JPH09190881A - Cooling method and device for graphite electrode for use in refining electric arc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the electrode original unit of a graphite electrode at the time of refining by blowing a cooling liquid/water continuously to the peripheral surface of the graphite electrode to be used in a steel making process or a melting and/or refining process of another metal by means of arc heating. SOLUTION: Graphite electrodes 1 are connected one by one through nipples, and a current is fed to them so that steel making or refining of another metal is performed, when a cooling liquid 2 is blown continuously between the lid of an arc electro-furnace and an electrode holder to grasp the top of the graphite electrode 1 in the upper part in such a condition that a nozzle of a cooling pipe 3 is inclined downward to the outside surface of the graphite electrode 1 in the upper part, and thereby a cooling liquid film 2a sinking down along the electrode outside surface is formed so that the cooling is conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling a graphite electrode used for refining an electric arc and a cooling device for the graphite electrode used for refining the electric arc. More specifically, it is connected sequentially through nipples in an arc electric furnace. When electric current is applied to the graphite electrode and the arc heating by the graphite electrode is used to melt and smelt steel and other metals, arc electricity is applied to the outer peripheral surface of the graphite electrode held by the electrode holder. Electricity that greatly reduces the electrode unit consumption by continuously spraying a cooling liquid such as cooling water on the furnace lid to cool it and minimize the oxidation consumption of the outer peripheral surface of the graphite electrode during refining. The present invention relates to a method for cooling a graphite electrode used for arc refining and a cooling device for the graphite electrode used for the method.

[0002]

2. Description of the Related Art Conventionally, in electric arc refining utilizing arc heating by a graphite electrode such as steel and other metals, the tip portion and the outer peripheral surface of the graphite electrode are accompanied by a reduction in the cost of electric energy. It is desired to reduce the electrode unit consumption by suppressing the oxidation consumption of the above. A water-cooled non-consumable electrode is used as one means for suppressing this oxidative consumption.

[0003] This water-cooled non-consumable electrode has a graphite electrode which is sequentially connected from the upper portion, and which is sequentially subjected to arc heating from the lower graphite electrode when it reaches the electric furnace, and which is consumed. Differently, the inside is cooled by cooling water.
It is used for cooling the graphite electrode connected to the lower end through a nipple during refining operation without being subjected to heating.

[0004] Therefore, the graphite electrode is cooled by the non-consumable electrode on the upper part, and furthermore, the consumption of the graphite electrode is suppressed, and a refining method and an apparatus utilizing this part have been proposed.

For example, US Pat. No. 4,416,014,
In each of the specifications of 4.417.344 and 4.451.926, cooling water is introduced into a non-consumable electrode formed of a hollow cylinder made of aluminum, and the cooling water causes the wall surface and the lower end of the non-consumable electrode. Patent Document 1 discloses a structure for cooling a graphite electrode connected to a graphite electrode.

Further, Japanese Patent Application Laid-Open No. 60-501879 and Japanese Patent Application Laid-Open No. 60-501880 disclose the use of cooling water inserted in the center hole of a non-consumable electrode made of a graphite tubular body. A structure for cooling a wall surface of a consumable electrode and a graphite electrode connected thereto is described.

When the graphite electrodes connected by the non-consumable electrodes are cooled as described above, the consumption of oxidation at the tip and the outer peripheral portion of the graphite electrodes is suppressed, and the reduction of the electrode unit consumption can be achieved to some extent.

However, when the used graphite electrode is removed, the used graphite electrode is moved off-line to remove the used graphite electrode from the nipple, and when necessary, the nipple is also removed from the non-consumable electrode. When a new graphite electrode is connected, a nipple is attached to the non-consumable electrode, and a new graphite electrode is attached to this nipple. Therefore, as described above, when cooling with a non-consumable electrode of the cooling type, it is necessary to transfer the device off-line for replacement in this way, and to disconnect and connect heavy labor there, which is extremely laborious. Clutter. Also, if the removal and connection of the graphite electrode are repeated, the graphite electrode, non-consumable electrode, screw threads such as nipples will be deformed, crushed, broken, poor connection,
There is an increase in electrical resistance, which hinders operation.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks. Specifically, in refining steel and other metals using graphite electrodes connected in sequence,
Cooling the graphite electrode directly on the outer peripheral surface of the graphite electrode on the furnace lid of the electric furnace to continuously cool even the lower graphite electrode to reduce oxidative consumption and reduce the unit consumption of the electrode We propose a method and a graphite electrode cooling device to be used for the method.

Therefore, since the lower graphite electrode is continuously and well cooled, the outer peripheral surface of the lower graphite electrode and the oxidative consumption of the tip are effectively suppressed, so that the basic unit of the electrode is greatly reduced. .

[0011] In connection with this, as in the prior art, UH
Even without using P (ultra high power electrode)
High load operation can be carried out very economically with ordinary graphite electrodes.

In a conventional graphite electrode connected via a nipple, the graphite electrode on the furnace lid is cooled and refined by a cooling liquid such as cooling water. Unlike the case where cooling is carried out, there are few complicated and dangerous operations at the time of electrode connection, and steel making and other metal refining can be performed smoothly.

[0013]

That is, in the method of the present invention, in an arc electric furnace, graphite electrodes are sequentially connected through a nipple, and a current is passed through these graphite electrodes to smelt steel or other metals. In this case, between the lid of the arc electric furnace and the electrode holder that holds the upper end of the upper graphite electrode, the cooling liquid is continuously blown by inclining downward with respect to the outer peripheral surface of the upper graphite electrode. In addition, a cooling liquid film that descends downward along the outer peripheral surface of the graphite electrode is formed and cooled.

The apparatus for cooling the graphite electrode provided during the refining is provided between a furnace lid of an arc electric furnace and a graphite holder for gripping an upper graphite electrode on the furnace lid. An annular cooling pipe surrounding the outer periphery of the graphite electrode and partly divided by a dividing portion is arranged, and at least one of the cooling pipes is provided with at least one radially inclined and downwardly inclined inner peripheral surface. A cooling liquid spray nozzle is provided.

The configuration of these means and their effects will be specifically described below with reference to the drawings.

FIG. 1 is an explanatory view showing a cross-sectional view of a case where a graphite electrode is cooled by an example of a cooling apparatus for a graphite electrode in carrying out the present invention, and FIG. 2 is an explanatory view showing the same from the front. 3 is a sectional view taken along the line AA in FIG. 1, and FIG. 4 is an enlarged view of a part of FIG.

First, in FIGS. 1, 2 and 3, reference numeral 1 denotes an upper graphite electrode, that is, a graphite electrode when it is on a furnace lid. Among the upper graphite electrodes 1, the graphite electrode at the upper end is gripped by an electrode holder (not shown) as in the conventional example, and the lower end is connected to the graphite electrode (not shown) via a nipple (not shown). (Not shown) is connected. In an arc electric furnace using three-phase alternating current,
Three upper graphite electrodes corresponding to three-phase electric power are arranged at intervals on a circular circle having a predetermined radius centered on the center, and each upper graphite electrode 1 has a nipple as described above. The lower graphite electrodes are connected via the electrodes, and the respective electrodes are energized to perform steel refining and other metal refining. In an electric furnace utilizing direct current, one upper graphite electrode is naturally disposed on the furnace lid corresponding to this, and the arc is interposed through the upper graphite electrode and a graphite electrode connected thereunder. Heated.

Next, a cooling liquid 2 such as cooling water, for example, is continuously inclined downward and sprayed on the outer peripheral surface of at least one of the three upper graphite electrodes 1 for cooling.

At this time, the cooling liquid can be sprayed by any method. However, a cooling pipe 3 is disposed on the outer periphery of the upper graphite electrode 1 to which the cooling liquid is sprayed, and the cooling liquid from the introduction duct 3b is provided. Is sprayed downward from the inner peripheral surface of the cooling pipe 3. The cooling pipe 3 is disposed between an electrode holder that holds the upper end of the upper graphite electrode 1 and the upper part of the arc electric furnace, for example, a lid (not shown), and cools by spraying a cooling liquid from the cooling pipe 3. . The cooling pipe 3 is formed concentrically with the upper graphite electrode 1 in an annular shape so as to be separated from the periphery of the upper graphite electrode 1 by a predetermined distance. In this case, as described above, for example, when the graphite electrode is connected to each lower end of the three upper graphite electrodes and the operation is performed, the electromagnetic influence from the adjacent upper graphite electrode to one upper graphite electrode is performed. Easy to receive. For this reason, a part is divided in consideration of this electromagnetic influence and the cooling pipe 3
It is preferable that the dividing portion 3a is provided in a part of the portion.

That is, in an arc furnace using three-phase alternating current, at least two, usually three, upper graphite electrodes 1 are concentrically arranged corresponding to the three-phase alternating current power supply. Have been. Therefore, the upper graphite electrodes mutually affect each other electromagnetically. If the cooling pipe 3 is present due to this influence, the current flowing through the graphite electrodes is interrupted, which may hinder the operation. However, if the dividing portion 3a is provided in a part of the cooling pipe 3, the electromagnetic effect can be eliminated, and the current flows through the electrode without any trouble.
There is no problem in operation.

The cooling pipe 3 is made of a material that is not affected by electromagnetic influence and has excellent oxidation resistance and is excellent in moldability. For example, when the cooling pipe 3 is made of an iron-based material due to moldability, it is made of stainless steel. Even if it is made of a material other than an iron-based material, for example, it can be made of a material that is not affected by electromagnetic influences such as ceramics and has oxidation resistance.

In order to spray the cooling liquid 2 from the inner peripheral surface of the cooling pipe 3, a plurality of, for example, 4 to 8 spray nozzles are provided on the inner peripheral surface of the cooling pipe 3 at intervals. Each spray nozzle 4 is directed radially toward the center of the graphite electrode 1 to which the cooling water is to be sprayed, and the tip nozzle portion 4a of each spray nozzle 4 is inclined obliquely downward as shown in FIGS. When the spray nozzles 4 are attached in this manner, the cooling liquid 2 continuously supplied from the introduction duct 3b is supplied from each spray nozzle 4 of the cooling pipe 3 in FIGS.
As shown in FIG. 2, a thin coolant film 2a is formed on the outer peripheral surface of the graphite electrode 1 sprayed obliquely downward and sprayed with cooling water, and this film 2a descends downward along the outer peripheral surface of the graphite electrode 1. During this descent, the coolant is vaporized by the internal heat, and the heat of vaporization reveals the retained heat of the graphite electrode 1 and is cooled well. With this cooling, the upper graphite electrode sprayed with the cooling water is cooled. The lower graphite electrode, which is sequentially connected underneath, is also cooled, and the oxidative consumption of the graphite electrode thus connected is suppressed over the upper and lower graphite electrodes.

In this cooling, the cooling liquid 2 is formed only on the outer peripheral surface of the upper graphite electrode 1 on the furnace lid as the film 2a. Even if it enters into the inside of the arc electric furnace, it melts at the tip of the lower graphite electrode in the arc electric furnace.
It is undesirable to reach the tip involved in the refining.

In general, when cooling water reaches a molten metal or the like which is being refined in an electric furnace, the water contained therein comes into contact with the high-temperature molten metal and generates a hydrogen explosion, which is extremely dangerous. From this point,
In the conventional example, spraying a cooling liquid such as cooling water on the periphery of the graphite electrode 1 on the furnace lid is hardly performed. At the time of cooling, as described above, on the furnace lid, the upper part of the graphite electrode connected via the nipple is configured as a non-consumable electrode, and the lower part of the non-consumable electrode is formed by a cooling passage formed along the center axis thereof. The graphite electrode connected to is cooled. However, even if the cooling liquid 2 is sprayed on the outer peripheral surface of the upper graphite electrode 1 on the furnace lid as in the present invention, the spraying of the cooling liquid 2 and the formation of the film 2a are not performed on the upper graphite electrode 1 on the furnace lid. 1, the upper graphite electrode 1 is cooled effectively, and especially the upper graphite electrode 1 and the lower graphite electrode in the arc electric furnace are made of graphite. The lower graphite electrode in the arc furnace can be further cooled by the effective cooling of the upper graphite electrode 1 on the furnace lid because it is made of a conductive material. Can be achieved.

By the way, when the upper end of the upper graphite electrode on the furnace lid, which can be easily visually observed, is maintained at a black level without red heating, the outer peripheral portion of the lower graphite electrode and the oxidation consumption of the tip are considerably suppressed. Have been. For example, the state of the upper graphite electrode on the furnace lid is easily visible during operation. Therefore, 10% of the length of the upper graphite electrode
When the degree of the black state is maintained, even if the state of the lower graphite electrode in the electric furnace is not visible, the ratio of the unit electrode unit reduced by suppressing the oxidative consumption of the lower graphite electrode is 12% or more. Reached and greatly improved. As is clear from this, the cooling liquid is sprayed directly on the outer peripheral surface of the upper graphite electrode 1 by inclining it downward and a film is formed on the outer periphery of the graphite electrode 1 and cooled. A considerable portion, that is, 10% or more, can be maintained in a black state without red heating, and the electrode unit consumption is greatly reduced. Furthermore,
The status of reduction of the basic unit of electrode is clearly understood on site,
Very practical and effective cooling.

As described above, when cooling using the cooling pipe 3, the inner peripheral surface of the upper graphite electrode 1 and the spray nozzle 4
, That is, the distance to the tip nozzle 4a is 5 cm to
The injection angle of the cooling liquid 2, that is, the inclination angle θ with respect to the horizontal level of the spray nozzle 4 (see FIG.
It is preferable to spray the cooling liquid 2 at an angle of about 10 ° to 35 ° and inclined downward. When spraying in this manner, the cooling liquid 2 has a pressure of 0.5 to 3 kg / cm ^2.
It is preferable to set the spraying rate to 0.8 to 6.0 l / min.

That is, it is inclined downward, and then,
Under these conditions, even if the size, dimensions, and capacity of the arc electric furnace change to some extent, in the arc electric furnace currently in practical use, the cooling liquid 2 reaches the lower graphite electrode. The upper graphite electrode 1 on the furnace lid without reaching
Can be cooled well.

The spray nozzle has an inclination angle θ of 10 ° to 3 °.
The reason why the range of 5 ° is preferable is that, besides the above-mentioned reason, if the spraying angle is 0 ° and the coolant 2 is sprayed from the spray nozzle 4 in parallel with the horizontal level, the coolant 2 is supplied to the electrode holder side. And the electrode holder itself is easily damaged. In this respect, the lower limit is preferably set to 10 °. Further, if the inclination angle is inclined at 35 ° or more, the cooling liquid 2 spreads, a part of the cooling liquid 2 is applied to the lid of the electric furnace, the wear of the lid itself is accelerated, and there is a danger that the cooling effect is lost. .

Further, as the cooling liquid 2, it is possible to use ordinary tap water or the like as it is, and to use it as cooling water. However, an antioxidant such as calcium phosphate is mixed into the cooling liquid 2 and sprayed. You can also. When the antioxidant is mixed in this way, the antioxidant in the coolant at the time of spraying adheres to the outer peripheral surface of the graphite electrode when the graphite electrode is present as the upper graphite electrode 1 on the furnace lid, and the outer surface of the graphite electrode 1 Oxidation consumption can be more effectively prevented. As described above, when the upper graphite electrode having the antioxidant adhered to the outer peripheral surface enters the arc electric furnace and becomes involved in melting and refining as a lower graphite electrode, oxidation consumption from the outer peripheral surface is reduced. It is more effectively suppressed, and the basic unit of electrode is further reduced. In order to achieve such an effect, it is preferable to add an antioxidant in an amount of about 5% to 15% by weight.

The tip nozzle 4a of the spray nozzle 4 is
As shown in FIG. 1, it is preferable that the coolant 2 is applied to the outer peripheral surface of the upper graphite electrode 1 in the circumferential direction on average. As a preferable example, the tip nozzle 4
a is configured such that the coolant 2 is sprayed so as to form a fan shape that expands, and a filter 4a is provided in a part of the spray nozzle 4 to remove foreign matter such as dust in the coolant 2. It is preferable to do so.

Further, for example, the cooling pipe 3 shown in FIG. 1 is constructed symmetrically with respect to the dividing part 3a, but the dividing part 3a can be provided at any part. For example, in the example shown in FIG. 5, the dividing section 3a is provided near the introduction duct 3b. With the cooling pipe 3, the processing is extremely easy. Further, the cooling pipe 3 may be formed in a completely annular shape as shown in FIG. In this case, it is preferable to use a material that does not affect the electromagnetic effect as much as possible so that the electrode current is not interrupted by the electromagnetic effect.

[0032]

EXAMPLE First, various graphite electrodes as shown in Table 1 were used as the upper graphite electrode and the lower graphite electrode, and the scrap material was removed by arc heating of the lower graphite electrode in the arc electric furnace. The graphite electrode melted and thus subjected to arc refining was cooled by spraying cooling water while inclining downward with respect to the upper graphite electrode on the furnace lid.

This cooling is performed as shown in FIG. 1 and FIG. 2. Tap water is continuously supplied to the cooling pipe 3 as a cooling liquid, and the cooling water 2 is sprayed downwardly from each spray nozzle 4. . In this case, for each of the case where cooling is performed via the non-consumable electrode as in the conventional example and the case where cooling is performed by the cooling water jet according to the present invention, the respective electrode basic units are obtained and the improvement effect is shown. 1

[0034]

[Table 1]

At this time, the cooling water was sprayed at a distance of 17 cm between the upper graphite electrode and the spray nozzle, the inclination angle θ of the spray nozzle was 15 °, the pressure of the cooling water was 1 to 3 kg / cm ² , and the amount of water was 1-2 liters / minute, the number of nozzles was six.

As a result, as shown in Table 1, the improvement effect was at least 11% or more, and when spraying downward in such a manner, there was no danger such as hydrogen explosion due to infiltration of cooling water. .

Further, in the case of Test No. 4, the operation was a high load operation using a UHP electrode. In this operation, when cooling is performed by spraying the cooling water according to the method of the present invention, the effect of the improvement is as large as 19%, and the oxidative consumption is greatly suppressed. Even during high load operation requiring electrodes, normal graphite electrodes could be used.

Furthermore, calcium phosphate 10 is added to the cooling water.
When the wt% was uniformly mixed and sprayed in each of the above cases, the calcium phosphate remained as a white thin film formed on the electrode, and the oxidation resistance was greatly improved. As a result, the improvement effect was at least 1 in each case in Table 1.
It increased by about 2%, and it was found that the basic unit of electrode could be further reduced.

[0039]

As described above in detail, in the present invention, the graphite electrode used for steelmaking of an arc electric furnace, refining of metal, etc. is provided with a cooling liquid between the furnace lid and the electrode holder. It is inclined downward with respect to the outer circumference and continuously sprayed for cooling.

Therefore, the oxidative consumption of the outer peripheral surface and the tip of the graphite electrode at the time of refining is minimized, whereby the basic unit of the electrode can be greatly reduced. In particular, a normal graphite electrode can be used even in a high load operation. .

Further, the cooling liquid sprayed downward and inclined cools the graphite electrode while descending over the outer peripheral surface of the graphite electrode. For this reason, the degree of cooling of the lower graphite electrode involved in refining in the furnace can be determined by looking at the degree of blackness of the upper graphite electrode that can be visually observed on the furnace lid, and the graphite electrode can be more effectively cooled.

When an antioxidant is blended into the cooling liquid and sprayed, the oxidative consumption of the outer peripheral surface and the tip is more effectively suppressed, and the basic unit of the electrode is further reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a case where a graphite electrode is cooled by an example of a graphite electrode cooling device when carrying out the present invention, as a cross-sectional view.

FIG. 2 is an explanatory diagram showing it from the front.

FIG. 3 is a sectional view taken along the line AA in FIG.

FIG. 4 is an enlarged view of a part of FIG. 3;

FIG. 5 is a plan view of an electrode cooling device used when carrying out the present invention.

FIG. 6 is a plan view of an electrode cooling device used in carrying out the present invention.

[Explanation of symbols]

 1 Upper Graphite Electrode 2 Cooling Liquid 3 Cooling Pipe 3a Dividing Part 3b Introduction Duct 4 Spraying Nozzle

Claims (5)

[Claims] 1. In an arc electric furnace, graphite electrodes are sequentially connected through nipples, and a current is passed through these graphite electrodes to make a lid for the arc electric furnace when refining steel or other metals. And the electrode holder that holds the upper end of the upper graphite electrode, the cooling liquid is continuously sprayed by inclining downward with respect to the outer peripheral surface of the upper graphite electrode, along the outer peripheral surface of the graphite electrode. A method for cooling a graphite electrode used for electric arc refining, which comprises cooling by forming a cooling liquid film that descends downward. 2. The method for cooling a graphite electrode used in electric arc refining according to claim 1, wherein the cooling liquid is sprayed downwardly with respect to the horizontal level with an inclination of θ10 to 35 °. 3. The method for cooling a graphite electrode used in electric arc refining according to claim 1, wherein the cooling liquid is cooling water. 4. The method for cooling a graphite electrode used in electric arc refining according to claim 1, wherein the cooling liquid contains an antioxidant. 5. The outer circumference of the upper graphite electrode is surrounded by a furnace lid of an arc electric furnace and a graphite holder that holds the upper graphite electrode on the furnace lid, while part of the graphite electrode is divided. An annular cooling pipe divided by a portion is arranged, and at least one cooling liquid spray nozzle that is inclined downward and is directed in the radial direction is provided on the inner peripheral surface side of the cooling pipe. Cooling device for graphite electrode used for arc refining.