JPH05285632A - Method for electrically melting slag - Google Patents

Abstract

PURPOSE:To manufacture a large diameter ingot having no segregation in its center part by specifying the ratio of the cross-sectional area of a consumable electrode to the cross-sectional area of a water-cooled mold and positioning the consumable electrode adjacent to the mold. CONSTITUTION:Since a specific voltage is applied between the consumable electrode 3 and a starting plate 9, the consumable electrode 3 is melted by an electric resistance of a molten slag 9 melted in the water-cooled mold 1 to form a molten metal pool 10. The bottom face of the molten metal pool 10 is cooled to be solidified and the ingot is formed in the water-cooled mold 1. In this case, since the consumable electrode 3 is equal or less than 25% in its cross-sectional area to the water-cooled mold 1, the thermal efficiency of electrode melting is lowered and the skin of the ingot 11 is excellent under high power. Since contact area to the slag is small, the melting rate is low and the solidifying time is shortened. Consequently, the segregation is hardly caused.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroslag melting process for making large diameter ingots.

[0002]

2. Description of the Related Art In electroslag melting (hereinafter referred to as ESR), a consumable electrode is immersed in molten slag in a water-cooled mold to conduct electricity, and the consumable electrode is melted by the Joule heat generated in the molten slag to generate it. The droplets drop in the molten slag while undergoing the refining action and are sequentially cast into the water-cooled mold. According to this ESR method, the effects of desulfurization, deoxidation, reduction and miniaturization of non-metallic inclusions are shown by the refining action of slag, and there is little segregation, and it is possible to obtain a high-quality ingot with a clean skin. Because of this, it has come to be used successively in recent years.

[0003]

Recently, it has been desired to manufacture large diameter ingots by the ESR method. In the conventional ESR method, as a consumable electrode, a normal fill ratio (a diameter ratio of the mold and the electrode) of 0.5 to 0.
The range of 9 is used, but when a large diameter ingot is obtained using a large diameter consumable electrode, the segregation occurs at the center of the ingot generated due to the slow solidification rate. was there. By the way, E
In the SR method, it is known that the solidification rate becomes slower as the mold diameter increases, that is, the solidification time becomes longer, and in order to shorten the solidification time,
It is known that the melting rate of the electrode may be reduced. In order to prevent the segregation, the solidification time may be shortened, but when the mold diameter is large, the solidification time does not become shorter than a certain degree even if the melting rate is reduced. Moreover, if the dissolution rate is reduced to shorten the solidification time, the slag temperature decreases,
There is a problem that a dirty ingot is formed on the skin. That is, in the conventional technique, in the case where the diameter of the mold is large, in order to produce an ingot with a clean skin and no segregation, it is necessary to reduce the melting rate to shorten the solidification time and increase the slag temperature. However, these cannot be compatible. That is, decreasing the melting rate and increasing the slag temperature are in a mutually contradictory relationship. Therefore, in the case of a material in which segregation is likely to occur, it was extremely difficult to produce an ingot having a large diameter and good skin by the ESR method without segregation at the center.

The present invention has been made in view of the above situation in the prior art, and an object thereof is to provide an ESR method for producing an ingot having a large diameter without segregation.

[0005]

According to the present invention, when an ingot is produced from a consumable electrode by an electroslag melting method, the consumable electrode has a cross-sectional area of 25% or less with respect to that of a water-cooled mold. It is characterized in that electroslag melting is performed so that the electrodes are located near the mold. In the present invention, the consumable electrode needs to have a cross-sectional area of 25% or less with respect to the cross-sectional area of the water-cooled mold, and preferably in the range of 8% to 20% (hereinafter referred to as area ratio). When the area ratio of the consumable electrode becomes larger than 25%, in the case of an ingot with a large diameter,
Segregation will occur in the central part.

Further, in one embodiment of the present invention, the consumable electrode may be composed of a plurality of electrodes each having a small cross-sectional area. In that case, each electrode is not particularly limited in its cross-sectional shape as long as the total of the cross-sectional areas of the electrodes is within the range of the above area ratio, and may have any shape such as a circle or a square. .. Further, these electrodes are arranged so as to be located near the mold. FIG. 1A shows an example thereof, and shows a case where the consumable electrode is composed of six electrodes having a small cross-sectional area. In the figure, reference numeral 1 denotes a mold, and electrodes 31 to 36 are arranged near the mold. In another embodiment of the present invention, the consumable electrode may be a hollow electrode having a ring-shaped cross section. Figure 1 (b) shows
This is an example, and a hollow electrode 37 is arranged near the mold 1. In yet another embodiment of the invention, the consumable electrode may consist of a single electrode, which is configured to rotate within the mold. FIG. 1C shows such a case, and the electrode 38 is adapted to make a circular motion in the mold. In the present invention, in any of the above-described embodiments, the consumable electrode is located near the mold and electroslag melting is performed. If the consumable electrode is located in the center of the mold, the central part of the molten slag is heated excessively due to the small cross-sectional area of the consumable electrode, and therefore the molten metal pool does not have a flat bottom shape, but only the central part. Becomes deeper and segregation occurs at the center of the ingot.

[0007]

In the present invention, since the consumable electrode has a smaller cross-sectional area than that of the conventional one, it is possible to reduce the thermal efficiency of electrode melting. Therefore, since high power can be applied, the slag temperature becomes high and the skin of the ingot becomes good. Further, since the area in contact with the slag is small, the dissolution rate is low and the solidification time is short. Therefore, segregation does not occur. Furthermore, since the consumable electrode is arranged in the vicinity of the mold, the molten metal pool formed in the mold also has a flat shape with a shallow central portion. Therefore, the concentrated layer is less likely to be trapped between dendrites formed during solidification, and segregation is less likely to occur.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic configuration diagram of an ESR device for carrying out the present invention. Reference numeral 1 denotes a water-cooled mold, which is configured to be cooled by cooling water introduced into the cooling water jacket 2. Reference numeral 3 denotes a plurality of consumable electrodes, each of which is held by a clamp 4 provided on an electrode supporting mast 5 so as to be movable up and down so as to be movable in the vertical direction. Further, the electrode can be exchanged to the quasi side by another electrode supporting mast 5 '. A voltage is applied to each of the consumable electrodes 3 by a power source 6, and a current flows between the consumable electrodes 3 and the starting plate 7. The starting plate 7 is movable downward by the operation of the drive device 8. 9 is a slag pool composed of molten slag, 10 is a molten metal pool, and 11 is an ingot. In the above ESR device, since a predetermined voltage is applied between the consumable electrode 3 and the starting plate 9, the consumable electrode 3 is melted by the electric resistance of the molten slag in the water-cooled mold 1 to melt the molten metal pool 10 To form. The lower surface of the molten metal pool solidifies by cooling, forming an ingot in the water-cooled mold. The ingot is continuously pulled downward by the operation of the drive device 10.

The consumable electrode of the present invention has an area ratio of 25% or less with respect to the cross-sectional area of the water-cooled mold. In this embodiment, six small-diameter electrodes are as shown in FIG. 1 (a). It is arranged in various configurations.

Next, a more specific example will be shown. As a consumable electrode, 0.03C-0.25Si-0.2Mn-42
Ni-16Cr-2.7Nb-0.4Al-2.0Ti
2 electrodes (100 mm in diameter) made of a Ni-based alloy having the composition of FIG.
Arranged as shown in, current of 10KA is applied, and 34kg
ESR dissolution was performed at a dissolution rate of / hr. The area ratio of the consumable electrode in this case was 8.3%, and as a result, a good skin ingot was obtained, and no segregation was observed in the center. Comparative Example ESR melting was performed under the same conditions as above, except that a consumable electrode having a diameter of 590 mm was used. As a result, it was confirmed that segregation occurred in the center of the formed ingot.

[0011]

According to the present invention, as described above, the consumable electrode having an area ratio of 25% or less is provided in the vicinity of the mold to perform the ESR melting. Not large diameter ingots can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a form and an installation state of a consumable electrode used in the present invention.

FIG. 2 is a schematic configuration diagram of an ESR device for carrying out the present invention.

[Explanation of symbols]

1 ... Water cooling mold, 2 ... Cooling water jacket, 3 ... Consumable electrode, 4
... Clamps, 5, 5 '... Electrode supporting masts, 6 ... Power supplies,
7 ... Starting plate, 8 ... Drive device, 9 ... Molten slag, 10 ... Molten metal pool, 11 ... Ingot, 3
1-36 ... Electrode, 37 ... Hollow electrode, 38 ... Electrode.

Claims (4)

[Claims] 1. When producing an ingot from a consumable electrode by the electroslag melting method, the consumable electrode has a cross-sectional area of 25% or less of the cross-sectional area of a water-cooled mold, and the consumable electrode is positioned near the mold. An electroslag melting method, characterized in that the electroslag melting is performed. 2. The electroslag melting method according to claim 1, wherein the consumable electrode comprises a plurality of electrodes. 3. The electroslag melting method according to claim 1, wherein the consumable electrode is a hollow electrode having a ring-shaped cross section. 4. The electroslag melting method according to claim 1, wherein the consumable electrode is rotated in the mold.