JPH07188795A - Electroslag melting method - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide an electroslag melting method capable of obtaining an ingot free from arc spots and segregation even if a start block having an uneven surface is used. According to the electroslag melting method of the present invention, a start block is placed on a copper stool that is in contact with the mold bottom of an electroslag melting device, a consumable electrode is introduced onto the start block, and a flux is filled. When melting is started by melting, a metal plate that can be welded to the heat block is laid on the copper stool, and a start block is placed on the metal plate to start melting. The metal plate is preferably welded to the start block.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroslag melting method.

[0002]

2. Description of the Related Art Electroslag melting (hereinafter referred to as "ES
R ”. ), The consumable electrode immersed in the molten slag in the water-cooled mold is energized, the consumable electrode is melted by the Joule heat generated in the molten slag, and the resulting droplets perform refining action in the molten slag. It drops while receiving and is sequentially cast into a water-cooled mold. By the way, conventionally, when starting the melting, there are a hot start method using a slag that has been melted in advance and a cold start method using a start block made of the same material as the material of the consumable electrode, but the cold start method is usually adopted. That is, FIG.
As shown in FIG. 3, a copper stool 5 is brought into contact with the bottom of a water-cooled mold 1 provided with a cooling water jacket 2 in an electroslag melting apparatus, and a start block 7 is placed on the copper stool 5.
After placing, the ignition material 8 is placed on the start block. After placing the consumable electrode 3 thereon, the flux 9 is filled, a voltage is applied to the consumable electrode, and a current is passed between the consumable electrode and the start block. As a result, an arc is generated between the consumable electrode and the start block, the flux is melted, and molten slag is formed. As a start block in this case, conventionally, the remaining portion of the used consumable electrode (hereinafter referred to as "residual steel") is used.

[0003]

However, when the remaining steel of the used consumable electrode is placed on a copper stool as a start block and melting is started, the residual steel surface of the consumable electrode becomes uneven. As a result, it becomes difficult for current to flow on the contact surface, the arc flies, and the unevenness becomes more remarkable, and the copper stool is damaged and unevenness is formed on the surface. As a result, there is a problem that molten slag invades between the start block and the copper stool to cause a phenomenon such as an insulating portion, and an arc spot or segregation occurs on the side surface of the cast ingot. An ingot having such arc spots or segregation has an abnormal solidification structure in the arc spots or segregation portions, and therefore the ingot cannot be used as a whole. In order to prevent the generation of arc spots, a damaged copper stool can be replaced, but the labor and cost for doing so are significant. Although the above problems can be solved by using a saw block having a smooth surface as a start block, sawing the residual steel of the consumable electrode used as the start block requires much labor and cost. , Was not practically available. Therefore, there is a demand for the development of a technique that does not cause the above-mentioned problems even when a start block having an uneven surface such as residual steel of a used consumable electrode is used. The present invention has been made for the purpose of satisfying the above-mentioned requirements in the conventional technique. That is, an object of the present invention is to obtain an ESR that can obtain an ingot without arc spots or segregation even if a start block having an uneven surface is used.
It is to provide a dissolution method.

[0004]

As a result of the study, the inventors of the present invention have found that when the ESR device is melted by a cold start method, an iron spot is laid on a copper stool so that an arc spot is formed on the ingot during the ESR melting. They found that it would not occur, and completed the present invention.

That is, in the melting method of the present invention, a start block is placed on a copper stool that is in contact with the mold bottom of an electroslag melting device, a consumable electrode is introduced onto the start block, and a flux is filled. When the melting is started by melting, a metal plate that can be welded to the heat block is laid on the copper stool, and a start block is placed on the metal plate to start melting. In the present invention, the metal plate is preferably welded to the start block.

The ESR dissolution method of the present invention will be described in detail below. FIG. 1 is a schematic configuration diagram of an ESR device for explaining the ESR melting method of the present invention. Reference numeral 1 denotes a water-cooled mold, which is configured to be cooled by the cooling water introduced into the cooling water jacket 2. 3 is a consumable electrode,
It is gripped by a clamp (not shown) that is vertically movable. The consumable electrode 3 has
A voltage is applied by the power source 4 so that a current flows between it and the copper stool 5.
The copper stool 5 is engraved with a recess into which a metal plate is fitted, and the metal plate 6 is fitted into the recess and laid. The start block 7 is placed on the metal plate 6. In addition, 8 is an ignition material and 9 is a flux.

When melting is started by the cold start method in the above ESR apparatus, the copper stool 5 in which the metal plate 6 is fitted in the recess and laid is brought into contact with the bottom of the water-cooled mold 1 to start the block on the metal plate. Place 7. In this case, it is preferable to weld the start block 7 and the metal plate 6 by spot welding.
After placing the ignition material on the start block and introducing the consumable electrode onto the start block, the flux is filled between the consumable electrode and the water-cooled mold to start the melting. When a voltage is applied to the consumable electrode in this state, an arc is generated between the consumable electrode and the start block, the flux is melted by the action of the ignition material, and melting of the consumable electrode is started.
After the melting operation is completed, the formed ingot may be taken out of the water-cooled mold, and the bottom portion to which the metal plate is fixed may be removed by an appropriate means.

In the above case, the metal plate is laid in such a manner that it is fitted into the concave portion formed in the copper stool, but the metal plate may be simply laid on the copper stool. Good. The shape is arbitrary, and may be, for example, a circle or a quadrangle. The material of the metal plate is
It is preferable that the material is similar to the material of the start block. For example, an iron plate is used when the start block is a Fe-based alloy, and a Ni plate is used when the start block is a Ni-based alloy.

The ESR device shown in FIG. 1 is a fixed type in which a copper stool is fixed to a water-cooled mold.
It can also be applied to an ESR device of a type in which a copper stool is moved downward to pull out an ingot.
FIG. 2 is for explaining an example of the case,
Each symbol has the same meaning as in FIG. In the figure, a metal plate 6 is laid on a copper stool 5, and a start block 7 is placed thereon. This ES
In the R apparatus, the ingot formed in the water-cooled mold 1 is continuously pulled down by moving the copper stool downward, and is pulled up and taken out after completion of the melting operation. Therefore, the metal plate laid on the copper stool needs to be sized to fit within the cross section of the mold.

[0010]

In the present invention, since the start block and the weldable metal plate are laid on the copper stool and the start block is placed on the copper stool, the contact state between the copper stool and the metal plate is tight. Further, the contact between the metal plate and the heat block is also tightly made by pre-welding or by automatically applying a current to be in a welded state. Therefore, the current applied to the consumable electrode will flow through the copper stool without causing arcing due to poor insulation, and therefore arc spots and segregation will not occur in the formed ingot.

[0011]

EXAMPLE ESR dissolution was performed using the ESR apparatus shown in FIG. The conditions for ESR dissolution were as follows. Φ175 mm high carbon steel (SKH9) is used as a consumable electrode, and φ240 mm × length 2000 is used as a water-cooled mold.
A copper mold with a size of mm was used. As the copper stool, one in which a concave portion was formed was used, and as the start block, the remaining portion of the used consumable electrode having irregularities on the surface was used. In this start block, with a thickness of 7 mm, 1
An iron plate having a size of 90 mm × 190 mm was welded at several points by spot welding, and the iron plate was fitted into the recess of the copper stool. After this copper stool was brought into contact with the bottom of the copper mold, an ignition material was placed on the start block, and then a consumable electrode was introduced. As a flux between the consumable electrode and the copper stool, 60 CaF ₂ -20
15 kg of a powder having a composition (% by weight) of Al ₂ O ₃ -20CaO was filled, and a current of 50 V and 7 kA was passed to start melting. No arc spot was formed on the formed 1400 mm ingot.

[0012]

As described above, according to the present invention, the heat block and the weldable metal plate are laid on the copper stool as described above, and the start block is placed on the metal plate to start melting. Even if a block having an uneven surface is used, a poor contact with the copper stool does not occur. Therefore, even if a consumable electrode that has been consumed and remains, such as a consumable electrode, having irregularities on its surface is used as a start block, an ingot without arc spots or segregation can be produced.

[Brief description of drawings]

FIG. 1E for explaining the ESR dissolution method of the present invention
It is a schematic structure figure of an example of SR apparatus.

FIG. 2E for explaining the ESR dissolution method of the present invention
It is a schematic block diagram of another example of SR apparatus.

FIG. 3 ES for explaining a conventional ESR melting method
It is a schematic block diagram of an example of an R dissolution apparatus.

[Explanation of symbols]

1 ... Water cooling mold, 2 ... Cooling water jacket, 3 ... Consumable electrode, 4
... power supply, 5 ... copper stool, 6 ... metal plate, 7 ... start block, 8 ... ignition material, 9 ... flux.

Claims (2)

[Claims] 1. When a start block is placed on a copper stool that is in contact with the bottom of a mold of an electroslag melting apparatus, a consumable electrode is introduced onto the start block, and flux is filled to start melting. An electroslag melting method, wherein a metal plate that can be welded to a heat block is laid on the copper stool, and a start block is placed on the metal plate to start melting. 2. The electroslag melting method according to claim 1, wherein the metal plate is welded to the start block.