JPH0368318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC electric arc furnace having at least one electrode connected to the cathode and at least one hearth connection connected to the anode.

This type of furnace is disclosed in US Pat. No. 4,228,314 {October 1980.
Patent granted to ASEA Co., Ltd. in Sweden on April 14th;
It is known from the inventor Sven Einar Stenkvist.
The conductive bottom lining of this or other similar furnaces is reinforced with a top consumable lining and a back lining and contact plate. According to the above-mentioned patent, the back lining consists of carbon-containing bricks, ie conductive bricks that carry an electric current to the bottom contact plate. The difficulty in this connection is that such back linings not only have good electrical conductivity but also good thermal conductivity. Therefore, the heat flux through the back lining is very large and therefore
The contact plate (anode connection) becomes very hot.

Proposals have been carried out to insert an intermediate layer of insulating bricks surrounded by metal in the back lining;
In this regard, there are often difficulties, namely, temperature resistance is limited due to the encapsulation of the metal, and temperature resistance is limited because the metal absorbs carbon from the carbon-bearing material above and from the carbon-bearing material below. It was encountered that the resistance was gradually lowered. Of course, the temperature at the hearth bottom should not be high.

The present invention aims to provide a solution to the problems mentioned above and other problems related thereto. The furnace according to the invention is characterized in that the bottom lining of the DC electric arc furnace closest to the melt forms the furnace vessel part and consists of a tamped molding material layer with conductive metal parts, i.e. bricks with sheet metal spacers; The lining under the conductive metal part is the first conductive brick.
a second layer of insulating bricks without sheet metal present after the first layer and laterally alternating with conductive bricks; characterized in that it consists of a second layer of insulating bricks with metal spacers, and a third layer of electrically conductive bricks present after the second layer, and a bottom contact device present after the third layer. There is. By electrically conductive bricks is meant, for example, magnesia graphite bricks, carbon bricks or graphite bricks; and by insulating bricks is meant, for example, diamond bricks or any other electrically conductive bricks.

The first layer below the tamped molding compound layer prevents carbon from penetrating into the metal and, in addition, equalizes the current distribution. The second layer is thermally insulating but also conducts current, thus protecting the back lining, contact members, etc. from overheating. The third layer has the same effect as the first layer.

In a preferred embodiment, the bottom of the furnace or ladle and the lowest part of the side of the furnace or ladle are covered with conductive pins, conductive rods or conductive plates or conductive bricks extending from one end of the layer to the other. or non-conductive bricks, respectively, alternating with each other, thus obtaining a bottom contact part containing the bottom and the lowest part of the sides of the furnace/ladle.

This arrangement provides a furnace or ladle to which one or more electromagnetic stirring devices can be added. And the magnetic field of the electromagnetic stirring device is not influenced by the bottom contact device. The electromagnetic stirring devices can be suitably mounted on the side of the oven/ladle.

A DC electric arc furnace according to the invention is illustrated in greater detail in the attached drawings.

FIG. 1 shows a furnace with side walls 1 and a furnace roof 2 with a through-direct current electrode 3 which is normally solid in a melting furnace and hollow in a reduction or smelting furnace; The ore concentrate, coke and lime fed into and the electric arc produced at 5 are shown. The through-hole DC electrode 3 is normally connected to a cathode.

The furnace lining, in its part located closest to the melt 6, consists of an oxide brick or monolith 7 with conductive metal feedthroughs 8 or conductive metal feedthroughs. The consumable surface lining may also consist of a graphite-containing electrically conductive material. Process waste gases, such as those containing carbon monoxide CO, are discharged from 9 (known).

The first layer 10 is closest to the layer of the surface consumable lining and consists of a graphite-containing material such as magnesite graphite bricks, carbon bricks, graphite bricks or monolithic. The purpose of this first layer is to pass and distribute the current from the feedthrough DC electrode through the melt 6 and to provide protection against welding and temperature equalization.

The second layer 11 (closest to the first layer), according to one of the two embodiments, consists of conductive bricks 13 (magnesite graphite bricks, carbon bricks,
Consists of insulating bricks arranged laterally alternating with graphite bricks). This provides good electrical conductivity towards the bottom contact while providing good thermal insulation. The temperature at the bottom contact device can be kept at a low value in a simple manner.

The second layer 11 is, for example, of magnesite graphite to the extent of 50%, i.e. every second brick (first
(see brick 13 shown in the figure);
The remaining portion consists of siyamoto or other oxidized material 12.
It consists of 50%. The content of magnesite graphite may be 33%, ie an amount corresponding to every third brick. If pure graphite brick is chosen,
Since the conductivity of each brick is good, such bricks13
The amount of should be reduced to a magnitude grade of 2-5%. See Figure 2.

By the expression "alternately with...", as used above, we mean not only "every second" (=50%), but also any relationship from a few percent to more than 90%. There is.

According to a second embodiment, the second layer 11 consists of metal-cased diamond bricks 13 or any other metal-cased bricks.

The third layer 14 may be of the same type as the first layer 10. The purpose of the third layer is then to conduct current and provide protection against welding and provide temperature equalization.

The first and third layers 10, 14 may consist of bricks partially encased in metal.
The bricks placed in the metal case are then arranged in such a way as to form a through current path.

The bottom contact device consists of a current carrying copper rod or plate 15. The connection of the DC power source or rectifier to the anode is indicated at 16 (see FIG. 1). Below these current copper rods or copper plates there is a steel grain 17 (see Figure 2).

Cooling air for the bottom contactor 16 is blown in at 18 and exhausted at 19 (see FIG. 1).

Another embodiment of the invention is shown in FIG.
A furnace or ladle is shown having at least one arc electrode 32 connected to the cathode of a DC power source (not shown). The furnace/ladle can be used for all types of metals or alloys, including steel.

The layer 21 immediately below the melt 33 consists of conductive bricks, such as magnesite graphite bricks, with alternating non-conductive bricks. In this layer,
Good electrical conductivity and good heat insulation properties can be obtained at the same time. The layer 21 may also consist of a layer of compacted molding material which is electrically non-conductive and equipped with pins or plates 34 passing through the layer for conducting current.

The sides of the furnace/ladle are provided with a layer 22 of electrically conductive bricks, preferably arranged along sheet metal. This layer 22 may have the same components as those of the layer described as layer 21. Preferably, the layer 22 is made of bricks with steel plates. Layer 22 may be included in the bottom contact device along with layer 21.

Below the layer 21 is a bottom plate 2 with welded steel pins, steel rods or steel plates 34 passing through the layer 21.
3 is installed. Overall bottom contact part 21~
23 was previously described and is formed as a cylindrical shape onto which a pin, rod or plate 34 is welded. Between these pins, rods or plates a non-conductive compacted molding compound is then filled in the usual manner. The cylindrical sheet mold includes a side 22 that covers the lowest part of the inside of the oven/ladle. A heat-insulating and non-conductive layer 28 of dry compacted magnesite molding compound or the like is disposed behind the side part 22. The non-conductive layer 28 is followed by a thermally insulating and non-conductive layer 27 of shimots or the like.

Under the bottom layer 21, magnesite graphite bricks,
A second layer 24 of conductive bricks, such as carbon bricks or graphite bricks, may be provided. The second
Beneath layer 24 is disposed a layer 25, usually thicker, consisting of non-conductive bricks such as Shamotsu mixed with conductive bricks such as magnesite graphite bricks or graphite bricks. . The layer 25 must be able to conduct electrical current.
Below said layer 25 a new layer 24 of conductive bricks similar to the layer 24 described above may be placed. Underneath the new layer 24 or in contact with said layer 25, a copper terminal 2 is placed.
A copper plate 26 or other conductive plate is disposed in front of the terminal such as 9. The ladle is equipped with a metal shroud 30.

A hot water outlet equipped with a valve or stop device 31 is provided in the center of the bottom of the ladle/furnace intended for tapping the ladle/furnace. In layer 25 the non-conductive bricks can also be equipped with conductive metal sheet spacers.

Bottom contact part 21-2 equipped with bottom plate 23
In embodiment 2-34, space is provided on the side of the ladle/furnace for one or several electromagnetic stirring devices 35. The flux of these magnetic stirrers is not affected by the bottom contact. Regular stirring then takes place, for example for refining, reduction and/or homogenization purposes. Thus, the bottom contact part can be kept free from magnetic fields.

The bottom of the furnace/ladle may be straight, as shown, or curved, but has upwardly extending side edges.

The invention may be varied in many ways within the scope of the appended claims.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of a DC electric arc furnace according to the present invention, Fig. 2 is a detailed view of the back lining of the DC electric arc furnace of Fig. 1, and Fig. 3 is a diagram showing a special example. be. In the figure, 3: one electrode connected to the cathode, 7:
tamped molding material layer, 8: conductive metal part, 10: first layer, 11: second layer, 12: insulation brick, 13: conductive brick, 14: third layer, 1
6: One bottom contact device connected to the anode.

Claims (1)

Claims: 1. At least one electrode 3 connected to the cathode and at least one bottom contact device 16 connected to the anode.
in a DC electric arc furnace, the bottom lining of the DC electric arc furnace closest to the melt forms the furnace vessel bottom and has a tamped molding material layer 7 with conductive metal parts 8, i.e. sealed metal spacers or inserts; a first layer 10 of conductive bricks;
a second layer 11 of insulating bricks without sheet metal present after the layer and laterally alternating with conductive bricks, or an insulating layer 11 present after the first layer and comprising sheet metal spacers; a second layer 11 of bricks, and a third layer 14 of conductive bricks present after the second layer, and a bottom contact device 16 present after the third layer; By electrically conductive bricks, we mean, for example, magnesite graphite bricks, carbon bricks or graphite bricks; and by insulating bricks, we mean, for example, ceramic bricks or any other conductive bricks. DC electric arc furnace. 2. The DC electric arc furnace according to claim 1, wherein the second layer 11 is composed of adjacently placed bricks, that is, insulating bricks 12 and conductive bricks 13 placed alternately; A DC electric arc furnace characterized in that both conductive bricks continue throughout the second layer. 3. In the DC electric arc furnace according to claim 2; every second or third brick in the second layer 11 is made of a conductive brick, or the conductive brick is made of a conductive brick. A direct current electric arc furnace characterized in that when the second layer is made of graphite bricks, the graphite bricks account for 2 to 10% of the second layer. 4. In the DC electric arc furnace according to claims 2 and 3; the second layer 11 is composed of bricks placed adjacently, that is, insulation bricks 12 and conductive bricks 13 placed alternately; characterized in that both the insulating brick and the conductive brick continue throughout the second layer; and/or the second layer 11
Each second or third brick is made of a conductive brick, or if the conductive brick is made of graphite brick, the graphite brick accounts for 2 to 10% of the second layer. A DC electric arc furnace characterized by occupying . 5. In a DC electric arc furnace comprising at least one electric arc electrode and at least one bottom contact device or bottom lining as claimed in claim 1; The lowest part 22 of the side of the ladle is also tamped with alternating bricks or conductive bricks with sheet metal strips running across the bottom layer 21 of the furnace or ladle. Direct current electric arc furnace, characterized in that it consists of molding material or non-conductive bricks, thus obtaining a bottom contact device containing the bottom and the lowest part of the sides of the furnace/ladle. 6. In the furnace or ladle of a DC electric arc furnace as claimed in claim 5; a layer 24 of conductive bricks is provided below the bottom contact device and a layer 24 of conductive bricks is provided behind the sides of the bottom contact device. A DC electric arc furnace characterized in that a compacted molding material 28 is provided. 7 In a furnace or ladle of a DC electric arc furnace according to claims 5 and 6; in or outside the furnace/ladle, for example on the outside of the side wall above the bottom contact device at least one electromagnetic A DC electric arc furnace characterized in that a space for mounting a stirring device 35 is provided. 8. In the furnace or ladle of a DC electric arc furnace according to claims 5 to 7; the bottom contact devices 21 to 23 include a prefabricated cylindrical sheet form 23; A DC electric arc furnace characterized in that the bottom of the frame is equipped with a vertical conductive plate or conductive rod or conductive pin 34 welded.