JPH08170884A - Electrode for furnace wall of d.c. arc furnace - Google Patents

Abstract

PURPOSE: To stably produce a fusion surface in a bar-like electrode as above as possible, by a method wherein a lower part of the bar-like electrode at the bottom of an electric furnace is cooled with a molten metal of which Prandtle number is small, and cooling of the whole of the bar-like electrode is strengthened. CONSTITUTION: The lower part of a bar-like electrode 4 is immersed in a molten metal 9 of which Prandtle number is smaller than that of a non-metallic liquid such as water, a cooling sleeve 5 is formed in the periphery of a bath for the molten metal 9, and the molten metal 9 is cooled. Since a capacity of cooling the whole of the bar-like electrode 4 is sharply improved compared with a conventional method, a fusion surface in the bar-like electrode 4 can be stabilized at a high position, and hence the life of the electrode is sharply improved. Furthermore, frequencies of the work of repairing the electrode for a furnace wall can be reduced, and hence this device contributes to the improvement of productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace wall electrode of a DC arc furnace used for melting metal materials, refining molten metal and the like.

[0002]

2. Description of the Related Art As an arc furnace for refining, an electric current is passed between an electrode arranged above a molten metal charged in the furnace and an electrode attached to a furnace wall such as a furnace bottom or a side wall to melt the molten metal. A DC arc furnace for refining is known. The furnace wall electrode in this type of DC arc furnace is exposed to an extremely harsh atmosphere due to heat received from the high-temperature molten metal in the furnace, Joule heat generated when a supply current passes through, and the like. Therefore, various proposals have been made to withstand this atmosphere and improve the durability of the furnace wall electrode. For example, in the furnace wall electrode described in JP-B-63-43675,
Attach a cooling sleeve for the refrigerant passage around the electrode portion protruding from the furnace wall (hereinafter referred to as the rear end portion),
It is disclosed that the electrode is forcibly cooled by circulating a coolant such as water in the coolant passage.

[0003]

However, since the cooling sleeve has an integral cylindrical shape, a gap is required between the rod-shaped electrode and the cooling sleeve, and even if the rear end of the electrode is cooled by the cooling sleeve. There is a case where the cooling effect becomes insufficient because there is a distance between the rod-shaped electrode and the rear end surface of the rod-shaped electrode. Although it is possible to directly cool the rod-shaped electrode in order to enhance the cooling, it is not preferable for safety if the position of the melting surface in the rod-shaped electrode is lowered during operation due to abnormal operation or the like. In order to solve such a problem of the prior art, the present invention enhances cooling of the entire rod-shaped electrode by cooling the lower portion of the rod-shaped electrode with a molten metal having a small Prandtl number. As a result, the molten surface in the rod-shaped electrode is stably generated as high as possible. As a result, it is an object of the present invention to provide a furnace wall electrode that suppresses the melting rate of the rod-shaped electrode and has excellent durability.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, a furnace wall electrode of a DC arc furnace according to the present invention is a rod-shaped electrode whose tip portion is embedded in the furnace wall and faces the furnace. A hot water bath is disposed so as to cover a portion located outside the furnace wall, and a portion of the rod-shaped electrode located outside the furnace wall is immersed in the molten low melting point metal contained in the hot water bath, The molten metal cools the portion of the rod-shaped electrode located outside the furnace wall.

[0005]

In order to stabilize the position of the melting surface in the rod-shaped electrode at a position as high as possible, it is necessary to cool the lower part of the rod-shaped electrode more strongly. Conventionally, water is often used as a refrigerant, but it is more effective to use a liquid metal having a smaller Prandtl number from the viewpoint of effective cooling of the rod electrode. Sodium cooling of a fast breeder reactor is known as a means for removing heat and exchanging heat with a liquid, but it is a fused metal type having a melting point of 100 ° C. or less instead of a halogen type metal such as sodium having a large oxidizing power. By using the above metal as a refrigerant, a safer and more effective cooling capacity can be obtained.

[0006]

EXAMPLE FIG. 1 shows an example in which an electrode is attached to the bottom of a DC arc furnace. At the bottom of the DC arc furnace, an indeterminate refractory 2 is lined inside the perm brick 1, and the outside is supported by a steel shell 3. Penetrating through the furnace wall composed of these iron skin 3, perm brick 1 and amorphous refractory 2,
The rear end of the rod-shaped electrode protruding to the outside is immersed in a bath 9 filled with molten metal. The hot water bath 9 is made of a metal having a high thermal conductivity, such as copper, and the cooling sleeve 5 is arranged around the water bath. The refrigerant 8 sent from the refrigerant pipe 7 to the cooling sleeve 5 removes heat from the outer wall of the hot water bath while passing through the cooling sleeve 5. The molten metal in the hot water bath is heated around the rod-shaped electrode and rises, and the molten metal in contact with the inner wall of the hot water bath is cooled and descends. This allows the molten metal to generate thermal convection in the hot water bath and effectively cool the lower portion of the rod-shaped electrode.

[0007]

As described above, in the furnace wall electrode of the present invention, the cooling capacity of the entire rod-shaped electrode is significantly improved as compared with the conventional method, and therefore the position of the melting surface in the rod-shaped electrode is increased. It is possible to stabilize. Therefore, the life of the electrode is significantly improved. Further, the frequency of maintenance work of the furnace wall electrode can be reduced, which contributes to improvement in productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example in which a furnace wall electrode of the present invention is applied to a furnace bottom of a DC arc furnace.

[Explanation of symbols]

 1 Permanent Bricks 2 Amorphous Refractory 3 Iron Crust 4 Rod Electrode 5 Cooling Sleeve 6 Hot Water Bath 7 Piping 8 Refrigerant 9 Molten Metal

Claims (1)

[Claims] 1. A rod-shaped electrode having a tip portion embedded in a furnace wall and facing the inside of the furnace, is provided with a hot-water bath so as to cover a portion of the rod-shaped electrode located outside the furnace wall. It is configured such that a portion of the rod-shaped electrode located outside the furnace wall is immersed in a molten low-melting-point metal that is internally contained, and the portion of the rod-shaped electrode located outside the furnace wall is cooled by the molten metal. Wall electrode of DC arc furnace.