JPH07234080A - Structure of metal electrode for dc arc generator - Google Patents

Abstract

PURPOSE:To reduce a melting loss of an immersion type metal electrode used for a ladle refining device with DC arc. CONSTITUTION:A metal electrode 7 has a structure in which many rod like metal electrodes 23 are radially provided on the outer peripheral surface at the lower end of a central conductive metal tube member 22 having cooling gas passages 20 therein and the lower part of the conductive metal tube member 22 capable of coming into contact with a molten metal 2 including the lower end face of the member 22 is coated with a refractory material 21 so that the ends of the rod like metal electrodes 23 are exposed and come into contact with the molten metal 2. Only the ends of the rod like metal electrodes 23 come into contact with the molten metal 2. Other lower part in contact with the molten metal 2 is protected by the refractory material 21. Therefore, the thermal load of the metal electrodes can be reduced, a melting loss can be reduced and life can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a metal electrode having a cooling gas passage inside which is immersed in a molten metal in a container, and a graphite electrode which is not immersed in the molten metal. The present invention relates to a metal electrode structure of a DC arc generator that generates an arc.

[0002]

2. Description of the Related Art A ladle refining furnace that receives molten metal in a container, for example, molten steel that has undergone primary refining in a steelmaking furnace such as a converter or an electric furnace in a ladle and performs secondary refining in the ladle Are known. As described above, the ladle refining furnace is a steelmaking furnace, and de-flow (S),
Dephosphorization (P) is mainly performed to remove the oxidizing slag generated in this primary refining stage and tap the steel into a ladle, and a new slag (flux) is added to the ladle to add basic slag. It is to make and refine and reduce.

As a DC type ladle refining apparatus, as shown in FIG. 5, a ladle 1 receives molten steel 2 produced from a converter and is then carried on a carriage 3. A ladle lid 4 is detachably covered with a winch or the like on the ladle 1, and one of the two electrode through holes 5 formed in the ladle lid 4 penetrates the graphite electrode 6 on the cathode side, and the other one. A metal electrode 7 having a cooling gas passage therein is penetrated therethrough. The tip of the graphite electrode 6 is not immersed in the molten steel 2 in the ladle 1, while the graphite electrode 6
The tip of the metal electrode 7 made of a conductor such as iron arranged apart from is deeply immersed in the molten steel 2. A lid 15 is provided in each of the two electrode through holes 5 formed in the pot lid 4, and the lid 15 is put on after the two electrodes 6 and 7 are pulled out from the furnace.

As described above, the ladle 1 contains the molten steel 2 which is primarily refined in the converter, and the slag 19 is placed on the molten steel 2.
Is emerging. After covering the ladle 1 transferred to the secondary refining position by the trolley 3 with the pan lid 4, the lids 15 of the two electrode through holes 5 are opened and the graphite electrodes 6 supported by the support frame 8 respectively. The metal electrode 7 and the metal electrode 7 are swung upward from the retracted position by a turning device (not shown) to perform positioning. Subsequently, the power cylinder 10 is operated to lower the graphite electrode 6 and the metal electrode 7 independently, penetrate each electrode through hole 5 and insert them into the furnace, and the tip of the graphite electrode 6 is melted into the molten steel 2 in the ladle 1. It is located near the upper side of the slag 19 existing above, and the tip of the metal electrode 7 is deeply immersed in the molten steel 2.

Next, a DC current rectified by a rectifier 14 such as a thyristor is applied to the graphite electrode 6 from the cathode side and to the metal electrode 7 from the anode side, and when the cylinder 10 is operated, a high current near the slag 19 is applied. The molten steel 2 is heated by the direct current arc from the graphite electrode 7 while controlling the voltage between the electrodes 6 and 7 by adjusting the height. Then, when a powdered flux composed of CaO, MgO or the like for S removal and P removal is supplied onto the molten steel 2, the slag 19 is promoted to be slag by heating by the arc from the graphite electrode 6, and the molten steel 2 is removed from the S,
The P removal processing is performed.

In the refining of molten steel by such a DC type ladle refining apparatus, the metal electrode 7 is cooled by passing a cooling gas such as N ₂ gas through a cooling gas passage provided inside the molten metal 2. The current-carrying surface immersed in it is large. For this reason, there is a problem in that the heat received from the current-carrying surface is large and the amount of electrode melting loss is significant and the life of the metal electrode 7 is short. In order to reduce the melting loss of the metal electrode, Japanese Patent Laid-Open No. 60-254592 discloses that the metal electrode 7a having the cooling gas passage 20a therein may come into contact with the molten metal 2a as shown in FIG. It is disclosed that the refractory material 21a for heat insulation is applied and covered in the side surface area so that only the lower surface of the metal electrode 7a is in contact with the molten metal 2a to reduce melting loss. 19a shows the slag on the molten metal 2a.

[0007]

Since the side surface portion of the metal electrode 7a disclosed in the above publication is covered with the refractory material 21a, it is possible to prevent melting damage from the side surface. However, since the current-carrying surface of the metal electrode 7a is the entire lower surface open to the molten metal 2a, even if the inside is cooled by the cooling gas, the current-carrying surface is large and the amount of heat received is large. The problem of shortening the life remarkably remained. In addition, there is a problem that the slag 19a adheres to the lower surface of the metal electrode 7a, the current is unevenly distributed, and uneven wear due to Joule heat is likely to occur.

The present invention solves the above-mentioned problems of the prior art,
An object of the present invention is to provide a metal electrode structure of a DC arc generator capable of reducing the amount of electrode melting loss.

[0009]

The present invention was made by paying attention to the fact that the heat receiving area should be made as small as possible in order to reduce the melting loss of the metal electrode. The gist of the invention is as follows. Is the street. The present invention includes a metal electrode having a cooling gas passage inside which is immersed in a molten metal in a container, and a graphite electrode which is not immersed in the molten metal, and a DC arc in which an arc is generated between the graphite electrode and the molten metal. In the metal electrode structure of the generator, the metal electrode has a central conductive metal cylinder having a cooling gas passage therein, and a large number of rods radially arranged on the outer peripheral surface of the lower end of the conductive metal cylinder. A metal electrode, and a refractory covering a lower area that may come into contact with the molten metal including the lower surface of the conductive metal cylinder so that the tips of these rod-shaped metal electrodes are exposed and come into contact with the molten metal; It is a metal electrode structure of a DC arc generator characterized by comprising.

[0010]

[Function] As an immersion type metal electrode structure, a large number of rod-shaped metal electrodes are radially arranged from a central conductive metal cylinder whose interior is gas-cooled, and the surrounding area is protected by a refractory material to reduce the area. Only the tip of the rod-shaped metal electrode contacts the molten metal. Therefore, the heat load applied to each rod-shaped metal electrode is reduced, and the amount of electrode melting loss can be reduced.

Further, since the metal electrode is divided into a large number, for example, even if a slug is attached to a part of the rod-shaped metal electrode, the remaining rod-shaped metal electrode is activated, so that a significant current deviation is unlikely to occur and the current flow is stabilized. be able to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a front view of a metal structure of a DC arc generator according to the present invention, FIG. 2 is a vertical cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is B- in FIG.
It is a transverse cross-sectional view showing the arrow B.

As shown in FIGS. 1 to 3, the metal electrode 7 of the present invention has a central conductive metal cylinder 22 having a cooling gas passage 20 therein and a lower end of the conductive metal cylinder 22. A large number of rod-shaped metal electrodes 23 radially arranged on the outer peripheral surface by welding.
And so that the tips of these rod-shaped metal electrodes 23 are exposed and contact the weld metal 2, the lower area that may contact the molten metal 2 including the lower end surface of the conductive metal cylinder 22 is covered. It consists of irregular refractory materials 21.

As shown in FIG. 3, the cooling gas passage 20 is provided.
A partition rib 24 is provided in the inside to separate the supply side and the discharge side of the cooling gas, and the cooling gas is supplied to the inner tip of the metal electrode 7 and then discharged to efficiently cool the gas. The structure for cooling the inside of the metal electrode 7 with the cooling gas is not limited to the above-mentioned function. For example, as shown in FIG. 4, the conductive metal cylindrical body 22 has a bottomed hollow,
The cooling gas supply pipe 25 may be inserted into the hollow portion and the tip may be opened, and the cooling gas supplied to the cooling gas supply pipe 25 is discharged from the opening of the tip and then cooled. The inside of the metal electrode 7 is cooled by gas while being discharged through the working gas passage 20.

Such a metal electrode 7 is immersed in the molten metal 2, and the molten metal 2 is heated by the arc generated in the other graphite electrode 6. The cooling medium at this time may be gas (air, N _2, etc.), but dry fog (those in which water droplets are dispersed in the gas and made to float) removes heat by collision of water droplets and vaporization. It is effective because a higher heat transfer coefficient is obtained. In the case of dry fog, even if the molten metal 2 enters the inside of the metal electrode 7 due to some accident, the danger of steam explosion can be avoided, which is safe.

Next, a rod-shaped metal electrode that directly contacts the molten metal 2
23, the material may be an inexpensive iron electrode. In particular, when the object to be heated is steel, even if it is melted, its composition is not affected and it is effective. (In the case of a graphite electrode, which is a conventional non-immersion type electrode, carbon was melted and the carbon component increased.) Then, the required power input was determined depending on the heating target. The number may be increased or decreased to adjust the current density to the allowable current density or less. In addition, when the number of lines increases, a multi-layer structure may be used as shown in FIG.

Further, in this case, since there are a plurality of contact surfaces with the molten metal 2, even if some of the rod-shaped metal electrodes 23 are slagged.
Even if 19 adheres and becomes invalid, the other rod-shaped metal 23 is operating, which is advantageous because stable operation can be performed without significant current drift. Although various shapes such as a square and an ellipse can be considered for the cross-sectional shape of the rod-shaped metal electrode 23, a circular shape is preferable in consideration of the uniformity of joining (welding, etc.) at the bases through which an electric current passes.

In the ladle refining apparatus using a DC arc according to the present invention, 30 rod-shaped steel electrodes having a diameter of 10 mm and a length of 100 mm are radially arranged below a conductive metal cylindrical body having a cooling gas passage and having a length of 4000 mm. In addition, the diameter of the refractory is 5
Approximately 200 mm of metal electrode coated to 00 mmφ
It was immersed in ton of molten steel. A flux with CaO and MgO as the main components is added to the molten steel in the ladle, and the transformer capacity is 20000K.
VA (400V, 50KA) DC heat generated between the other graphite electrode and molten steel to heat and heat the molten steel to remove S,
De-P treatment was performed.

As a result, according to the conventional metal electrode shown in FIG. 5, the electrode durable charge number was limited to 50, but according to the rod-shaped metal electrode of the present invention shown in FIGS. 1 to 3, the durable charge number was 200. It has become possible to extend the life to the charge level.

[0020]

As described above, according to the present invention, the tips of a large number of rod-shaped metal electrodes radially arranged are exposed on the outer peripheral surface of the central conductive metal cylinder whose interior is gas-cooled. The lower area, which may come into contact with the molten metal around it, is a metal electrode structure covered with a refractory and protected.

Therefore, the tip end of the rod-shaped metal electrode having a small area receives a reduced heat load from the molten metal and the amount of electrode melting loss is reduced, so that the service life can be extended. Also, since the metal electrode is divided into many in the form of a rod, even if some slag adheres to some of the rod-shaped metal electrodes, the remaining rod-shaped metal electrodes will operate, and it will be difficult for the current to flow unevenly and stable energization will be performed. You can

[Brief description of drawings]

FIG. 1 is a front view showing a metal electrode of a DC arc generator according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view taken along the line AA of FIG.

FIG. 3 is a transverse cross-sectional view taken along the line BB of FIG.

FIG. 4 is a vertical cross-sectional view showing another embodiment of the present invention.

FIG. 5 is a front view showing a partial section of a ladle molten steel processing apparatus according to a conventional example.

FIG. 6 is a cross-sectional view showing a conventional metal electrode structure.

[Explanation of symbols]

 1 Ladle 2 Molten Metal (Molten Steel) 3 Cart 4 Pan Lid 5 Electrode Through Hole 6 Graphite Electrode 7 Metal Electrode 8 Support Frame 9 Guide Post 10 Power Cylinder 13 Transformer 14 Rectifier 15 Lid 19 Slag 20 Cooling Gas Passage 21 Refractory 22 Conductive metal cylindrical body 23 Rod-shaped metal electrode 24 Partition rib 25 Cooling gas supply pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display H05B 7/12 C

Claims (1)

[Claims] 1. A direct current in which an arc is generated between the graphite electrode and the molten metal, comprising a metal electrode having a cooling gas passage inside which is immersed in the molten metal in a container, and a graphite electrode which is not immersed in the molten metal. In the metal electrode structure of the arc generator, the metal electrode has a central conductive metal cylinder having a cooling gas passage therein, and a large number of radially arranged outer peripheral surfaces of the lower end of the conductive metal cylinder. A fire resistance covering rod-shaped metal electrodes and a lower range that may come into contact with the molten metal including the lower end surface of the conductive metal cylinder so that the tips of the rod-shaped metal electrodes are exposed and come into contact with the molten metal. A metal electrode structure for a DC arc generator, which is characterized by comprising: