten aluminum itself is under way, for example, Japanese Patent Laid-Open No. 1-1044.
No. 57 discloses an inner cylinder whose upper end is connected to the gate of a mold and whose lower end is kept higher than the molten metal level in a holding furnace, and whose upper end is hermetically sealed between the outer surface of the inner cylinder and said lower end. A differential pressure casting stalk having an outer cylinder immersed in the molten metal and having a hole communicating between the annular region formed between the inner and outer cylinders and the outside,
A method is disclosed in which an inert gas heavier than air is supplied through the holes to replace the air on the surface of the molten metal with the inert gas, and then the molten metal is introduced into the cavity by differential pressure.

[0004]

However, for example, in the case where the inner and outer cylinders of the stalk are constructed as one body,
If the molten metal in the annular area rises and the molten metal should flow into the holes and solidify, the entire stalk must be put in a furnace to heat it, and it takes a lot of time to restore it. . Therefore, it is an object of the present invention to provide a differential pressure casting stalk that is suitable for a method of separating a product and a molten metal by supplying an inert gas and that can be easily restored in the event of an accident.

[0005]

SUMMARY OF THE INVENTION According to the present invention, the inner cylinder can be inserted and removed from the upper side to gradually reduce the outer diameter of the inner cylinder, or the inner cylinder can be inserted and removed from the upper side to form the outer cylinder. By forming the material with a larger coefficient of thermal expansion than
The above object is achieved.

[0006]

Even if the molten metal near the hole is solidified, the inner cylinder can be easily pulled out upward if the outer diameter of the inner cylinder is gradually reduced downward, and the inner cylinder can be easily pulled out. When the inner cylinder is made of a material having a larger coefficient of thermal expansion than that of the outer cylinder, the inner cylinder has a smaller diameter than the outer cylinder due to cooling, and thus the inner cylinder can be easily pulled upward.

[0007]

The present invention will be described with reference to the drawings. FIG. 1 shows an example of a low-pressure casting machine to which a differential pressure casting stalk according to the present invention is applied, in which a cavity 1 adapted to the shape of a product to be cast is formed by a mold 2 composed of an upper mold 3 and a lower mold 4. The lower mold 4 has a sprue 5 communicating with the cavity 1.
Is open. The stalk 10 has an inner cylinder 11 and an outer cylinder 12 both formed of sialon, the upper end of the inner cylinder 11 is connected to the gate 5 of the mold, and the lower end is the molten metal surface 8 of the molten metal 7 in the holding furnace 6. Is kept higher than. Further, as shown in FIG. 2, the inner cylinder 11 is attached to the outer cylinder 12 so that it can be inserted and removed from above, and the outer surface of the inner cylinder 11 is formed as a tapered surface 11a having a diameter reduced downward. The upper end of the outer cylinder 12 is sealed between the outer surface of the inner cylinder 11 and the lower end of the molten metal 7
And an annular region 13 opened downward is formed between the inner and outer cylinders 11 and 12. The outer cylinder 12 is formed with a hole 14 that communicates the upper portion of the annular region 13 with the outer surface of the outer cylinder, and an argon gas cylinder 20 is connected to the hole 14 via a valve 21.

To cast a product using this low pressure casting machine, first, the valve 21 is opened and the air in the stalk 10 is replaced with argon gas through the hole 14. Until the air in the stalk 10 was replaced with argon gas, the molten metal surface 8 was exposed to air, so the molten metal 7 near the molten metal surface 8 was oxidized. When the valve 21 is closed and the pressure in the holding furnace 6 is increased after the air in the stalk 10 is replaced with argon gas, the molten metal surface 8 rises and comes into contact with the lower end of the inner cylinder 11, and thereafter the molten metal 7 is divided into two parts. As shown in FIG. 3, one enters the cavity 1 while excluding the argon gas, and the other enters the annular region 13 while compressing the argon gas 22. The volume of the space from the valve 21 to the lower end of the annular region 13 is determined so that the molten metal surface 8 in the annular region 13 does not rise higher than the opening on the inner surface side of the hole 14, and thus the hole 14 and the hole 14 are connected thereto. The piping and the molten metal 7 are protected. After a certain period of time has passed after the molten metal 7 has been filled in the cavity 1, the molten metal 7 solidifies and becomes a product, but since the oxidized metal was supplied first, the first product becomes a defective product.

After the solidification of the first product, the valve 21 is opened to supply the argon gas 22 into the annular region 13, and the argon gas 22 gradually pushes down the molten metal surface 8 in the annular region 13 as shown in FIG. Finally, it moves from the annular region 13 into the inner cylinder 11 and rises in the molten metal in the inner cylinder 11,
And the surface 8 of the molten metal are collected to separate them. That is, the unsolidified molten metal 7 forms a free surface by being separated from the product 9 by the argon gas 22 after being in contact with the product 9 which has been the molten metal until then, so that the molten metal surface 8 is always formed when the molten metal surface 8 is formed. The molten metal surface 8 will be covered with the argon gas 22. After the product 9 and the molten metal surface 8 are separated by the argon gas 22 and the pressure in the holding furnace 6 is released, the upper mold 3 is opened to discharge the first product, that is, the defective product, and the upper mold 3 is closed. . Then, the valve 21 is closed and the holding furnace 6 is pressurized to cast a second product. Molten metal for the second product 7
Since it was completely isolated from the air, only good products can be cast thereafter.

When the molten metal 7 enters the annular region 13 by the pressurization of the holding furnace 6 and the molten metal 7 enters the annular region 13, if the valve 21 leaks, the argon gas in the annular region 13 If the compression of 22 is not performed, the molten metal 7 may reach the hole 14 and solidify in the vicinity of the hole 14. At this time, even if the pressurization of the holding furnace 6 is released, since the holes 14 are closed by the solidified molten metal 7a, the molten metal 7 that has risen to the height of the holes 14 cannot be dropped. As shown in FIG. 3, there is a risk that the entire area except the upper part of the annular region 13 may be filled with the solidified molten metal 7a.

However, in the stalk 10 of this embodiment, as described above, the inner cylinder 11 is attached so that it can be inserted and removed from above, and the outer surface of the inner cylinder 11 is formed as a tapered surface 11a having a diameter reduced downward. Therefore, even if the molten metal in the annular region 13 is solidified, the inner cylinder 11 can be easily pulled out upward, and thereafter the solidified molten metal 7a can be melted by, for example, a burner or the like.

In this embodiment, both the inner and outer cylinders 11 and 12 are made of sialon, and the outer diameter of the inner cylinder 11 is gradually reduced. However, as another embodiment, the coefficient of thermal expansion is smaller than that of the outer cylinder 12. The inner cylinder 11 can also be formed of a large material. That is, for example, a sialon can be used as the outer cylinder 12, and the inner surface of JIS-SKD61 hot die steel can be thermally sprayed with ceramics as the inner cylinder 11, and at this time, the inner cylinder 11 is better than the outer cylinder 12 due to cooling. Since the diameter of the inner cylinder 11 is also reduced, the inner cylinder 11 can be easily pulled out upward.

[0013]

EFFECTS OF THE INVENTION The inner cylinder according to the present invention can be easily pulled upward even if the melt in the annular region between the inner and outer cylinders is solidified. Therefore, the product and the melt can be separated by supplying the inert gas. A stalk for differential pressure casting that is suitable for the separation method and is easy to recover in the event of an accident.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an example of a low-pressure casting machine to which the present invention is applied.

FIG. 2 is a vertical sectional view showing an embodiment of the present invention.

FIG. 3 is a diagram corresponding to FIG. 1 when the holding furnace is pressurized.

FIG. 4 is a diagram corresponding to FIG. 1 when a product and a molten metal are separated by supplying argon gas.

[Explanation of symbols]

1 ... Cavity 2 ... Mold 3 ... Upper mold 4
... Lower mold 5 ... Gate 6 ... Holding furnace 7 ... Molten metal 7a ... Solidified melt 8 ... Molten surface 9 ... Product 10 ... Stoke 11 ... Inner cylinder 1
1a ... Tapered surface 12 ... Outer cylinder 13 ... Annular region 14 ... Hole 20 ... Argon gas cylinder 21 ... Valve 2
2 ... Argon gas

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshinori Yashiro             1-9-1 Kitahama, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture               Hitachi Metals Co., Ltd. Wakamatsu Factory

Claims (2)

[Claims] 1. An inner cylinder having an upper end connected to a sprue of a mold and a lower end kept higher than a molten metal level in a holding furnace, and an upper end sealed between an outer surface of the inner cylinder and a lower end of the molten metal. In a differential pressure casting stalk having an outer cylinder dipped in, and a hole communicating between the annular region formed between the inner and outer cylinders and the outside, the inner cylinder can be inserted and removed from above, A differential pressure casting stalk characterized in that the outer diameter of the cylinder is gradually reduced downward. 2. An inner cylinder having an upper end connected to a sprue of a mold and a lower end kept higher than a molten metal surface in a holding furnace, and an upper end sealed between an outer surface of the inner cylinder and a lower end of the molten metal. In a differential pressure casting stalk having an outer cylinder dipped in, and a hole communicating between the annular region formed between the inner and outer cylinders and the outside, the inner cylinder can be inserted and removed from above, A differential pressure casting stalk characterized in that the inner cylinder is formed of a material having a coefficient of thermal expansion larger than that of the cylinder.