JPH0716724A - Precision casting method and casting device therefor - Google Patents

Abstract

PURPOSE:To produce an improved precision cast product without needing inter ruption of melting and casting by forming a tapered part enlarged upward from the halfway of the inner wall of a crucible, allowing molten metal to flow down, and solidifying the molten metal by bringing the molten metal into contact with the surface of the tapered part. CONSTITUTION:A base metal 2 is melted by a levitation melting method using a cold crucible 1. The molten metal 7 is sucked and poured into a ceramic shell mold to execute the precision casting. Then, by using the crucible 1 having no bottom, the base metal 2 to be melted is supplied in the form of a bar material having the cross section of a shape corresponding to the inside cross section of the crucible 1 while pushing up the crucible 1 from the lower part. In this case the tapered part 3 enlarged upward from the halfway is formed on the inner wall of the crucible 1. Then the melted metal 7 flows down, and comes into contact with the tapered surface 3 and solidified, by which, while always held in the state of being restrained with the crucible 1, the bar material of the base metal 2 is subjected to precision casting. By this method, this method can easily cope with the production of many kinds in small quantities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method and a casting apparatus in which a technique for supplying a molten material is improved in precision casting of metal.

[0002]

2. Description of the Related Art Precision casting of a metal having a high melting point and high activity, such as a titanium alloy, uses a cold crucible induction melting crucible to minimize the contamination of the molten metal by the melting crucible. It is preferable to use levitation melting, in which is present away from the crucible wall due to the electromagnet.

On the other hand, it has been widely practiced to manufacture a precision casting mold by assembling a plurality of wax models in a tree shape, forming a ceramic shell on the wax model, and then performing dewaxing. This is efficient in that a large number of castings can be obtained all at once, but the work of separating the individual castings from the tree is laborious. In order to improve this point, one or a small number of castings may be continuously manufactured.

Therefore, the inventor has developed a technique for producing a clean molten metal by performing levitation melting using the cold crucible type crucible, and pouring the molten metal into a mold having one or a few casting cavities by suction. However, it has already been proposed (JP-A-3-47170). In this technique, a cold crucible type crucible having no bottom is used, and a base metal in the form of a rod having a cross-sectional shape corresponding to the inner cross section of the crucible is pushed up from below the crucible and supplied. The upper end of this rod is melted in the crucible and supported by the unmelted rod, so the molten metal thus obtained is sucked and cast. As the molten metal is consumed, the rod is pushed up and further melted, so that the molten metal is replenished.

In this way, one or a few precision castings can be carried out continuously within certain limits.
Needless to say, what defines this limit is the length of the base metal rod to be melted, and when one bar is completely melted,
Melting and casting must be stopped once. If you prepare a rod material that is as long as possible, you can continue casting many times accordingly, but there is a limit on your own, and even if you try to connect two or more pieces by welding etc. Becomes taller, which is also impractical.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to overcome this problem and to improve the remelting of the base metal bar without the need for interrupting the melting and casting. It is to provide a method and an apparatus for precision casting.

[0007]

The precision casting method of the present invention is a precision casting method in which a metal is melted by a levitation melting method using a cold crucible type crucible, and the molten metal is sucked and poured into a ceramic shell mold. Yes, Figure 1
As shown in Fig. 5, a bottomless crucible (1) is used, and the base metal to be melted is pushed up from below the crucible and supplied in the form of a bar (2) having a cross-sectional shape corresponding to the inner cross section of the crucible. In the method, as shown in detail in FIG. 2, the inner wall of the crucible is provided with a tapered surface (3) that expands upward from the middle, and the melted metal (7) flows down and touches the tapered surface to solidify. The base metal bar (2) is always held while being held in the crucible.

The precision casting apparatus of the present invention for carrying out this method is a ceramic mold having a cold crucible type crucible (1) and a snout (5) for sucking up the molten metal.
A precision casting apparatus essentially comprising (4) and a vacuum suction means (not shown), wherein the crucible has no bottom and has a cross-sectional shape corresponding to the inner cross section of the crucible (2). In a casting apparatus comprising a supply means (6) for supporting and pushing up the base metal from below the crucible, a taper (3) that expands upward from the middle is provided inside the crucible, and the molten metal ( It is characterized in that the bar material (2) of the base metal is always locked in the crucible by flowing down 7) and coming into contact with the taper surface to solidify and become solidified metal (8).

[0009]

When the levitation melting is performed in the cold crucible type crucible, the melted metal (7) forms a column with a round head as shown in FIG. The mold (4) is lowered and the snout (5) is put in the position shown by the broken line, and the molten metal (7) is sucked and poured into the mold. After pulling up the mold, when the rod material (2) of the base metal is pushed up according to the amount of the molten metal sucked and consumed, a part of the molten metal sways and flows down along the surface of the column. As shown in FIG. 2, the molten metal that has flowed down is cooled near the taper start point of the inner wall of the crucible, that is, near the point where the inner diameter expands and begins to be cooled, where it solidifies at least partially with the unmelted base metal.

For this reason, the base metal bar has a wedge-shaped cross-section that extends on the circumference in the vicinity of the boundary with the molten metal, whereby it is locked in the crucible and is not supported from below. Do not fall. If the remaining bar becomes shorter, a new one may be added, and during that time, the bar supporting means may be separated from the bottom of the bar being melted, so it is not necessary to stop the melting and casting. Absent. The device can be configured so that the replenishment of the base metal rod is performed automatically.

If the fusion of the solidified portion having a wedge-shaped cross section that goes around the surface of the base metal with the base metal is incomplete, it may not be possible to support the weight. Depending on the weight of the metal rod and the like, it may be preferable to use a means for clamping the rod for safety. The clamp means is optional, but a push pin as shown in the drawing may be convenient.

[0012]

According to the precision casting technique of the present invention, it is possible to obtain a desired cast product without interrupting the melting and casting operations even when refilling a new base metal rod. Work can continue as long as needed. Successive casting with one or a few mold cavities can be advantageously carried out without forming a large tree-shaped mold.

Therefore, the present invention can easily cope with high-mix low-volume production, which tends to occur in precision casting products, and can supply low-cost casting products.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main part of an apparatus in use for explaining the principle of a precision casting method of the present invention.

FIG. 2 is a detailed view of a portion A of FIG.

[Explanation of symbols]

 1 Cold crucible type crucible 2 Base metal rod 3 Crucible inner wall taper surface 4 Ceramic mold 5 Snout 6 Supply means 7 Molten metal (molten metal) 8 Solidified metal

Claims (3)

[Claims] 1. A precision casting method in which a metal is melted by a levitation melting method using a cold crucible type crucible, and the molten metal is sucked and poured into a ceramic shell mold. In the casting method in which the base metal to be pushed up is supplied from below the crucible in the form of a rod having a cross-sectional shape corresponding to the inner cross-section of the crucible,
A taper that expands upward from the middle is provided on the inner wall of the crucible, and the molten metal flows down and touches the tapered surface and solidifies, so that the rod of the base metal is always locked in the crucible. A precision casting method characterized by carrying out. 2. A precision casting apparatus essentially comprising a cold crucible type crucible, a ceramic mold provided with a snout for sucking molten metal, and a vacuum suction means,
The crucible has no bottom, and in a casting apparatus comprising a feed means for supporting and pushing up the base metal in the shape of a rod having a cross-sectional shape corresponding to the inner cross-section of the crucible from below the crucible,
Inside the crucible, there is a tapered surface that expands upward from the middle, so that the molten metal flows down and touches the tapered surface to solidify, so that the base metal bar is always locked in the crucible. A casting apparatus having the above-mentioned structure. 3. The casting apparatus according to claim 2, further comprising a clamp means below the crucible for temporarily supporting the bar material of the base metal.