JPH0931558A - Vacuum arc remelting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the production of a consumable electrode for secondary melting without executing machining and welding of a stub, to improve the efficiency and to reduce a cost, in the production of a metallic ingot by executing a vacuum arc remelting(VAR), what is called, a double VAR method. SOLUTION: The stub 5 is descended during existence of molten metal pool 8 on an ingot 7 in a water cooling mold 2, just after completing a primary melting, and the lower end thereof is pushed into the molten metal pool and the molten metal pool is solidified as it is to weld the stub 5 and the ingot 7, and the consumable electrode for secondary melting is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to vacuum arc melting (VA).
R) again, the so-called "double VAR" process for the production of metal or alloy ingots. The present invention has great significance when applied to the melting of pure titanium or a titanium alloy (hereinafter represented by the term "titanium").

[0002]

2. Description of the Prior Art The double VAR method is often carried out as a method for producing a metal containing few impurities or a homogeneous alloy,
In particular, it is a standard method for manufacturing titanium ingots. In the titanium double VAR, briquettes obtained by press-molding a raw material mainly composed of titanium sponge are welded in plural to form a cylindrical base material, and a stub is welded at one end to form a consumable electrode. As shown in FIG. 1, primary VAR is performed, and the resulting primary ingot is used as a consumable electrode by connecting a stub to secondary VAR as shown in FIG. In FIG. 1, reference numerals
(1) is a vacuum chamber, (2) is a water-cooled mold, (3) is an arc power source, (4) is a base material, (5) is a stub, (6) is a stinger rod, (7) is an ingot, ( 8) is a molten metal pool.

As a consumable electrode used in this secondary VAR, a base material and a stub welded as shown in FIG. 2 have come to be used. This welding is performed by TIG welding or plasma arc welding. Welding must be performed without any defects, and when suspended in a VAR furnace, the weight of the base material causes partial peeling between the stub and the base material, which is inconvenient for passing a large current. However, if the core of the consumable electrode shifts, the end may approach the water-cooled mold, causing a side arc. Welding difficulties are particularly pronounced when the target of VAR is titanium. As is well known, titanium is a highly active metal, and skill is required to perform good welding.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems associated with the double VAR method and to realize the connection between the primary melting ingot and the stub without welding. It is to provide a method for advantageously performing.

[0005]

According to the vacuum arc remelting method of the present invention, a stub is connected to a metal base material to form a consumable electrode, which is vacuum arc melted and solidified in a water-cooled mold to form a primary ingot. In the vacuum remelting method, the primary melting is performed, and the consumable electrode is formed by connecting the stub to the primary ingot, and the secondary melting is performed again by vacuum arc melting and solidifying in the water-cooled mold to form the product ingot. Immediately after the completion and while the molten metal remains on the ingot, the stub is lowered and pushed into the molten metal pool, and the molten metal is solidified as it is to weld the stub and the ingot to connect the primary ingot and the stub. It is characterized by performing.

Since the stub will melt into the top of the product ingot in the secondary VAR, if it is desired to avoid fluctuations in the alloy composition or to prevent contamination, the stub is made of the same material as the material of the primary ingot. It is preferable that the above-mentioned connection is carried out by using the above-mentioned one.

[0007]

Operation The situation during the implementation of the VAR method is as shown in FIG. When all the base metal (4) is completely dissolved,
Since only the stub (5) remains as shown in FIG. 4, the power supply is stopped and the stinger rod (6) is removed as shown in FIG.
Push down to push the lower end of the stub (5) into the molten metal (8). The surface of the stub that is in contact with the molten metal melts, but the molten metal loses heat to the ingot and the stub and soon solidifies to form an ingot in which the stub is welded to the top.

The taken-out electrode is the consumable electrode shown in FIG. 6, which is used as it is for the second melting of VAR to obtain a product ingot.

The shape of the stub used in the present invention is preferably a shape in which a large-diameter cylinder and a small-diameter cylinder overlap each other as shown in FIG. The small diameter part should be chucked at the lower end of the Stinger rod to have a shape and dimensions that facilitate connection. The diameter of the large diameter part is made to be almost the same as the diameter of the consumable electrode for primary melting, and at the end of primary melting, it is pushed into the molten metal pool on the primary ingot and welded, and the obtained electrode is used as it is for secondary melting. Therefore, stubs are used through both primary and secondary lysis. The stub remaining after the completion of the secondary dissolution can be returned to the primary dissolution to the extent possible and can be used multiple times. Therefore, this stub can be used many times until it is recovered and reused as scrap.

[0010]

According to the method of the present invention, in the production of a metal ingot by the double VAR method, the production of the consumable electrode for the secondary melting does not require welding and can be realized in an instant, with a high yield (substantially). It becomes possible to obtain a product ingot by melting the base metal. As a result, VA
The R method can be carried out efficiently and at a reduced cost.

The vacuum arc remelting method of the present invention is particularly suitable as a double VAR method performed on titanium or a titanium alloy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a VAR furnace for explaining a vacuum arc remelting (VAR) method.

FIG. 2 is a partial cross-sectional view showing the configuration of a conventional consumable electrode used for secondary melting in the double VAR method.

FIG. 3 is a side view showing a shape of a stub used in the VAR method of the present invention, which is partially shown in a vertical cross section.

FIG. 4 is a diagram showing a stage in which melting of a base material is completed in a series of diagrams for explaining the VAR method of the present invention.

FIG. 5 is a view showing a state where a stub is pushed into a molten metal pool on an ingot out of a series of diagrams for explaining the VAR method of the present invention.

6 is manufactured by the process of FIGS. 4 and 5,
The figure which shows the consumable electrode for secondary melting.

[Explanation of symbols]

 1 Vacuum Chamber 2 Water Cooling Mold 3 Arc Power Supply 4 Base Material 5 Stub 6 Stinger Rod 7 Ingot 8 Molten Metal Pool 9 Consumable Electrode for Secondary Melting

Claims (3)

[Claims] 1. A stub is connected to a metal base material to form a consumable electrode, which is vacuum-arc melted and solidified in a water-cooled mold to be a primary ingot, and a stub is connected to the primary ingot and consumed. In the vacuum remelting method in which electrodes are formed, vacuum arc melting is performed again, and solidification is performed in a water-cooled mold to form a product ingot and secondary melting is performed immediately after the completion of the primary melting and while the molten metal remains on the ingot. The vacuum arc remelting method, characterized in that the stub is lowered and pushed into a molten metal pool, the molten metal is solidified as it is, and the stub and the ingot are welded to each other to connect the primary ingot and the stub. 2. The vacuum arc remelting method according to claim 1, wherein the vacuum arc remelting method is carried out using a stub manufactured from a material substantially the same as the material of the primary ingot. 3. The vacuum arc remelting method according to claim 1, which is carried out for titanium or a titanium alloy.